Kevin P O'Brien [MIT]

Abstract:

Superconducting qubits are one of the leading quantum computing platforms in part due to the nonlinearity of the Josephson junction. High quantum efficiency broadband amplification is a key requirement for high fidelity qubit readout and thus implementing quantum error correction. We illustrate the modeling and design of high quantum efficiency broadband parametric amplifiers using our open source package JosephsonCircuits.jl [1]. These amplifiers are engineered to match the Floquet modes in the amplifier to the eigenmodes of the environment, eliminating a previously ubiquitous noise mechanism in broadband amplifiers [2]. We present the fabrication of such amplifiers using a high-Q qubit fabrication process with state of the art junction critical current uniformity. We detail the characterization of these amplifiers including the highest reported quantum efficiency for a traveling wave parametric amplifier [3] and future directions of on-chip integration and isolation. Finally, we show how qubits with quartic [4] rather than the familiar weakly anharmonic potential enable the first demonstration of near-ultrastrong nonlinear coupling [5] with applications in fast qubit readout [6] and gates.

Research interests: Superconducting qubits, quantum computing, quantum sensing, nonlinear optics, metamaterials