Freezing motion-induced dephasing in an atomic-ensemble quantum memory

TL;DR

This paper introduces a novel technique to eliminate motion-induced dephasing in atomic-ensemble quantum memories by engineering the spin-wave momentum, significantly extending memory lifetime and preserving high fidelity.

Contribution

The authors develop a coherent manipulation method to zero the spin-wave momentum, effectively freezing motion-induced dephasing in quantum memories.

Findings

Memory lifetime extended to atom cloud expansion limit

High cross-correlation (>20) maintained after manipulation

Dephasing frozen regardless of detection angle

Abstract

Motion-induced dephasing is a dominant decoherence mechanism for atom-gas quantum memories. In this paper, we develop a new coherent manipulation technique which enables arbitrary engineering of the spin-wave momentum with neglectable noise. By zeroing the spin-wave momentum, motion-induced dephasing can be frozen completely. We experimentally demonstrate this scheme with laser-cooled atoms in a DLCZ configuration. By applying the freezing pulses, memory lifetime gets extended significantly to the limit of atom cloud expansion and does not depend on the detection angle anymore. The observed high cross-correlation above 20 proves that high-fidelity memory operation is well preserved after coherent manipulation.