Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

Acta Physica Sinica

Entanglement between charge qubit and quantized field

Zhaoxin Li, Zou Jian, Cai Jin-Fang, Shao Bin, 北京理工大学物理系,北京 100081

Published Jan 1, 2006• 4 citations
Publisher

Abstract

We investigate time evolution of the entanglement between charge qubit initially in mixed states and quantized field. By calculating the concurrence lower bound, we study the effect of initial mixedness λ and detuning Δ on the entanglement of the system. In the case of weak field, the degree of entanglement for charge qubit being initially in excited state is much larger than that for charge qubit being initially in ground state, and detuning Δ can efficiently reduce the entanglement. But in the case of strong field, the time evolution of the entanglement is about the same for charge qubit being initially in excited and ground states, the more mixed the initial state of charge qubit is prepared, the weaker the entanglement is, and Δ has less effect on the entanglement than in the case of weak field.

DOI
10.7498/aps.55.1580

Related papers

Entanglement of Two Superconducting Charge Qubits Induced by Quantized Radiation Field

Zou Jian, Shao Bin, Qian‐Shu Li

We consider two superconducting charge qubits coupled by a single-mode quantized field. We suppose that the two superconducting charge qubits be initially prepared in the mixed and separable state. As time evolves, we will investigate the entanglement between two superconducting charge qubits induced by the quantized field.

Communications in Theoretical Physics•Jun 15, 2004•13 citations

ENTANGLEMENT BETWEEN TWO SUPERCONDUCTING CHARGE QUBITS

Eugene K. Bashkirov

In this paper, we investigated the dynamics of entanglement of two identical charge qubits with Josephson junctions in the case when one of the qubits is exposed to a microwave field in a coherent or thermal state. We have found the exact solution of the quantum time equation of evolution of the system under consideration for the statistical operator in the case of initial separable and entangled states of qubits. The exact solution for the complete statistical operator is used to calculate the qubit entanglement criterion - concurrence. The results of numerical simulation of the time dependence of the concurrence in the case of the coherent field showed that, with a certain choice of model parameters, the system can realize long-lived entangled states. It is also shown that for the thermal state of the field and the entangled initial state of qubits, the qubits retain a certain degree of entanglement during evolution even in the case of very intensive fields. In this case, for any intensities of thermal noise, there is no effect of the sudden death of entanglement.

Vestnik of Samara University Natural Science Series•Aug 31, 2023•0 citations

Entanglement of Two Superconducting Charge Qubits Induced by QuantizedRadiation Field

ZOUJian, SHAOBin, LIQian-Shu

We consider two superconducting charge qubits coupled by a single-mode quantized field. We suppose that the two superconducting charge qubits be initially prepared in the mixed and separable state. As time evolves, we will investigate the entanglement between two superconducting charge qubits induced by the quantized field.

理论物理通讯：英文版•Jan 1, 2004•0 citations

MIXED-STATE ENTANGLEMENT IN A SINGLE-COOPER-PAIR BOX DETUNED WITH A COHERENT FIELD

Zhaoxin Li, Yan Xu, LUYIN ZHANG +1 more

A system composed of a single-Cooper-pair box irradiated by a single-mode quantized field has been considered. The entanglement relative to the mixedness μ and the detuning δ is investigated with negative partial transpose. It is found that in the case of initial mixed state, the entanglement is weakened, but increases as time evolves. For a detuned system, the entanglement is further suppressed but more stationary than that for a resonant system.

International Journal of Modern Physics B•Apr 6, 2011•0 citations

Generation of Entanglement Between Two Noninteracting Qubits via Interaction with Nonclassical Radiation Field

Jian Zou, Cai Jin-Fang, Bin Shao +1 more

We study the interaction between a single-mode quantized field and a quantum system composed of two qubits. We suppose that two qubits initially be prepared in the mixed and separable state, and study how entanglement between two qubits arises in the course of evolution according to the Jaynes–Cummings type interaction with nonclassical radiation field. We also investigate the relation between entanglement and purity of qubit subsystem. We show that different photon statistics have different effects on the dynamical behavior of the qubit subsystem. When the qubits are initially prepared in the maximally mixed and separable state, for coherent state field we cannot find entanglement between two qubits; for squeezed state field entanglement between two qubits exists in several short period of time; for even and odd coherent state fields of large photon number, the dynamical behavior of the entanglement between two qubits shows collapse and revival phenomenon. For odd coherent state field of small photon number, the entanglement with both qubits initially prepared in maximally mixed state can be stronger than that with both qubits initially prepared in pure states. For fields of small photon number, the entanglement strongly depends on the states they are initially prepared in. For coherent state field, and odd and even coherent state fields of large photon number, the entanglement only depends on the purity of the initial state of qubit subsystem. We also show that during the evolution the unentangled state may be purer than the entangled state, and the maximum degree of entanglement may not occur at the time when the qubit subsystem is in the purist state.

Communications in Theoretical Physics•Aug 1, 2005•1 citation

Entanglement generation between a charge qubit and its bosonic environment during pure dephasing: Dependence on the environment size

Tymoteusz Salamon, Katarzyna Roszak

We study entanglement generated between a charge qubit and a bosonic bath due to their joint evolution which leads to pure dephasing of the qubit. We tune the parameters of the interaction, so that the decoherence is quantitatively independent of the number of bosonic modes taken into account and investigate how the entanglement generated depends on the size of the environment. A second parameter of interest is the mixedness of the initial state of the environment which is controlled by temperature. We show analytically that for a pure initial state of the environment, entanglement does not depend on environment size. For mixed initial states of the environment, the generated entanglement decreases with the increase of environment size. This effect is stronger for larger temperatures, when the environment is initially more mixed, but in the limit of an infinitely large environment, no entanglement is created at any finite temperature.

arXiv:1704.08180•Physical Review A•Sep 22, 2017•13 citations
We investigate time evolution of the entanglement between charge qubit initially in mixed states and quantized field. By calculating the concurrence lower bound, we study the effect of initial mixedness λ and detuning Δ on the entanglement of the system. In the case of weak field, the degree of entanglement for charge qubit being initially in excited state is much larger than that for charge qubit being initially in ground state, and detuning Δ can efficiently reduce the entanglement. But in the case of strong field, the time evolution of the entanglement is about the same for charge qubit being initially in excited and ground states, the more mixed the initial state of charge qubit is prepared, the weaker the entanglement is, and Δ has less effect on the entanglement than in the case of weak field.
In this paper, we investigated the dynamics of entanglement of two identical charge qubits with Josephson junctions in the case when one of the qubits is exposed to a microwave field in a coherent or thermal state. We have found the exact solution of the quantum time equation of evolution of the system under consideration for the statistical operator in the case of initial separable and entangled states of qubits. The exact solution for the complete statistical operator is used to calculate the qubit entanglement criterion - concurrence. The results of numerical simulation of the time dependence of the concurrence in the case of the coherent field showed that, with a certain choice of model parameters, the system can realize long-lived entangled states. It is also shown that for the thermal state of the field and the entangled initial state of qubits, the qubits retain a certain degree of entanglement during evolution even in the case of very intensive fields. In this case, for any intensities of thermal noise, there is no effect of the sudden death of entanglement.
We study the interaction between a single-mode quantized field and a quantum system composed of two qubits. We suppose that two qubits initially be prepared in the mixed and separable state, and study how entanglement between two qubits arises in the course of evolution according to the Jaynes–Cummings type interaction with nonclassical radiation field. We also investigate the relation between entanglement and purity of qubit subsystem. We show that different photon statistics have different effects on the dynamical behavior of the qubit subsystem. When the qubits are initially prepared in the maximally mixed and separable state, for coherent state field we cannot find entanglement between two qubits; for squeezed state field entanglement between two qubits exists in several short period of time; for even and odd coherent state fields of large photon number, the dynamical behavior of the entanglement between two qubits shows collapse and revival phenomenon. For odd coherent state field of small photon number, the entanglement with both qubits initially prepared in maximally mixed state can be stronger than that with both qubits initially prepared in pure states. For fields of small photon number, the entanglement strongly depends on the states they are initially prepared in. For coherent state field, and odd and even coherent state fields of large photon number, the entanglement only depends on the purity of the initial state of qubit subsystem. We also show that during the evolution the unentangled state may be purer than the entangled state, and the maximum degree of entanglement may not occur at the time when the qubit subsystem is in the purist state.
We study entanglement generated between a charge qubit and a bosonic bath due to their joint evolution which leads to pure dephasing of the qubit. We tune the parameters of the interaction, so that the decoherence is quantitatively independent of the number of bosonic modes taken into account and investigate how the entanglement generated depends on the size of the environment. A second parameter of interest is the mixedness of the initial state of the environment which is controlled by temperature. We show analytically that for a pure initial state of the environment, entanglement does not depend on environment size. For mixed initial states of the environment, the generated entanglement decreases with the increase of environment size. This effect is stronger for larger temperatures, when the environment is initially more mixed, but in the limit of an infinitely large environment, no entanglement is created at any finite temperature.