Entanglement of qubits via a nonlinear resonator

Marcin Kurpas, Jerzy Dajka

Published Nov 26, 2012• 11 citations

Abstract

Coherent coupling of two qubits mediated by a nonlinear resonator is studied. It is shown that the amount of entanglement accessible in the evolution depends both on the strength of nonlinearity in the Hamiltonian of the resonator and on the initial preparation of the system. The created entanglement survives in the presence of decoherence. PACS numbers: 03.67.Lx 03.67.Bg 42.50.Ct 85.25.DqEntanglement of qubits via a nonlinear resonator 2 1.

Related papers

Entanglement of qubits via a nonlinear resonator

M Kurpas, J Dajka, E Zipper

Coherent coupling of two qubits mediated by a nonlinear resonator is studied. It is shown that the amount of entanglement accessible in the evolution depends on both the strength of nonlinearity in the Hamiltonian of the resonator and on the initial preparation of the system. The created entanglement survives in the presence of decoherence.

arXiv:0812.3791Journal of Physics Condensed MatterMay 13, 20097 citations

Measurement-induced entanglement of two superconducting qubits

Jian Li, K Chalapat, Gheorghe Sorin Paraoanu

We study the problem of two superconducting quantum qubits coupled via a resonator. If only one quanta is present in the system and the number of photons in the resonator is measured with a null result, the qubits end up in an entangled Bell state. Here we look at one source of errors in this quantum nondemolition scheme due to the presence of more than one quanta in the resonator, previous to the measurement. By analyzing the structure of the conditional Hamiltonian with arbitrary number of quanta, we show that the scheme is remarkably robust against these type of errors. PACS:03.67.Lx,85.25.Cp,74.50.+r

arXiv:0806.3148Journal of Physics Conference SeriesFeb 1, 200910 citations

Entanglement between two charge qubits taking account the Kerr media

Evgeny K. Bashkirov

Background. The need to implement controlled coupling between qubits, which are the logical elements of quantum devices such as quantum computers and quantum networks, requires, along with the use of traditional methods, the development of new, more effective ways to organize the interaction of qubits with the microwave fields of resonators used to generate and control the entanglement of qubits. As one of these methods, a method based on the influence of frequency-regulated radio frequency signals on a superconducting Josephson qubit connected by a large Josephson junction to a free qubit has been proposed. Aim. The influence of the Kerr medium of the resonator, in which one of the two qubits is placed, on their entanglement induced by the coherent or thermal frequency-regulated radio frequency field of the resonator is considered. Methods. To analyze the dynamics of the system under consideration, the solution of the quantum Liouville equation for the full density matrix is studied. An exact solution o this equation is found in the case of initial separable and entangled states of qubits. The exact solution of the evolution equation is used to calculate the criterion of qubit-qubit entanglement – cconcurrence. Numerical modeling of the concurrence was carried out for various states of qubits, coherent and thermal fields of the resonator, as well as various values of the intensity of the resonator field and the Kerr nonlinearity parameter. Results. It is shown that for separable initial states of qubits, the inclusion of Kerr nonlinearity reduces the maximum degree of entanglement of qubits. For an entangled initial state of qubits, the possibility of creating long-lived entangled states in the presence of Kerr nonlinearity is shown. Conclusion. The type of initial states of qubits and the range of values of the intensities of the resonator fields and the Kerr nonlinearity parameters have been established, for which the most effective control and operation of the evolution of qubits, as well as the degree of their entanglement, in the physical system under consideration, is possible.

Physics of Wave Processes and Radio SystemsMar 29, 20240 citations

Generation of quantum coherence in two-qubit cavity system: qubit-dipole coupling and decoherence effects

A-B A Mohamed, H. A. Hessian, Hichem Eleuch

Abstract The intrinsic decoherence effect for two qubits interacting with a coherent field, under the dipole-dipole interaction and two-photon resonance, is analytically described. We investigate numerically the population inversion and the quantum coherence. The results show that the generated mixture entropy and the entanglement negativity, can be enhanced and protected by the dipole-dipole interaction and by reducing the initial coherent field intensity. In particular, we find that, the collapses and revivals of the population inversion present high sensitivity to these physical parameters. The nonlinearity of the two-photon processes leads to a generation of a strong two-qubit entanglement. This generated entanglement depends on the initial coherent field intensity, the dipole-dipole interaction and the intrinsic decoherence.

Physica ScriptaMay 1, 202012 citations

ENTANGLEMENT IN NONLINEAR TWO-QUBIT TAVIS — CUMMINGS MODEL

R. K. Zakharov, Eugene K. Bashkirov

In this work, we have studied the dynamics of entanglement of two identical superconducting qubits resonantly interacting with the one-mode field of a coplanar microwave cavity without loss through single-photon transitions in the presence of third- and fifth-order nonlinearities. Based on the solution of the equation of evolution of the system for the Fock initial states of the cavity field, the criterion of qubits entanglement negativity is calculated. The results of the negativity calculation show that for the initial separable states, the cavity nonlinearity can lead to a significant increase in the maximum degree of qubit entanglement. It is shown that for the initial entangledstates of qubits and intense cavity fields, taking into account nonlinearities leads to stabilization of the degree of entanglement of qubits in the cavity and contributes to the disappearance of the effect of the entanglement sudden death of qubits.

Vestnik of Samara University Natural Science SeriesAug 31, 20231 citation

Decoherence of two maximally entangled qubits in a lossy nonlinear cavity

Miranowicz, A

Decoherence effect on quantum entanglement of two optical qubits in a lossy cavity interacting with a nonlinear medium (Kerr nonlinearity) is analyzed. The qubits are assumed to be initially in the maximally entangled states (Bell or Bell-like states) or the maximally entangled mixed states, on the example of Werner and Werner-like states. Two kinds of measures of the entanglement are considered: the concurrence to describe a decay of the entanglement of formation of the qubits, and the negativity to determine a decay of an upper bound of the entanglement of distillation. It is observed that the Kerr nonlinearity does not affect the entanglement of the qubits initially in the Bell or Werner states, although the evolution of the qubits can depend on this nonlinearity explicitly. However, it is shown that for the initial Bell-like state and the corresponding Werner-like state, the loss of entanglement can be periodically reduced by inserting the Kerr nonlinearity in the lossy cavity.

Feb 3, 200414 citations