EPFL researchers developed a device that detects individual microwave photons with up to 70 % efficiency while working continuously and without requiring complicated reset processes. The results were reported in Science Advances.
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It is difficult to detect a single particle of light, let alone a single microwave photon. Microwave photons, the small packets of electromagnetic radiation employed in modern technologies such as Wi-Fi and radar, have far less energy than visible light. They are approximately 100,000 times weaker than optical photons.
Many current quantum technologies rely on detecting individual photons with excellent reliability. For visible light, this is well established, with devices that transform incoming light directly into electrical signals. However, at microwave frequencies (0.3–30 GHz), this fails because each photon does not have enough energy to liberate an electric charge in a material. This means that detecting individual microwave photons needs a whole different approach.
A long-term objective has been to develop a simple device capable of continually sensing microwave photons. EPFL scientists, led by Pasquale Scarlino, have created a semiconductor-based detector that represents a significant step forward in that direction.
The device combines a semiconductor structure known as a “double quantum dot” with a superconducting microwave cavity: a small resonant circuit that captures and stores microwave photons, allowing them to interact powerfully with the device. Together, these components transform incoming microwave photons into a small but measurable electrical current.
Beyond setting a new benchmark for semiconductor-based microwave photodetectors, the work opens new perspectives for quantum microwave optics, quantum sensing, and scalable quantum information platforms.
Pasquale Scarlino, Tenure Track Assistant Professor, Hybrid Quantum Circuits Laboratory, EPFL
Swiss State Secretariat for Education, Research and Innovation (SERI), Swiss National Science Foundation (SNSF) (NCCR SPIN), EPFL QSE Postdoctoral Fellowship Grant, and NanoLund funded the study.
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Journal Reference:
Oppliger, F. et al. (2026) Tunable high-efficiency microwave photon detector based on a double quantum dot coupled to a superconducting high-impedance cavity. Science Advances. DOI: 10.1126/sciadv.aeb9784. https://www.science.org/doi/10.1126/sciadv.aeb9784.