System-environment correlations for dephasing two-qubit states coupled to thermal baths

Abstract

Based on the exact dynamics of a two-qubit system and environment, we investigate system-environment (SE) quantum and classical correlations. The coupling is chosen to represent a dephasing channel for one of the qubits and the environment is a proper thermal bath. First we discuss the general issue of dilation for qubit phase damping. Based on the usual thermal bath of harmonic oscillators, we derive criteria of separability and entanglement between an initial $X$ state and the environment. Applying these criteria to initial Werner states, we find that entanglement between the system and environment is built up in time for temperatures below a certain critical temperature $T_{\mathrm{crit}}$. On the other hand, the total state remains separable during those short times that are relevant for decoherence and loss of entanglement in the two-qubit state. Close to $T_{\mathrm{crit}}$ the SE correlations oscillate between separable and entangled. Even though these oscillations are also observed in the entanglement between the two qubits, no simple relation between the loss of entanglement in the two-qubit system and the build-up of entanglement between the system and environment is found.

10 pages, published version

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• Parametrization and optimization of Gaussian non-Markovian unravelings for open quantum dynamics
• On the connection between microscopic description and memory effects in open quantum system dynamics
• Entanglement generation between a charge qubit and its bosonic environment during pure dephasing - dependence on environment size
• Detection of entanglement during pure dephasing evolutions for systems and environments of any size
• Qubit-environment entanglement outside of pure decoherence: hyperfine interaction
• Mechanisms of irreversible decoherence in solids
• Perturbation theory under the truncated Wigner approximation reveals how system-environment entanglement formation drives quantum decoherence
• Experimental realization of local-to-global noise transition in a two-qubit optical simulator