Quantum nonequilibrium equalities with absolute irreversibility
Quantum nonequilibrium equalities with absolute irreversibility
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DOI：
10.1088/1367-2630/17/7/075005
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发表时间：
2015-07-09
影响因子：
3.3
通讯作者：
Ueda, Masahito
中科院分区：
文献类型：
--
作者：
Funo, Ken;Murashita, Yuto;Ueda, Masahito
我们在绝对不可逆过程中推导出量子非平衡等式。这里，绝对不可逆性是指在后向过程中，密度矩阵不会返回到初始密度矩阵中具有非零权重的那些特征向量所跨越的子空间。由于存储器的初始状态和系统的测量后状态通常被限制在子空间内，因此在测量和反馈过程中会发生绝对不可逆性。为了导出非平衡等式，需要考虑绝对不可逆过程中产生的额外熵。我们讨论量子位系统的反馈控制模型来说明所获得的等式。通过引入每个由一个量子位组成的 Nheat 浴并让它们与系统交互，我们展示了如何通过反馈控制将熵减少转化为功。给出了在绝对不可逆性存在的情况下可提取功的明确形式。
We derive quantum nonequilibrium equalities in absolutely irreversible processes. Here by absolute irreversibility we mean that in the backward process the density matrix does not return to the subspace spanned by those eigenvectors that have nonzero weight in the initial density matrix. Since the initial state of a memory and the postmeasurement state of the system are usually restricted to a subspace, absolute irreversibility occurs during the measurement and feedback processes. An additional entropy produced in absolutely irreversible processes needs to be taken into account to derive nonequilibrium equalities. We discuss a model of a feedback control on a qubit system to illustrate the obtained equalities. By introducing Nheat baths each composed of a qubit and letting them interact with the system, we show how the entropy reduction via feedback control can be converted into work. An explicit form of extractable work in the presence of absolute irreversibility is given.