Detection of individual microwave photons using cavity-coupled semiconductor quantum dots: experimental and quantum challenges

In the rapidly evolving field of quantum information and quantum computing, high-fidelity readout and manipulation of microwave photon states are of paramount importance. Our research contributes to this imperative by addressing the challenge of realizing microwave photodetection at a single photon level. We utilize the unique properties of superconductor cavity-coupled semiconductor quantum dots to develop a microwave photodetector.[1,2] Here, a microwave photon (energy = 30 eV) can excite an electron across the discrete energy levels of quantum dots, which results in a photocurrent signal. Our device achieved a photodetection efficiency of 25% at 100-attowatt input power levels. Using an additional quantum dot as a charge sensor, we showed that our device can detect both the single and multi-photon absorption events individually.[3] One crucial aspect here is the detector back action effect, which is governed by fundamental laws of quantum mechanics. We also explored the coherent interaction of cavity photons with quantum dots and realized wave-particle duality in the microwave regime.[4] In this talk, I will present the experimental and inherent quantum challenges to detect a single microwave photon, unraveling the mysteries in the quantum realm and its vast potential applications in quantum technologies.

Fig.1 (a) Superconductor-semiconductor hybrid device for microwave single photon detection, (b) measured results showing the real-time single photon detection events, and (c) cavity-qubit coherent interactions.

[1] W. Khan et. al. Nat. Commun. 12, 5130 (2021) 
[2] S. Haldar et. al. Phys. Rev. Lett. 130, 087003 (2023) 
[3] S. Haldar et. al. arXiv:2401.06617 (2023) 
[4] S. Haldar et. al. Phys. Rev. B (Lett.) 109, L081403 (2024)