Quantum information processing has spurred interest in quantum optimal control for tasks such as state preparation, error correction, and realization of logical gates. Gradient Ascent Pulse Engineering (GRAPE) is a prominent technique for implementing quantum optimal control by adjusting parameters to minimize infidelity in state transfers or gate operations using gradient descent. Many efforts have […]

Decoherence errors, caused by the interaction of quantum systems with their environment, pose a major challenge for the practical implementation of quantum computing. Accurately modeling these errors is essential for analyzing and improving gate fidelities. While Lindblad master equation and its several generalizations have been proposed, there is still ongoing exploration for simpler and more […]

Together with theory collaborators from UChicago we analyze driven quantum systems subject to non-Markovian noise. These systems are typically difficult to model even if the noise is classical. We present a systematic method based on generalized cumulant expansions for deriving a time-local master equation for such systems. This master equation has an intuitive form that […]

The use of time-dependent flux is ubiquitous in the context of circuit quantum electrodynamics. It is critical to accurately model time-dependent flux in circuit Hamiltonians, which is what Xinyuan at al. did in our previous work. Working with Houck lab in Princeton, we provide experimental verification of what the flux allocation should be in the […]

Along with coworkers from the Schuster lab at UChicago, we introduce a coupling scheme for low frequency fluxonium qubits that allows for high-fidelity entangling gates. Long coherence times, large anharmonicity and robust charge-noise insensitivity render fluxonium qubits an interesting alternative to transmons. Recent experiments have demonstrated record coherence times for low-frequency fluxonia. Here, we propose […]

We present a formalism to quantize a general superconducting circuit with Josephson junctions. The formalism is amenable to an algorithmic implementation and we present an extension Circuit to the scqubits package which deals with a generic superconducting circuit. This algorithm is able to identify all the degrees of freedom and their boundary conditions. Moreover, the non dynamical […]