Advances in Light Science: Quantum Photonics & Ultrafast Phenomena

While numerous quantum applications benefit from efficient microwave photon detectors, achieving this at microwave frequencies remains challenging due to the low energies of these photons. A microwave cavity coupled to a qubit—acting as a two-level quantum system—can enable single-photon microwave detection if the cavity photon can resonantly excite the qubit. One promising approach utilizes a semiconductor-based quantum dot (QD) charge qubit embedded in a superconducting cavity, where photon-driven qubit excitation results in a measurable photocurrent [1,2]. In this work, we employ a high-impedance Josephson junction (JJ) array resonator coupled to a double QD charge qubit in GaAs to achieve efficient photodetection. Initial measurements indicate a photon-to-electron conversion efficiency of ~80% at the single-photon level, though with a finite increase in dark current. Additionally, we demonstrate that the tunability of both the JJ array resonator and the charge qubit enables efficient detection across varying frequencies. Through the study of different configurations, we aim to develop a comprehensive model for photon-to-electron conversion, incorporating the dark current effect. This research strives to establish a pathway toward a tunable microwave photon detector with unity efficiency at the single-photon level.

 

[1] C. Wong and M. G. Vavilov, Phys. Rev. A 95, 012325, 2017

[2] W. Khan et al., Nat. Commun. 12, 5130 (2021)