132,294 research outputs found
Measurement-induced nonlocality over two-sided projective measurements
Measurement-induced nonlocality (MiN), introduced by Luo and Fu [Phys. Rev.
Lett. 106(2011)120401], is a kind of quantum correlation that beyond
entanglement and even beyond quantum discord. Recently, we extended MiN to
infinite-dimensional bipartite system [arXiv:1107.0355]. MiN is defined over
one-sided projective measurements. In this letter we introduce a
measurement-induced nonlocality over two-sided projective measurements. The
nullity of this two-sided MiN is characterized, a formula for calculating
two-sided MiN for pure states is proposed, and a lower bound of (two-sided) MiN
for maximally entangled mixed states is given. In addition, we find that
(two-sided) MiN is not continuous. The two-sided geometric measure of quantum
discord (GMQD) is introduced in [Phys. Lett. A 376(2012)320--324]. We extend it
to infinite-dimensional system and then compare it with the two-sided MiN. Both
finite- and infinite-dimensional cases are considered.Comment: 12 page
Theory of quasiparticle interference on the surface of a strong topological insulator
Electrons on the surface of a strong topological insulator, such as Bi2Te3 or
Bi1-xSnx, form a topologically protected helical liquid whose excitation
spectrum contains an odd number of massless Dirac fermions. A theoretical
survey and classification is given of the universal features, observable by the
ordinary and spin-polarized scanning tunneling spectroscopy, in the
interference patterns resulting from the quasiparticle scattering by magnetic
and non-magnetic impurities in such a helical liquid. Our results confirm the
absence of backscattering from non-magnetic impurities observed in recent
experiments and predict new interference features, uniquely characteristic of
the helical liquid, when the scatterers are magnetic.Comment: 4 pages, 2 figures, 1 table. Version to appear in PRB/RC; Typos
correcte
Teleporting a rotation on remote photons
Quamtum remote rotation allows implement local quantum operation on remote
systems with shared entanglement. Here we report an experimental demonstration
of remote rotation on single photons using linear optical element. And the
local dephase is also teleported during the process. The scheme can be
generalized to any controlled rotation commutes with .Comment: 5 pages, 4 figure
Generating mid-IR octave-spanning supercontinua and few-cycle pulses with solitons in phase-mismatched quadratic nonlinear crystals
We discuss a novel method for generating octave-spanning supercontinua and
few-cycle pulses in the important mid-IR wavelength range. The technique relies
on strongly phase-mismatched cascaded second-harmonic generation (SHG) in
mid-IR nonlinear frequency conversion crystals. Importantly we here investigate
the so-called noncritical SHG case, where no phase matching can be achieved but
as a compensation the largest quadratic nonlinearities are exploited. A
self-defocusing temporal soliton can be excited if the cascading nonlinearity
is larger than the competing material self-focusing nonlinearity, and we define
a suitable figure of merit to screen a wide range of mid-IR dielectric and
semiconductor materials with large effective second-order nonlinearities
. The best candidates have simultaneously a large bandgap and a
large . We show selected realistic numerical examples using one of
the promising crystals: in one case soliton pulse compression from 50 fs to 15
fs (1.5 cycles) at 3.0\mic is achieved, and at the same time a 3-cycle
dispersive wave at 5.0\mic is formed that can be isolated using a long-pass
filter. In another example we show that extremely broadband supercontinua can
form spanning the near-IR to the end of the mid-IR (nearly 4 octaves).Comment: submitted to Optics Materials Express special issue on mid-IR
photonic
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