Enhanced long-wavelength signal detection via a quantum antenna

This is the authors' abstract. We don't add key points for this paper.

Detection of long-wavelength signal is of importance for diverse sensing and communication applications. Conventional metal antennas are limited in this regime, particularly when compactness and high sensitivity are both required. Despite intrinsic advantages for electric-field sensing across an ultra-broad range from DC to terahertz, Rydberg atoms still face challenges in practical long-wavelength signal detection, motivating the development of more sensitive and scalable approaches. In this work, we experimentally show that such a signal acting on the Rydberg state can be converted into a polarization variation of the probe laser, and realize signal extraction by appropriately utilizing the polarization degrees of freedom. Based on such a mechanism, we further design and implement a quantum weak measurement scheme, which clearly suppresses the technical noise and leads to considerable improvement of performance. Evaluation of the sensitivities across different post-selection angles demonstrates that the weak measurement results agree well with the theoretical model predictions. The advantages of our method are analyzed from multiple aspects, including characterizing the responses over different frequencies and comparing the responses of the weak measurement scheme and the traditional transmission-based method. After accounting for the screening effect of a measured ratio of 17% where the Rb 87 atoms experience a substantially reduced field inside the glass cell, the performance reaches 33 μV cm −1 Hz −1/2 in sensitivity and 1.0 μV cm −1 in minimal detectable field for an integration time of 1000 s, as perceived by the atoms.