Elimination of noise in optically rephased photon echoes

Photon echo is a fundamental tool for the manipulation of electromagnetic fields. Unavoidable spontaneous emission noise is generated in this process due to the strong rephasing pulse, which limits the achievable signal-to-noise ratio and represents a fundamental obstacle towards their applications in the quantum regime. Here we propose a noiseless photon-echo protocol based on a four-level atomic system. We implement this protocol in a Eu3+:Y2SiO5 crystal to serve as an optical quantum memory. A storage fidelity of 0.9520.018 is obtained for time-bin qubits encoded with single-photon-level coherent pulses, which is far beyond the maximal fidelity achievable using the classical measure-and-prepare strategy. In this work, the demonstrated noiseless photon-echo quantum memory features spin-wave storage, easy operation and high storage fidelity, which should be easily extended to other physical systems. Photon echo techniques are difficult to implement in the quantum regime due to coherent and spontaneous emission noise. Here, the authors propose a low-noise photon-echo quantum memory approach based on all-optical control in a four-level system, and demonstrate it using a Eu3+:Y2SiO5 crystal.

Automated summary

Photon echo is a fundamental tool for manipulating electromagnetic fields, but is limited by spontaneous emission noise. A proposed noiseless photon-echo protocol based on a four-level atomic system demonstrates high storage fidelity in an optical quantum memory setup using a Eu3+:Y2SiO5 crystal. This technique features spin-wave storage, easy operation, and potential for extension to other physical systems.