作者：Vincenzo Fiorentino Stefan Weigert
引入了量子理论的无坍缩版本来研究投影公设的作用。我们假设“被动”测量不会更新量子态，而测量结果仍有可能发生，这符合玻恩规则。量子理论的所有其他定义特征，如希尔伯特空间设置，都被保留了下来。由此产生的类量子理论只有一种动力学类型，即幺正演化。被动量子理论与标准量子理论有许多共同之处。其中包括代表性的不确定性关系、不可能动态克隆已知的量子态以及缺乏信号。然而，当协议涉及测量后状态时，会出现显著差异。例如，在无坍缩的情况下，不需要系综来通过被动测量断层摄影上完整的一组可观测量来重建系统的状态——单个系统就可以了。实际上，状态变成了一个可观测量
A collapse-free version of quantum theory is introduced to study the role ofthe projection postulate. We assume “passive” measurements that do not updatequantum states while measurement outcomes still occur probabilistically, inaccordance with Born’s rule. All other defining features of quantum theory,such as the Hilbert space setting, are retained. The resulting quantum-liketheory has only one type of dynamics, namely unitary evolution. Passive quantumtheory shares many features with standard quantum theory. These includepreparational uncertainty relations, the impossibility to dynamically cloneunknown quantum states and the absence of signalling. However, strikingdifferences emerge when protocols involve post-measurement states. For example,in the collapse-free setting, no ensemble is needed to reconstruct the state ofa system by passively measuring a tomographically complete set of observables -a single system will do. Effectively, the state becomes an observable quantity,with implications for both the ontology of the theory and its computationalpower. At the same time, the theory is not locally tomographic and passivemeasurements do not create Bell-type correlations in composite systems.
论文链接：http://arxiv.org/pdf/2303.13411v1
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