Qubit degradation due to cross-phase-modulation photon-number measurement
Qubit degradation due to cross-phase-modulation photon-number measurement
复制标题
交叉相位调制光子数测量导致的量子位退化
DOI：
10.1103/physreva.73.022301
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发表时间：
2006
影响因子：
2.9
通讯作者：
R. Bondurant
中科院分区：
文献类型：
--
作者：
J. Shapiro;R. Bondurant
提出了克尔效应交叉相位调制的信号和探针光束之间的方法，并证明了该方法是一种量子不拆除（QND）测量信号光束的光子数的方法。最近，这种QND测量被认为为光子量子计算提供了一条新的途径。对于以真空态和单光子态为计算基础的信号束量子比特，QND探测器的误差概率由交叉相位调制相互作用后的量子比特保真度决定，前者从0增加到$\frac{1}{2}$，后者从$\frac{2}{3}$增加到1。无论探测光束的输入状态如何，这种关系都保持不变。当交叉相位调制相互作用被更一般的酉变换所取代时，它也不加修改地适用。
Kerr effect cross-phase-modulation between signal and probe beams has been proposed and demonstrated as a means for quantum nondemolition (QND) measurement of the signal beam's photon number by homodyne detection of the probe beam. Recently, such QND measurements have been suggested as providing a new route to photonic quantum computation. For a signal-beam qubit, whose computational basis is the vacuum and one-photon states, the QND detector's error probability is shown to be determined by the qubit fidelity after the cross-phase-modulation interaction, with the former increasing from 0 to $\frac{1}{2}$ as the latter increases from $\frac{2}{3}$ to 1. This relationship is shown to hold regardless of the probe beam's input state. It also applies, without modification, when the cross-phase-modulation interaction is replaced with a more general unitary transformation.