Quantum memory on a nanophotonic silicon chip

TL;DR

This paper demonstrates a compact, high-fidelity quantum memory on a silicon chip using erbium-doped waveguides, achieving programmable delays exceeding 1 microsecond with a small footprint, advancing integrated quantum photonics.

Contribution

The authors realize on-chip quantum memories with erbium-doped silicon waveguides, showing programmable delays over 1 microsecond in a scalable silicon photonics platform.

Findings

Achieved light storage with 44.2 MHz bandwidth.

Demonstrated programmable delay exceeding 1 microsecond.

Preserved phase of read-out light with over 91% visibility.

Abstract

Integrated photonic circuits offer great promise for quantum technologies. However, due to the rapid propagation of light, many envisioned applications require efficient on-chip quantum memories with a programmable delay, compact footprint, and high fidelity. Implementing this based on standard semiconductor processing technology is an outstanding challenge. Here, we realize such memories using erbium-doped silicon waveguides, fabricated as part of a multi-wafer project by a nanophotonic foundry. We demonstrate light storage with a $44.2(9)\ \text{MHz}$ bandwidth and a programmable delay exceeding $1\ \mu \text{s}$ in a device with a footprint of only $1.5\times 10^{-2}\ \text{mm}^2$, outperforming on-chip delay lines by many orders of magnitude. The phase of the read-out light field is preserved with a visibility of $91.3(30)\ \%$. The efficiency of $1.89(28)\times 10^{-8}$ can be improved in future devices through resonator enhancement and higher dopant concentrations. With this, the demonstrated approach will pave the way towards applications in photonic quantum computing based on scalable silicon processing technology.