Date of Award

Spring 1-1-2025

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Physics

First Advisor

Schoelkopf, Robert

Abstract

Modern quantum experiments allow the precise manipulation and measurement ofmany-body quantum states, pushing quantum mechanics from a testable theory to a utilizable technology. The central promise of these experiments is to process quantum information for exponential advantages in computing, sensing, and communication. An interesting way to achieve such a processor is to manipulate quantum information stored in the continuous-variable (bosonic) phase space of electromagnetic radiation. Since photons in free space do not interact, such an approach necessarily requires the introduction of nonlinearity through strong light-matter couplings. However, since all matter is lossy, this inevitably introduces a trade-off between the speed of control and the inherited decoherence of the ‘light’. This thesis explores the control of microwave radiation trapped in a superconducting oscillator through interactions with Josephson junction-based nonlinearities. I first demonstrate novel ways to exchange single photons between two oscillators at different frequencies through carefully constructed driven nonlinearities, achieving several orders of magnitude higher fidelity than previously possible. I then introduce ways to utilize such a high-fidelity coupler to dynamically couple light and matter, in a way that breaks the tradeoff between universal control and inherited decoherence. Finally, I theoretically show how such universal control can autonomously protect any appropriate error-correction code in the bosonic mode, against a full Lindbladian error channel. Together, this thesis provides a promising path toward fault-tolerant bosonic quantum processors.

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