Multiplexed on-demand storage of polarization qubits in a crystal

TL;DR

This paper demonstrates a long-lived, multimode quantum memory for polarization qubits in a rare-earth-ion doped crystal, achieving high fidelity and enhanced rate through temporal multiplexing, advancing quantum communication capabilities.

Contribution

It introduces a method for temporally multiplexed storage of polarization qubits with spin refocusing in a rare-earth crystal, achieving over 0.5 ms storage and improved communication rates.

Findings

Stored 5 polarization qubits simultaneously

Achieved storage fidelity above classical limits

Extended coherence time to over 0.5 milliseconds

Abstract

A long-lived and multimode quantum memory is a key component needed for the development of quantum communication. Here we present temporally multiplexed storage of 5 photonic polarization qubits encoded onto weak coherent states in a rare-earth-ion doped crystal. Using spin refocusing techniques we can preserve the qubits for more than half a millisecond. The temporal multiplexing allows us to increase the effective rate of the experiment by a factor of 5, which emphasizes the importance of multimode storage for quantum communication. The fidelity upon retrieval is higher than the maximum classical fidelity achievable with qubits encoded onto single photons and we show that the memory fidelity is mainly limited by the memory signal-to-noise ratio. These results show the viability and versatility of long-lived, multimode quantum memories based on rare-earth-ion doped crystals.