14,373 research outputs found
Tuning Locality of Pair Coherence in Graphene-based Andreev Interferometers
We report on gate-tuned locality of superconductivity-induced phase-coherent magnetoconductance oscillations in a graphene-based Andreev interferometer, consisting of a T-shaped graphene bar in contact with a superconducting Al loop. The conductance oscillations arose from the flux change through the superconducting Al loop, with gate-dependent Fraunhofer-type modulation of the envelope. We confirm a transitional change in the character of the pair coherence, between local and nonlocal, in the same device as the effective length-to-width ratio of the device was modulated by tuning the pair-coherence length xi(T) in the graphene layer.open1133sciescopu
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Dust, Ice, and Gas in Time (DIGIT) Herschel Observations of GSS30-IRS1 in Ophiuchus
As a part of the "Dust, Ice, and Gas In Time" (DIGIT) key program on Herschel, we observed GSS30-IRS1, a Class I protostar located in Ophiuchus (d = 120 pc), with Herschel/Photodetector Array Camera and Spectrometer. More than 70 lines were detected within a wavelength range from 50 to 200 mu m, including CO, H2O, OH, and two atomic [O I] lines at 63 and 145 mu m. The [C II] line, known as a tracer of externally heated gas by the interstellar radiation field (ISRF), is also detected at 158 mu m. All lines, except [O I] and [C II], are detected only at the central spaxel of 9 ''.4 x 9 ''.4. The [O I] emissions are extended along a NE-SW orientation, and the [C II] line is detected over all spaxels, indicative of an external photodissociation region. The total [C II] intensity around GSS30 reveals that the far-ultraviolet radiation field is in the range of 3 to 20 G(0), where G(0) is in units of the Habing Field, 1.6 x 10(-3) erg cm(-2) s(-1). This enhanced external radiation field heats the envelope of GSS30-IRS1, causing the continuum emission to be extended, unlike the molecular emission. The best-fit continuum model of GSS30-IRS1 with the physical structure including flared disk, envelope, and outflow shows that the internal luminosity is 10 L-circle dot, and the region is externally heated by a radiation field enhanced by a factor of 130 compared to the standard local ISRF.NASANational Research Foundation of Korea (NRF) - Ministry of Education of the Korean government NRF-2012R1A1A2044689National Research Foundation (NRF) - Ministry of Education of KoreaAstronom
Quantification of Macroscopic Quantum Superpositions within Phase Space
Based on phase-space structures of quantum states, we propose a novel measure
to quantify macroscopic quantum superpositions. Our measure simultaneously
quantifies two different kinds of essential information for a given quantum
state in a harmonious manner: the degree of quantum coherence and the effective
size of the physical system that involves the superposition. It enjoys
remarkably good analytical and algebraic properties. It turns out to be the
most general and inclusive measure ever proposed that it can be applied to any
types of multipartite states and mixed states represented in phase space.Comment: 4 pages, 1 figure, accepted for publication in Phys. Rev. Let
Quantum states for perfectly secure secret sharing
In this work, we investigate what kinds of quantum states are feasible to
perform perfectly secure secret sharing, and present its necessary and
sufficient conditions. We also show that the states are bipartite distillable
for all bipartite splits, and hence the states could be distillable into the
Greenberger-Horne-Zeilinger state. We finally exhibit a class of secret-sharing
states, which have an arbitrarily small amount of bipartite distillable
entanglement for a certain split.Comment: 4 page
Concurrence of assistance and Mermin inequality on three-qubit pure states
We study a relation between the concurrence of assistance and the Mermin
inequality on three-qubit pure states. We find that if a given three-qubit pure
state has the minimal concurrence of assistance greater than 1/2 then the state
violates some Mermin inequality.Comment: 4 pages, 1 figur
Searching for Dark Photons with Maverick Top Partners
In this paper, we present a model in which an up-type vector-like quark (VLQ)
is charged under a new gauge force which kinetically mixes with the SM
hypercharge. The gauge boson of the is the dark photon, .
Traditional searches for VLQs rely on decays into Standard Model electroweak
bosons or Higgs. However, since no evidence for VLQs has been found at
the Large Hadron Collider (LHC), it is imperative to search for other novel
signatures of VLQs beyond their traditional decays. As we will show, if the
dark photon is much less massive than the Standard Model electroweak sector,
, for the large majority of the allowed parameter space
the VLQ predominately decays into the dark photon and the dark Higgs that
breaks the . That is, this VLQ is a `maverick top partner' with
nontraditional decays. One of the appeals of this scenario is that pair
production of the VLQ at the LHC occurs through the strong force and the rate
is determined by the gauge structure. Hence, the production of the dark photon
at the LHC only depends on the strong force and is largely independent of the
small kinetic mixing with hypercharge. This scenario provides a robust
framework to search for a light dark sector via searches for heavy colored
particles at the LHC.Comment: 40 pages and 11 figure
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