On-demand Integrated Quantum Memory for Polarization Qubits

TL;DR

This paper demonstrates a reliable on-demand integrated quantum memory for polarization qubits using a Eu-doped crystal, achieving high fidelity and bandwidth, advancing quantum network development.

Contribution

It introduces a novel integrated quantum memory for polarization qubits with uniform absorption and high fidelity, overcoming longstanding polarization-dependent storage challenges.

Findings

Achieved 99.4% fidelity in qubit storage

Demonstrated a 10 MHz storage bandwidth

Used a Eu-doped Y2SiO5 crystal with a new pump sequence

Abstract

Photonic polarization qubits are widely used in quantum computation and quantum communication due to the robustness in transmission and the easy qubit manipulation. An integrated quantum memory for polarization qubits is a fundamental building block for large-scale integrated quantum networks. However, on-demand storing polarization qubits in an integrated quantum memory is a long-standing challenge due to the anisotropic absorption of solids and the polarization-dependent features of microstructures. Here we demonstrate a reliable on-demand quantum memory for polarization qubits, using a depressed-cladding waveguide fabricated in a 151Eu3+: Y2SiO5 crystal. The site-2 151Eu3+ ions in Y2SiO5 crystal provides a near-uniform absorption for arbitrary polarization states and a new pump sequence is developed to prepare a wideband and enhanced absorption profile. A fidelity of 99.4\pm0.6% is obtained for the qubit storage process with an input of 0.32 photons per pulse, together with a storage bandwidth of 10 MHz. This reliable integrated quantum memory for polarization qubits reveals the potential for use in the construction of integrated quantum networks.