Niril George
About
My research project
Towards Fault-Tolerant Quantum Computing with Superconducting QubitMy PhD research focuses on making superconducting quantum computers more reliable so they can support fault-tolerant quantum computation. Current superconducting qubits suffer from decoherence, control errors, crosstalk, leakage, and parameter drift, which keep physical error rates too high for effective quantum error correction. In this project, I use a framework called Robust Optimal Control (ROC) to design microwave and flux-control pulses that maintain high gate fidelity even when the hardware parameters are uncertain and the environment is noisy. I apply ROC to both single- and two-qubit gates (including cross-resonance and flux-tunable entangling gates) and study their performance through analytical modeling, large-scale simulations, and experiments on state-of-the-art superconducting processors. The long-term goal is to integrate these robust gates with surface-code error correction and magic-state protocols to reduce resource overheads and move closer to scalable, fault-tolerant quantum computing.
My PhD research focuses on making superconducting quantum computers more reliable so they can support fault-tolerant quantum computation. Current superconducting qubits suffer from decoherence, control errors, crosstalk, leakage, and parameter drift, which keep physical error rates too high for effective quantum error correction. In this project, I use a framework called Robust Optimal Control (ROC) to design microwave and flux-control pulses that maintain high gate fidelity even when the hardware parameters are uncertain and the environment is noisy. I apply ROC to both single- and two-qubit gates (including cross-resonance and flux-tunable entangling gates) and study their performance through analytical modeling, large-scale simulations, and experiments on state-of-the-art superconducting processors. The long-term goal is to integrate these robust gates with surface-code error correction and magic-state protocols to reduce resource overheads and move closer to scalable, fault-tolerant quantum computing.
Publications
High-fidelity quantum gates are crucial for achieving fault-tolerant quantum computing; however, decoherence significantly reduces gate fidelities during long operation times. Although optimal control techniques can theoretically minimize these operation times, they often neglect realistic uncertainties in system parameters. In this work, we demonstrate that by using robust optimal control strategies, the cross-resonance gate in superconducting systems can be operated within 64 ns, achieving fidelities of F > 0.99 while maintaining robustness against up to 10% uncertainty in a single parameter. Alternatively, by extending the control time to 71 ns, we achieve fidelities of F > 0.99 with robustness against up to 3% uncertainty. Our results identify the minimal control times attainable with experimentally feasible pulses and system parameters, as well as the maximum allowable static parameter error for high-fidelity operations. Furthermore, we demonstrate simultaneous robustness against both static and time-dependent errors by generating 100 ns control pulses (F > 0.99) that maintain robustness against 10% static parameter error and time-dependent parameter fluctuations two orders of magnitude stronger than typical experimental noise. These findings demonstrate a viable open-loop strategy for implementing fast, high-fidelity quantum gates in the presence of realistic system uncertainties that would otherwise degrade conventional control pulses.