scalable-quantum-integrated-circuits-on-superconducting-two

Scalable Quantum Integrated Circuits on Superconducting Two-Dimensional Electron Gas Platform

To form a coherent quantum transport in hybrid superconductor-semiconductor (S-Sm) junctions, the formation of a homogeneous and barrier-free interface ...

University of Cambridge

 We report the experimental evidence for the formation of multi-quantum dots in a hydrogenated single-layer graphene flake. The existence of multi-quantum dots is supported by the low-temperature measurements on a field effect transistor structure device. The resulting Coulomb blockade diamonds shown in the color scale plot together with the number of Coulomb peaks exhibit the characteristics of the so-called 'stochastic Coulomb blockade'. A possible explanation for the formation of the multi-quantum dots, which is not observed in pristine graphene to date, was attributed to the impurities and defects unintentionally decorated on a single-layer graphene flake which was not treated with the thermal annealing process. Graphene multi-quantum dots developed around impurities and defect sites during the hydrogen plasma exposure process.

Evidence for formation of multi-quantum dots in hydrogenated graphene.

A superconducting hard gap in hybrid superconductor-semiconductor devices has been found to be necessary to access topological superconductivity that hosts Majorana modes (non-Abelian excitation). This requires the formation of homogeneous and barrier-free interfaces between the superconductor and semiconductor. Here, a new platform is reported for topological superconductivity based on hybrid Nb-In Ga As-quantum-well-Nb that results in hard superconducting gap detection in symmetric, planar, and ballistic Josephson junctions. It is shown that with careful etching, sputtered Nb films can make high-quality and transparent contacts to the In Ga As quantum well, and the differential resistance and critical current measurements of these devices are discussed as a function of temperature and magnetic field. It is demonstrated that proximity-induced superconductivity in the In Ga As-quantum-well 2D electron gas results in the detection of a hard gap in four out of seven junctions on a chip with critical current values of up to 0.2 µA and transmission probabilities of >0.96. The results, together with the large g-factor and Rashba spin-orbit coupling in In Ga As quantum wells, which indeed can be tuned by the indium composition, suggest that the Nb-In Ga As-Nb system can be an excellent candidate to achieve topological phase and to realize hybrid topological superconducting devices.

Reuben Puddy

Department of Physics,
Cavendish Laboratory,
Department of Physics, Cavendish Laboratory

University of Cambridge

Scalable Quantum Integrated Circuits on Superconducting Two-Dimensional Electron Gas Platform

Reuben Puddy

.css-o250i3{font-size:18px;font-family:Open Sans,sans-serif;line-height:21.6px;}Department of Physics,Cavendish Laboratory,Department of Physics, Cavendish Laboratory

University of Cambridge

Scalable Quantum Integrated Circuits on Superconducting Two-Dimensional Electron Gas Platform

Department of Physics,
Cavendish Laboratory,
Department of Physics, Cavendish Laboratory