Quantum Optics Seminar: Niels Kjaergaard, University of Otago, New Zealand

There are no four-level atoms and rubidium is not one of them

In a basic realization of an atomic electrometer, an optical electromagneticallyinduced transparency (EIT) scheme reads out a simple Autler-Townes (AT) splitting of a Rydberg state resulting from the presence of an RF-field. For a suitable choice of atomic states, the electrometer can be configured with the readout of the AT-signal to be insensitive to the orientation of a linearly polarized incoming RF field [1]. This realizes an isotropic RF-receiver – something that is fundamentally impossible within conventional antenna technology.

Alternatively, quantum states can be selected to achieve a polarization-dependent response that enables atom-based RF vector electrometry: specific combinations of atomic terms give rise to distinctive fingerprints in the detected optical fields upon rotating the RF field polarization. Here we report on the realization of complementary output-modes for two types of detection ladders where the prominence of a central EIT peak presents an out-of-phase oscillation as the polarization angle of an incoming RF field is scanned [2]. Our study adds exciting new prospects for Rydberg RF-polarimeters and provides important insights into the remarkably different polarization-response that can be displayed by ostensibly similar systems.

[1] M. Cloutman, M. Chilcott, A. Elliott, J. S. Otto, A.B. Deb and N. Kjærgaard, Polarizationinsensitive microwave electrometry using Rydberg atoms, Physical Review Applied 21, 044025 (2024).

[2] M. Cloutman, M. Chilcott, A. Elliott, J. S. Otto, A.B. Deb and N. Kjærgaard, Quantumenabled Rydberg atomic polarimetry of radio-frequency fields, arXiv:2503.17997 (2025).