Rotational Coherence Times of Polar Molecules in Optical Tweezers

TL;DR

This paper demonstrates a significant increase in rotational coherence times of laser-cooled CaF molecules in optical tweezers, reaching nearly half a second with spin-echo, highlighting their potential as high-fidelity qubits.

Contribution

The study reports the first long coherence times for polar molecule qubits in optical tweezers, achieved through polarization tuning and magnetic field optimization.

Findings

Achieved 93 ms rotational coherence time in CaF molecules.

Extended coherence to nearly 0.5 seconds with spin-echo.

Identified residual differential polarizability as a limiting factor.

Abstract

Qubit coherence times are critical to the performance of any robust quantum computing platform. For quantum information processing using arrays of polar molecules, a key performance parameter is the molecular rotational coherence time. We report a 93(7) ms coherence time for rotational state qubits of laser cooled CaF molecules in optical tweezer traps, over an order of magnitude longer than previous systems. Inhomogeneous broadening due to the differential polarizability between the qubit states is suppressed by tuning the tweezer polarization and applied magnetic field to a "magic" angle. The coherence time is limited by the residual differential polarizability, implying improvement with further cooling. A single spin-echo pulse is able to extend the coherence time to nearly half a second. The measured coherence times demonstrate the potential of polar molecules as high fidelity qubits.