Shaped, on-demand microwave single-photon generator

We demonstrate the full functionality of a circuit that generates single microwave photons on-demand, with a wavepacket that can be modulated with a near-arbitrary shape. We achieve such a high tunability by coupling a superconducting qubit near the end of a semi-infinite transmission line. A DC-SQUID shunts the line to ground and is employed to modify the spatial dependence of the electromagnetic mode structure in the transmission line. This allows us to couple and decouple the qubit from the line, shaping its emission rate on fast-time scales. Our decoupling scheme is applicable to all types of superconducting qubits and other solid state systems and can be generalized to multiple qubits as well as to resonators.