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Chinese Science Bulletin

Amplifying stationary quantum discord and entanglement between a superconducting qubit and a data bus by time-dependent electromagnetic field

Zhang Ye

Published Jan 1, 2012• 0 citations
OpenAlex

Abstract

We study the dynamics of quantum discord and entanglement between a superconducting qubit and a data bus,which is driven by a controllable time-dependent electromagnetic field,in the presence of phase decoherence and find that the quantum discord and entanglement remain at a stationary non-zero value for long time evolution.It is shown that the amount of stationary quantum discord and entanglement can be enhanced by applying the time-dependent electromagnetic field.

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We study the dynamics of quantum discord and entanglement between a superconducting qubit and a data bus,which is driven by a controllable time-dependent electromagnetic field,in the presence of phase decoherence and find that the quantum discord and entanglement remain at a stationary non-zero value for long time evolution.It is shown that the amount of stationary quantum discord and entanglement can be enhanced by applying the time-dependent electromagnetic field.
We investigate a two-level atom interacting with a quantized cavity field and a classical driving field in the presence of phase decoherence and find that a stationary quantum discord can arise in the interaction of the atom and cavity field as the time turns to infinity. We also find that the stationary quantum discord can be increased by applying a classical driving field. Furthermore, we explore the quantum discord dynamics of two identical non-interacting two-level atoms independently interacting with a quantized cavity field and a classical driving field in the presence of phase decoherence. Results show that the quantum discord between two atoms is more robust than entanglement under phase decoherence and the classical driving field can help to improve the amount of quantum discord of the two atoms.
We study the effects of the interaction strength and the initial phase on the dynamics of quantum discord in a two-qubit system under both spontaneous emission and dephasing noisy channels. It is shown that the time evolution of quantum discord displays quicker oscillations with increasing inter-qubit interaction strength but the effect of the initial phase closely depends on the interaction between the qubits. Only for non-zero inter-qubit interaction cases, the evolution of quantum discord is affected by the initial phase and its oscillating amplitude increases with increasing initial phase. A comparison between evolutions of quantum discord and entanglement is also made.
We investigate the quantum discord dynamics in a cavity quantum electrodynamics system, which consists of two noninteracting two-level atoms driven by independent optical fields and classical fields, and find that the quantum discord vanishes only asymptotically although entanglement disappears suddenly during the time evolution in the absence of classical fields. It is shown that the amount of quantum discord can be increased by adjusting the classical driving fields because the increasing degree of the amount of quantum mutual information is greater than classical correlation by applying the classical driving fields. Finally, the influence of the classical driving field on the fidelity of the system is also examined.
Abstract We investigate the influence of a time-dependent electromagnetic field (TDEF) on the double sudden change of the 1-norm geometric quantum discord (GQD) and sudden change of quantum coherence for superconducting circuit systems under spontaneous emission, where two superconducting qubits are each coupled to their own LC circuit or uniformly coupled to a common LC circuit, respectively. It is shown that the double sudden change of the GQD can be controlled, and the frozen time during which the GQD keeps nearly constant can be lengthened by applying the TDEF. Furthermore, we also find that the TDEF can delay the ‘critical point’ of sudden change for quantum coherence and slow down the decay of quantum coherence. Finally, we explore how the TDEF affects the superconducting circuits system’s information flow by using trace distance and the optimal control scheme is sought by comparing the two coupled modes.
We investigate how quantum measurements affect the dynamics of quantum correlations of the system which consists of two noninteracting superconducting qubits each locally coupling to its own data bus. It is shown that the geometric discord and entanglement between two superconducting qubits can be increased by applying a sequence of selective measurements. The optimal measurement time at which the quantum correlations achieve their maximal values is also analyzed. Moreover, we find that the selective measurements on the data buses can protect quantum information of two superconducting qubits and force information to flow back to the superconducting qubits from the data buses by a witness of the trace distance.