PhD Defense - Stijn de Graaf

Event time: 
Tuesday, October 22, 2024 - 11:00am to 12:00pm
Audience: 
YQI Researchers
Location: 
YQI Seminar Room See map
Event description: 
The dissertation defense of Stijn de Graaf will take place at 11am on October 22, 2024 in the YQI Seminar Room, 17 Hillhouse, and via Zoom at the following link:  https://yale.zoom.us/j/91561893461
 
The committee members are:

Prof. Rob Schoelkopf

Prof. Michel Devoret
Prof. Steve Girvin
 
Any faculty wishing to review the dissertation prior to the defense should contact me.
 
Title:  Microwave Beamsplitters for Oscilator-based Quantum Information Processing
 
Abstract:  A single high-Q harmonic oscillator with a fixed ‘dispersive’ coupling to an ancillary qubit provides a remarkably hardware-efficient platform for a wide range of quantum technologies, capable of acting as a dark matter detector, a simulator of quantum chemistry or a quantum memory with a lifetime longer than its underlying components. The strength of this platform lies in the linearity and favorable decoherence rates of the high-Q oscillator mode. The question then arises: how can we scale this oscillator-based platform to practically useful sizes without compromising a) the speed of operations or b) the properties that make oscillators an attractive platform in the first place? The addition of a tunable oscillator-oscillator coupling, equivalent to an optical beamsplitter, has extended the power of this platform to enable multi-mode entanglement, a key element for quantum computation, but until now, implementations have been limited to low interaction strengths and introduced unwanted oscillator nonlinearity. Inspired by advances in parametric amplification, we show how a three-wave mixing element solves this challenge by acting as a switch, with beamsplitter interaction strengths exceeding those of the dispersive coupling when turned on, and the ability to fully decouple the modes when turned off. We then demonstrate how this regime unlocks a powerful new toolbox of high-fidelity multimode operations which are the analogs of established single-mode control techniques. In particular, we show how these techniques can be leveraged to perform a mid-circuit erasure check, the vital building block for a newly-proposed quantum computer made out of superconducting cavity dual-rail qubits.