Sensing microwave photons with a Bose\u2013Einstein condensate

Orsolya Kálmán,Peter Domokos

doi:10.1140/epjqt/s40507-020-0078-7

Abstract

We consider the interaction of a magnetically trapped Bose–Einstein condensate of Rubidium atoms with the stationary microwave radiation field sustained by a coplanar waveguide resonator. This coupling allows for the measurement of the magnetic field of the resonator by means of counting the atoms that fall out of the condensate due to hyperfine transitions to non-trapped states. We determine the quantum efficiency of this detection scheme and show that weak microwave fields at the single-photon level can be sensed.

Highlights

Sensing extreme low-intensity radiation fields in the quantum regime requires highefficiency, low-noise detectors
Analogous schemes have been demonstrated for microwave waveguide resonators integrated in a circuit with strongly coupled superconducting non-linear elements [2,3,4,5,6,7]
In this paper we evaluate the detection capabilities of a Bose–Einstein condensate (BEC) in the microwave regime

Summary

Introduction

Sensing extreme low-intensity radiation fields in the quantum regime requires highefficiency, low-noise detectors. There are approaches to photon detection, in the microwave frequency regime too, which are based on the same principle as that of commonly used optical detectors, i.e., the absorption by a ground-state material probe In this regime, the naturally occurring transitions in material quantum systems are magnetic ones, which are weaker than the electric dipole transitions typically by a factor of the fine structure constant α = 1/137. The near-field microwave radiation of a coplanar waveguide resonator (CPW) has been successfully coupled to ultracold atoms [20] In this experiment the light-shift of a hyperfine transition induced by the strongly driven resonator mode in the large photon number regime was detected by Ramsey interferometry and the possibility of coherent control of the hyperfine states was demonstrated by directly observing resonant Rabi oscillations.

The Bose–Einstein condensate

Conclusion