Shannon entropy for lower position and momentum eigenstates of Pöschl—Teller-like potential is evaluated. Based on the entropy densities demonstrated graphically, we note that the wave through of the position information entropy density ρ(x) moves right when the potential parameter V1 increases and its amplitude decreases. However, its wave through moves left with the increase in the potential parameter |V2|. Concerning the momentum information entropy density ρ(p), we observe that its amplitude increases with increasing potential parameter V1, but its amplitude decreases with increasing |V2|. The Bialynicki—Birula—Mycielski (BBM) inequality has also been tested for a number of states. Moreover, there exist eigenstates that exhibit squeezing in the momentum information entropy. Finally, we note that position information entropy increases with V1, but decreases with |V2|. However, the variation of momentum information entropy is contrary to that of the position information entropy.

We find that the analytical solutions to quantum system with a quartic potential [Formula: see text] (arbitrary [Formula: see text] and [Formula: see text] are real numbers) are given by the triconfluent Heun functions [Formula: see text]. The properties of the wave functions, which are strongly relevant for the potential parameters [Formula: see text] and [Formula: see text], are illustrated. It is shown that the wave functions are shrunk to the origin for a given [Formula: see text] when the potential parameter [Formula: see text] increases, while the wave peak of wave functions is concaved to the origin when the negative potential parameter [Formula: see text] increases or parameter [Formula: see text] decreases for a given negative potential parameter [Formula: see text]. The minimum value of the double well case ([Formula: see text]) is given by [Formula: see text] at [Formula: see text].

Present days efforts for building up an operative quantum computer made of silicon soon they will take shape. One of the main challenges to this task is to implement qubit coherence in a practical way. We make emphasis in some physical characteristics (such as the structure) of the basic components (qubits) of a silicon one'e-way quantum computer which can be exploited in order to implement qubit coherence. Altogether with this, we introduce form factors (accounting for the qubit structure), and calculate times of coherence. It is found that the nuclei states last longer than their electronic counterpart. However, this stability of nuclei qubits limits the speed at which the computer can carry out instructions and process the information.

In the framework of collective measurements, efforts have been made to reconstruct onequbit states. Such schemes find an obstacle in the no-cloning theorem, which prevents full reconstruction of a quantum state. Quantum Mechanics thus restricts us to obtaining estimates of the reconstruction of a pure qubit. We discuss the optimal estimate on the basis of the Uhlmann-Josza fidelity, respecting the limitations imposed by the no-cloning theorem. We derive a realistic optimal expression for the average fidelity. Our formalism also introduces an optimization parameter L. Values close to zero imply full reconstruction of the qubit (i. e., the classical limit), while larger L's represent good quantum optimization of the qubit estimate. The parameter L is interpreted as the degree of quantumness of the average fidelity associated with the reconstruction.

Speeding up of the processing of quantum algorithms has been focused on from the point of view of an ensemble quantum computer (EQC) working in a parallel mode. As a consequence of such efforts, additional speed up has been achieved for processing both Shor's and Grover's algorithms. On the other hand, in the literature there is scarce concern about the quantity of entanglement contained in EQC approaches, for this reason in the present work we study such a quantity. As a first result, an upper bound on the quantity of entanglement contained in EQC is imposed. As a main result we prove that equally weighted states are not appropriate for EQC working in parallel mode. In order that our results are not exclusively purely theoretical, we exemplify the situation by discussing the entanglement on an ensemble of n 1 = 3 diamond quantum computers.Résumé : L'accélération de traitement des algorithmes quantiques s'est concentrée sur l'idée d'ordinateur quantique sur les ensembles (EQC) travaillant dans un environnement parallèle. Ces efforts ont mené à une accélération dans le traitement des algorithmes de Shor et de Grover. D'autre part, il y a peu d'intérêt dans la littérature pour le niveau d'intrication dans les approches EQC, et c'est pourquoi nous nous penchons ici sur cette question. Notre premier résultat indique qu'il y a un niveau maximum d'intrication dans une approche EQC. Comme résultat principal, nous prouvons que des états de même poids statistique ne sont pas appropriés pour un EQC travaillant en mode parallèle. Afin que notre résultat ne reste pas un résultat purement théorique, nous prenons en exemple l'intrication d'un ensemble de n 1 = 3 ordinateurs quantiques à diamant. [Traduit par la Rédaction]