P. J. Salas

Universidad Politécnica de Madrid | UPM · Departamento de Fotónica y Bioingenría

We report on the Madrid Quantum Network, designed to demonstrate that a telecommunications network can also host quantum communications in a unified, logical and physical infrastructure. Using new Quantum Key Distribution systems paired with modern networking paradigms, we demonstrate a high technology readiness level of QKD installing the network...

The security of a passive plug-and-play QKD arrangement in the case of finite (resources) key lengths is analysed. It is assumed that the eavesdropper has full access to the channel so an unknown and untrusted source is assumed. To take into account the security of the BB84 protocol under collective attacks within the framework of quantum adversari...

At present, several models for quantum computation have been proposed. Adiabatic quantum computation scheme particularly offers this possibility and is based on a slow enough time evolution of the system, where no transitions take place. In this work, a new strategy for quantum computation is provided from the opposite point of view. The objective...

The states needed in quantum computation are extremely affected by decoherence. Several methods have been proposed to control error spreading. They use two main tools: fault-tolerant constructions and concatenated quantum error correcting codes. In this work, we estimate the threshold conditions necessary to make a long enough quantum computation....

The decoherence effect on Grover algorithm has been studied numerically through a noise modelled by a depolarizing channel. Two types of error are introduced characterizing the qubit time evolution and gate application, so the noise is directly related to the quantum network construction. The numerical simulation concludes an exponential dampin...

CSS codes are a subfamily of stabilizer codes especially appropriate for fault-tolerant quantum computations. A very simple method is proposed to encode a general qudit when a Calderbank-Shor-Steane quantum code, defined over a q-ary alphabet, is used.

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The goal of this paper is to review the theoretical basis for achieving a faithful quantum information transmission and processing in the presence of noise. Initially encoding and decoding, implementing gates and quantum error correction will be considered error free. Finally we will relax this non realistic assumption, introducing the quantum faul...

The error correcting capabilities of the Calderbank-Shor-Steane [[7,1,3]] quantum code, together with a fault-tolerant syndrome extraction by means of several ancilla states, have been numerically studied. A simple probability expression to characterize the code ability for correcting an encoded qubit has been considered. This probability, as a cor...

The states needed in a quantum computation are extremely affected by decoherence. Several methods have been proposed to control error spreading. They use two main tools: fault-tolerant constructions and concatenated quantum error correcting codes. In this work, we estimate the threshold conditions necessary to make a long enough quantum computation...

In this work we discuss the ability of different types of ancillas to control the decoherence of a qubit interacting with an environment. The error is introduced into the numerical simulation via a depolarizing isotropic channel. The ranges of values considered are 10−4⩽ε⩽10−2 for memory errors and 3×10−5⩽γ∕7⩽10−2 for gate errors. After the correct...

A simple way for continuously controlling the population inversion in a possible ultraviolet laser is considered as a subprocess of an alkaline (Li and Na) proton collision. This behaviour is understood in terms of the main couplings related to the electronic capture mechanisms.

Decoherence is the main problem to be solved before quantum computers can be built. To control decoherence, it is possible to use error correction methods, but these methods are themselves noisy quantum computation processes. In this work, we study the ability of Steane’s and Shor’s fault-tolerant recovering methods, as well as a modification of St...

Using a numerical simulation of the evolution of a qubit interacting with the environment we show that quantum error detection and correction can work effectively even when the recovery procedure introduces errors.

Electronic excitation and capture processes are studied in collisions involving systems with only one active electron such as the alkaline (Li)-proton in the medium-energy region (0.1-15 keV). Using the semiclassical impact parameter method, the probabilities and the orientation parameter are calculated for transitions between initial and/or final...

Li(n = 2) to H*(n = 2,3) and Li*(2p, n = 3) charge transfer and excitation processes are studied in the medium-energy range 0.1-10 keV. The static model includes a basis of 26 molecular states. The lithium atom is described using a model potential and the semiclassical impact parameter method with straight trajectories is used for the dynamical sim...

Electronic excitation and capture processes are studied in collisions involving systems with only one active electron such as the alkaline (Li)-proton in the medium-energy region (0.1-15 keV). Using the semiclassical impact parameter method, the probabilities and the orientation parameter are calculated for transitions between initial and/or final...

The authors investigate sodium-proton charge transfer using 14-state adiabatic, molecular-basis classical trajectory calculations in which a common translation factor and dynamical radial and rotational coupling terms are included. The differential cross sections are evaluated by the eikonal procedure from S-matrix elements obtained over 283 impact...

Proton-sodium charge transfer is studied, using 9- and 19-state adiabatic molecular bases and the impact parameter method, in the energy range 0.5-5 keV. The dynamical radial and rotational coupling terms and a common translation factor (CTF) are included. The effect of the choice of the coordinate centre on the total charge exchange cross sections...

Capture and excitation processes are studied in collisions involving one active electron systems, like alkaline-proton, in the medium energy range (0.1-15 keV). The Semiclassical Impact Parameter Method is used to calculate total cross sections and probabilities involving initial and/or final aligned and oriented states in order to get an intuitive...

Li(2s,2p)-H+ charge transfer is studied using an eight adiabatic molecular basis and the impact parameter method with a common translation factor in the range 0.5–10 keV. The Lyα enhancement for capture to H(2p) from excited Li(2p) and orientation preference from Li (2p−1) is obtained.

Initial orbital alignment and orientation effects, have been studied in slow (0.2–10 keV) quasi-resonant charge-transfer collisions of laser-excited Li*(2p) atoms with H+ ions. The standard semi-classical impact parameter method with a common translation factor has been employed using an adiabatic molecular basis. Pronounced alignment effects for t...

The Projected Valence Bond potential energies of NaHe system calculated by Courbin-Gaussorgues and Sidis are used in an 8-state model to study the direct excitation, deexcitation probabilities and the orientation of the charge cloud of Na★ (3p). The corresponding calculation are carried out using the impact parameter method in the 0.5 Kev < ECM <...

The direct excitation and deexcitation probabilities of Na(3p) are calculated in an 8-state model using the Projected Valence Bond potential energies of NaHe, the impact parameter method is used in the 0.5 keV<E CM<100 keV energy range. A 3-state model predicts propensity rules which are confirmed by the present more elaborate model in the energy r...

The authors show that, contrary to what is usually supposed, for one-electron heteronuclear diatomic molecules there exists no reference frame with respect to which the radial electronic flux of the molecular wavefunctions vanishes as the internuclear distance tends to zero. The relevance of this fact to the properties of electron translation facto...