Single-photon Kerr nonlinearities do not help quantum computation
Single-photon Kerr nonlinearities do not help quantum computation
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DOI：
10.1103/physreva.73.062305
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发表时间：
2006-06-01
影响因子：
2.9
通讯作者：
Shapiro, Jeffrey H.
中科院分区：
文献类型：
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作者：
Shapiro, Jeffrey H.
通过在适当的光子晶体微腔内嵌入能够电磁诱导透明的原子，可以实现响应于单光子激发而可以赋予π-rad-峰值相移的光学非线性。这样的设备，如果它在高保真度下运行，那么将完成全光量子计算的通用门组。这里表明，因果关系，任何卡（（3））非线性的非瞬时行为是足以排除这样的高保真操作。特别地，当单光子敏感的χ（3）非线性具有比量子计算机的单光子脉冲的持续时间短得多的响应时间时，基本上没有整体相移通过交叉相位调制被赋予这些脉冲。相反，当这种非线性的响应时间比脉冲持续时间长得多时，单光子脉冲可以通过交叉相位调制引起π-rad的总相移，但是由因果关系注入的相位噪声，非瞬时响应函数排除了高保真操作。
By embedding an atom capable of electromagnetically induced transparency inside an appropriate photonic-crystal microcavity it may become possible to realize an optical nonlinearity that can impart a pi-rad-peak phase shift in response to a single-photon excitation. Such a device, if it operated at high fidelity, would then complete a universal gate set for all-optical quantum computation. It is shown here that the causal, noninstantaneous behavior of any chi((3)) nonlinearity is enough to preclude such a high-fidelity operation. In particular, when a single-photon-sensitive chi((3)) nonlinearity has a response time that is much shorter than the duration of the quantum computer's single-photon pulses, essentially no overall phase shift is imparted to these pulses by cross-phase modulation. Conversely, when this nonlinearity has a response time that is much longer than this pulse duration a single-photon pulse can induce a pi-rad overall phase shift through cross-phase modulation, but the phase noise injected by the causal, noninstantaneous response function precludes this from being a high-fidelity operation.