Schack Rüdiger
Department of Mathematics, Royal Holloway, University of London, Egham, Surrey TW20 0EX UK.
Int J Theor Phys (Dordr). 2024;63(10):254. doi: 10.1007/s10773-024-05790-w. Epub 2024 Oct 5.
In the QBist approach to quantum mechanics, a measurement is an action an agent takes on the world external to herself. A measurement device is an extension of the agent and both measurement outcomes and their probabilities are personal to the agent. According to QBism, nothing in the quantum formalism implies that the quantum state assignments of two agents or their respective measurement outcomes need to be mutually consistent. Recently, Khrennikov has claimed that QBism's personalist theory of quantum measurement is invalidated by Ozawa's so-called intersubjectivity theorem. Here, following Stacey, we refute Khrennikov's claim by showing that it is not Ozawa's mathematical theorem but an additional assumption made by Khrennikov that QBism is incompatible with. We then address the question of intersubjective agreement in QBism more generally. Even though there is never a necessity for two agents to agree on their respective measurement outcomes, a QBist agent can strive to create conditions under which she would expect another agent's reported measurement outcome to agree with hers. It turns out that the assumptions of Ozawa's theorem provide an example for just such a condition.
在量子力学的量子贝叶斯方法中，测量是主体对其自身之外的世界采取的一种行动。测量装置是主体的一种延伸，测量结果及其概率对于主体而言都是个人化的。根据量子贝叶斯理论，量子形式体系中没有任何内容表明两个主体的量子态赋值或其各自的测量结果需要相互一致。最近，克莱尼科夫声称量子贝叶斯的量子测量个人主义理论因小泽的所谓主体间性定理而无效。在此，我们遵循斯泰西的观点，通过表明与量子贝叶斯不相容的不是小泽的数学定理，而是克莱尼科夫所做的一个额外假设，来反驳克莱尼科夫的说法。然后，我们更全面地探讨量子贝叶斯中的主体间一致性问题。尽管两个主体从来没有必要就其各自的测量结果达成一致，但一个量子贝叶斯主体可以努力创造条件，使得她预期另一个主体报告的测量结果会与她自己的一致。事实证明，小泽定理的假设恰好提供了这样一种条件的示例。
