Long-lived circular Rydberg states of laser-cooled rubidium atoms in a cryostat

Abstract

The exquisite properties of Rydberg levels make them particularly appealing for emerging quantum technologies. The lifetime of low-angular-momentum laser-accessible levels is however limited to a few 100μs by optical transitions and microwave blackbody radiation (BBR) induced transfers at room temperature. A considerable improvement would be obtained with the few 10ms lifetime of circular Rydberg levels in a cryogenic environment reducing the BBR temperature. We demonstrate the preparation of long-lived circular Rydberg levels of laser-cooled rubidium atoms in a cryostat. We observe a 3.7ms lifetime for the circular level of principal quantum number n=52. By monitoring the transfers between adjacent circular levels, we estimate in situ the microwave BBR temperature to be (11±2)K. The measured atomic coherence time (270μs) is limited here only by technical magnetic field fluctuations. This work opens interesting perspectives for quantum simulation and sensing with cold circular Rydberg atoms.