论文标题
侧身看量子相关的忠诚
A sideways look at faithfulness for quantum correlations
论文作者
论文摘要
尽管试图将因果模型的课程应用于纠缠两分量子系统的典型相关性，但木材和斯派肯人认为，任何旨在解释这些相关性的因果模型都必须进行微调。也就是说，它必须违反忠实的假设。忠诚的假设是一种简约的原则，其背后的直觉是基本的和引人注目的：当一对事件的发生之间不存在统计相关性时，我们没有理由假设它们之间存在因果关系。本文试图破坏量子背景下忠实假设的合理性。我认为，由单个光子依次通过两个偏光剂通过单个光子传递的“侧面两部分量子系统”之间的对称关系，我认为木材和Spekkens的分析同样适用于该侧向系统。如果这是正确的，那么对普通纠缠的量子系统的木材和Spekkens认可的后果也等于拒绝侧面的因果解释，即单光子系统。除非拒绝这种因果解释是足够合理的，否则看来侧向系统是微调的，因此违反了普通纠缠系统中忠实的行为可能比首先想到的更可容忍。因此，将古典的“无需微调”放在量子领域可能太匆忙了。
Despite attempts to apply the lessons of causal modelling to the observed correlations typical of entangled bipartite quantum systems, Wood and Spekkens argue that any causal model purporting to explain these correlations must be fine tuned; that is, it must violate the assumption of faithfulness. The faithfulness assumption is a principle of parsimony, and the intuition behind it is basic and compelling: when no statistical correlation exists between the occurrences of a pair of events, we have no reason for supposing there to be a causal connection between them. This paper is an attempt to undermine the reasonableness of the assumption of faithfulness in the quantum context. Employing a symmetry relation between an entangled bipartite quantum system and a `sideways' quantum system consisting of a single photon passing sequentially through two polarisers, I argue that Wood and Spekkens' analysis applies equally to this sideways system. If this is correct, then the consequence endorsed by Wood and Spekkens for an ordinary entangled quantum system amounts to a rejection of a causal explanation in the sideways, single photon system, too. Unless rejecting this causal explanation can be sufficiently justified, then it looks as though the sideways system is fine tuned, and so a violation of faithfulness in the ordinary entangled system may be more tolerable than first thought. Thus extending the classical `no fine-tuning' principle of parsimony to the quantum realm may well be too hasty.
