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Quantum Optics and Quantum Information - Science topic

Electromagnetically Induced Transparency, Slow light, Quantum Information, Nonlinear Optics and Quantum Computing.
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In quantum Communication we encode information in polarisation state. But this can also be done performing phase modulation. And infact, we can go to more number of states using phase modulation. So, What is the difference between the two?
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I may add that phase at any instance of a wave is a relative property or changes in the phase are what we detect. On the other hand polarsation state, of a fully
polarised wave, can be measureed in an absolute sense in the laboratory frame.
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Hello,
I wanted to enrich my knowledge about nonlinear optics and quantum technologies. Are there any resources to study them?
Thank you.
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rp-photonics.com - simple explanation + references for more detailed study
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I am interested to know the opinion of experts in this field.
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Photons are massless and therefore non-localisable (consider any typical solution of Maxwell's equations, ), i.e. there are none that stay at a fixed and specific point-like location in space. In contrast, the wavefunction of a massive particle can be so localised.
Thus I would say that photons never match the common definition of a particle (because they are not point-like localisable, even in principle). However, since they can be counted, I would, if prevailed upon to suggest a qualitative description, instead describe them as "countable waves".
This is because in QED we quantize inside "mode" solutions of Maxwell's equations (see any quantum optics text, or the paper I cite above), and can describe the quantum state within each mode in terms of combinations of photon number states.
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A rigid body with vertical proper length J rises along the Y direction in an inertial frame S(T,X,Y) with constant proper acceleration, therefore me may write the equation of hyperbolic motion of the body along the Y direction as:
1) J2 = Y2 - c2 T2
Using Born´s definition of rigidity, the proper length “J” must be invariant under Lorentz transformations between instant commoving inertial frames where the proper length (squared) J2 coincides with the line element (squared) along the Y direction: Y2 - c2 T2. It is straightforward to see that this is the case just for boosts along the Y direction. If the velocity of the body and its inertial commoving frames have an aditional constant component along the X direction, the line element is different, the vertical length J cannot be invariant in the inertial comoving frames and we get a violation of Born´s rigidity.
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And it is a pitty that the students fail to take into account simultaneity of relativity since it is a straighforward consequence of the two more basic priciples of SRT:
1) Constancy of speed of light.
2) Equivalence of inertial frames.
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How do I should do to determine the energy band of superlattice? I want to determine the valence band offset of the superlattice .However, I am confused the methods to determine the valence band offset. What I know is that valence band offset can be derived by XPS, electronegativity, but I am still confused of determining the superlattice energy band ,including the valence band energy , condunciton band energy.
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I assume you have a vertical superlattice arrangement, right? Because if you could somehow access the lattice layers from sideways, you might be able to access them with STS. But of course when you have it vertically, you would have to make a section and that often goes with the generation of new states in the cleaving or cutting region.
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Consider two particles A and B in translation with uniformly accelerated vertical motion in a frame S (X,Y,T) such that the segment AB with length L remains always parallel to the horizontal axis X (XA = 0, XB = L). If we assume that the acceleration vector (0, E) is constant and we take the height of both particles to be defined by the expressions YA = YB = 0.5 ET2, we have that the vertical distance between A and B in S is always (see fig. in PR - 2.pdf):
1) YB - YA = 0
If S moves with constant velocity (v, 0) with respect to another reference s(x,y,t) whose origin coincides with the origin of S at t = T = 0, inserting the Lorentz transformation for A (Y = y, T = g(t - vxA/c2), xA = vt) into YA= 0.5 ET2 and the Lorentz transformation for B (Y = y, T = g(t - vxB/c2), xB = vt + L/g) into YB= 0.5 ET2 we get that the vertical distance between A and B in s(x,y,t) is:
2) yB - yA = 0.5 E (L2v2/c4- 2Lvt/c2g)
which shows us that, at each instant of time "t" the distance yB - yA is different despite being always constant in S (eq.1). As we know that the classical definition of translational motion of two particles is only possible if the distance between them remains constant, we conclude that in s the two particles cannot be in translational motion despite being in translational motion in S.
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Larissa, I might be wrong but I believe that you wanted to post in another quest on dark matter and dark energy.
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1) Can the existence of an aether be compatible with local Lorentz invariance?
2) Can classical rigid bodies in translation be studied in this framework?
By changing the synchronization condition of the clocks of inertial frames, the answer to 1) and 2) seems to be affirmative. This synchronization clearly violates global Lorentz symmetry but it preserves Lorenzt symmetry in the vecinity of each point of the flat spacetime.
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We may consider the time of a clock placed at an arbitrary coordinate x to be t and the time of a clock placed at an arbitrary coordinate xP to be tP. Let the offset (t – tP) between the two clocks be:
1) (t – tP) = v (x - xP)/c2
where (t-tP) is the so-called Sagnac correction. If we insert 1) into the time-like component of the Lorentz transformation T = g (t - vx/c2) we get:
2) T = g (tP - vxP/c2)
On the other hand, if we consider the space-like component of the Lorentz transformation X = g(x-vt) we know that the origin of both frames coincide x =X = 0 at t = 0. If we want x = X = 0 at tP = 0 we have to write:
3) X = g(x - vtP)
Assuming that both clocks are placed at the same point x = xP equations 2)3) become:
4) X = g (xP - vtP)
5) T = g (tP - vxP/c2)
which is the local Lorentz transformation for an event happening at point P. On the other hand , if the distance between x and xP is different from 0 and xP is placed at the origin of coordinates, we may insert xP = 0 into 2)3) to get:
6) X = g (x - vtP)
7) T = g tP
which is a change of coordinates that it:
- Is compatible with GPS simultaneity.
- Is compatible with the Sagnac effect. This effect can be explained in a very straightfordward manner without the need of using GR or the Langevin coordinates.
- Is compatible with the existence of relativistic extended rigid bodies in translation using the classical definition of rigidity instead of the Born´s definition.
- Can be applied to solve the 2 problems of the preprint below.
- Is compatible with all experimenat corroborations of SR: aberration of light, Ives -Stilwell experiment, Hafele-Keating experiment, ...
Thus, we may conclude that, considering the synchronization condition 1):
a) We get Lorentz invariance at each point of flat space-time (eqs. 4-5) when we use a unique single clock.
b) The Lorentz invariance is broken out when we use two clocks to measure time intervals for long displacements (eqs. 6-7).
c) We need to consider the frame with respect to which we must define the velocity v of the synchronization condition (eq 1). This frame has v = 0 and it plays the role of an absolute preferred frame.
a)b)c) suggest that the Thomas precession is a local effect that cannot manifest for long displacements.
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Cameron Rebigsol I understand your world view and Sir Isaac Newton would have agreed with you. Newton explained gravity and made the connection between the gravity on Earth (e.g. the falling apple) and the motion of the moon. He worked out that it would all be explained by an inverse square law of distance. Even Newton was a bit puzzled about how this "action at a distance" worked.
James Clerk Maxwell pointed out that this "action at a distance" was not a good explanation and felt that there had to be some mechanism through the medium to produce electromagnetism and gravity.
I agree with the viewpoint of Maxwell and I do take as my starting assumption that General Relativity is completely correct as there is sufficient evidence for this. Then the question of "action at a distance" is resolved because it is the state of the medium (i.e. spacetime) which is the underlying cause of the gravitational and electromagnetic forces.
Richard
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Please, see the attached file RPVM.pdf. Any comment will be wellcome.
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I think that an interesting point is that, using units with c = 1, the 4-velocity (dt,dx,0,0) is a 1-tensor that is the same for any offset of clocks of the inertial frame. Then we have that the 4-velocity (dt,dx,0,0) transforms the same for any synchronization, it satisfies the Einstein addition of velocities and consequently it also satisfies the principle of constancy of speed of light. On the other hand, as it behaves like a tensor under Lorentz transformations, the relativity principle holds for it an for all derived 1-tensors like velocity, acceleration and so on.
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You can find the wording in the attached file PR1-v3.pdf. Any comment will be wellcome.
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I think that an interesting point is that, using units with c = 1, the 4-velocity (dt,dx,0,0) is a 1-tensor that is the same for any offset of clocks of the inertial frame. Then we have that the 4-velocity (dt,dx,0,0) transforms the same for any synchronization, it satisfies the Einstein addition of velocities and consequently it also satisfies the principle of constancy of speed of light. On the other hand, as it behaves like a tensor under Lorentz transformations, the relativity principle holds for it an for all derived 1-tensors like velocity, acceleration and so on.
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As stated in title.
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Due to the many-body physics and qubit state in quantum mechanics give a simple method to dealing with systems of coupled nonlinear quantum resonators.
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We read and hear everywhere in conferences that QM is time reversible, but even for us laymen, the collapse of the wave function seems quite irreversible. It is also the case for interactions : if we take for example the e- + e+ -> ph + ph ; if you reverse the time the result will not be the initial state of the system since 1) the photons may not interact at all, 2) the result of the interaction may be a different type of particles, 3) the electron/positron pair will be ejected in a different direction.
It seems to me that the laws of QM that are time reversible are all statistical, but their realizations are in practice not time reversible, neither in fact deterministic.
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You can look at the following article:
Your statement that is a statistical claim seems to be true, the time invariance was introduced mainly because of the spin-statistics. Probably a good look into a QED textbook could have a better understanding of the issue.
Chronologically, time reversal in QM was proposed by Prof. E. Wigner in 1932, then in the 50s with the effort of Profs. J. Schwinger, G. Lüders, and W. Pauli, it became clear that time-reversal (T) in QED is naturally considered in combination with charge conjugation (C) and spatial reflection (P), called in QED as a CPT-invariant.
Best Regards.
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Hello everyone
As a beginning to my Masters thesis, I'm seeking to find resources about a single photon behavior in a a Mach-Zehnder interferometer cell.
more generally I'm trying to simulate the nanophotonic processor for quantum computing purposes in the paper bellow.
I would be very happy if anyone could help about the processes that need to be considered in this project.
It is worth mentioning that the preferred platform of simulation is MATLAB but any other simulating software would also be welcomed.
the paper that I mentioned above could be found here:
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Hi Mobin,
I've found the paper, “Interference with correlated photons: Five quantum mechanics experiments for undergraduates,” E. J. Galvez, C. H. Holbrow, M. J. Pysher, J. W. Martin, N. Courtemanche, L. Heilig, and J. Spencer, American Journal of Physics 73, 127-140 (2005). to be particularly useful for understanding single-photon interference in Mach-Zehnder interferometers. In particular, the paper works through the example of the quantum eraser. Hope this helps!
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Hi, I am looking forward for collaborators (academic and research work) who are interested to work in the following area:
Quantum Attacks
Quantum Computing
Quantum Artificial Intelligence
Post-quantum Cryptography
Internet of Drones
Blockchain and Quantum Computing
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Hello Sir,
I am interested in the suggested topics. My domain is cloud computing security using cryptographic techniques. I have few publications in this domain. Please have a look.
Regards
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Talking to Dr. Jörn Schliewe inspired me to raise this illustrated question and how you may call these barriers in the experiment of diffraction? Would you call it n-slits or n-obstacles?
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Well, first, it’s N+1 obstacles or if you don’t want to count the long walls at either end for some reason, N-1obstacles, but certainly not N obstacles.
It certainly doesn’t matter what you call it. In your picture the two terms are both correct, and not mutually exclusive. It is in, in fact, N+1 obstacles forming N slits.
I don’t think anyone misunderstands that slits are formed by barriers, and if you talk about N slits everyone will instantly picture a barrier with slits in it. However, on a practical note, at optical wavelengths it generally isn’t possible to have free standing barriers like this. Instead the solid wall continues above and below. Generally a transmissive grating looks like a solid barrier with ”slits” cut into it. So the ”slits” term is constructivist. It is indicative of how the structure is created. You cut slits into a foil or similar. That is the dictionary definition of slit: a narrow cut. That is also how this became the standard terminology in optics because in the early experiments that is literally how gratings were made. We’ve greatly improved our “knife”, but fundamentally that is still how subtractive transmission gratings are still made today.
Terminology is for understanding, and often it uses similarity for recognition. No one thinks the arrow slits in a castle wall were literally made by cutting, but they look like cuts. If you call them slits everyone understands what you are talking about. That is the only important cr for terminology.
In optics we always talk about the slits. This is probably because we are focused on the light. Each slit is treated as a source, we propagate on using Huygen’s principle, etc. It doesn’t really matter what the barriers are so long as they exist. However, we have to talk about slit width and slit spacing, so in what an artist might call “negative space” we are inevitably also describing the barrier. Everyone gets that. I don’t think I’ll switch to explicitly talking about the barriers any time soon
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Is there a simple proof that the signal and idler photons created by spontaneous parametric down-conversion (SPDC) are entangled, whereas those that are created by optical parametric amplification (OPA) are not? SPDC has been used in the optical band to create entangled photons. A view of this is that the SPDC just amplifies the vacuum (zero-point energy) photon to create a signal photon, whilst an idler photon is created to preserve conservation of energy when the pump photon annihilates. In the OPA process a seed photon is parametrically amplified likewise to create a signal photon and idler photon, whilst the pump photon annihilates. What is the proof therefore that the signal and idler photon pair from OPA are not entangled?
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Hi Paul,
thank you for that, yes agreed.
I'm happy that SPDC signal and idler are entangled, so now 'all' that is needed now is some mathematical proof to show that OPA signal and idler photons are entangled or not.
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The hydrogen spectral lines are organized in various series. Lyman series are the lines corresponding to transitions targeting the ground state.
Most pictures dealing with hydrogen spectra and available in the web are recordings dealing with extraterrestrial hydrogen sitting in celestial entities. Otherwise they are illustrations obtained not from experimental recordings, but from the well known Rydberg formula.
Of interest for the undersigned are pictures of Lyman series as recorded in laboratory observations of hydrogen atoms, with the atoms sitting in the laboratory itself. Not extraterrestrial hydrogen, nor molecules H2, even if the molecules are sitting nearby.
Presumably such recordings would have required ultraviolet sensitive CCDs, UV photographic plates, or similars. Particularly relevant would be careful raw recordings of Lyman series that INCLUDE THE ALPHA-LINE at 1216 Å.
Experimental remarks about the Lyman alpha-line, difficulties to observe it ---if any---, line width, line broadening, etc., and difficult-to-explain anomalies, are of particular concern. So far Web searching has not been successful.
I would appreciate any link or suggestions as to how to obtain the pictures and experimentally based information of the kind explained above.
Most cordially,
Daniel Crespin
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Dear Daniel Crespin
The article “Anomalous Behavior of Atomic Hydrogen Interacting with Gold Clusters” contains information that might be useful for finding answers to your question....
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Hi, i am sudying some quantum computer science and I am really struggling to find an explanation to the question done above.
Any kind of help would be wonderfull.
Greets.
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The Toffoli gate serves as a universal gate for Boolean logic, if we can provide fixed input bits and ignore output bits. If z is initially 1, then x ↑ y = 1 − xy appears in the third output — we can perform NAND. If we fix x = 1, the Toffoli gate functions like an XOR gate, and we can use it to copy. The Toffoli gate θ (3) is universal in the sense that we can build a circuit to compute any reversible function using Toffoli gates alone (if we can fix input bits and ignore output bits).
The Toffoli gate and the negation gate together yield a universal gate set, in the sense that every permutation of {0,1}n can be implemented as a composition of these gates. Since every bit operation that does not use all of the bits performs an even permutation, we need to use at least one auxiliary bit to perform every permutation, and it is known that one bit is indeed enough. Without auxiliary bits, all even permutations can be implemented.
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The fact that the measurement of vanishing distances is physically impossible, which preempts continuity, may lead us to not consider renormalization as a proper procedure in particle physics.
Also, it may lead us to disconsider it, as not needed to define derivatives using infinitesimals, and use Galois fields instead.
We may be pushing our equations too close, to limits where they probably do not apply, and renormalization just tries to solve the symptoms -- to avoid infinities. But the "problem" remains -- there are no infinitesimals in Nature, nor can be created.
Can we not use a concept that we cannot find nor encounter? Infinitesimals do not exist? Then, is renormalization necessary?
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HS: thanks. But infinities and infinitesimals do not exist, so they are a pseudo problem. That’s what the question also says, that renormalization, in spite of its Nobel prize fame, is a pseudo problem. They are caused by assuming them to exist, and then "solving" them -- while they are already solved when using the correct formalism to start wit -- which is Galois fields. Nothing is continuous in Nature, not even numbers.
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Dear colleagues,
Since band gap energy is related to material size, somehow, the quantum phenomenon could be found in the range of Bohr atomic radius for semicondutor based materials. Did you know about that? How I can collect the data of atomic Bohr radii for photocatalysts?
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Good discussion!
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I have tried to study quantum mechanics before but never understood it. After learning basics about quantum computing and quantum information including quantum hardware and qubit types, I wish to start studying quantum physics again. What are few of the areas of quantum mechanics that Quantum information systems relate or are based on?
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The Mathematical framework of Quantum information theory carries over to address the issue of dynamics of nuclear spin ensembles ,e.g the NMR spectroscopy or MRI , nmr spin systems were one of the earliest candidates for scalable quantum computers.
In my opinion the concepts of Quantum information theory do not only relate to quantum mechanics but provide a great impetus for research on Linear algebra, Matrix theory , Multivariate statistics and Matrix Calculus of real and complex variables.
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The very common experiment in optics to demonstrate that light behaves same as the wave is single-slit diffraction.
If we assume that the thickness of the barriers is 0.1 mm, then the length of a slot along the optical axis will be a long route as a green photon will measure it nearly two hundred times larger than its own size.
Now the question is how the photon behaves along with that long route? Does it behave as a particle or wave? If the exit of the slot or a pinhole is causing photon behaves as a wave then why the entrance wouldn't do that? And if we accept that photon behaves like a wave as it enters the single slit or the pinhole, then formally we should apply the Fresnel diffraction equation from the entry of the slot that will lead us to nowhere.
In my opinion, wave-particle duality is leading us solely to some useful approximation but it doesn't talk about reality, as it cannot explain a sort of experiments that unfortunately have been ignored or left behind such as the glory of the shadow, and also the stretching the shadows when they meet each other and so on.
For sure, wave-particle duality is not the end of science and for sure five hundred years later people will not consider the existence as do we do now the same as us that we don't see the things same as our ancestors, so we should be open-minded to be able to open the new horizons.
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Natalia S Duxbury > “Particle is a real physical object. But what is the wave made of???? Wave function is a mathematical construction”.
Very well said, could not agree more! Theoretical physics for the last (more than) hundred years and specially since Albert Einstein has been an enormous waste in terms of human, natural and economic resources and most of all at the heavy cost of intellectual advance of humanity.
The truth is that formally trained modern theoretical physicists unwittingly follow a philosophy/epistemology (a branch of knowledge that they routinely disparage!), namely Kantianism that has already been discredited long ago by G.W.F. Hegel, the worthy protégé of Kant himself! Modern theoretical “physicists” - following Einstein, are not concerned with knowing objective reality as it is in-itself (ontology), but only with the subjective data (epistemology) they can gather about it; so in actual sense they are trying to understand the working of their own minds, rather than external reality!
The Kantian premise is that objective reality is a messy, chaotic, unwieldy and unknowable thing-in-itself; because it does not follow the pristine precincts of good old commonsense, causality, formal logic and the notions of rationality that have been developed by philosophers starting from the early Greeks. The only thing man can do (Kant posited) is to use his sense perceptions, experimental data, his thought, imagination, fantasy or whatever subjective data he can gather about the objective reality to get on with life. What man at best can do, is to organize this data through his subjective thought, mental tools, logical schemata, mathematical (geometrical, algebraic, symmetry) structures and representations, logical categories, theories etc. to get as much of an “understanding” of objective reality as possible, to deal with it comfortably! A good theory is the one that can cover as much of this data, as well as future possible ones (predictability). This is what is historically known as scholasticism - an endless debate to justify one's subjective choice from various theories; but there is no way to judge who is right, except the power of individual’s proficiency in debating skills!
After the quantum phenomena, the Kantian view of the world became a "self-evident truth" for natural science, if there was any doubt about it before, at all. Theoretical physics led by Albert Einstein embraced the Kantian view of the world whole heartedly and universally and like Moses led an Exodus of the physicists to the promised land of thought and mathematics - his "Castle in the Air", as we see now. According to the Kantian view, objective reality is like an invisible Cheshire cat, which remains unknown, we only deal with the “smile” of the cat that we can perceive through our sense perceptions and process through our subjective mental tools.
From a materialist dialectical world view (that I subscribe to) the quantum phenomena is the most fundamental aspect of objective reality, which abolishes “spacetime” or any other esoteric “fields". All forces are mediated by the exchange of virtual particles. The virtual particles become real particles if enough energy equivalence of their mass is available. Light at all wavelengths are particles that can propagate as wave. Please see the following articles and other related publications, questions and comments in my RG profile:
Ambartsumian, Arp and the Breeding Galaxies:
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In recent research perspective this is very important field. Parity operation is reversal of co-ordinate (x->-x, p->-p)and time reversal operation is reversal of time (x->x,p->-p, i->-i).
But talking about this combined PT-symmetry in any field of science and engineering, what it implies?
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Dear Prof. Samit Kumar Gupta,
In superconductors, a PT symmetry invariance broken state could be the main manifestation of anionic superconductivity. There are not agreements so far on the subject.
Please see this external reference:
Selected Topics in Superconductivity by L. C. Gupta, M. S. Multani
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The ideas which I have come across are:
  1. By creating an entangled state between two distant NV centers, by combining the control of multiple qubits in nodes with optical links and then measuring the outcome. This will also help in security as the origin of the state will be unknown to the detectors.
  2. Using semiconductor transmon qubits, which are to be interacted by quantum gates and using circuit QED, the readout is obtained from a quantum processor.
Taking into account the noise and distortion challenges along with controlling qubits and building the complex software and hardware systems, how will we be able to send and receive large quantum information from one quantum system to another, over very long distances like in millions, for example, for an error-free and undelayed satellite communication?
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Now scientific progress rests on the implementation of quantum repeaters (if we are talking about optical fiber). You can also use satellite key distribution (open space) ... see the latest Chinese experiment.
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The superposition principle is moslety used in physical and natural phenomena modeling: The response caused by two or more stimulus is the SUM (integration, average) of the responses that would have been caused by each stimulus individually (Ex: quantum chemistry, chemistry interaction, visual perception, linear system, etc.). These effects happened naturally. I try to understand physical interpretation of Multiplication operation applied to two or more object with similar nature (Ex: waves, functions, forces, etc.). I wonder if there is, for example, linking between "Compression" "Attraction", or "Collision" and the multiplication result of their properties.
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Dear Ait Mansour El Houssain In general, any mathematical operation (*) is defined over some set A, and this operation should be well defined. It means that if a and b belong to A, then a*b belongs to A. We are familiar with many operations such as (multiplication, addition, subtraction, division, etc..) each has a different formula. For example, multiplication of complex numbers is different from the multiplication of matrices, because we have different objects. So we need to define some set of objects. Then we define the required operations that are consistent and satisfy a family of axioms according to the presented mathematical model. In your example, the "collision operation" can be considered as a multiplication operation between objects, to do so, you need to show an explicit formula of this physical activity and then prove that it is well defined. You may consider the forces that exert on the objects, and the collision is the ( resultant force = some formula) that produced after this action. So all elements should be forces ( represented by vectors) controlled by the proposed formula. Best regards
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I have hands on with IBM quantum experience (QISKIT). I am in exploration phase now. I have studied all the basics related to quantum computing. I am also looking for fully funded Phd in quantum artificial intelligence. I would be happy to help in related research if anyone needs helping hand.
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This might be a little old now (revised in 2018), but you can certainly look for references inside this review article. It will also give you a flavor of what is out there.
or the book by Schuld and Petruccione (Supervised Learning w/Quantum Computers) should also be a nice place to start your explorations.
Good luck finding a PhD in the subject :)
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If we consider hypothetically and philosophically, i.e., why we always think light is spreading out. May be dark is fading away as an entity everytime faster than the light. Why faster? Because we haven't detected speed of darkness till now. And I want to connect this concept with Quantum Entanglement. Because according to this concept information is transfered faster than the speed of light between two entity separated by infinite distance. Who knows dark entity may be the answer to Quantum Entanglement??
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All: One can think that shadows move infinitely quicker, because they are always there. Light moves on the "Tohu wa-bohu" or nothingness, which is dark, and one could equate the dark with the shadows, but the dark is meant to be even less than the shadows, which is the absence of light. Mathematically, the shadows are light in quantum field theory (QFT) as the null solution (where the solution is zero, exactly) of the equations.
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At first, the answer seems obvious, as E/h = f, where E is the energy of the photon, h is the Planck constant, and f is the frequency of the photon. But then one realizes that the photon would need an infinite duration in order to have a single frequency (e.g., Fourier transform relation, and Heisenberg uncertainty principle).
The probability doctrine of quantum mechanics (QM) asserts that the indetermination, of which we have just given an example, is a property inherent in Nature, and not merely a profession of our temporary ignorance from which we expect to be relieved by a future better and more complete theory.
Such more complete theory appears to be Quantum Field Theory (QFT). The Heisenberg uncertainty principle in QM may then have to be reexamined.
Obviously, then, E/h = f is not the correct answer.
Nothing is infinite in Nature. We can't wait forever to measure a photon, and nothing can. The Universe would not exist.
The answer is to realize that something is wrong with the QM picture of a photon. The frequency of a photon is defined by its physical conditions in QFT, not by itself.
And it is not described by a Fourier transform either, which is a mathematically "continuous" procedure -- with the hypothesis of infinitely close frequencies -- and should never be used to represent a discrete phenomena, or artifacts of the interpolation will appear.
As Juan Weisz asks -- why is QFT better than QM? The answer may be relevant here, as QM is subjective but QFT is intersubjective. Like math, it is not enough to be subjective, as follows.
QM is based on two deep untruths, as revealed by Nature, in addition to the rather formalist easy-to-solve fact that QM is not combining the principles of Lorentz invariance (SR-MINKOWSKI-EINSTEIN). They are:
1. One needs to abandon the single-particle approach of QM (subjectivity). In any relativistic quantum theory, particle number need not be conserved, since the relativistic dispersion relation in SR, that E^2 = c^2p^2 + m^2c^4, implies that energy can be converted into particles and vice versa. This requires a multi-particle framework (intersubjectivity), a many-body interaction with SR included and uses QM. It is a many-body-relativistic-QM, not just QM.
2. Unitarity (basically, preserving the inner product) and causality cannot be combined in a single-particle approach, requires intersubjectivity.
QFT solves these two problems by using a different approach:
A. The fundamental entities are not the particles, but the field, an abstract object that penetrates spacetime.
B. Particles appear as the vibrations of the field.
The physical model of the photon, for example, is given as a vibration of the EM field, and follows QFT. Then, in QFT the frequency of the photon does NOT depend on the photon itself and only (that would be subjective), but on its physical conditions in a many-body-relativistic-QM (intersubjective). Then, that intersubjectivity can obtain objectivity to different observers, in different experiments, at differing spacetimes.
and
Sean Carroll recently at https://www.youtube.com/watch?v=rBpR0LBsUfM and after the 45 minute mark specially.
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I accept that the photon is constructed by superposition of vibrations in a definite manner. Every fundamental particle have there own mode of vibration.
Now let us focus on some collection of photons with different energy. Here intrinsic property, like spin, is same for all particles. Hence the reason which gives intrinsic angular momentum is also same. So the vibration which make this particle "photon" is also same.
What I am trying to say is that the frequency which gives energy is not same as frequency that makes the particle photon.
The energy is decided by the situation by which it is credited and it is stored in the form of rate of change of phase.
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The diffraction of light has been referred to as its wave quality since it seemed there was no other solution to describe that phenomenon as its particle quality and subsequently, it exhibited wave-particle duality.
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Berndt Barkholz Similarly, I would say electrons cannot be particles too, because they behave like photons in many experiments, such as double slit experiment.
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Following well-known books in quantum mechanics (QM), such as "Quantum Mechanics" by Eugen Merzbacher, once influential and authoritative on QM, is today a slippery slope in many parts.
The simultaneous appearance of classical wave and particle aspects no longer can be defended in QM. The only thing that exists in Nature, as we know from quantum field theory (QFT), is quantum waves, NOT particles and NOT waves as in Fourier analysis (classical).
The Heisenberg uncertainty principle in QM seems, thus, to have to be modified -- as it is, in contradiction with itself, based on continuity by using the Fourier transform. Can we express it in QFT terms (not based on continuity)? Can that influence LIGO and other applications?
See also Sean Carroll recently at https://www.youtube.com/watch?v=rBpR0LBsUfM and after the 45 minute mark specially.
Thus, there is only one (not two or even three) case of photon interference in the two-slit experiment, and that is the case that is often neglected -- the quantum wave case. See the two-slit experiment at low-intensity, for example at: https://www.youtube.com/watch?v=GzbKb59my3U
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All: For a background on why we can suspect that the Heisenberg uncertainty principle is fundamentally wrong, one can see its supposed "justification" using the classical theory (not quantum) of Fourier transform, see:
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Quantum entanglement experiments are normally carried out in the regime (hf>kT - where T is the temperature of the instrument) to minimise thermal noise, which means operating in the optical band, or in the lower frequency band (<6 THz) with cryogenically cooled detectors.
However, the omnipresent questions are whether in the millimetre wave band where hf<kT:
1) Could quantum entanglement be detected by novel systems in the at ambient temperature?
2) How easy might it be to generate entangled photons (there should be nothing intrinsically more difficult here than in the optical band - in fact it might be easier, as you get more photons for a given pump power)?
3) How common in nature might be the phenomenon of entanglement (this would be in the regimes where biological systems operate)?
Answers to 1) may lead to routes to answering 2) and 3).
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Dear Dimitry,
it may be possible to used the system proposed in:
to determine if entangled photons are generated by biological systems.
many thanks,
Neil
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For quantum applications we need more coherent wave distribution. To increase the coherency we need some strategies. What do you suggest for this application?
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One way is to increase the more round trip radiation in the resonator which emphasizes the reflectivity of the mirrors and increases the saturation of the phase coherence.
The next point is to be more accurate in fixing the distance of the mirrors to the correct ratio of the net wavelength generated to create some kind of static wave mode.
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Let's assume that states |1> and |2> are degenerate states and the system is prepared in state |1>. Also, the matrix element of electric dipole moment is not zero between these two states (<1|mu|2>=!0). If we interact this system with vacuum field, does this system remain in its initial state? (I know from Wigner Weisskopf theory that if these two levels were not degenerate and level |1> was the excited state, the system would decay with Einstein rate.)
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Hi Omid,
The spontaneous emission rate from an excited state |1> to a ground state |2> is proportional to |<1|mu|2> |^2 and w^3, where <1|mu|2> is the matrix dipole moment and w=w1-w2 is the atomic transition frequency (see Ficek, Quantum interference and coherence). It is clear that if both the states are degenerate, then w=0 since they have the same energy. Therefore, spontaneous emission does not take place between degenerate states.
When an atom decays from an excited state to a ground state, it emits a photon with frequency equal to the transition frequency. It does not make sense physically for spontaneous emission to take place between degenerate states. Please check your problem thoroughly.
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Assume that you are living in the time when the Gregorian calendar was introduced by Pope Gregory XIII in October 1582, when
Galileo Galilei was about eighteen years old. However, he was tried by the Inquisition, found "vehemently suspect of heresy", and forced to recant 1632, and then he spent the rest of his life under house arrest.
The most noticeable thing in this matter is that people of those years could realize the rotation and subsequently, they could calculate the rate and the duration of the rotation but what was not clear for them was what is rotating around what. At that time what would be your solution?
Now, if I can take this sad historical event as the fact, then I would ask myself if the integral theorem of Helmholtz and Kirchhoff plays a central role in the derivation of the scalar theory of diffraction along with the concept of the wave-particle duality, or it obtains the propagation of light in the diffracted space with an inhomogeneous refractive index?
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One more thing: In all this, mathematics is totally neutral. People often confuse "mathematical models" (sothing that a natural scientist does) with mathematics (which mathematicians do). Mathematics is not concerned with "truth" at all. All math theorems say "if A than B", but they NEVER tell you whether A is true or not. Math creates pre-fabricated logic containers, it is not concerned with the truth values of their "inputs".
Hence, you should re-formualate you question as "Do mathematical models present solutions for understanding the reality of the universe?". The answer is then obvious: some do, some don't. And often several model lead to the same conclusion. That's all, folks :-)
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In solid-state physics, a band gap/energy gap is an energy range in a solid where no electron states can exist. In graphs of the electronic band structure of solids, the band gap generally refers to the energy difference (in eV) between the top of the VB and the bottom of the CB in insulators and semiconductors. It is the energy required to promote a valence electron bound to an atom to become a conduction electron, which is free to move within the crystal lattice and serve as a charge carrier to conduct electric current.
A semiconductor will not absorb photons of energy less than the band gap and the energy of the electron-hole pair produced by a photon is equal to the band gap energy.
The band gap is a major factor determining the electrical conductivity of a solid. Band-gap engineering is the process of controlling/tuning the band gap of a material by controlling the composition of certain semiconductor alloys, such as GaAlAs, InGaAs, and InAlAs. Band gap depends on doping, size, temperature, pressure etc. It is also possible to construct layered materials with alternating compositions by techniques like molecular-beam epitaxy. These methods are exploited in the design of heterojunction bipolar transistors (HBTs), laser diodes and solar cells.
In a quantum dot crystal, the band gap is size dependent and can be altered to produce a range of energies between the valence band and conduction band. Band gap increases with decrease in size due to electron confinement at Nano-scale. It is also known as Quantum confinement effect.
However, I am working on inorganic semiconducting silicide materials for potential applications in solar cells. Beta phase Iron di-silicide (β-FeSi2) has a band gap of about 0.87 eV which can be tuned from 0.8 eV to less than 0.9 eV.
How can we increase its band gap further, beyond 0.9 eV? In particular, can we tune its band gap near to optimum band gap of 1.5 eV for solar energy harvesting?
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Thank you, Rüdiger Mitdank sir for your precious reply. This is actually what I was waiting for. Your thought is extraordinary. Now, I can discuss about it with my Supervisor.
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Hi experts.. Can you explains why the excitation-“dependent” emission of aqueous N-CDs suddenly changed to ”independent” while binding with PVA (solid film). Is this related to PVA nature? Please help And thanks in advance.
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Its because of 'Traps' as explained in
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We have learned that they remain in superposition state unless detected. Can anyone elaborate it in theoretical terms?
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Nonclassical objects with the de Broglie wavelengths too significant to ignore
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In quantum key distribution (QKD) optical fiber networks, the quantum channel (QCh) is used for establishing and updating secure keys which are used to encrypt data [1]. Public interaction channel (PICh) is used for exchanging other key related information [1]. Traditional data channel is used for transmitting encrypted data [1].
My question is, what are the modulation schemes to be used for QCh and PICh?
I could not find information regarding the modulation scheme in any of the published articles I read. Please answer this question or suggest some articles that contain this information.
Please note that I am not looking for modulation schemes used for transmitting traditional data.
Thanks
[1] Zhao, Y., Cao, Y., Wang, W., Wang, H., Yu, X., Zhang, J., Tornatore, M., Wu, Y. and Mukherjee, B., 2018. Resource allocation in optical networks secured by quantum key distribution. IEEE Communications Magazine, 56(8), pp.130-137.
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Dear Anuj, the point raised by you is really timely. From your points, it is understood that traditional methods will not help much. However, I would like to say QAM may be an option along with orbital angular momentum multiplexing. Just have a look at the articles attached.
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If metamaterials could be designed to have non-linear susceptibilities (magnetic or electric) and phase matching properties for the refractive indices in the mm-wave band they might enable novel quantum processes. In naturally occurring dielectrics non-linear susceptibilities arise in non-centrosymmetric crystals. Perhaps something could be synthesized in synthetic materials. There might be magnetic counterparts to this. Scientists working on metamaterials must have considered this, so where is this at the moment? Comments welcome. N
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Sebastian and Rajib, thanks, those are interesting papers, Cheers, Neil
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As you know I had proposed
Achimowicz formulae stating that Information can be transformed to energy by the relation: (1) E = I x c2 in analogy to reasoning that E= m x c2 = h x omega as proposed by Planck
The next step is quantomize information so I shoud write:
E= I x c2 = h x omega
where h - Planck constant and omega is the information frequency.
Next question is : Does DNA have the own frequencies i.e. stable information frequencies at which it resonates?
. So what the quanta of information means ????
What is its interpretation ???
Any one wishing to answer this question ???
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The Epistemological Crisis in Modern Physics
Amrit Sorli*, Steven Kaufman*
ABSTRACT
In physics today it often happens that experimental data is interpreted as proof of a phenomenon that has not been
directly observed, but for which phenomenon there is a theoretical model. With the obtained data acting thereby as
proof, the model then becomes recognized as “real,” after which the theoretical phenomenon that the model
describes also then becomes recognized as “real” – that is, the heretofore purely theoretical phenomenon is
acknowledged as a physical reality, even though it has never been observed, by either instruments or human
senses. This relatively new situation, in which unobserved phenomenon come to be treated as if they had been
directly observed, has lead modern physics into deep epistemological crisis of which it is not yet aware. The
purpose of this article is both to identify the epistemological crisis created by this situation, as well as to present a
solution to overcoming this crisis.
Key Words: Epistemology, Higgs field, gravitational waves
DOI Number: 10.14704/nq.2018.16.2. NeuroQuantology 2018; 16, 2:
Introduction
Recently, two Nobel prizes were given for the
discovery of phenomena that have not yet been
observed by either instruments or human senses,
namely: the Higgs field and gravitational waves.
In the Higgs field research, it was found that
extremely rarely (one in millions of collisions of
protons) a characteristic flux of energy can be
measured that has been named the “Higgs
boson.” For modern physics, the discovery of the
Higgs boson stands as proof of the existence of
the Higgs field, even though such a field has been
neither measured by instrument nor observed by
human senses. Similarly, in gravitational wave
research, it has been found that the laser light
motion in the LIGO interferometer sometimes
takes a bit longer or shorter time when passing
the beams, and this has been interpreted as
occurring when a gravitational wave is
theoretically passing through the interferometer.
For modern physics, the minimal time variability
of the laser light stands as proof of the existence
of gravitational waves, even though such waves
have been neither measured by instrument nor
observed by human senses. In both of these cases,
there is an “epistemological gap” between
obtained data and the interpretation of that data
that represents a serious problem from the
standpoint of the epistemology of physics.
The weak point of the methodology of modern
physics
The Special Theory of Relativity (STR), published
in 1905, deeply changed the methodology of
physics. As a result of STR, it became and remains
an accepted truth that time is the 4th dimension of
space, and as such has an actual physical
existence. The formalism X 4 = ict has
convinced the majority of physicists that time is
the 4th dimension in the space-time model. And
so, as a consequence of the acceptance of the
space-time model, physicists are also convinced
that time, as the 4th dimension of space, has a real
physical existence, although there is no direct
experimental evidence whatsoever for this, nor
Corresponding author: Amrit Sorli, Steven Kaufman
Address: Foundations of Physics Institute – FOPI, Slovenia
Relevant conflicts of interest/financial disclosures: The authors declare that the research was conducted in the absence of any
commercial or financial relationships that could be construed as a potential conflict of interest.
Received: 12 July 2017; Accepted: 7 September 2017
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I am really confusing at this point, and i really need your help, my question is:
Assume that we have an atomic vapor cell, for example rubidium, and we send a strong linear polarized laser light (which is a coherent state) and at the end of the cell we observe that our polarization is rotated, and then we see that anything that is produced in orthogonal polarization is squeezed state, now i want to consider a full-quantum approach and write the equations and see the rotation of polarization and overall the evolution of the field in my formalism. please note that i want to consider the Zeeman sublevels, and my problem is, how should i consider this interaction between my light with multi-Zeeman-sublevel atoms and find out the rotation of polarization and etc?
Thank you in advance
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The guided beam approach will help you out here. As you say that there are polarization levels after impingement of laser beam, it is worthy to take into account polarizability of the medium. Supposing it to be arbitrary medium of a known refractive index, the polarizability can be attained. Simultaneously, with incorporation of energy levels beacause of your assumed Zeeman splitting, you can now tune the intensity by varying the amplitude level to see the eventual effcet. I would be glad to look into your findings.
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For the double slit interference (Thomas Young 1901) the distance between the peaks b on the screen is derived by the well known formula b=H.l /D where H is the distance ftom the slits to the screen. D the distance between the slits and l is the wavelenght. So if D is not small (1-2 mm) the visibility of the peaks is unobservable.
Now the same must apply for the distance between the reference beam and points from the object. When this is D in holography and the same formula applies then there must not be intereference visibility - b should be very small. But holography interefernce is visible. How is that? Is there another formula and if yes why? I think holography is the closest to double slit Young experiment?
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Air turbulence does not prevent hologram recording in room conditions.
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1. I have been wondering if the state of a quantum system (n) could be represented with a non-integer. I saw a lecture note recently where it was claimed that there is actually no reason why this case will not hold. I would really appreciate your expert opinions and text suggestions. I have attached a file for more information on this.
2. If this case is possible, what are the likely implications for the quantum oscillator.
Thank you.
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Dear Michael Dada,
Gert Van der Zwan pointed out the actual reason. Here, I am giving a more transparent way of looking at the same which may be helpful to you.
Thanking you and best regards....NG.
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I would like to put to the critic of the RG participants a hypothesis about the nature of the wave function (WF) - more specifically about WF collapse.
According to it: the particle is a real entity and creates a real wave, which has real nature and is described by the WF. This wave can interract with the particle by changing its trajectory as is evident from double slit and Mach Zehnder interferometer. So far it looks like de Broglie interpretation.
But the WF collapse is explained as impossibility of the wave to interact with the particle after the particle is affected in the process of measurement. After measurement the particle creates a new wave and can interact only with it. Maybe as a prove can be regarded the fact that when the measurement is weak there is partlial visibility of the interference.
Then there are two possibilities about the wave. First - It can not interact with other particles following Diracs sentence that “An electron interferes only with itself”.Then this wave is no more observable. Or can get observable after removing all consequences from the measurent (erasing the measurement). There can maybe offered an experiment (I didn’t thought about).
Second the wave can interfere with another particle provided it is in a state the original particle was in before the measurement. Indication of this are some papers of interference of two lasers and Hong-Mandel-Ou intereference. If this is the case I propose an experiment which may solve the case. The plot is the following file.
WF hipothesis plot.doc    
There scheme is checked for D2 and D1 events and t2<t1 and vice versa. That would mean that the particle 1 is not in the right arm of the MZI and the wave had interacted with the second particle.
I would like to know is there an existing interpretation of QM like the presented. I myself never read a similar.
Does  the idea show weak points and what?
 
 
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@ ilian
Remember the wave is composed of phase wave and group wave elements. And we must stop thinking of the particle as a single entity. According to its frequency an electron consists of 10^20 individual qaunta. So like a water wave consisting of many molecules it acts as a wave with a group wave and a phase wave velocity the latter being is the velocity of the individual molecules. Collapse is inevitable if we measure the position of the particle as a whole as the single electron experiment shows. But not if we only partially measure it, that is we measure some of the individual quanta at a time, which is what your partial experiment shows.
So what the wave experiments prove is that the electron is not a single entity, but that its components are cohesive when it forms the single electron.
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In fact, I'm working on a thesis project on Quantum Information and precisely on quantum error correcting codes. I just started not long ago my research on the subject, and specifically how one can go from a classical signal to a quantum signal to describe the algorithms of error correction codes in physical channels.
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There is a lot of work going on here, it is a very active field of research. Also your question does not seem clear. Do you mean the uploading of classical information with a quantum oracle (alike Quantum RAM?)
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"I thought about quantum mechanics a hundred times more than general relativity, but I still don't understand," Einstein said.
Perhaps the most difficult to understand is the wave-particle duality, which may be because the understanding of it is only in the form of mathematics.In fact, no one can actually verify the wave-particle duality, because the experiment can't verify a single photon.
Electrons orbiting the nucleus of the cycle and the volatility of the particles there are closely linked, we can think of chemical bonds between atoms and atomic are fluctuating, at a certain moment because electronic is only a position on the orbit, and from the time a constantly changing position, the this kind of change has the regularity.When two atoms of electrons near each other, two atoms repel each other, and when electrons in an atom near the nucleus of another atom when they will attract each other, so that can form regularity of volatility.
Inner surface cracks in the double-slit experiment of atom has been in a regular wave conditions, when the particle is trying to through the gap, when near the atom will be fluctuations in the perforated of atomic bomb, a reflection of photonic and electronic electromagnetic ejection in such a state of regular fluctuations, as the accumulation of time and the number of regular interference fringes are formed.The smaller the momentum of a particle is, the larger the Angle of the ejection is, the greater the spacing of the stripes, the longer the wavelength is.
Electronic counter near the double slit to observe, emitting a large number of photon hits the aperture inner surface of atoms, and makes the surface atomic wave interference, can be seen as inhibits such a state of regular wave, the particles will no longer through double slit by regular reflection and ejection, which in turn has emerged two bright stripe.
This is why increasing gap width will not cause interference and diffraction, because of the emitted particles and gap edge contact and collision probability becomes a matter of fact interference and diffraction and crack width, crack of fluctuations, particle momentum, launch position and the Angle of aperture.
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No there isn't. All this is understood and taught in physics courses, so it would be useful to actually study quantum mechanics, instead of trying to guess.
These lectures: http://www.feynmanlectures.caltech.edu/III_toc.html might be a good place to start.
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I was wondering if graphene plasmonic waveguides could be synergic with some perhaps tunable non-reciprocal photonic devices?
For instance, coupled graphene SPPs with some non-reciprocal phase shift and interference / mode conversion scheme like Aharonov–Bohm effect?
Or could graphene or other 2D materials might possibly utilized in some somewhat tunable non-Hermitian photonics regarding perhaps PT-symmetric/ -broken schemes?
Thanks.
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up to my knowledge grephene should be combined to other materials to harvest photons and why not conduct them in integrated optics
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All the research papers I found so far, are just showing measurement of the squeezing parameter or quantum Fisher Information (QFI). Of course authors mention that, due to large QFI or strong squeezing this setup can be used for metrological purposes beyond standard quantum limit (SQL). I could not find any papers, which actually perform estimation of the unknown phase and show that the precision is beyond SQL. I am curious from the point of view of estimation in the presence of decoherence (which is always present). Theoretical papers indicate that entangled states are basically useless if frequency is estimated (e.q. Ramsey spectroscopy).
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I am not actually expert in this field and I am not sure whether the following paper is of your help, I just referred this if I could learn something from you and others.
Entanglement-free Heisenberg-limited phase estimation
BL Higgins, DW Berry, SD Bartlett, HM Wiseman, GJ Pryde, Nature 450 (7168), 393
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If one of the two photons of an entangled pair stimulates the generation of a third photon, by stimulated emission, does this destroy the entanglement of the original entangled pair? If it does destroy the entanglement, might there be anyway of using the third photon as a way of maintaining the entangled information. For example, if the stimulating and the simulated photon were both used together in the reception, perhaps the information would remain protected until detection was required.
many thanks, neil
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Dear Neil,
Great question. The short answer to your question is an unambiguous "YES".
The longer answer is genuinely interesting and essentially your question led to one of the most profound insights into the fundamentals of quantum physics, namely the No Cloning Theorem.
Back in 1982, the journal Foundations of Physics published a rather odd little article entitled "FLASH - A superluminal communicator based upon a new kind of quantum measurement" [N. Herbert, Found. Phys. 12, 1171 (1982)]. The paper proposed a scheme where there was a source of entangled photons in the control of Alice, who chooses to measure one half of the Bell pair in either the rectilinear or circular basis. The other photon is sent to Bob.
So far this is almost canonical E91 type quantum crypto (and as you can tell, older by 9 years). Where it differs is by the clear understanding that a single photon polarisation cannot be measured to arbitrary accuracy with no a priori information. (This is, of course, the source of the shared randomness in E91). So what Herbert proposed was to place a gain medium on the Bob side to amplify the single photon. Stimulated emission should give exact copies of the input photon, and so with an ensemble of identical photons, it is trivial to determine the polarisation of the incoming photon, and hence to determine the basis in which Alice's measurement encoded the photon. Because the Bell-type correlations are thought to be instantaneous (and the Gisin group has already put lower bounds on the speed of Bell correlations and they are orders of magnitude faster than c), then hey presto! Simple, superluminal communication!
Except it doesn't work, and it can't work. This is rather beautifully discussed in Asher Peres' paper "How the no-cloning theorem got its name" [Fortschritte der Physik 51, 458 (2003)]. As Peres points out (and indeed, he was one of the reviewers of the paper), the idea must be wrong because it violates special relativity: but the mechanism that protects relativity (and causality, and all of those things that we really want physics to have) is not obvious in the scheme.
The key to unlocking the secret of why the signally cannot work is in measurement. I think of the protocol this way: a photon comes into a gain medium, it must be measured to create two photons with the same properties. This measurement, although it is ultimately not destructive (and indeed is amplifying) still is a measurement of the photons' quantum numbers, including its polarisation. Hence the entanglement must be broken. This is at the heart of the no-cloning theorem, which states that an unknown quantum state cannot be cloned (ie copied).
So at it's simplest level, the entanglement is destroyed.
However, there are some caveats here. Firstly, there is remarkable work on quantum state amplification, where there are probabilistic amplifiers. Nothing that lets you get around superluminal propagation, but results that can be very useful for sensing (for example).
There is quantum erasure, where I think you might find your intuition of the third photon taking you. This is more commonly considered with the entanglement of a photon with a massive particle, and where appropriate measurement of the massive particle can be used to determine whether or not the entanglement is broken by the interaction with that massive particle.
And this is not unlike one of my favourite quantum protocols, again by Peres: Delayed Choice Entanglement Swapping [Peres, J. Mod. Opt. 47, 139 (2000)], and indeed I'm sure you could find a nice analogue of such work in a simpler three photon protocol. (perhaps already done - the field is large and memories finite ;) ).
Hope this helps
Andy Greentree
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Hi all,
I would like your opinions/solutions to a purportedly paradoxical scheme I propose below.
I wrote down only the bare-bones mathematical description of the scheme (attached file). It employs linear polarization and switching half-wave plates (HWPs).
Here is the summary to accompany the file:
An SPDC source, pumped by a CW/monochromatic laser, creates energy-degenerate product states |HH>. Now, because of the CW/monochromatic pump, the photon pairs are created at random times but the two photons in each pair are created simultaneously and they are strictly correlated in energy. So, if a photon on the left made it past its narrow-band filter (centered on the half-energy of the pump photons), its partner, on the right, will also make it past its (identical) filter.
There are two perfectly synchronized switching HWPs that implement "|H> to |V>" when in the ‘ON’ state and do nothing when in the ‘OFF’ state; one HWP in mode A and one HWP in mode B. The switching interval is significantly longer than the coherence time of the emitted (and still unfiltered) SPDC photons; however, after the HWPs, a subset of the SPDC photons does get filtered and, for this subset (which is the only subset to be detected), the coherence time of the photons is taken to be significantly longer than the switching interval—it is this hierarchy that enables us to superpose the two quantum states corresponding to the two macroscopic HWP states, respectively. Why? Since the coherence time of the filtered photons exceeds the switching interval of the HWPs, it is impossible, even in principle, to determine if the photons encountered the 'OFF' or 'ON' state, since the time-of-creation (and thus the time-of-flight) of these filtered photons is limited to their coherence time.
I consider two cases:
*Alice (left wing) and Bob (right wing) both have their HWPs synchronously switching, resulting in a maximally entangled state 1/sqrt2(|HH>+|VV>) and a mixed single-photon state ½(|H><H|+|V><V|) at either wing.
*Alice keeps her HWP always ‘OFF’ while Bob keeps his HWP switching, resulting in a joint state 1/sqrt2(|HH>+|HV>)=|H>1/sqrt2(|H+V>), which is a product state and Bob’s photon is in a pure state of linear polarization |+>=1/sqrt2(|H+V>) !!
Note: The initial two-photon state is in a polarization product-state, but there is initial entanglement in the time-energy domain; the time-energy entanglement is exploited to create polarization entanglement at Alice's and Bob's sites.
Demetrios
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I don't think that your synchronous switching will result in 1/√2(|HAHB>+|VAVB>), rather it will produce 1/2|HA+VA>|HB+VB>. The switch on Alice's side can act only on the A factor of the wave function, the switch on Bob's side only on the B side. So if you start with |HAHB>, Alice's switch turns that into 1/√2|HA+VA>|HB> and Bob's switch produces 1/2|HA+VA>|HB+VB>. You can have Bob's switch act first to have the intermediate state1/√2|HA>|HB+VB> and, after Alice's switch has acted, get again 1/2|HA+VA>|HB+VB>. Since the sequence of the switches does not matter, you'll also get the same final state if they act simultaneously.
Now the state 1/2|HA+VA>|HB+VB> is not distinguishable, by Bob, from 1/√2|HA>|HB+VB> .
Anyway, if you have the Kennedy paper, I would like to read it -- it is not open access and my institution does not provide access to this philosophical journal. My suspicion is that the purported "circular" argument will turn out not to be circular after all and that the no-signalling theorem will stand. Otherwise the result would have made it to the physics community.
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So-called "Light with a twist in its tail" was described by Allen in 1992, and a fair sized movement has developed with applications. For an overview see Padgett and Allen 2000 http://people.physics.illinois.edu/Selvin/PRS/498IBR/Twist.pdf . Recent investigation both theoretical and experimental by Giovaninni et. al. in a paper auspiciously titled "Photons that travel in free space slower than the speed of light" and also Bereza and Hermosa "Subluminal group velocity and dispersion of Laguerre Gauss beams in free space" respectably published in Nature https://www.nature.com/articles/srep26842 argue the group velocity is less than c. See first attached figure from the 2000 overview with caption "helical wavefronts have wavevectors which spiral around the beam axis and give rise to an orbital angular momentum". (Note that Bereza and Hermosa report that the greater the apparent helicity, the greater the excess dispersion of the beam, which seems a clue that something is amiss.)
General Relativity assumes light travels in straight lines in local space. Photons can have spin, but not orbital angular momentum. If the group velocity is really less than c, then the light could be made to appear stationary or move backward by appropriate reference frame choice. This seems a little over the top. Is it possible what is really going on is more like the second figure, which I drew, titled "apparent" OAM? If so, how did the interpretation of this effect get so out of hand? If not, how have the stunning implications been overlooked?
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Here is a sort of "proof" that there is no photon-level quantum property corresponding to "OAM" which I developed in a series of interesting discussions (debates really) with Judy Kupferman:
We assume OAM is "not spin" but something else. We know at the beam level it is an angular momentum about the center of the beam. The question is whether it arises as a sum of photon quantum properties, or as a sum of external angular momenta components.
If you measure photons they will have either well defined position or momentum. The angular momentum, however, is a conjugate of orientation (angular position). Here is a list of conjugate pairs https://en.wikipedia.org/wiki/Conjugate_variables .
So one can precisely measure position of a photon in the beam without affecting angular momentum, since it is not paired with angular momentum.
Then the angular momentum, at each position, can be measured without scrambling the position measurements. How to do this experimentally I don’t really care, just that it is theoretically possible.
At that point, the linear momentum and angular orientation of the photon will be uncertain. They are obviously related to each other, and neither are of concern.
Notice I have not said what kind of angular momentum, other than “of the photon.” Doesn’t matter. Just measure its total angular momentum.
There are several ways to achieve non-zero angular momentum when summing the individual photon measurements:
  1. We will rule out having the measurements unevenly distributed about the beam center, because that is just external angular momentum, well understood and not OAM.
  2. I think we can rule out different magnitudes as a function of position, as that is just external angular momentum as well. So the magnitudes are either uniform or randomly or otherwise evenly and symmetrically distributed.
  3. That leaves only the vector direction of measurements. These are quantized, and we can take the beam direction as reference. They are either along the beam (+ or -) or transverse to it. The transverse angular momenta don’t matter for our purposes, so throw them out. The + and – amount to magnitude differences, and as noted in 2 will have no relevance unless distributed unevenly which amounts to external angular momentum.
Well, those three cases are all that there are, and there is no room in them for a net non-zero sum over the beam, except for external angular momentum. Therefore, a hypothetical property “orbital angular momentum” which is different than ordinary quantum angular momentum, aka spin, is some form of external angular momentum.
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We have a linear chain of 3 trapped ions system (the interaction are taken XX interaction). We want to apply the external local magnetic field to each of this individual ions. Is it possible experimentally?
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Dear Muhammad Usman Khan sir,
I have specified question. Can you please give some light on this. I find the paper from which you have taken the abstract. Thanks for this suggestion. I am reading this article.
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In the large cavity-laser detuning, the cavity modes can be eliminated adiabatically with the required condition that its decay rate should dominates the other interaction rates present in the system. However, the steady state can be obtained in the large detuning regimes by substituting the time derivative of cavity mode equals to zero( t approaches infinity). Can I correlates these two?
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I would more usually adiabatically eliminate a mode with a different time rate so that I could solve the dynamics of the remaining modes. Adiabatic elimination isn't only for steady states.
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Dear experts,
I think that CaSiO3 has direct and indirect band gap. I am trying to know the direct and indirect band gaps of wollastonite( location of BZ point). A band gab  of 5.022 eV at gamma (G) point  according to LDA (castep code) ( is that direct or indirect band ). There is another interesting minimum conduction band at B point ( is it related to indirect band gap) with valence band minimum at C point . I really need to interpret the results shown in the figure below accurately. any help will be appreciated.   
best regards
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Materials Studio software.
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Hi to all,
Consider the following scenario (shown in the attached file):
Two mutually coherent and collimated light beams intersect as shown, creating the depicted 'bright' and 'dark' stationary interference fringes (fig. 'A'). Suppose we insert a very thin (compared to the fringe width) and, ideally, perfectly conducting 'sheet' across, say, the central 'dark fringe'(fig. 'B').
It certainly appears as though we can "cut each of the light beams in two, across an impassable barrier", yet they will persist and continue to freely propagate! This appears to be the case both for 'classical' EM waves as well as quantum-optical wavefunctions. Of course, no infinitely thin and perfectly conducting sheet exists, but it does seem that this effect will remain sufficiently intact under realistic conditions. 
Is this possible??
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@Kassner
"A perfect conductor or perfect electric conductor (PEC) is an idealized material exhibiting infinite electrical conductivity or, equivalently, zero resistivity (cf. perfect dielectric). "
it is perfectly defined and it reflects back anything. A non ideal or non perfect conductor is influenced by its thickness . 
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In quantum physics,  the no-communication theorem states that it is not possible to transmit information from one observer to another observer, whether entangled or not, by making a measurement of a subsystem of a total state, common to both observers.
Most people think that the theorem is important because it limits quantum entanglement, that separated events cannot be correlated in any way to lead to the possibility of communication. 
However, the double-slit experiment [1] says that what one observer does (e.g. turn on a detector) influences what is detected at the other observer (e.g. the electron did not pass here).
What is your reference or position on this question, could the double-slit experiment be used to negate the no-communication theorem?
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Hello all,
Thank you for your participation. As you know, Jacques can ask his own question in RG. This question is not that, it's whether an observer's own decision about the use of a detector may lead to communication to another (spatially separated, independent) observer, an observer that is just not "downstream" from the former one  -- but it is peer. It's not the place to use words that are unacceptable by a scientific study, but to build, to mine the gold of truth using fair, polite, cogent public discussions.
Jacques, if you do not agree with this, you can continue to observe, or even join in, albeit in fair terms. Otherwise, life itself may become harder, even to all of us, life is a school.
Cheers, Ed Gerck 
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Usually, the double slit experiment is viewed as two cases, with the quantum case as a proposed mixture of two classical cases: "The modern double-slit experiment is a demonstration that light and matter can display characteristics of both classically defined waves and particles." However, in a deeper view, there is only one case, the quantum case. The other cases, namely classically defined waves and particles, are NOT real, in the strict sense they do not actually exist!
The question is whether it would better for students to view the double slit experiment not as a Young's experiment but in all its aspects as three cases, particle, wave and quantum, where the quantum case is not somehow a mixture of particle and wave. 
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Dear Vladimir and all,
You wrote, above, that "I am convinced that quantum mechanics is no longer able to correctly describe the dynamics of molecular quantum transitions, since the transient state there is a chaotic motion of electrons and nuclei with a continuous spectrum of energies, and consequently, it is classical."
Discrete levels of energy are not always needed or used in quantum physics. For example, of many, there are kinetic energy of atoms, and plasma temperature, that are continuous. See the reference below where a multiphoton (continuous levels of energy being accessible from a single photon that is NOT absorbable per se) band generate  laser action to a lower level.
where a sequential three-photon pumping process is proposed for the three cases. There are other examples in my own published research, where I have measured broad ground state energy bands (in infrared excimers of XeI), calculated broad bands in H atoms near ionization (Rydberg states), and calculated a shift of quantum-well levels when dressed by a lower frequency photon, all of which show a continuous spectrum of energies, and, yet, are not classical.
Cheers,  Ed Gerck 
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I need a feedback on review o myu paper on EMF effects in nonthermal doses on living creatures which is based on storage capacity of DNA. Can reincarnation be explained by physical mechanisms and can DNa MEMORIZE THE KNOWLEDGE OF OUR ANCESTORS ?
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No.  There's no evidence for what you're discussing.  More than 350,000 people are born every day, and if such things as you're discussing existed, there'd surely be evidence that some of those newborn infants had some kind of conscious knowledge without needing to learn it -- e.g., a child born in China who could speak Japanese, without being exposed to it.  You seem to be positing a kind of Lamarckian inheritance of acquired characteristics, or in this case, acquired knowledge.  Do you really think that the more you study physics, the better your children and grandchildren will be at physics, simply because they inherit your DNA?  There's no evidence for that.  Certainly, we inherit a range of reflexes, instinct, capacities, and even emotions.  This can be explained based on natural selection, and to some extent, accounted for by molecular genetics.  We humans inherit the ability to learn language -- however we don't inherit conscious knowledge of any particular existing (or ancient) languages.  In a way, certain kinds of knowledge may be passed down from previous generations -- for example, fear of heights or reactions to certain kinds of predators -- this can be explained through natural selection.  But there's no evidence of inheritance of the kinds of things you're talking about (e.g., knowledge of science).  To say that "the total number of souls is constant," and try to justify that statement with reference to conservation laws in physics, makes no sense.  Those laws say that (for example) energy is conserved BUT can be transformed.  So whatever energy may be associated with conscious activity could be transformed (for example) into thermal energy.  You seem to be starting with a conclusion that you want to justify (reincarnation) and then to be searching around for anything that might support such a conclusion.  That's not how science is supposed to work.  If anything, you should be looking to see if there is any evidence to falsify your conclusion, and the theories associated with your conclusion.  You are free to have whatever faith you want about life after death.  But pretending that science supports that faith is a completely different matter, and really not acceptable.  
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Is the following function F:[0,1] to [0,1]
F strictly monotonic increasing F(1)=1,(i presume this unnecessary as its specified by the first two
(1)ie x+y=1 if and only iof F(x)+F(y)=1 F(x)+F(1-x)=1; F-1(x)+F-1(1-x)=1
(2)F homomorphic(2) x+y+z=1 if and only F(x)+F(y)+F(m)= 1
(3) x+y+z+m=1; if and only ifF(x)+F(y)+F(z)+F(M)=1
Give F(x)=x and F continuous (it appears to entail cauchys equation with F(1)=1 over ethe unit triangle due tot he common term). F(x+y)+F(z)=1, F(x)+F(y)+F(z)=1, etc, F(x+y)=1-F(z)=F(x)+F(y)
.
I
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t appears that the third equation is redundant and I presuming any further equation where they sum to one (any given four, any given five, which sum to one is derivable from the first two) at least given that the first two entail some form of cauchy additivity. Is that correct
e
the above equation for any (4)given four points in the domain which sum to one
Does this generalize to Cauchy equation over the unit triangle. Ithough that one had to show that it held for any arbitary number of components not just 2 and three (although it appeas that the equations just generalize
F:[0,1] to [0,1]
F(1)=1 F(0)=1
F strictly monotonic increasing
(1)ie F(x)+F(1-x)=1; F-1(x)+F-1(1-x)=1
(2)F homomorphic(2) x+y+z if and only F(x)+F(y)+F(m)= 1
(3)x+y+z=2 if and only if F(x)+F(y)+F(z)=2, and th
(4) x+y+m+z=1 if and only F(x)+F(y)+F(z)+F(M)=1
Are the latter two redundant, ie do the first two generalize to any arbitrary factor; as the first two appears to entail cauchy equations of the unit trial
F(x+y+M)+F(Z)=1 F(Z)+F(x+y)+F((M)=1
so F(X+y+M)=F(x+y)+F(M)
but also x+y+z+m=1 entails
((x+y)+(1-x+y)) entails
F(x)+F(Y)+F(1-x+y) by (1) and (2)
F(x+y)+F(1-x-y)=1, so  by cancelling out common terms F(X)+F(Y)=F(x+Y)
and so
F(x+y+M)=F(x+y)+F(M)=F(X)+F(y)+F(M)
z+ (x+y+M)=1 entials F(z)+F(x+y+M)=1 so F(x+y+m)=1-F(z)
so 1-F(Z)=F(X+Y)+M)=F(X)+F(Y)+F(M), and so F(X)+F(Y)+F(Z)+F(M)=1 x+y+z+m=1, appears in addition to a form of cauchy equation s
These appear to entail those first two fixed pints
These appear to entail F(x+y)=F(x)+F(y), over x,y,(x +y)\in in [0,1],;
I thought one required that any for any n=2.........infinity which sum to one. But I presume this is entailed by these first both collectively working, as any given four example which sum to one can always be express as (x+y) +z+m = 1F(x+y)+F(m)+F(z)=1;
F(x+y+M)+F(Z)=1 so F(x+y+M)=F(x+y)+F(M) so -F(x+y)=-F(X+y+
F(M)+F(Z)=1-F(x+y)
F(x+y+m,)+F(Z)=1,
F(x+y+M)=F(x+y)+F(M)
yet 1-F(1-(X+y+M)=F(Z) as  so 1-F(1-x+
x+y+M+z=1 z=1-(x+y+M), then F((x+y+M))+F(z)=1, F(z)=1-F(x+y+z) so as z=1-x-m-y F(z)=F(1-(x+y-+M)=1-F(x+y+M)=F(z)
so 1-F(x+y+M)=1-F(x+y)-F(M), F(1-x+y+=F(M_M= ;1-F(x+y)=F(M)+F(Z)
(2) appears to just say this ie F(1-x-y)=1-F(x)-F(y)
which given 2 entails F(0)=0, F(1)=1; ie (1) specifies F(0.5)=0.5, and F(0)+F(1)=1 and F(0.5)+F(0.5)=1
(2) entails that 0 +0.5+0.5=1 so that F(0.5)+F(0.5)+F(0)=1,
so that 2 times 0.5+F(0)=1; 1+F(0)=1,which gives, F(0)=0
which by subsitution into into one gives F(1)=
and that (2)  F(1/3)=1/3 however when one has both
Moreover if(A) (x+y) +z =1 then (B)x+y+z =1 so clearly by (1) on A, (2) on (B)
F(x+y)+F(z)=1 and F(x)+F(y)+F(z)=1,
F(x+y)+F(z)=F(x)+F(y)+F(z) but F(z) is common
so \forall (x)(y)\in [0,1] so long as x+y is in [0,1]F(x+y)=F(x)+F(y)
where F(1)=1 and F non negative and strictly monotone increasing. Is this a pair wise result. It appears to generalize to F(x)=x for all rationals as far i can see
ie F(10)=2F(20), as 10+10+80=1 so F(10)+F(10)+F(80)=1, so 2F(10)+F(80)=1 and by the first equation 20 +80=1 so F(20)+F(80)=1 so that
F(20)=2F(10)
and F(30)=F(10)+F(20) use 10+20+70=1=F(10)+F(20)+F(70)=1 and F(30)+F(70)=1 and one can 10 F(10)=1=0.1 and one can seeiming building this standard sequence, It appears to entail F(x)=x for all rations even x>0..5 and F(x+y) generalizes to arbitarily many components if x+y in [0,1[
Or is just a cauchy function on the restricted interval with with strictly monononitc and positive, on [0,1] to [0,1] then F(x)=x
forall(x,y)
They appear t
and otherwise x+y+z>1 then F(x)+F(y)+F(z)>1 and x+y+z<1 if and only if F(x)+F(z)+F(m)>1
x+y =1 iff F(x)+F(y)=1
where otherwise x+y>1 iff F(x+y)>1, and x+y<1 if and only F(x)+F(y)<1
x+y+z=1 if and only if F(x)+F(y)+F(z)=1
x+y+z>1 if and only F(x)+F(y)+F(z)>1; x+y+z+m<1 iff and only F(x)+F(y)+F(z)+F(M)<1
x+y+z+m iff F(x)+F(y)+F(z)+F(m)=1
otherwise x+y+m +z>1 if and only if F(x)+F(y)+F(M)>1
x+y+z=2 if and only F(x)+F(y)+F(z)=2
where x+y+z>2 if and only if F(x)+F(y)+F(z)>2
x+y+z<2 F(x)+F(z)+F(m)<2
where other x+y+z>z
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In the Feymann QED strange theory of light he describes the partial reflection. There he mention that Newton made an experiment which poined for intereference of 34 000 wavelenghts thick transperant glass. Even more Feymann insists that if you use a laser 100 million wavelenghts interference is possible (50 meters thick glass). 
1. I tried to find something on Internet about this experiment of Newton but I failed (Newtons experiments were very often not re-created by others). Can some point out where is this considered. Also about this experiments with laser - does somebody made them?
2. As far as I know the QM probabilistic wave is moving at speed of light for photons (by the way the question for a wave with photons is not clear in QM). So how is it possible that the photon would 'know' what happens 50 meters away (as it is reflected from the first surface). This looks suspiciously like breaking the Special Relativity postulate.
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I could imagine there is a conflict between the concept of "photon" (as an eigenmode of the electromagnetic field with Eph=\hbar\omega) and the notion of the photon being somewhere (such as "at surface 1" or "at surface 2") at some specific point in time. A "localized photon" cannot be monochromatic and imho there is a clash of classical pictures immediately. I would tend to think that this might just be another way of making F. Leyvraz' statement on long time scales involved with interference.
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  Dear all researchers, nowadays i devote myself to solving the optical constant of nanoparticles and recently investigate the K-K model. However, there is one confusing thing that is the calculation of the intrinsic frequency. My idea is that for any particle, since i know E=m*c^2 and E=h*v, is the v calculated here equal to the intrinsic frequency?
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Thank you for your helpful hand! Your replies really mean a lot to me.  Recently i am learning about the K-K relation to calculate the optical constant of particles and i wonder if anybody could provide a guide-book for learning? Thank you! ^_^
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During the treatment of the gauge transformations for showing the A(r,t) in the context of Goeppert-Mayer gauge; it is expressed as the difference between the two transverse gauges vector potentials for the light-atom interaction picture, and when we go to derive the Hamiltonian for longer wavelength of the radiation field compared to the average size of the atom, we invoke the long-wavelength approximation which kills the GM gauge vector potential, i.e. the two potentials are equal. Why is that? and how can i derive explicitly this equality for long wavelengths?
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Maxwell defined the vector potential as electromagnetic momentum per unit charge. Momentum, inexorably and unequivocally, relates to inertia, which is an electromagnetic phenomenon (so, dependent of the vector potential). Therefore, the vector potential has a close connection with momentum, which from the de Broglie relation, p=h/λ, vanishes in the long-wavelength limit.
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Both entanglement state and mixed state can generate correlation. What is the difference between them ?
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I'm a little confused by some of the answers above, so I will try and help out.
In the question, you specifically mention "generate correlation".  I guess that this is probably a typo, but if not, I would not think of the states as generating correlation.  The correlations are created as the states are created.  This is a subtle, but important distinction in my opinion.
Now to return to what I think you are intended to ask.  
Classical correlations are all around us, and perhaps no better illustrated than the example of Bertlemann's socks, introduced by Bell.  Bertlemann always wears odd socks, so if you see that one of his socks is pink, you don't need to introduce any kind of sophisticated physics to know that the other sock he wears is not pink.  This is an example of a classical correlation - where there is a classical correlation between two, in principle knowable outcomes.
A quantum correlation is where the states of two particles are independently unknown, for example unknown polarisation states of photons, but there is a correlation between the two states - for example it is known that the total angular momentum is equal to some value.  These are the correlations that are observed in EPR type experiments.
Note I have been careful here to talk about classical and quantum correlations, and not entangled or mixed states.
Entangled states are typically those that exhibit quantum correlations, and we would probably want to think of these as 'pure states'.  By this we mean that the state is represented by a unit vector on the appropriate Bloch hypersphere, or to be more colloquial, that there system is isolated from the environment and 'as quantum as possible'.
Mixed states, as has been said above, generalise this result.  They are often defined in terms of ensembles of pure states, however I like to think of them, and explain them, in the limit of maximum mixedness.  In this limit, mixed states describe classical probabilities.  Perhaps the clearest example is to consider a coin that is tossed and the result hidden.  The coin is either heads or tails with equal probabilities.  We describe this state by a mixed state of 50% heads and 50% tails.  There are no quantum correlations whatsoever.  Contrast this with a spin-half system (e.g. electron spin) that is aligned along the X axis, about to be measured by a Stern-Gerlach filter in the z axis.  This will still result in 50% probability of being measured spin up, 50% spin down, but because it is in a pure state, the phase between these probability amplitudes is non-trivial and one can perform other non-trivial rotations.
Now we must also be precise.  There are entangled states that are not pure states, so entanglement can be preserved in the limit of finite mixedness.  There are also non-entangled states that show non-classical correlations (quantum discord).  However I hope that this brief discussion gives you a useful place to start.
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 Can you give me the English translation of it?
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In Quantum Computing, there is something known as the Holevo bound - which basically says that a q-bit cannot deliver more than a bit of information into our spacetime, although it can carry more.
The question is - where is the extra information kept?
The usual answer is that the extra info lies embedded in a superimposition of entangled states, and that any accessing of the information destroys the superimposition and with it, the extra information itself.
So far, so good.
But a number of experiments make it appear as far too simple an explanation. For starters, the extra information can be shown to be carried by a single photon, and only a later actualization decision determines which part of the information becomes actualized within our spacetime (so that the above explanation would necessitate a photon superimposed with itself, which then leads to a superimposition of spacetime). In other words, a form of time travel must be allowed (the photon being then 'told' by its future state which part of the information it should carry and which part it should not even take on board.)
But in other experiments (Michael Goggin et al.), the time travel possibility is not enough to explain what is going on, and the inescapable conclusion is that the photon not only carries more info than is accessible, but  more information that could be stored in simple particle superimposition states.
Where is that information?
Is it carried in a parallel universe, as David Deutsch says, and therefore inaccessible to us in this space time?
Or, as Hamlet famously put it,  is there more to it than we conceptualize, and the parallel universe idea is nothing but a reflection of our tendency to think in familiar boxes, and space time itself an illusion, woven by quantum correlations which are more fundamental than spacetime itself? (Spacetime being then, in effect, a byproduct of quantum correlations, which pops up when choices are made and the other latent possibilities become thus barred from becoming realized)? If the latter view is the case, then how many Spacetimes are precipitated that way, and does this explanation then, in effect, rejoin David Deutsch's?
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The development of a quantum computer is a promising challenge for work in specific areas of science. Unfortunately, there is insufficient knowledge of the quantum laws to implement this idea. But most importantly, in a variety of scientific research does not disrupt the development of ideas.
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can one say about atomic injection rates and atomic exit rates in an open atomic system?
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The atomic injection rates and atomic exit rates is dependent to increase and decrease of populations on the relevant  levels of the system. This can be realized, for example, by  incoherent pump fields connecting inside and outside levels of the system. 
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The realism hypothesis in QM says that results of measurements on quantum systems, are completely determined by subquantal parameters (hidden or detectable, local or non-local). These parameters are supposed to get definite values before the measurement.
Is there an experiment that rules out the realism hypothesis? Please pay attention: realism does not necessarrily mean locality. Local realism was already disproved. My question is general, it refers to real factors, eventually non-local.
NOTE: at my question "Is the locality assumption necssary in Bell's inequality?", a polemic began about the particular issue whether Bohm's mechanics is correct or not. I invite all those who want to participate to that polemic, to post their comments here, not at that question.
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This looks to be the recreation time in this thread :=)
“The most incomprehensible thing about the world is that it is at all comprehensible.” (A. Einstein)
Nature is structured. As making part of nature, our brain is structured.
Making philosophy / logic is inventing coherent descriptions of structures.
Making mathematics is making philosophy / logic in the frame of a specific language called mathematics.
Making science is discovering structures in nature.
Sometimes, invented coherent descriptions of structures match natural structures. They are then called models and/or theories (in function of their extent), involve laws and hold as long as they are not contradicted by experiment and / or observation.
An example is natural selection.
When the models and / or theories use the specific language of mathematics to describe the discovered structures in nature, they are called physical.
Examples are Newton’s mechanics, Einstein’s General Relativity Theory, Standard Quantum Mechanics and Bohmian Mechanics.
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When a spin possessing particle is in magnetic field B the spin 'rotates' around B. By example electron with spin on X will rotate perpendicular to B. But is this real? Can it be observed? Does this precession change the current in the coil creating B?
Secondly I tried to find out something about the classical situation. E.g. a compass must classically rotate then around B even when its blades are perpendicular to B.  But than I could not find anything. Also it will look like perpetum mobile. 
Thirdly I didn't see or can read about small magnets precessing around B? The spins must look like small magnets but there is nothing to confirm this?? And less about their effect on the B? Do really small magnet move precessingly around B and does this show up on the current of the coil?
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