Closed-loop control system and hardware-aware compilation protocols for quantum simulation with neutral atoms in optical trap arrays
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Date
2023-09-25
Authors
Padia, Parth
Journal Title
Journal ISSN
Volume Title
Publisher
University of Waterloo
Abstract
Quantum materials offer tremendous potential for advancing electronic devices beyond traditional semiconductor-based technologies. Understanding the dynamics of these materials requires the use of quantum simulators. Quantum simulators are controlled many-body quantum systems that mimic the dynamics of a targeted quantum system. The three key
features of a quantum simulator are controllability, scalability, and interactability. Controllability denotes the ability to address an individual quantum system. Scalability refers to extending this control to multiple quantum systems while maintaining their interconnectivity with a polynomial increase in resources. Interactability, on the other hand, denotes the capability to establish strong tunable interactions between a pair of quantum systems.
This thesis addresses the challenges of attaining controllability and scalability within the current Noisy Intermediate-Scale Quantum (NISQ) era, characterized by limited and error-prone qubits, for a neutral atom-based quantum simulator.
The constraints in qubit interconnectivity necessitate the use of additional swap gates for operations between non-adjacent qubits, increasing errors. To reduce these gate-based errors, we improve qubit interconnectivity by displacing atoms during simulation, thus enhancing our simulator’s scalability. We compare approaches with and without atom displacement analytically and numerically, employing metrics like circuit fidelity and quantum volume. Our analysis introduces a novel metric, denoted as $\eta_{protocol}$, for comparing compilation protocols incorporating atom displacement. Additionally, we establish an inequality involving the $\eta_{platform}$ metric to compare operational protocols with and without atom displacement. We conclude from our quantum volume study that protocols assisted by atom displacement can achieve a quantum volume of 2^7, a significant improvement over the 2^6 attainable without atom displacement with the state-of-the-art two-qubit gate infidelity of 5e-3 and atom displacement infidelity of 1.8e-4.
Implementing a dedicated closed-loop control and acquisition system showcases our simulator’s controllability. The system integrates machine learning techniques to automate experiment composition, execution, and analysis, resulting in faster and automated control parameter optimization. A practical demonstration of this optimization is conducted through imaging an atomic cloud composed of Rb-87 atoms, the first step in undertaking quantum simulations with neutral atom arrays.
The research presented in this thesis contributes to the understanding and advancement of quantum simulators, paving the way for developing new devices with quantum materials.
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Keywords
Control system, Quantum simulation, Hardware-aware quantum circuit compilation, Neutral atom arrays