Long lifetime and high-fidelity quantum memory of photonic polarization qubit by lifting Zeeman degeneracy

TL;DR

This paper demonstrates a millisecond-long, high-fidelity quantum memory for photonic polarization qubits using an EIT-based system with a magnetic field to lift Zeeman degeneracy, significantly improving storage duration and fidelity.

Contribution

The study introduces a method to store photonic polarization qubits with extended lifetime and high fidelity by employing magnetic-field-insensitive spin waves in cold atoms.

Findings

Achieved 98.6% fidelity at 200 microseconds

Achieved 78.4% fidelity at 4.5 milliseconds

Extended quantum memory lifetime significantly compared to previous methods

Abstract

Long-lived and high-fidelity memory for photonic polarization qubit (PPQ) is crucial for constructing quantum networks. Here we present an EIT-based millisecond storage system in which a moderate magnetic field is applied on a cold-atom cloud to lift Zeeman degeneracy. PPQ states are stored as two magnetic-field-insensitive spin waves. Especially, the influence of magnetic-field-sensitive spin waves on the storage performances is almost totally avoided. The measured average fidelities of polarization states are 98.6% at 200 us and 78.4% at 4.5 ms, respectively.