2,635 research outputs found
Coulomb Oscillations in Antidots in the Integer and Fractional Quantum Hall Regimes
We report measurements of resistance oscillations in micron-scale antidots in
both the integer and fractional quantum Hall regimes. In the integer regime, we
conclude that oscillations are of the Coulomb type from the scaling of magnetic
field period with the number of edges bound to the antidot. Based on both
gate-voltage and field periods, we find at filling factor {\nu} = 2 a tunneling
charge of e and two charged edges. Generalizing this picture to the fractional
regime, we find (again, based on field and gate-voltage periods) at {\nu} = 2/3
a tunneling charge of (2/3)e and a single charged edge.Comment: related papers at http://marcuslab.harvard.ed
Quantum simulation of artificial Abelian gauge field using nitrogen-vacancy center ensembles coupled to superconducting resonators
We propose a potentially practical scheme to simulate artificial Abelian
gauge field for polaritons using a hybrid quantum system consisting of
nitrogen-vacancy center ensembles (NVEs) and superconducting transmission line
resonators (TLR). In our case, the collective excitations of NVEs play the role
of bosonic particles, and our multiport device tends to circulate polaritons in
a behavior like a charged particle in an external magnetic field. We discuss
the possibility of identifying signatures of the Hofstadter "butterfly" in the
optical spectra of the resonators, and analyze the ground state crossover for
different gauge fields. Our work opens new perspectives in quantum simulation
of condensed matter and many-body physics using hybrid spin-ensemble circuit
quantum electrodynamics system. The experimental feasibility and challenge are
justified using currently available technology.Comment: 6 papes+supplementary materia
Overdistention Operation of Cascaded Multilevel Inverters
In the past decade, the multilevel power converter has transitioned from an experimental concept to a standard product of many medium-voltage drive manufacturers. By utilizing small voltage steps, the multilevel topology offers higher power quality, higher voltage capability, lower switching losses, and improved electromagnetic compatibility over standard topologies. Recently, several researchers have focused on the cascaded multilevel inverter whereby two multilevel inverters are series connected to a motor load by splitting the neutral connection. The resulting performance is exceptional in terms of power quality since the overall number of voltage levels is effectively the product of the two cascaded inverters. This paper demonstrates that it is possible to extend this performance to an even higher number of voltage levels referred to as overdistended operation. This further improves the power quality that is significant in applications that have stringent total harmonic distorsion requirements, such as naval ship propulsion. A new control is introduced for overdistention operation and is validated with computer simulation and laboratory measurements
Over-Distention Operation of Cascaded Multilevel Inverters
Established research has shown that cascaded multilevel inverters can provide more voltage vectors per number of active semiconductors compared to typical multilevel converters. This feature is significant for increasing the drive performance as well as reducing the drive complexity and losses. When two inverters are cascaded, the maximum number of effective levels (or maximal distention operation) is the product of the number of levels of the individual inverters. It is possible to operate the cascaded inverter beyond maximum distention. The over-distention operation is desirable since it effectively increases the number of voltage levels in spite of some missing switching levels. This paper studies over-distention operation based on an inverter system where two three-level inverters are cascaded, which can generate eleven equivalent converting levels instead of nine levels under maximal distention condition. An advanced modulation technique is introduced to handle both the missing line-to-ground voltage levels and the balance of DC link capacitor voltages in over-distention operation. Computer simulation and experimental validation are presented to verify the proposed methods
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