Date of Award
Doctor of Philosophy
Elena Litvinova, Ph.D.
Kyle A. Wendt, Ph.D.
Denis Lacroix, Ph.D.
Zbigniew Chajecki, Ph.D.
Nuclear theory, open quantum systems, quantum algorithms, quantum equation of motion, quantum many-body physics, quantum optimal control
The complexity of the nuclear many-body problem is a severe obstacle to finding a general and accurate numerical approach needed to simulate medium-mass and heavy nuclei. Even with the advent of exascale classical computing, the impediment of exponential growth of the Hilbert space renders the problem intractable for most classical calculations. In the last few years, quantum algorithms have become an attractive alternative for practitioners because quantum computers are more efficient in simulating quantum physics than classical computers. While a fully fault-tolerant universal quantum computer will not be realized soon, this dissertation explores quantum algorithms for simulating nuclear physics suitable for noisy intermediate-scale quantum (NISQ) devices. To achieve high simulation accuracy on the currently available NISQ hardware, one must design noise-resilient algorithms and utilize techniques that suppress noise errors while maximizing quantum gate fidelity. This work satisfies this desideratum by employing variational quantum algorithms, error-mitigation techniques, and numerically engineered high-fidelity custom gates. First, an efficient encoding scheme for the Lipkin model is proposed, and the quantum equation of motion algorithm is shown to have a special quantum benefit for simulating strongly coupled many-body systems. Second, microwave pulses to perform custom two-qubit gates on a superconducting quantum computer are engineered. This results in significantly higher gate fidelity and lower execution duration than the default quantum hardware gates. Lastly, simulations are done for model nuclear Hamiltonians, and the results from using IBM superconducting quantum computers are in close agreement with classical calculations. Therefore, this study contributes toward transformative nuclear physics simulations on near-term quantum computers.
Hlatshwayo, Manqoba Qedindaba, "Simulating Strongly Coupled Many-Body Systems with Quantum Algorithms" (2023). Dissertations. 4011.