Date of Award

Spring 1-1-2025

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Applied Physics

First Advisor

Devoret, Michel

Abstract

Detecting and correcting decoherence errors is essential for the preser- vation of encoded information in quantum systems. Quantum error correction (QEC) based on bosonic codes where the information is stored in the multiple levels of harmonic oscillators has shown much promise recently. Bosonic codes, specifically those implemented in superconducting cavities, suffer from microwave photon losses which lead to increase in entropy of the system. How can we reduce this entropy, or in other words, can we detect and/or correct the errors associated with microwave photon loss of the cavity? This thesis work proposes and implements novel codes to address these errors. First, we realized a novel QEC code involving two modes of the cav- ity: the pair-binomial code, which corrects for photon losses in either of the modes. Additionally, we discuss a fault-tolerant implementa- tion in which the code is resilient to errors in the auxiliary qubit that is used to provide nonlinearity to the system. Next, we implement a dual-rail qubit within this architecture, enabling detection of photon losses in the system. We develop novel techniques for control and tomography to fully characterize the system. We show that we can detect over 99% of the photon loss errors in the system, with residual errors of 0.2% per check. Finally, we develop another error detection code by encoding a logical qubit using the 0 and 2 Fock states of a single oscillator. In addition to error detection, we demonstrate logical readout and fault-tolerant single-qubit gates for this code. Moreover, we also propose a two-qubit gate between two such 0-2 qubits. These results demonstrate the potential of bosonic codes for error correction and detection in superconducting systems.

Download

Share

COinS