Longhi S
Opt Lett. 2017 Jul 1;42(13):2551-2554. doi: 10.1364/OL.42.002551.
Time reversal is one of the most intriguing yet elusive wave phenomena of major interest in different areas of classical and quantum physics. Time reversal requires in principle to flip the sign of the Hamiltonian of the system, leading to a revival of the initial state (Loschmidt echo). Here it is shown that Loschmidt echo of photons can be observed in an optical setting without resorting to reversal of the Hamiltonian. We consider photonic propagation in a binary waveguide lattice and show that, by exchanging the two sublattices after some propagation distance, a Loschmidt echo can be observed. Examples of Loschmidt echoes for single photon and NOON states are given in one- and two-dimensional waveguide lattices.
时间反演是经典物理和量子物理不同领域中最引人入胜却又难以捉摸的主要波动现象之一。原则上，时间反演需要翻转系统哈密顿量的符号，从而导致初始状态的复兴（洛施密特回波）。本文表明，无需借助哈密顿量的反转，就能在光学环境中观测到光子的洛施密特回波。我们考虑光子在二元波导晶格中的传播，并表明，在经过一定传播距离后交换两个子晶格，就能观测到洛施密特回波。在一维和二维波导晶格中给出了单光子和NOON态的洛施密特回波示例。
