Pauli blocking of stimulated emission in a degenerate Fermi gas

TL;DR

This paper demonstrates that Pauli blockade affects not only spontaneous emission but also coherent processes in a degenerate Fermi gas, leading to a sub-Doppler narrowing of a forbidden transition, with implications for quantum control of fermionic systems.

Contribution

It reveals the influence of Pauli blockade on coherently driven transitions in a Fermi gas, extending understanding beyond spontaneous emission suppression.

Findings

Observation of sub-Doppler narrowing due to Pauli blockade

Breaking coherence lifts the narrowing effect

Pauli blockade influences transition profiles in fermionic systems

Abstract

The Pauli exclusion principle in quantum mechanics has a profound influence on the structure of matter and on interactions between fermions. Almost 30 years ago it was predicted that the Pauli exclusion principle could lead to a suppression of spontaneous emission, and only recently several experiments confirmed this phenomenon. Here we report that this so-called Pauli blockade not only affects incoherent processes but also, more generally, coherently driven systems. It manifests itself as an intriguing sub-Doppler narrowing of a doubly-forbidden transition profile in an optically trapped Fermi gas of $^3\mathrm{He}$. By actively pumping atoms out of the excited state, we break the coherence of the excitation and lift the narrowing effect, confirming the influence of Pauli blockade on the transition profile. This new insight into the interplay between quantum statistics and coherent driving is a promising development for future applications involving fermionic systems.