Models of quantum disentanglement are developed for nanometer-scale molecular charge qubits (MCQs). Two MCQs, $A$ and $B$, are prepared in a Bell state and separated for negligible $A$-$B$ interactions. Interactions between the local environment and each MCQ unravels $A$-$B$ entanglement during coherent system+environment evolution. Three models are used for dynamics: (1) a previously-developed, numerical model, in which both $AB$ and environment $\mathcal{E}$ are modeled explicitly; (2) an exact, semi-analytic model, in which only the dynamics of $AB$ are calculated, and (3) an approximate model developed from the semi-analytic model and assumptions about randomness in $\mathcal{E}$. In the approximate model, the non-zero coherences of the density operator for $AB$ decay with a Gaussian time dependence. This provides a time scale for system dynamics in the exact models as well. This time scale is related directly to the strength of AB-$\mathcal{E}$ interaction. This time scale describes cases where environmental interaction with one target MCQ is dominant, generalizing a previous time scale applicable only when both MCQs have roughly the same strength of interaction with the local environment. Entanglement is measured using two-qubit correlation functions, the dynamics of which are used to demonstrate the effectiveness of the time scale. The early-time decay of coherences and the loss of entanglement is well-characterized as Gaussian, a behavior that Markovian models for memoryless environments cannot capture. The approximate Gaussian model may be used to describe the dynamics of MCQ disentanglement under the influence of environments modeled here, as well as other environments where randomness is present.
Simple proof of the robustness of Gaussian entanglement in bosonic noisy channels
高斯态的极值被利用来表明，高斯态是最强大的，在所有可能的二分连续变量状态在固定的能量，对解纠缠由于噪声的演变马尔可夫高斯信道涉及耗散和热跳变。这证明了最近在[M. Allegra，P. Giorda，and M. G. A. Paris，Phys. Rev. Lett. { \bf 105}，100503（2010）]，提供了对该工作结论的严格验证。在更一般的玻色子开放系统动力学演化中，识别具有最大弹性的连续变量状态的问题仍然是开放的，可能包括相关噪声和非马尔可夫效应。
An exact Markovian decoherence dynamics of two interacting harmonic oscillators coupled to a bosonic heat bath
HUN-REN Wigner Research Centre for Physics（匈牙利科学院维格纳物理研究中心）；Department of Pharmaceutics, Semmelweis University（塞梅尔维斯大学药剂学系）；Forschungszentrum Jülich, Institute of Quantum Control (PGI-8)（于利希研究中心量子控制研究所）；Institute of Physics, University of Pécs（佩奇大学物理研究所）；Department of Physics of Complex Systems, Eötvös Loránd University, ELTE（罗兰大学复杂系统物理系）
A Breakdown Case Study of the Lindblad Approach via Entanglement and Purity
Università di Salerno, and INFN — Gruppo Collegato di Salerno（萨莱诺大学，意大利国家核物理研究所萨莱诺协作组）；University of Camerino（卡梅里诺大学）；Institut Ruđer Bošković（鲁德·博什科维奇研究所）
