量子测量的最优控制
Optimal Control of Quantum Measurement
摘要：
控制量子系统时间演化的脉冲可以用最优控制理论来设计。在大多数情况下，它是可以控制的相干过程，并优化的时间演变到一个目标单一的过程，有时也在不可控的非相干过程的存在。在这里，我们展示了如何扩展的GRAPE算法的情况下，非相干过程是可控的和目标的时间演化是一个非幺正的量子信道。我们执行梯度搜索的保真度措施的基础上Choi矩阵。我们通过优化相位量子比特测量脉冲来说明我们的算法。我们展示了这种技术如何能够导致接近99%的大测量对比度。我们还表明，在我们的模型的有效性，该算法可以产生短的1.4纳秒脉冲与98.2%的对比度。
英文摘要：
Pulses to steer the time evolution of quantum systems can be designed with optimal control theory. In most cases it is the coherent processes that can be controlled and one optimizes the time evolution towards a target unitary process, sometimes also in the presence of non-controllable incoherent processes. Here we show how to extend the GRAPE algorithm in the case where the incoherent processes are controllable and the target time evolution is a non-unitary quantum channel. We perform a gradient search on a fidelity measure based on Choi matrices. We illustrate our algorithm by optimizing a phase qubit measurement pulse. We show how this technique can lead to large measurement contrast close to 99%. We also show, within the validity of our model, that this algorithm can produce short 1.4 ns pulses with 98.2% contrast.
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