638 research outputs found
Conductance of p-n-p graphene structures with 'air-bridge' top gates
We have fabricated graphene devices with a top gate separated from the
graphene layer by an air gap--a design which does not decrease the mobility of
charge carriers under the gate. This gate is used to realise p-n-p structures
where the conducting properties of chiral carriers are studied. The band
profile of the structures is calculated taking into account the specifics of
the graphene density of states and is used to find the resistance of the p-n
junctions expected for chiral carriers. We show that ballistic p-n junctions
have larger resistance than diffusive ones. This is caused by suppressed
transmission of chiral carriers at angles away from the normal to the junction.Comment: to be published in Nano Letter
Field-induced insulating states in a graphene superlattice
We report on high-field magnetotransport (B up to 35 T) on a gated
superlattice based on single-layer graphene aligned on top of hexagonal boron
nitride. The large-period moir\'e modulation (15 nm) enables us to access the
Hofstadter spectrum in the vicinity of and above one flux quantum per
superlattice unit cell (Phi/Phi_0 = 1 at B = 22 T). We thereby reveal, in
addition to the spin-valley antiferromagnet at nu = 0, two insulating states
developing in positive and negative effective magnetic fields from the main nu
= 1 and nu = -2 quantum Hall states respectively. We investigate the field
dependence of the energy gaps associated with these insulating states, which we
quantify from the temperature-activated peak resistance. Referring to a simple
model of local Landau quantization of third generation Dirac fermions arising
at Phi/Phi_0 = 1, we describe the different microscopic origins of the
insulating states and experimentally determine the energy-momentum dispersion
of the emergent gapped Dirac quasi-particles
Quantum teleportation of EPR pair by three-particle entanglement
Teleportation of an EPR pair using triplet in state of the
Horne-Greenberger-Zeilinger form to two receivers is considered. It needs a
three-particle basis for joint measurement. By contrast the one qubit
teleportation the required basis is not maximally entangled. It consists of the
states corresponding to the maximally entanglement of two particles only. Using
outcomes of measurement both receivers can recover an unknown EPR state however
one of them can not do it separately. Teleportation of the N-particle
entanglement is discussed.Comment: 7 pages, LaTeX, 3 figure
Giant Nonlocality near the Dirac Point in Graphene
Transport measurements have been a powerful tool for uncovering new
electronic phenomena in graphene. We report nonlocal measurements performed in
the Hall bar geometry with voltage probes far away from the classical path of
charge flow. We observe a large nonlocal response near the Dirac point in
fields as low as 0.1T, which persists up to room temperature. The nonlocality
is consistent with the long-range flavor currents induced by lifting of
spin/valley degeneracy. The effect is expected to contribute strongly to all
magnetotransport phenomena near the neutrality point
On the Mass Eigenstate Composition of the 8B Neutrinos from the Sun
The present data of gallium experiments provide indirectly the only
experimental limit on the fraction of mass eigenstate for the B
neutrinos from the Sun. However, if to use the experimental data alone, the
fraction of and, consequently, still is allowed to
be varied within a rather broad range. The further experimental efforts are
needed to clear this point.Comment: 13 pages, 1 figure, 1 table. Corrected version, published in
JCAP04(2007)00
Quantum teleportation of entangled coherent states
We propose a simple scheme for the quantum teleportation of both bipartite
and multipartite entangled coherent states with the successful probability 1/2.
The scheme is based on only linear optical devices such as beam splitters and
phase shifters, and two-mode photon number measurements. The quantum channels
described by multipartite maximally entangled coherent states are readily made
by the beam splitters and phase shifters.Comment: 4 pages, no figure
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