Generation and efficient measurement of single photons from fixed frequency superconducting qubits

Understand

We demonstrate and evaluate an on-demand source of single itinerant microwave photons.

• Photons are generated using a highly coherent, fixed-frequency qubit-cavity system, and a protocol where the microwave control field is far detuned from the photon emission frequency.
• By using a Josephson parametric amplifier (JPA), we perform efficient single-quadrature detection of the state emerging from the cavity.
• We characterize the imperfections of the photon generation and detection, including detection inefficiency and state infidelity caused by measurement backaction over a range of JPA gains from 17 to 33 dB.