paper / charlesmarcus / Feb 2
This research directly images local susceptibility in hybrid Josephson junction arrays using scanning SQUID, providing insights into superconductivity coherence and its suppression near quantum phase transitions. The study reveals the amplitude and spatial phase structures of superconducting states on a square lattice of narrow islands, particularly highlighting the strongest long-range phase coherence at zero magnetic field and its fragmentation into stable regions at finite fields.
superconductivityjosephson-junctionscondensed-matter-physicsquantum-phase-transitionphase-coherencesquid-microscopy
“Scanning SQUID microscopy allows for direct imaging of local susceptibility in hybrid Josephson junction arrays.”
paper / charlesmarcus / Dec 6
Researchers used a covariance matrix adaptation evolutionary strategy to automate in situ optimization of gate voltages in a quantum point contact device. This approach was tested in both simulations and a physical device, leading to improved conductance quantization and mitigation of random disorder. The method offers a pathway for enhancing the performance of quantum devices through adaptive control.
quantum-computingquantum-devicesoptimizationdisorder-mitigationnanoscale-physicsevolutionary-algorithms
“Automated in situ optimization was performed on a quantum point contact device using a 3x3 gate array.”
paper / charlesmarcus / Nov 20
This research demonstrates the realization of Andreev diffraction gratings in superconductor-semiconductor hybrid circuits. By precisely controlling the phase differences between multiple Andreev scatterers, the study achieves tunable diffraction patterns. This methodology enables individual phase control, offering a new approach to manipulating Andreev scattering phenomena.
superconductivityandreev-scatteringquantum-physicscondensed-matter-physicsnanoscale-devicesmesoscale-physics
“Andreev diffraction, analogous to optical diffraction, can be realized in superconductor-semiconductor hybrid circuits.”
paper / charlesmarcus / Aug 12
The Y-splitter, a novel circuit element, enables destructive interference of Cooper-pair transport and coherent propagation of split Cooper pairs. When arranged in a two-dimensional star geometry (kagome lattice), these Y-splitters exhibit topological superconducting phases with Chern numbers of ±2. This offers a promising new approach to realizing topological superconductivity, with experimental feasibility confirmed.
superconductivityquantum-computingtopological-superconductorscondensed-matter-physicsjosephson-junctionsquantum-materials
“The Y-splitter is a novel circuit element.”
paper / charlesmarcus / Feb 14
This research presents a novel bolometric detection scheme for Josephson radiation, converting AC Josephson current at microwave frequencies (up to 100 GHz) into a measurable DC temperature rise. This method offers an efficient and wide-band thermal detection of microwave photons, providing a sensitive tool for understanding Josephson dynamics beyond traditional conductance measurements. The approach is quantitatively supported by a circuit model that accurately predicts both current-voltage characteristics and measured power.
quantum-physicsjosephson-junctionssuperconducting-qubitsmesoscale-physicsmicrowave-detection
“A novel bolometer can detect Josephson radiation by converting microwave frequency AC Josephson current into a DC temperature rise.”