Handsteiner Johannes, Friedman Andrew S, Rauch Dominik, Gallicchio Jason, Liu Bo, Hosp Hannes, Kofler Johannes, Bricher David, Fink Matthias, Leung Calvin, Mark Anthony, Nguyen Hien T, Sanders Isabella, Steinlechner Fabian, Ursin Rupert, Wengerowsky Sören, Guth Alan H, Kaiser David I, Scheidl Thomas, Zeilinger Anton
Institute for Quantum Optics and Quantum Information (IQOQI), Austrian Academy of Sciences, Boltzmanngasse 3, 1090 Vienna, Austria.
Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
Phys Rev Lett. 2017 Feb 10;118(6):060401. doi: 10.1103/PhysRevLett.118.060401. Epub 2017 Feb 7.
Bell's theorem states that some predictions of quantum mechanics cannot be reproduced by a local-realist theory. That conflict is expressed by Bell's inequality, which is usually derived under the assumption that there are no statistical correlations between the choices of measurement settings and anything else that can causally affect the measurement outcomes. In previous experiments, this "freedom of choice" was addressed by ensuring that selection of measurement settings via conventional "quantum random number generators" was spacelike separated from the entangled particle creation. This, however, left open the possibility that an unknown cause affected both the setting choices and measurement outcomes as recently as mere microseconds before each experimental trial. Here we report on a new experimental test of Bell's inequality that, for the first time, uses distant astronomical sources as "cosmic setting generators." In our tests with polarization-entangled photons, measurement settings were chosen using real-time observations of Milky Way stars while simultaneously ensuring locality. Assuming fair sampling for all detected photons, and that each stellar photon's color was set at emission, we observe statistically significant ≳7.31σ and ≳11.93σ violations of Bell's inequality with estimated p values of ≲1.8×10^{-13} and ≲4.0×10^{-33}, respectively, thereby pushing back by ∼600 years the most recent time by which any local-realist influences could have engineered the observed Bell violation.
贝尔定理指出，量子力学的某些预测无法由局域实在论理论重现。这种冲突由贝尔不等式来表述，贝尔不等式通常是在测量设置的选择与任何其他可能因果影响测量结果的因素之间不存在统计相关性的假设下推导出来的。在以往的实验中，通过确保经由传统“量子随机数发生器”选择测量设置与纠缠粒子的产生在类空上分离，解决了“选择自由”问题。然而，这留下了一种可能性，即直到每次实验尝试前仅仅几微秒，一个未知原因同时影响了设置选择和测量结果。在此，我们报告一项贝尔不等式的新实验测试，该测试首次使用遥远的天体源作为“宇宙设置发生器”。在我们对偏振纠缠光子的测试中，利用对银河系恒星的实时观测选择测量设置，同时确保局域性。假设对所有探测到的光子进行公平采样，并且每个恒星光子的颜色在发射时就已确定，我们分别观测到对贝尔不等式具有统计显著的≳7.31σ和≳11.93σ的违背，估计的p值分别为≲1.8×10⁻¹³和≲4.0×10⁻³³，从而将任何局域实在论影响可能导致观测到的贝尔违背的最近时间推前了约600年。
