YQI Seminar - Michael Hatridge - University of Pittsburgh

Event time: 
Tuesday, November 26, 2019 - 11:00am to 12:00pm
YQI Seminar Room See map
Event description: 

Better parametric amplifiers via Hamiltonian engineering

High-fidelity, quantum non-demolition qubit measurement is a vital prerequisite for robust, large-scale quantum machines. In superconducting quantum circuits, the typical information carriers for qubit readout are coherent states of light, which must be amplified before they can be efficiently recorded in room-temperature electronics. Typically, these amplifiers consist of one or two microwave modes linked by a parametrically driven coupling. Such amplifiers regularly approach the quantum limit for amplification, allowing us to closely track qubits’ states. However, conventional parametric amplifiers lack almost every other desirable property, including high saturation power, large bandwidth, and directional operation.  I will present our recent theoretical and experimental efforts to realize amplifiers with enhanced dynamic range by careful engineering of the overall device Hamiltonian to control the effects of unwanted higher-order terms.   A second route to superior amplifiers is by combining multiple, simultaneous parametric drives between a pair of microwave modes.   In a single device, by varying the parametric drives, we can produce desired behaviors including transmission-only phase-sensitive amplification, matched inputs, and broad, gain-independent bandwidth.  I will discuss the prospects for adding the final desired property –directionality–  via further parametric couplings to a third microwave mode.