Non-Markovian Dynamics in Fiber Delay-Line Buffers

Abstract

The non-Markovian effect is studied on a two-photon polarization entangled state, in which one photon from the pair is stored in a fiber delay-line buffer. A model of a photonic qubit coupled to fiber birefringence and a fiber reservoir representing the environment is proposed. Analytically, a non-Markovian probability function is derived for the buffered photon and its paired photon. To verify the probability function, full quantum state tomography of the photon pairs is performed. The probability function fits well with the experimental data and physical values. These results indicate that the quantum system operates slightly above the threshold for a non-Markovian transition. We observe a unique polarization dynamic of the buffered photon. Measures of quantum mutual information are further exploited to study the quantumness of the photon pairs. Werner's well-known separability criterion occurs at a buffer time of about 0.9 ms. These results imply that quantum discord can surpass Werner's criterion, and hence, quantum bi-partite correlation can exist for buffer times greater than 0.9 ms.