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arXiv 1107.4646quant-ph
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无源单轨线性光学量子计算的不通过定理

No-go theorem for passive single-rail linear optical quantum computing

Lian-Ao Wu, Philip Walther, Daniel A. Lidar

摘要:

光子量子系统是量子计算机最有前途的体系结构之一。众所周知,对于双轨光子,有效的非线性和接近确定性的非平凡两量子比特门可以通过测量过程和引入辅助光子来实现。虽然原则上这为可扩展的线性光学量子计算开辟了一条合法的道路,但技术要求仍然非常具有挑战性,因此正在积极研究其他光学编码。另一种选择是使用单轨编码光子,其中可以确定性地产生纠缠态。在这里,我们证明,即使是这样的系统,通用的光学量子计算只使用无源光学元件,如分束器和移相器是不可能的。这个不通过定理证明了即使使用额外的辅助模式和任意数量的光子,光子聚束也不能被被动地抑制。我们的结果为光量子计算机的设计提供了有益的指导。

英文摘要:

Photonic quantum systems are among the most promising architectures for quantum computers. It is well known that for dual-rail photons effective non-linearities and near-deterministic non-trivial two-qubit gates can be achieved via the measurement process and by introducing ancillary photons. While in principle this opens a legitimate path to scalable linear optical quantum computing, the technical requirements are still very challenging and thus other optical encodings are being actively investigated. One of the alternatives is to use single-rail encoded photons, where entangled states can be deterministically generated. Here we prove that even for such systems universal optical quantum computing using only passive optical elements such as beam splitters and phase shifters is not possible. This no-go theorem proves that photon bunching cannot be passively suppressed even when extra ancilla modes and arbitrary number of photons are used. Our result provides useful guidance for the design of optical quantum computers.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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