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Dephasing of Coupled Superconductor Qubits in Contact with a Common Environment

Yan‐Li Ji, Ya-Fei Yu, Yan Jun Hu

Published Jan 1, 2011• 0 citations
OpenAlex

Abstract

environment on the entanglement dynamics in non-Markov process. Our results show that the entanglement degree is strongly related with the initial quantum state and the coupling between the qubits and the environment. The interaction between the qubits and the environment suppresses the decay of the entanglement. The sudden death of entanglement (ESD) can be prevented only by using and controlling targeted the interaction model between the different qubits and the environment. We also find the dissipation phenomenon always exists when the qubits system is initially in the maximally entangled mixed states.

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environment on the entanglement dynamics in non-Markov process. Our results show that the entanglement degree is strongly related with the initial quantum state and the coupling between the qubits and the environment. The interaction between the qubits and the environment suppresses the decay of the entanglement. The sudden death of entanglement (ESD) can be prevented only by using and controlling targeted the interaction model between the different qubits and the environment. We also find the dissipation phenomenon always exists when the qubits system is initially in the maximally entangled mixed states.
The entanglement evolution of the coupled qubits interacting with a non-Markov environment is investigated in terms of concurrence. The results show that the entanglement of the quantum systems depends not only on the initial state of the system but also on the coupling between the qubit and the environment. For the initial state , the coupled qubits will always been in the maximum entangled state under an asymmetric coupling. For the initial state , in contrast, the entangling degree of the coupled qubits is always equal to unity and does not depend on the evolving time under the symmetric coupling. We find that the stronger the interaction between the qubits is, the better the struggle against the entanglement sudden death is.
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The evolution of entangled decoherence of coupling superconducting qubits in non-Markovian environment is investigated in detail using concurrence function.The results show that,for coupling superconducting qubit under different entangled initial states,because of the role of memory feedback due to environmental effect,the entanglement of coupling superconducting qubits under a thermal bath always tends to zero monotonically.Further results also showed that,the sudden death of entanglement will soon occur in non-Markovian process,stronger the dissipation,faster the death of entanglement.But in Markovian process,it tends to death of entanglement slowly.
We make the study of the relationship between symmetrical coupling of coupling qubits and non-Markovian relaxation characteristics by utilizing concurrence. The results show that the relaxation characteristics of quantum system strongly depend on the coupling way between qubits and environment and the decoherence-free subspace may form under certain conditions. We find that when the system is initially at [Formula: see text] state or the mixed state generated by this state, we can make the quantum system always at the entangled state without entanglement sudden death (ESD) phenomenon by regulating the coupling between qubits and environment at complete anti-symmetric state. In contrast, when the system is initially at [Formula: see text] state or the mixed state generated by this state, then we must regulate the coupling way between qubits and environment at complete symmetric state to make the quantum system maintain at the entanglement state.
In this work, we consider non-interacting atomic two level and three level (qubit-qutrit) systems interacting with a common environment in vacuum state. The interaction with the environment leads to the decoherece of the system due to spontaneous emission of atomic excited states which results in the decay of entanglement and other correlations of the qubit-qutrit system. We study the dynamics of entanglement for different initial class of states and negativity is used as a measure to quantify the degree of entanglement of qubit-qutrit system, the three level systems are considered in V configuration. We construct a class of rank dependant mixed boundary qubit-qutrit states as initial states. We observe entanglement sudden death for higher rank mixed boundary qubit-qutrit states.