论惠勒延迟选择实验中的因果性  

On Causality in Wheeler's Delayed-choice Experiment

作　　者：张君睿 ZHANG Junrui(Department of the History of Science,Tsinghua University,Beijing,100084)

机构地区：[1]清华大学科学史系,北京100084

出　　处：《自然辩证法通讯》2024年第3期58-63,共6页Journal of Dialectics of Nature

摘　　要：本文指出,惠勒延迟选择实验并没有推翻量子力学中的因果关系,它只是推翻了光子自通过第一个分光镜以后,就必须选择一条路径的假设。这是由于分光镜无法对光子所走的路径进行区分,所以当光子通过分光镜时,分光镜的量子态会和光子的叠加态整体形成直积态(分光镜是个幺正算符)。单个光子在通过第一个分光镜后,光子会处于“走上路”和“走右路”的本征态之叠加态中;分光镜并没有对光子进行“测量”,从而导致光子的波函数“塌缩”,使光子要在“走上路”或“走右路”两者中二选一(分光镜并不会导致光子的波函数退相干)。因此,不论后来实验者是否在终点放置第二个分光镜,光子的波函数都是处于两条路径的叠加态,所以,后来的观测操作不会反过来影响过去光子的行为。This research indicates Wheeler's delayed-choice experiment does not imply retrocausality in quantum mechanics.It only disproves the assumption that the photon must decide which path to travel after passing through the first beam splitter because the beam splitter cannot distinguish between the paths taken by the photon.When the photon passes through the beam splitter,the quantum state of the beam splitter forms a product state with the superposition state of the photon as a whole(the beam splitter is a unitary operator).The beam splitter does not cause a photon to decohere,so there is no which-way information stored anywhere in the mirrors(the photon is in a pure superposition instead of a mixed state).Whether or not the experimenter later places a second beam splitter at the end,the wave function of the photon is supported on both paths simultaneously.Therefore,the later operation of the experimenter will not influence the behavior of the past photon retroactively.

关 键 词：惠勒延迟选择实验 量子力学 因果性 

分 类 号：O413[理学—理论物理]