Deterministic generation and partial retrieval of a spin-wave excitation in an atomic ensemble

TL;DR

This paper demonstrates near-deterministic generation of a spin-wave excitation in an atomic ensemble with a feedback scheme, and explores partial retrievals, advancing quantum repeater technology.

Contribution

It introduces a feedback-based method for near-unity probability spin-wave generation and demonstrates partial quantum regime retrievals in an atomic ensemble.

Findings

Achieved near-unity probability spin-wave excitation.

Demonstrated partial retrievals with quantum regime anti-correlation.

Extended coherence time using magnetic-field-insensitive transitions.

Abstract

In this paper, we report a generation of a spin-wave excitation (SWE) with a near-unity () probability in a given time (~730). Such deterministic generation relies on a feedback scheme with a millisecond quantum memory. The millisecond memory is achieved by maximizing the wavelength of the spin wave and storing the SWE as the magnetic-field-insensitive transition. We then demonstrate partial retrievals of the spin wave by applying a first read pulse whose area is smaller than the value of . The remained SWE is fully retrieved by a second pulse. Anti-correlation function between the detections in the first and second readouts has been measured, which shows that the partial-retrieval operation on the SWE is in the quantum regime. The presented experiment represents an important step towards the realization of the improved DLCZ quantum repeater protocol proposed in Phys. Rev. A 77, 062301 (2008).