Readout of Spin Qubits in Si/SiGe Quantum Dots Using a Cavity Embedded Cooper Pair Transistor

Spin qubits in Si/SiGe quantum dots are expected to enjoy very long coherence times, due to the weak interaction of the spins with their environment. The same weakness of interaction makes it difficult to determine the state of the qubits, and to transfer the quantum information they contain to other devices. In this project, we plan to use a superconducting device, the Cooper pair transistor, as a charge-tunable inductance that influences the resonant frequency of a superconducting microwave cavity. The expected interaction between photons and spins is so strong that we should be able to read out the state of a qubit with a single photon. Conversely, we should be able to use a single photon to manipulate the state of a qubit. This research is performed in collaboration with the semiconductor qubit group at the University of Wisconsin.