Author ORCID Identifier

0009-0002-3164-3941

Defense Date

2025

Document Type

Thesis

Degree Name

Master of Science

Department

Mechanical and Nuclear Engineering

First Advisor

Jayasimha Atulasimha, PhD

Abstract

This thesis introduces a novel qubit architecture: the ferromagnetic exchange-coupled spin ensemble qubit (E-qubit), designed to address the noise-induced instability. In this work, the time evolution of the ensemble’s density matrix is studied using the Liouville–von Neumann equation. To benchmark against a single-spin qubit, the gate fidelity of an E-qubit is computed in the presence of thermal noise. Coherence time is also analyzed under identical thermal condition and a linear scaling is observed with qubit size . The results show that, at 6 K , the gate fidelity error (0.7 % ) of the seven- spin ensemble is an order of magnitude lower than that of a single-spin qubit (5 %).At 2 K, the coherence time of seven spin ensemble (1.1 ms) is also an order of magnitude longer than single spin qubit (0.14 ms). The result predicts both fidelity and coherence can be scaled further with increasing ensemble size. Furthermore, the fidelity and effective dephasing time of the exchange coupled seven-spin ensemble are investigated and compared with non-interacting spin ensembles in the presence of static field inhomogeneity, revealing the qubit’s robustness against spatial field variation. An exchange-coupled E qubit offers a promising path toward a scalable quantum device, opening opportunities for real-world applications in quantum computing and sensing. Although this thesis focuses on spin qubits, the underlying framework is applicable to other physical quantum platforms. As future work, it can be implemented on a quantum annealer for experimental validation.

Rights

© The Author

Is Part Of

VCU University Archives

Is Part Of

VCU Theses and Dissertations

Date of Submission

12-15-2025

Download

Share

COinS