Why the two-pulse photon echo is not a good quantum memory protocol

TL;DR

This paper experimentally demonstrates that the two-pulse photon echo protocol in rare-earth doped crystals is highly efficient, challenging its suitability as a quantum memory, and discusses its limitations and potential benefits for future quantum storage methods.

Contribution

The study provides the first experimental evidence that the two-pulse photon echo can be highly efficient, revealing its limitations and inspiring new quantum memory protocols.

Findings

The two-pulse photon echo is more efficient than previously believed.

It has significant limitations for quantum memory applications.

Potential benefits can guide the development of improved protocols.

Abstract

We consider in this paper a two-pulse photon echo sequence as a potential quantum light storage protocol. It is widely believed that a two-pulse scheme should lead to very low efficiency and is then not relevant for this specific application. We show experimentally by using a Tm${}^{3+}$:YAG crystal that such a protocol is on contrary very efficient and even too efficient to be considered as a good quantum storage protocol. Our experimental work allows us to point out on one side the real limitations of this scheme and on the other side its benefits which can be a source of inspiration to conceive more promising procedures with rare-earth ion doped crystals.