Bright On-Demand Source of Antibunched Microwave Photons Based on Inelastic Cooper Pair Tunneling

The ability to generate single photons is not only an ubiquitous tool for scientific exploration with applications ranging from spectroscopy and metrology to quantum computing, but also an important proof of the underlying quantum nature of a physical process. In the microwave regime, emission of anti-bunched radiation has so far relied on coherent control of Josephson qubits, where precisely calibrated microwave pulses are needed and the achievable bandwidth is limited by the anharmonicity of the qubit. Here, we demonstrate the operation of a bright on-demand source of quantum microwave radiation capable of emitting anti-bunched light from inelastic Cooper pair tunneling. Our source does not require external microwave signals and can be triggered. Its rate is tunable in situ and exceeds values obtained with current microwave single photon sources by more than one order of magnitude.