Truly noiseless probabilistic amplification
Truly noiseless probabilistic amplification
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DOI：
10.1103/physreva.86.042322
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发表时间：
2012-10-18
影响因子：
2.9
通讯作者：
Andersson, Erika
中科院分区：
文献类型：
--
作者：
Dunjko, Vedran;Andersson, Erika
最近吸引了理论和实验兴趣的大多数相干态“无声”放大方案都有一个共同的特点：对于非零的成功概率，放大并不是真正无声的，或者说不是完美的。虽然这对所有的相位独立放大方案都是正确的，但在这项工作中，我们指出，如果我们希望放大的状态来自有限集合，那么真正的无噪声放大确实是可能的。然后，具有无限平均增益的完美放大是可能的，而成功概率是有限的，例如，使用明确区分量子态的技术。这种实现只需要线性光学，不需要单光子源，也不需要光子计数。我们还研究了对称相干态的完美放大的最佳成功概率。有两种模式：低幅度放大，即目标幅度低于1，以及一般放大。对于低幅度区，可以得到最佳放大成功概率的解析结果。在这种情况下，由源和放大状态的最佳明确区分的成功概率之比施加的自然界限总是可以达到的。我们还证明了对于一般的放大，这个界并不总是被满足的。
Most of the schemes for "noiseless" amplification of coherent states, which have recently been attracting theoretical and experimental interest, share a common trait: The amplification is not truly noiseless, or perfect, for nonzero success probability. While this must hold true for all phase-independent amplification schemes, in this work we point out that truly noiseless amplification is indeed possible, provided that the states which we wish to amplify come from a finite set. Perfect amplification with unlimited average gain is then possible with finite success probability, for example, using techniques for unambiguously distinguishing between quantum states. Such realizations require only linear optics, no single-photon sources, and no photon counting. We also investigate the optimal success probability of perfect amplification of a symmetric set of coherent states. There are two regimes: low-amplitude amplification, where the target amplitude is below one, and general amplification. For the low-amplitude regime, analytic results for the optimal amplification success probabilities can be obtained. In this case a natural bound imposed by the ratio of success probabilities of optimal unambiguous discrimination of the source and amplified states can always be reached. We also show that for general amplification this bound cannot always be satisfied.