Publications using HERD
Experiments on superconducting qubits, including work on quasiparticle tunneling, coherence and high-fidelity readout.
Raising the Cavity Frequency in cQED
Demonstrates raising cavity frequency to 21 GHz while maintaining a standard 5 GHz transmon qubit. Achieves 8% quantum efficiency readout, qubit quality factor exceeding 10⁷, and coherence times reproducibly exceeding 100 μs.
A transmon qubit realized by exploiting the superconductor-insulator transition
Demonstrates a transmon-type qubit made from an NbN thin film weak link created by tuning near the superconductor–insulator transition. The junction-less design avoids oxide barriers and parasitic capacitance, showing feasibility of planar, high-gap superconducting qubits.
Recovery dynamics of a gap-engineered transmon after a quasiparticle burst
Gap-engineered transmons show reduced sensitivity to quasiparticle bursts. Burst rates drop by a factor of a few, but elevated substrate temperature during radiation impacts lets quasiparticles overcome the engineered gap. Relaxation recovers in ~0.7 ms, while chip heating persists for several milliseconds, revealing limits of gap engineering without improved phonon evacuation.
Lumped-element broadband SNAIL parametric amplifier with on-chip pump filter for multiplexed readout
Describes a broadband SNAIL amplifier with integrated matching network and on-chip pump filtering, enabling wideband multiplexed qubit readout with improved isolation.
2D transmons with lifetimes and coherence times exceeding 1 millisecond
Tantalum transmons on high-resistivity silicon achieve 2D qubit lifetimes up to ~1.7 ms and echo coherence exceeding T₁, while supporting 99.994% single-qubit gate fidelity on a wafer-scalable platform.
An rf-SQUID-based traveling-wave parametric amplifier with -84 dBm input saturation power
Demonstrates an rf-SQUID-based Josephson TWPA with -84 dBm average saturation power and ~20 dB gain over 3.5-8.5 GHz, achieving near-quantum-limited noise with 0.8-1.5 photons excess noise.