Searching for wave-like dark matter with QSHS
SciPost Physics Proceedings SciPost 12 (2023) 40
Abstract:In 2021 the Quantum Sensors for the Hidden Sector (QSHS) collaboration was founded in the UK and received funding to develop and demonstrate quantum devices with the potential to detect hidden sector particles in the μeV to 100 μeV mass window. The collaboration has been developing a range of devices. It is building a high-field, low-temperature facility at the University of Sheffield to characterise and test the devices in a haloscope geometry. This paper introduces the collaboration's motivation, aims, and progress.
High coherence and low cross-talk in a tileable 3D integrated superconducting circuit architecture.
Science advances 8:16 (2022) eabl6698
Abstract:We report high qubit coherence as well as low cross-talk and single-qubit gate errors in a superconducting circuit architecture that promises to be tileable to two-dimensional (2D) lattices of qubits. The architecture integrates an inductively shunted cavity enclosure into a design featuring nongalvanic out-of-plane control wiring and qubits and resonators fabricated on opposing sides of a substrate. The proof-of-principle device features four uncoupled transmon qubits and exhibits average energy relaxation times T1 = 149(38) μs, pure echoed dephasing times Tϕ,e = 189(34) μs, and single-qubit gate fidelities F = 99.982(4)% as measured by simultaneous randomized benchmarking. The 3D integrated nature of the control wiring means that qubits will remain addressable as the architecture is tiled to form larger qubit lattices. Band structure simulations are used to predict that the tiled enclosure will still provide a clean electromagnetic environment to enclosed qubits at arbitrary scale.
Spatial Charge Sensitivity in a Multimode Superconducting Qubit
Physical Review Applied American Physical Society (APS) 17:2 (2022) 024058
Radio-frequency characterization of a supercurrent transistor made of a carbon nanotube
Materials for Quantum Technology IOP Publishing 1:3 (2021) 035003
Abstract:A supercurrent transistor is a superconductor–semiconductor hybrid device in which the Josephson supercurrent is switched on and off using a gate voltage. While such devices have been studied using DC transport, radio-frequency measurements allow for more sensitive and faster experiments. Here a supercurrent transistor made from a carbon nanotube is measured simultaneously via DC conductance and radio-frequency reflectometry. The radio-frequency measurement resolves all the main features of the conductance data across a wide range of bias and gate voltage, and many of these features are seen more clearly. These results are promising for measuring other kinds of hybrid superconducting devices, in particular for detecting the reactive component of the impedance, which a DC measurement can never detect.
Circuit Quantum Electrodynamics with Carbon-Nanotube-Based Superconducting Quantum Circuits
PHYSICAL REVIEW APPLIED 15:6 (2021) 64050