A quantum memory at telecom wavelengths

TL;DR

This paper demonstrates a mechanical quantum memory operating at telecom wavelengths with a 2 ms energy decay time, using nanofabricated resonators as transducers and memory elements for quantum communication.

Contribution

It introduces a novel optical scheme to create superposition states in a mechanical quantum memory at telecom wavelengths, achieving long coherence times.

Findings

Energy decay time of approximately 2 ms.

Coherence times between 15 and 112 microseconds.

Successful creation of superposition states with arbitrary ratios.

Abstract

Nanofabricated mechanical resonators are gaining significant momentum among potential quantum technologies due to their unique design freedom and independence from naturally occurring resonances. With their functionality being widely detached from material choice, they constitute ideal tools to be used as transducers, i.e. intermediaries between different quantum systems, and as memory elements in conjunction with quantum communication and computing devices. Their capability to host ultra-long lived phonon modes is particularity attractive for non-classical information storage, both for future quantum technologies as well as for fundamental tests of physics. Here we demonstrate such a mechanical quantum memory with an energy decay time of $T_1\approx2$ ms, which is controlled through an optical interface engineered to natively operate at telecom wavelengths. We further investigate the coherence of the memory, equivalent to the dephasing $T_2^*$ for qubits, which exhibits a power dependent value between 15 and 112 $\mu$s. This demonstration is enabled by a novel optical scheme to create a superposition state of $\rvert{0}\rangle+\rvert{1}\rangle$ mechanical excitations, with an arbitrary ratio between the vacuum and single phonon components.