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arXiv 1504.07718quant-ph
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利用纠缠抑制微弱测量中的技术噪声

Suppressing technical noises in weak measurement by entanglement

Shengshi Pang, Todd A. Brun

摘要:

后选弱测量因其独特的放大小物理量的能力而引起了广泛的兴趣。然而,后选择效率低,以获得一个大的弱值,已成为一个很大的障碍,在实际应用中,它可能会浪费资源,并降低测量精度。在[Phys.Rev.Lett. 113,030401(2014)],以通过使用纠缠使后选择的弱测量显著地更有效。这样的协议可以增加测量的Fisher信息,以近似饱和众所周知的海森堡极限。本文详细介绍了后选择弱测量的纠缠辅助协议,并研究了其对技术噪声的鲁棒性。我们专注于读取错误。读出误差会大大降低后选弱测量的性能,特别是当读出误差概率与后选概率相当时。我们表明,纠缠可以显着减少读出错误的两个主要不利影响:测量结果的不准确性,和费舍尔信息的损失。我们通过引入多数投票方案来扩展该协议,以进一步补偿读出错误。通过适当的阈值,几乎不会丢失Fisher信息。这些结果表明纠缠在保护后选择弱测量对读出错误的有效性。

英文摘要:

Postselected weak measurement has aroused broad interest for its distinctive ability to amplify small physical quantities. However, the low postselection efficiency to obtain a large weak value has been a big obstacle to its application in practice, since it may waste resources, and reduce the measurement precision. An improved protocol was proposed in [Phys. Rev. Lett. 113, 030401 (2014)] to make the postselected weak measurement dramatically more efficient by using entanglement. Such a protocol can increase the Fisher information of the measurement to approximately saturate the well-known Heisenberg limit. In this paper, we review the entanglement-assisted protocol of postselected weak measurement in detail, and study its robustness against technical noises. We focus on readout errors. Readout errors can greatly degrade the performance of postselected weak measurement, especially when the readout error probability is comparable to the postselection probability. We show that entanglement can significantly reduce the two main detrimental effects of readout errors: inaccuracy in the measurement result, and the loss of Fisher information. We extend the protocol by introducing a majority vote scheme to postselection to further compensate for readout errors. With a proper threshold, almost no Fisher information will be lost. These results demonstrate the effectiveness of entanglement in protecting postselected weak measurement against readout errors.

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