Department of Electrical and Computer Engineering, National University of Singapore, Singapore.
Phys Rev Lett. 2011 Dec 30;107(27):270402. doi: 10.1103/PhysRevLett.107.270402. Epub 2011 Dec 29.
In astronomy, interferometry of light collected by separate telescopes is often performed by physically bringing the optical paths together in the form of Young's double-slit experiment. Optical loss severely limits the efficiency of this so-called direct detection method, motivating the fundamental question of whether one can achieve a comparable performance using separate optical measurements at the two telescopes before combining the measurement results. Using quantum mechanics and estimation theory, here I show that any such spatially local measurement scheme, such as heterodyne detection, is fundamentally inferior to coherently nonlocal measurements, such as direct detection, for estimating the mutual coherence of bipartite thermal light when the average photon flux is low. This surprising result reveals an overlooked signature of quantum nonlocality in a classic optics experiment.
在天文学中，通过将光学路径以 Young 双缝实验的形式物理地组合在一起，通常可以对单独望远镜收集的光进行干涉测量。光学损耗严重限制了这种所谓的直接检测方法的效率，这促使人们提出了一个基本问题，即在将两个望远镜的测量结果组合之前，是否可以使用单独的光学测量在两个望远镜中实现类似的性能。利用量子力学和估计理论，我在这里表明，在平均光子通量较低时，对于估计双部分热光的互相干性，任何这种空间局部测量方案，例如外差检测，与相干非局部测量，例如直接检测相比，本质上都是劣的。这个令人惊讶的结果揭示了经典光学实验中量子非局域性的一个被忽视的特征。
