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arXiv 0905.4222quant-phgr-qchep-thmath-phmath.MP
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量子测量中的不可判定性和结果问题

Undecidability and the problem of outcomes in quantum measurements

Rodolfo Gambini, Luis Pedro Garcia Pintos, Jorge Pullin

摘要:

我们认为,这是根本不可能恢复量子叠加的信息时,一个系统已经与足够大的自由度的环境相互作用。这是因为重力对测量的准确性施加了根本性的限制。这导致了不可判定性的概念:由于基本限制,没有办法告诉量子系统是酉演化的还是遭受波函数坍缩的。这反过来又为量子测量的结果问题提供了一个解决方案,为定义事件何时发生提供了一个明确的标准。我们详细分析的例子中的两种情况下,在原则上可以恢复有关量子相干性的信息:a)“复兴”的相干性的系统与环境的相互作用和b)测量的系统加设备加环境的全球可观测量。我们在例子中表明,由于引力和量子力学在测量中的基本限制,既阻止了复苏的发生,也阻止了对全局可观测量的测量。因此可以说,新出现的图像为量子力学中的测量问题提供了一个完整的解决方案。

英文摘要:

We argue that it is fundamentally impossible to recover information about quantum superpositions when a system has interacted with a sufficiently large number of degrees of freedom of the environment. This is due to the fact that gravity imposes fundamental limitations on how accurate measurements can be. This leads to the notion of undecidability: there is no way to tell, due to fundamental limitations, if a quantum system evolved unitarily or suffered wavefunction collapse. This in turn provides a solution to the problem of outcomes in quantum measurement by providing a sharp criterion for defining when an event has taken place. We analyze in detail in examples two situations in which in principle one could recover information about quantum coherence: a) "revivals" of coherence in the interaction of a system with the environment and b) the measurement of global observables of the system plus apparatus plus environment. We show in the examples that the fundamental limitations due to gravity and quantum mechanics in measurement prevent both revivals from occurring and the measurement of global observables. It can therefore be argued that the emerging picture provides a complete resolution to the measurement problem in quantum mechanics.

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