Perimeter Institute for Theoretical Physics, Waterloo, Ontario, Canada.
Nat Commun. 2011 Aug 2;2:411. doi: 10.1038/ncomms1416.
According to quantum theory, measurements generate random outcomes, in stark contrast with classical mechanics. This raises the question of whether there could exist an extension of the theory that removes this indeterminism, as suspected by Einstein, Podolsky and Rosen. Although this has been shown to be impossible, existing results do not imply that the current theory is maximally informative. Here we ask the more general question of whether any improved predictions can be achieved by any extension of quantum theory. Under the assumption that measurements can be chosen freely, we answer this question in the negative: no extension of quantum theory can give more information about the outcomes of future measurements than quantum theory itself. Our result has significance for the foundations of quantum mechanics, as well as applications to tasks that exploit the inherent randomness in quantum theory, such as quantum cryptography.
根据量子理论，测量会产生随机结果，这与经典力学形成鲜明对比。这就提出了一个问题，即是否存在一种可以消除这种不确定性的理论扩展，爱因斯坦、波多尔斯基和罗森曾对此表示怀疑。尽管已经证明这是不可能的，但现有结果并不意味着当前的理论提供了最大信息量。在这里，我们更广泛地询问是否可以通过任何对量子理论的扩展来实现任何改进的预测。在假设测量可以自由选择的前提下，我们的回答是否定的：量子理论的任何扩展都不能比量子理论本身提供更多关于未来测量结果的信息。我们的结果对于量子力学的基础以及对于利用量子理论固有的随机性的应用（例如量子密码学）都具有重要意义。
