Thomas Hazard
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Suppressing Counter-Rotating Errors for Fast Single-Qubit Gates with Fluxonium Open
Qubit decoherence unavoidably degrades the fidelity of quantum logic gates. Accordingly, realizing gates that are as fast as possible is a guiding principle for qubit control, necessitating protocols for mitigating error channels that beco…
Dephasing in Fluxonium Qubits from Coherent Quantum Phase Slips Open
Phase slips occur across all Josephson junctions (JJs) at a rate that increases with the impedance of the junction. In superconducting qubits composed of JJ-array superinductors—such as fluxonium—phase slips in the array can lead to decohe…
Suppressing Counter-Rotating Errors for Fast Single-Qubit Gates with Fluxonium Open
Qubit decoherence unavoidably degrades the fidelity of quantum logic gates. Accordingly, realizing gates that are as fast as possible is a guiding principle for qubit control, necessitating protocols for mitigating error channels that beco…
Decoherence in Andreev spin qubits Open
We theoretically study the dephasing of an Andreev spin qubit (ASQ) due to electric and magnetic noise. Using a tight-binding model, we calculate the Andreev states formed in a Josephson junction where the link is a semiconductor with stro…
Characterization of superconducting through-silicon vias as capacitive elements in quantum circuits Open
The large physical size of superconducting qubits and their associated on-chip control structures presents a practical challenge toward building a large-scale quantum computer. In particular, transmons require a high-quality-factor shuntin…
High-Fidelity, Frequency-Flexible Two-Qubit Fluxonium Gates with a Transmon Coupler Open
We propose and demonstrate an architecture for fluxonium-fluxonium two-qubit gates mediated by transmon couplers (FTF, for fluxonium-transmon-fluxonium). Relative to architectures that exclusively rely on a direct coupling between fluxoniu…
Characterization of superconducting through-silicon vias as capacitive elements in quantum circuits Open
The large physical size of superconducting qubits and their associated on-chip control structures presents a practical challenge towards building a large-scale quantum computer. In particular, transmons require a high-quality-factor shunti…
High-Fidelity, Frequency-Flexible Two-Qubit Fluxonium Gates with a Transmon Coupler Open
We propose and demonstrate an architecture for fluxonium-fluxonium two-qubit gates mediated by transmon couplers (FTF, for fluxonium-transmon-fluxonium). Relative to architectures that exclusively rely on a direct coupling between fluxoniu…
Extensible circuit-QED architecture via amplitude- and frequency-variable microwaves Open
We introduce a circuit-QED architecture combining fixed-frequency qubits and microwave-driven couplers. In the appropriate frame, the drive parameters appear as tunable knobs enabling selective two-qubit coupling and coherent-error suppres…
Superconducting-semiconducting voltage-tunable qubits in the third dimension Open
We propose superconducting-semiconducting (super-semi) qubit and coupler designs based on high-quality, compact through-silicon vias (TSVs). An interposer "probe" wafer containing TSVs is used to contact a sample wafer with, for example, a…
Single-Spin Relaxation in a Synthetic Spin-Orbit Field Open
Strong magnetic field gradients can produce a synthetic spin-orbit\ninteraction that allows for high fidelity electrical control of single electron\nspins. We investigate how a field gradient impacts the spin relaxation time T_1\nby measur…
Nanowire Superinductance Fluxonium Qubit Open
We characterize a fluxonium qubit consisting of a Josephson junction\ninductively shunted with a NbTiN nanowire superinductance. We explain the\nmeasured energy spectrum by means of a multimode theory accounting for the\ndistributed nature…
SKIFFS: Superconducting Kinetic Inductance Field-Frequency Sensors for sensitive magnetometry in moderate background magnetic fields Open
We describe sensitive magnetometry using lumped-element resonators fabricated from a superconducting thin film of NbTiN. Taking advantage of the large kinetic inductance of the superconductor, we demonstrate a continuous resonance frequenc…
Nanowire Superinductance Fluxonium Qubit Open
We characterize a fluxonium qubit consisting of a Josephson junction inductively shunted with a NbTiN nanowire superinductance. We explain the measured energy spectrum by means of a multimode theory accounting for the distributed nature of…
Scalable Gate Architecture for a One-Dimensional Array of Semiconductor Spin Qubits Open
We demonstrate a 12 quantum dot device fabricated on an undoped Si/SiGe heterostructure as a proof-of-concept for a scalable, linear gate architecture for semiconductor quantum dots. The device consists of 9 quantum dots in a linear array …