2,483 research outputs found
Radio-frequency methods for Majorana-based quantum devices: fast charge sensing and phase diagram mapping
Radio-frequency (RF) reflectometry is implemented in hybrid
semiconductor-superconductor nanowire systems designed to probe Majorana zero
modes. Two approaches are presented. In the first, hybrid nanowire-based
devices are part of a resonant circuit, allowing conductance to be measured as
a function of several gate voltages ~40 times faster than using conventional
low-frequency lock-in methods. In the second, nanowire devices are capacitively
coupled to a nearby RF single-electron transistor made from a separate
nanowire, allowing RF detection of charge, including charge-only measurement of
the crossover from 2e inter-island charge transitions at zero magnetic field to
1e transitions at axial magnetic fields above 0.6 T, where a topological state
is expected. Single-electron sensing yields signal-to-noise exceeding 3 and
visibility 99.8% for a measurement time of 1 {\mu}s
Development of superconducting YBa2Cu3O(x) wires with low resistance electrical contacts
Materials exhibiting superconductivity above liquid nitrogen temperatures (77 K) will enable new applications of this phenomena. One of the first commercial applications of this technology will be superconducting magnets for medical imaging. However, a large number of aerospace applications of the high temperature superconducting materials have also been identified. These include magnetic suspension and balance of models in wind tunnels and resistanceless leads to anemometers. The development of superconducting wires fabricated from the ceramic materials is critical for these applications. The progress in application of a patented fiber process developed by Clemson University for the fabrication of superconducting wires is reviewed. The effect of particle size and heat treatment on the quality of materials is discussed. Recent advances made at Christopher Newport College in the development of micro-ohm resistance electrical contacts which are capable of carrying the highest reported direct current to this material is presented
Report of the Electromechanical Subsystems Panel
Deficiencies in electromechanical flight technology are evaluated and development recommendations are made. Specific items discussed include magnetic bearings, lubrication for long life, signal and power transfer devices, servo sensing devices, deployment/retraction devices, cryogenic devices, data storage, and ordnance substitutes
Direct cavity detection of Majorana pairs
No experiment could directly test the particle/antiparticle duality of
Majorana fermions, so far. However, this property represents a necessary
ingredient towards the realization of topological quantum computing schemes.
Here, we show how to complete this task by using microwave techniques. The
direct coupling between a pair of overlapping Majorana bound states and the
electric field from a microwave cavity is extremely difficult to detect due to
the self-adjoint character of Majorana fermions which forbids direct energy
exchanges with the cavity. We show theoretically how this problem can be
circumvented by using photo-assisted tunneling to fermionic reservoirs. The
absence of direct microwave transition inside the Majorana pair in spite of the
light-Majorana coupling would represent a smoking gun for the Majorana
self-adjoint character.Comment: 6 pages, 4 figure
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