Park Jiho, Kim Heonoh, Moon Han Seb
Department of Physics, Pusan National University, Geumjeong-Gu, Busan, 46241, South Korea.
Sci Rep. 2022 Mar 31;12(1):5456. doi: 10.1038/s41598-022-09516-y.
The phenomenon of Franson interference with time-energy entangled photon pairs beyond the single-photon coherence length observed upon nonlocal measurement at two space-like separated locations is of particular research interest. Herein, we determine the coherence length of temporally separated pairwise two-photon (TSPT) states of thermal photons emitted from a warm atomic ensemble in Franson-type interferometry, with the setup consisting of two spatially separated unbalanced Michelson interferometers beyond the coherence length of a thermal photon. Using a novel method of square-modulated thermal photons, we show that the sinusoidal Franson-type interference fringe of thermal photons is determined by the presence or absence of TSPT states (corresponding to the time delay between the long and short paths in Franson-type interferometry). We find that the indistinguishability of the TSPT state in the Franson-type interference is independent of the temporal separation of the thermal photons in the TSPT states.
在两个类空分离位置进行非局域测量时观察到的、超出单光子相干长度的时间 - 能量纠缠光子对的弗朗森干涉现象具有特别的研究意义。在此，我们在弗朗森型干涉测量中确定了从温暖原子系综发射的热光子的时间分离成对双光子（TSPT）态的相干长度，该装置由两个空间分离的不平衡迈克尔逊干涉仪组成，其间距超出了热光子的相干长度。通过一种新颖的方波调制热光子方法，我们表明热光子的正弦弗朗森型干涉条纹由TSPT态的存在与否决定（对应于弗朗森型干涉测量中长路径和短路径之间的时间延迟）。我们发现，弗朗森型干涉中TSPT态的不可区分性与TSPT态中热光子的时间分离无关。
