New arXiv preprint: Robust Quantum Optimal Control with Trajectory Optimization

The ability to engineer high-fidelity gates on quantum processors in the presence of systematic errors remains the primary barrier to achieving quantum advantage. Quantum optimal control methods have proven effective in experimentally realizing high-fidelity gates, but they require exquisite calibration to be performant. We apply robust trajectory optimization techniques to suppress gate errors arising from […]

New Editor’s Suggestion Phys. Rev. Applied publication: Engineering Dynamical Sweet Spots to Protect Qubits from 1 / f Noise

Protecting superconducting qubits from low-frequency noise is essential for advancing superconducting quantum computation. Based on the application of a periodic drive field, we develop a protocol for engineering dynamical sweet spots, which reduce the susceptibility of a qubit to low-frequency noise. Using the framework of Floquet theory, we prove rigorously that there are manifolds of […]

New Phys. Rev. X Publication: Experimental Realization of a Protected Superconducting Circuit Derived from the 0 – π Qubit

In collaboration with the Houck group at Princeton, the Blais group at Sherbrooke, and David Schuster at UChicago, we provided theoretical support to the experimental realization of the 0–π circuit. Encoding a qubit in logical quantum states with wave functions characterized by disjoint support and robust energies can offer simultaneous protection against relaxation and pure dephasing. […]

New Nature publication: Protecting a bosonic qubit with autonomous quantum error correction

We provided theoretical support to our experimental colleagues at UMass Amherst on an experiment demonstrating autonomous quantum error correction. To build a universal quantum computer from fragile physical qubits, effective implementation of quantum error correction (QEC) is an essential requirement and a central challenge. Existing demonstrations of QEC are based on an active schedule of error-syndrome measurements and […]

New Phys. Rev. X Publication: Universal Fast-Flux Control of a Coherent, Low-Frequency Qubit

In collaboration with the Schuster Lab at UChicago, we provided theory support for an experiment studying the heavy-fluxonium circuit. The heavy-fluxonium circuit is a promising building block for superconducting quantum processors due to its long relaxation and dephasing time at the flux-frustration point. However, the suppressed charge matrix elements and low transition frequency make it […]

New Phys. Rev. Research Publication: Positive- and negative-frequency noise from an ensemble of two-level fluctuators

The analysis of charge noise based on the Bloch-Redfield treatment of an ensemble of dissipative two-level fluctuators generally results in a violation of the fluctuation-dissipation theorem. The standard Markov approximation (when applied to the two-level fluctuators coupled to a bath) can be identified as the main origin of this failure. The resulting decoherence rates only […]

New arxiv preprint: Floquet-engineered enhancement of coherence times in a driven fluxonium qubit

In a collaboration with the Houck Lab, we use the quasienergy structure that emerges when a fluxonium superconducting circuit is driven periodically to encode quantum information with dynamically induced flux-insensitive sweet spots. The framework of Floquet theory provides an intuitive description of these high-coherence working points located away from the half-flux symmetry point of the […]

New arxiv preprint: Positive- and negative-frequency noise from an ensemble of two-level fluctuators

The analysis of charge noise based on the Bloch-Redfield treatment of an ensemble of dissipative two-level fluctuators generally results in a violation of the fluctuation-dissipation theorem. The standard Markov approximation can be identified as the main origin of this failure. The resulting decoherence rates only involve the bath response at the fluctuator frequency, and thus […]

New arxiv preprint: Engineering Dynamical Sweet Spots to Protect Qubits from 1/f Noise

Protecting superconducting qubits from low-frequency noise is essential for advancing superconducting quantum computation. We here introduce a protocol for engineering dynamical sweet spots which reduce the susceptibility of a qubit to low-frequency noise. Based on the application of periodic drives, the location of the dynamical sweet spots can be obtained analytically in the framework of […]

Protecting a bosonic qubit with autonomous quantum error correction

To build a universal quantum computer from fragile physical qubits, effective implementation of quantum error correction (QEC) is an essential requirement and a central challenge. Existing demonstrations of QEC are based on a schedule of discrete error syndrome measurements and adaptive recovery operations. These active routines are hardware intensive, prone to introducing and propagating errors, […]