A faithful solid-state spin-wave quantum memory for polarization qubits

TL;DR

This paper demonstrates a high-fidelity, polarization-preserving quantum memory for single-photon qubits using a rare-earth-ion doped crystal and the photon echo protocol, advancing quantum network technology.

Contribution

It introduces a reliable, solid-state quantum memory for polarization qubits with high process fidelity, using a single crystal and the photon echo protocol.

Findings

Achieved a process fidelity of 0.919(24) for single-photon-level qubits.

Implemented a polarization-insensitive quantum memory in a rare-earth-ion crystal.

Demonstrated potential for scalable, transportable quantum networks.

Abstract

Polarization-encoded qubits are particularly useful in quantum information tasks due to the easy transportation in a single spatial and temporal mode, the accurate qubit manipulation and the high robustness against decoherence. Reliable storage of polarization-encoded qubits is essential for the construction of large-scale quantum networks. Here we demonstrate a faithful quantum memory for photonic polarization qubits using the noiseless photon echo protocol implemented in a rare-earth-ion doped crystal (151Eu3+:Y2SiO5). Based on a detailed spectroscopic investigation on the 151Eu3+ ions at the site 2 of Y2SiO5 crystals, the qubit memory is implemented using a single piece of crystal which provides a near-uniform absorption for two orthogonal polarization states. A process fidelity of 0.919(24) is obtained for the storage of qubits carried by single-photon-level coherent pulses, which is beyond the maximal fidelity that can be achieved using the classical measure-and-prepare strategy. This compact device shall provide a useful solution for the construction of a long-lived transportable quantum memory and the memory-based quantum networks.