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arXiv 1702.01609quant-ph
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利用最优投影测量分析量子芝诺和反芝诺效应

Analyzing the Quantum Zeno and anti-Zeno effects using optimal projective measurements

Muhammad Junaid Aftab, Adam Zaman Chaudhry

摘要:

量子力学中的测量不仅可以有效地冻结量子系统的态(量子芝诺效应),而且可以加速系统的时间演化(量子反芝诺效应)。在量子芝诺和反芝诺效应的研究中,一个量子态,通常是系统的激发态,通过一次又一次地将量子态投影到初始态上来重复制备。在本文中,我们用不同的方法反复制备初始量子态。而不是只执行投影测量,我们允许单一的操作进行,在一个非常短的时间尺度上,每次测量后。然后,我们可以通过执行一些投影测量来重复地准备初始量子态,并且此后,在每次测量之后,执行适当的幺正操作以重复地结束初始状态。因此,我们的目标是找到需要重复执行的投影测量,使得我们获得量子态的最小可能有效衰减率。因此,量子态被最大限度地保护免受其环境的影响。我们发现,这些优化的投影测量不断变化,依赖于测量时间间隔。我们明确地发现投影测量需要进行,以及优化的有效衰变率,为各种系统环境模型,如人口衰变模型,纯退相模型,自旋玻色子模型,和大自旋玻色子模型。我们发现,这种优化的有效衰变率和通常的衰变率之间可以有相当大的差异,通过反复投影到初始状态。特别是,芝诺和反芝诺制度可以大大修改。

英文摘要:

Measurements in quantum mechanics can not only effectively freeze the state of the quantum system (the quantum Zeno effect) but also accelerate the time evolution of the system (the quantum anti-Zeno effect). In studies of the quantum Zeno and anti-Zeno effects, a quantum state, usually an excited state of the system, is prepared repeatedly by projecting the quantum state onto the initial state again and again. In this paper, we repeatedly prepare the initial quantum state in a different manner. Instead of only performing projective measurements, we allow unitary operations to be performed, on a very short time-scale, after each measurement. We can then repeatedly prepare the initial quantum state by performing some projective measurement and thereafter, after each measurement, performing a suitable unitary operation to repeatedly end up with the initial state. Our objective thereafter is to find the projective measurements that need to repeatedly performed such that we obtain the minimum possible effective decay rate of the quantum state. Consequently, the quantum state is maximally protected from its environment. We find that these optimized projective measurements keep on changing depending on the measurement time interval. We explicitly find the projective measurements that need to be performed, as well as the optimized effective decay rate, for a variety of system-environment models such as the population decay model, the pure dephasing model, the spin-boson model, and the large spin-boson model. We find that there can be considerable differences between this optimized effective decay rate and the usual decay rate obtained by repeatedly projecting onto the initial state. In particular, the Zeno and anti-Zeno regimes can be considerably modified.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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