Adaptive phase measurements in linear optical quantum computation
Adaptive phase measurements in linear optical quantum computation
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DOI：
10.1088/1464-4266/7/10/007
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发表时间：
2005-10-01
期刊：
影响因子：
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通讯作者：
Wiseman, HM
中科院分区：
文献类型：
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作者：
Ralph, TC;Lund, AP;Wiseman, HM
光子计数在由线性光学从单光子导出的某些状态中引起有效的非线性光学相移。虽然这种非线性是非确定性的，但原则上足以允许可扩展的线性光学量子计算（LOQC）。对量子位进行光学编码的最明显的方式是将真空和单个光子叠加在一个模式中，即所谓的“单轨”逻辑。到目前为止，与“双轨”逻辑相比，这种方法被认为极其昂贵（在资源方面），“双轨”逻辑中，量子位由光子以两种模式存储。在这里，我们攻击这个问题的实时反馈控制，它可以实现一个量子限制的相位测量的单模，最近已经证明实验。我们表明，与此增加的测量资源，单轨LOQC的资源需求是没有实质性的不同，从双轨LOQC。特别地，利用自适应相位测量，可以确定性地制备任意量子比特状态α/0 > + β/1 >。
Photon counting induces an effective non-linear optical phase shift in certain states derived by linear optics from single photons. Although this non-linearity is non-deterministic, it is sufficient in principle to allow scalable linear optics quantum computation (LOQC). The most obvious way to encode a qubit optically is as a superposition of the vacuum and a single photon in one mode-so-called 'single-rail' logic. Until now this approach was thought to be prohibitively expensive (in resources) compared to 'dual-rail' logic where a qubit is stored by a photon across two modes. Here we attack this problem with real-time feedback control, which can realize a quantum-limited phase measurement on a single mode, as has been recently demonstrated experimentally. We show that with this added measurement resource, the resource requirements for single-rail LOQC are not substantially different from those of dual-rail LOQC. In particular, with adaptive phase measurements an arbitrary qubit state a alpha/0 > + beta/1 > can be prepared deterministically.