论文标题

周期性离散的连续可观察物既不是连续的也不是离散的

Periodic discretized continuous observables are neither continuous nor discrete

论文作者

Silva, Thais L., Rudnicki, Łukasz, Tasca, Daniel S., Walborn, Stephen P.

论文摘要

量子力学的大多数基本特征,例如非本地性和上下文性,都体现在离散的有限维系统中。但是,许多利用这些属性的量子信息任务不能直接适应连续变量的系统。为了访问这些量子功能,可以通过将其不同的值汇总在一起,从而使连续的量子变量离散,从而产生有限数字“ $ d $”结果的观察值。虽然直接测量确实证实了它们明显的离散特征,但在这里,我们采用了称为相互无偏见的量子物理学的显着特征,以表明这种粗粒的可观察物在某种意义上既不是连续也不是离散的。根据$ d $,可观察物可以复制离散或连续行为,或者都不是。为了说明这些结果,我们提供了一个构建此类测量结果的示例,并在光学实验中采用了该结果,证实了在连续变量系统中存在四个相互无偏的测量结果,其中$ d = 3 $结果超过了相互无偏见的连续可变可观察物的数量。

Most of the fundamental characteristics of quantum mechanics, such as non-locality and contextuality, are manifest in discrete, finite-dimensional systems. However, many quantum information tasks that exploit these properties cannot be directly adapted to continuous-variable systems. To access these quantum features, continuous quantum variables can be made discrete by binning together their different values, resulting in observables with a finite number "$d$" of outcomes. While direct measurement indeed confirms their manifestly discrete character, here we employ a salient feature of quantum physics known as mutual unbiasedness to show that such coarse-grained observables are in a sense neither continuous nor discrete. Depending on $d$, the observables can reproduce either the discrete or the continuous behavior, or neither. To illustrate these results, we present an example for the construction of such measurements and employ it in an optical experiment confirming the existence of four mutually unbiased measurements with $d = 3$ outcomes in a continuous variable system, surpassing the number of mutually unbiased continuous variable observables.

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