Efficient optical pumping and high optical depth in a hollow-core photonic-crystal fibre for a broadband quantum memory

TL;DR

This paper demonstrates efficient optical pumping and high optical depth in a hollow-core photonic-crystal fibre with warm atomic vapour, advancing the development of broadband, room-temperature quantum memories integrated into fibre systems.

Contribution

It introduces a large-core kagome-structured hollow-core fibre for quantum memory, achieving high optical depth and efficient atomic state preparation at room temperature for the first time.

Findings

90% atomic ground state preparation efficiency

Optical depths of 3×10^4 achieved

Narrow homogeneous linewidths without transit-time broadening

Abstract

The generation of large multiphoton quantum states - for applications in computing, metrology, and simulation - requires a network of high-efficiency quantum memories capable of storing broadband pulses. Integrating these memories into a fibre offers a number of advantages towards realising this goal: strong light-matter coupling at low powers, simplified alignment, and compatibility with existing photonic architectures. Here, we introduce a large-core kagome-structured hollow-core fibre as a suitable platform for an integrated fibre-based quantum memory with a warm atomic vapour. We demonstrate, for the first time, efficient optical pumping in a hollow-core photonic-crystal fibre with a warm atomic vapour, where (90 $\pm$ 1)% of atoms are prepared in the ground state. We measure high optical depths (3$\times 10^{4}$) and, also, narrow homogeneous linewidths that do not exhibit significant transit-time broadening. Our results establish that kagome fibres are suitable for implementing a broadband, room-temperature quantum memory.