We have observed an effect known as a quantum eraser, using a setup similar to one previously employed to demonstrate a violation of Bell's inequalities. In this effect, an interfering system is first rendered incoherent by making the alternate Feynman paths which contribute to the overall process distinguishable; with our apparatus this is achieved by placing a half wave plate in one arm of a Hong-Ou-Mandel interferometer so as to rotate the polarization of the light in that arm by 90°. This adds information to the system, in that polarization is a new parameter which serves to label the path of a given photon, even after a recombining beam splitter. The quantum ``eraser'' removes this information from the state vector, after the output port of the interferometer, but in time to cause interference effects to reappear upon coincidence detection. For this purpose, we use two polarizers in front of our detectors. We present experimental results showing how the degree of erasure (which determines the visibility of the interference) depends on the relative orientation of the polarizers, along with theoretical curves. In addition, we show how this procedure may do more than merely erase, in that the act of ``pasting together'' two previously distinguishable paths can introduce a new relative phase between them.
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"There have been many quantum optics experiments involving two photon entangled states and quantum eraser arrangements to prove the complementarity arguments above. Three of the better ones are   . One experiment in particular by Zeilinger's group  is worthy of a special note. "
[Show abstract][Hide abstract] ABSTRACT: This paper explains the delayed choice quantum eraser of Kim et al. in terms
of the transactional interpretation of quantum mechanics by John Cramer. It is
kept deliberately mathematically simple to help explain the transactional
technique. The emphasis is on a clear understanding of how the instantaneous
"collapse" of the wave function due to a measurement at a specific time and
place may be reinterpreted as a gradual collapse over the entire path of the
photon and over the entire transit time from slit to detector. This is made
possible by the use of a retarded offer wave, which is thought to travel from
the slits (or rather the small region within the parametric crystal where
down-conversion takes place) to the detector and an advanced counter wave
traveling backward in time from the detector to the slits. The point here is to
make clear how simple the Cramer transactional picture is and how much more
intuitive the collapse of the wave function becomes if viewed in this way. Also
any confusion about possible retro-causal signaling is put to rest. A delayed
choice quantum eraser does not require any sort of backward in time
communication. This paper makes the point that it is preferable to use the
Transactional Interpretation (TI) over the usual Copenhagen Interpretation (CI)
for a more intuitive understanding of the quantum eraser delayed choice
experiment. Both methods give exactly the same end results and can be used
Foundations of Physics 01/2015; DOI:10.1007/s10701-015-9956-8 · 1.03 Impact Factor
"Again, both the causal interpretation  and its extension to Boson fields  can explain the Wheeler delayed-choice experiment in a causal, non-paradoxical way. A further push of conceptual boundaries occurred with the introduction of quantum erasure experiments       . Perhaps the best example is the quantum eraser experiment of Kim et al . "
[Show abstract][Hide abstract] ABSTRACT: I argue that quantum optical experiments that purport to refute Bohr's
principle of complementarity (BPC) fail in their aim. Some of these experiments
try to refute complementarity by refuting the so called particle-wave duality
relations, which evolved from the Wootters-Zureck reformulation of BPC (WZPC).
I therefore consider it important for my forgoing arguments to first recall the
essential tenets of BPC, and to clearly separate BPC from WZPC, which I will
argue is a direct contradiction of BPC. This leads to a need to consider the
meaning of particle-wave duality relations and to question their fundamental
status. I further argue (albeit, in opposition to BPC) that particle and wave
complementary concepts are on a different footing than other pairs of
Foundations of Physics 08/2014; DOI:10.1007/s10701-015-9959-5 · 1.03 Impact Factor
"After the two slits, a photon is in a state that entangles the spatial slit states and the polarization states which might be represented as: |s1 ⊗ |h + |s2 ⊗ |v (for a discussion of this type of entanglement, see ). But as this superposition evolves, it cannot be separated into a superposition of the slit-states as before, so the interference disappears. "
[Show abstract][Hide abstract] ABSTRACT: There is a very common fallacy, here called the separation fallacy, that is
involved in the interpretation of quantum experiments involving a certain type
of separation such as the: double-slit experiments, which-way interferometer
experiments, polarization analyzer experiments, Stern-Gerlach experiments, and
quantum eraser experiments. It is the separation fallacy that leads not only to
flawed textbook accounts of these experiments but to flawed inferences about
retrocausality in the context of "delayed choice" versions of separation