近日，挪威奥斯陆大学科技系统系的Jan Gulla与物理系的Johannes Skaar等人合作并取得一项新进展。经过不懈努力，他们揭示实现单光子的极限范围。相关研究成果已于2023年12月13日在国际知名学术期刊《物理评论A》上发表。
为了量化可实现的光学状态与一维目标单光子的接近程度，研究人员提出了两种自然但不相容的方法来指定目标状态。一种方法是将目标状态表示为一个选择的正频谱的光子，另一种方法是将目标状态描述为一个选择的正时间脉冲的非物理光子。结果表明，对于足够短的目标脉冲，最接近的可实现状态包含大量的多光子成分。研究人员推导出了最大保真度的上界和下界，并分别表示为负时间或负频率下目标状态尾部大小的函数。此外，他们还将边界推广到任意光子数态。
据悉，精确的单光子不能按需产生，因为它们的尾部是无限的。
附：英文原文
Title: Limits for realizing single photons
Author: Jan Gulla, Kai Ryen, Johannes Skaar
Issue&Volume: 2023/12/13
Abstract: Exact single photons cannot be generated on demand due to their infinite tails. To quantify how close realizable optical states can be to some target single photon in one dimension, we argue that there are two natural but incompatible ways to specify the target state. Either it can be expressed as a photon with a chosen positive-frequency spectrum, or it can be described as an (unphysical) photon in a chosen positive-time pulse. The results show that for sufficiently short target pulses, the closest realizable states contain substantial multiphoton components. Upper and lower bounds for the maximum fidelity are derived and are expressed as functions of the size of the target states tail, for negative time or negative frequency, respectively. We also generalize the bounds to arbitrary photon-number states.
DOI: 10.1103/PhysRevA.108.063708
Source: https://journals.aps.org/pra/abstract/10.1103/PhysRevA.108.063708
来源：科学网 小柯机器人