Ultracold molecules for quantum simulation: rotational coherences in CaF and RbCs

TL;DR

This paper demonstrates coherent rotational state control in ultracold CaF and RbCs molecules, achieving millisecond-scale coherence times crucial for quantum simulation applications.

Contribution

It develops microwave control techniques and investigates coherence properties of two ultracold molecular species for quantum simulation.

Findings

Achieved Ramsey fringe spacings of ~1 kHz.

Measured coherence times of 0.61 ms for CaF.

Measured coherence times of 0.75 ms for RbCs.

Abstract

We explore the uses of ultracold molecules as a platform for future experiments in the field of quantum simulation, focusing on two molecular species, $^{40}$Ca$^{19}$F and $^{87}$Rb$^{133}$Cs. We report the development of coherent quantum state control using microwave fields in both molecular species; this is a crucial ingredient for many quantum simulation applications. We demonstrate proof-of-principle Ramsey interferometry measurements with fringe spacings of $\sim 1~\rm kHz$ and investigate the dephasing time of a superposition of $N=0$ and $N=1$ rotational states when the molecules are confined. For both molecules, we show that a judicious choice of molecular hyperfine states minimises the impact of spatially varying transition-frequency shifts across the trap. For magnetically trapped $^{40}$Ca$^{19}$F we use a magnetically insensitive transition and observe a coherence time of 0.61(3) ms. For optically trapped $^{87}$Rb$^{133}$Cs we exploit an avoided crossing in the AC Stark shift and observe a maximum coherence time of 0.75(6) ms.