Adamson R B A, Shalm L K, Mitchell M W, Steinberg A M
Centre for Quantum Information and Quantum Control, Institute for Optical Sciences, Department of Physics, 60 St. George St., University of Toronto, Toronto, Ontario, Canada, M5S 1A7.
Phys Rev Lett. 2007 Jan 26;98(4):043601. doi: 10.1103/PhysRevLett.98.043601. Epub 2007 Jan 22.
We address the problem of completely characterizing multiparticle states including loss of information to unobserved degrees of freedom. In systems where nonclassical interference plays a role, such as linear-optics quantum gates, such information can degrade interference in two ways, by decoherence and by distinguishing the particles. Distinguishing information, often the limiting factor for quantum optical devices, is not correctly described by previous state-reconstruction techniques, which account only for decoherence. We extend these techniques and find that a single modified density matrix can completely describe partially coherent, partially distinguishable states. We use this observation to experimentally characterize two-photon polarization states in single-mode optical fiber.
我们研究了完全表征多粒子态的问题，包括信息丢失到未观测自由度的情况。在非经典干涉起作用的系统中，例如线性光学量子门，此类信息会以两种方式降低干涉，即通过退相干和通过区分粒子。区分信息通常是量子光学器件的限制因素，先前的态重构技术未能正确描述它，这些技术仅考虑了退相干。我们扩展了这些技术，发现单个修正的密度矩阵可以完全描述部分相干、部分可区分的态。我们利用这一观察结果通过实验表征了单模光纤中的双光子偏振态。
