论文标题
通过量子广播的联合测量
Joint measurements through quantum broadcasting
论文作者
论文摘要
我们通过在投入量子状态下使用广播渠道进行操作来研究生成关节测量，然后在广播渠道的两个输出上进行局部测量。尽管由于不可能进行完美的广播或克隆，因此该方案无法为所有成对的量子观察物生成完美的共同观察力，但我们研究了预期的共同观察物和局部测量，可以执行该过程。对于局部尖锐的观察值，只要预期的关节可观察的可观察到由局部尖锐可观察物的张量产物主导，这总是可能的。该结果不包括与自己连续尖锐可观察物的联合测量的情况，我们确实表明这是不可能通过广播产生的。我们还为局部嘈杂的可观察物和预期的观测值提供了必要和足够的条件，以使广播方案成功，当局部可观察物是尖锐可观察物和白噪声的凸混合物时，它们很容易被检查。我们还研究了在对称性存在下的局部模糊可观察物的广播。最后，我们介绍了测量联合可观察物的方案，在该方案中，我们可以访问广播，本地测量和后处理，并表征这种情况下最机智的本地测量结果。
We study generating joint measurements by operating on the input quantum state with a broadcasting channel followed by local measurements on the two outputs of the broadcasting channel. Although, due to perfect broadcasting or cloning being impossible, this scheme cannot generate perfect joint observables for all pairs of quantum observables, we study for what intended joint observables and local measurements this procedure can be carried out. For local sharp observables this is always possible as long as the intended joint observable is dominated by the tensor product of the local sharp observables. This result excludes the case of joint measurements of continuous sharp observables with themselves which we indeed show to be impossible to be generated through broadcasting. We also derive necessary and sufficient conditions for the success of the broadcasting scheme for local noisy observables and intended joint observables which are easily checked when the local observables are convex mixtures of sharp observables and white noise. We also study broadcasting of local fuzzy observables in the presence of symmetries. Finally we introduce the scenario of measuring joint observables where we have access to broadcasting, local measurements and post-processing and characterize the most resourceful local measurements in this setting.
