Institut UTINAM, Université de Franche-Comté, CNRS UMR 6213, 25030 Besançon Cedex, France.
J Chem Phys. 2013 Aug 7;139(5):054103. doi: 10.1063/1.4817303.
The decoherence of a qubit coupled with the phonons of a finite-size lattice is investigated. The confined phonons no longer behave as a reservoir. They remain sensitive to the qubit so that the origin of the decoherence is twofold. First, a qubit-phonon entanglement yields an incomplete true decoherence. Second, the qubit renormalizes the phonon frequency resulting in fake decoherence when a thermal average is performed. To account for the initial thermalization of the lattice, the qua- ntum Langevin theory is applied so that the phonons are viewed as an open system coupled with a thermal bath of harmonic oscillators. Consequently, it is shown that the finite lifetime of the phonons does not modify fake decoherence but strongly affects true decoherence. Depending on the values of the model parameters, the interplay between fake and true decoherence yields a very rich dynamics with various regimes.
研究了与有限尺寸晶格声子耦合的量子位的退相干。受限声子不再表现为储层。它们仍然对量子位敏感，因此退相干的起源是双重的。首先，qubit-phonon 纠缠导致不完全的真正退相干。其次，当执行热平均值时，qubit 会使声子频率重新归一化，从而导致虚假退相干。为了说明晶格的初始热化，应用量子 Langevin 理论，使声子被视为与热浴中的谐振子耦合的开放系统。因此，结果表明，声子的有限寿命不会改变虚假退相干，但会强烈影响真实退相干。根据模型参数的值，虚假退相干和真实退相干之间的相互作用产生了具有各种模式的非常丰富的动力学。
