Single microwave-photon detector using an artificial $\Lambda$-type three-level system

Understand

Single photon detection is a requisite technique in quantum-optics experiments in both the optical and the microwave domains.

• However, the energy of microwave quanta are four to five orders of magnitude less than their optical counterpart, making the efficient detection of single microwave photons extremely challenging.
• Here, we demonstrate the detection of a single microwave photon propagating through a waveguide.
• The detector is implemented with an "impedance-matched" artificial $\Lambda$ system comprising the dressed states of a driven superconducting qubit coupled to a microwave resonator.