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 $100\,\mu\mathrm{s}$ by optical transitions and microwave blackbody radiation (BBR) induced transfers at room temperature. A considerable improvement would be obtained with the few $10\,\mathrm{ms}$ 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 $3.7\,\mathrm{ms}$ 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 $(11\pm 2)\,\mathrm{K}$. The measured atomic coherence time ($270\,\mu\mathrm{s}$) is limited here only by technical magnetic field fluctuations. This work opens interesting perspectives for quantum simulation and sensing with cold circular Rydberg atoms.
Highlights
The exquisite properties of Rydberg levels make them appealing for emerging quantum technologies
I.e., atoms prepared in levels with a high principal quantum number n, are the focus of a renewed interest [1,2]
Their large coupling to electromagnetic fields, their large mutual dipole-dipole interactions, and their long lifetimes make them ideally suited to cavity quantum electrodynamics [3,4], quantum sensing [5,6,7], quantum information [1,8], and quantum simulations of spin systems [2,9,10,11,12]
Summary
The lifetime of low-angular-momentum laser-accessible levels is limited to a few 100 μs by optical transitions and microwave blackbody radiation (BBR) induced transfers at room temperature. We demonstrate the preparation of long-lived circular Rydberg levels of laser-cooled rubidium atoms in a cryostat. The laser-accessible low-orbital-angular-momentum ( ) Rydberg levels lifetime, mainly determined by optical transitions, limits evolution and measurement times to a few 100 μs. The high number of BBR photons per mode (100 photons at 50 GHz) significantly reduces the Rydberg levels lifetimes, for the circular ones (by two orders of magnitude for |52C ). We demonstrate the preparation in a 4 K cryostat of the n = 52 circular Rydberg state from laser-cooled rubidium atoms at a 10 μK temperature.
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