Fig. 2: The evolution of coherence for three initial quantum states in the \({{{{{{{\mathcal{P}}}}}}}}{{{{{{{\mathcal{T}}}}}}}}\)-symmetric system.
From: Experimental demonstration of coherence flow in PT- and anti-PT-symmetric systems
a The initial state \(\left|H\right\rangle\), b the initial state \((\left|H\right\rangle +\left|V\right\rangle )/\sqrt{2}\), and c the inital state \((\left|H\right\rangle +\sqrt{3}\left|V\right\rangle )/2\). In a–c, the periodic oscillation (coherence periodic backflow) happens when a = 0.31 (blue curve) and a = 0.47 (red curve) (the \({{{{{{{\mathcal{P}}}}}}}}{{{{{{{\mathcal{T}}}}}}}}\) symmetry unbroken regime), whereas the phenomenon of stable value (PSV) of coherence occurs when a = 1.5 (black curve) and a = 2.8 (green curve) (the \({{{{{{{\mathcal{P}}}}}}}}{{{{{{{\mathcal{T}}}}}}}}\) symmetry broken regime). In a–c, T = 3.30 for a = 0.31 and T = 3.56 for a = 0.47. In a, SV = 0.67 for a = 1.5 and SV = 0.36 for a = 2.8. In b, SV = 0.67 for a = 1.5 and SV = 0.36 for a = 2.8. In c, SV = 0.67 for a = 1.5 and SV = 0.36 for a = 2.8. “SV” means stable value. All curves are theoretical results, whereas the dots are the experimental data. The experimental errors of one standard deviation (1 SD) are estimated from the statistical variation of photon counts, which satisfy the Poisson distribution.
