Quantum Storage of a Photonic Polarization Qubit in a Solid

TL;DR

This paper demonstrates the successful quantum storage and retrieval of photonic polarization qubits in a solid state device using a praseodymium doped crystal, achieving high fidelity and efficiency.

Contribution

It introduces a method for storing polarization qubits in a solid state memory with high fidelity, extending quantum memory capabilities to polarization encoding.

Findings

Storage and retrieval efficiency of 10%

Conditional fidelity exceeds 95% for mu=0.4

Storage duration of 500 ns

Abstract

We report on the quantum storage and retrieval of photonic polarization quantum bits onto and out of a solid state storage device. The qubits are implemented with weak coherent states at the single photon level, and are stored for 500 ns in a praseodymium doped crystal with a storage and retrieval efficiency of 10%, using the atomic frequency comb scheme. We characterize the storage by using quantum state tomography, and find that the average conditional fidelity of the retrieved qubits exceeds 95% for a mean photon number mu=0.4. This is significantly higher than a classical benchmark, taking into account the Poissonian statistics and finite memory efficiency, which proves that our device functions as a quantum storage device for polarization qubits, even if tested with weak coherent states. These results extend the storage capabilities of solid state quantum memories to polarization encoding, which is widely used in quantum information science.