18,559 research outputs found
Terahertz detection based on nonlinear Hall effect without magnetic field
We propose a method for broadband long-wavelength photodetection using the
nonlinear Hall effect in non-centrosymmetric quantum materials. The inherently
quadratic relation between transverse current and input voltage at zero
magnetic field is used to rectify the incident terahertz or infrared electric
field into a direct current, without invoking any diode. Our photodetector
operates at zero external bias with fast response speed and has zero threshold
voltage. Remarkably, the intrinsic current responsivity due to Berry curvature
mechanism is a material property independent of the incident frequency or the
scattering rate, which can be evaluated from first-principles electronic
structure calculations. We identify the Weyl semimetal NbP for terahertz
photodection with large current responsivity reaching A/W without
external bias.Comment: 4 pages, 3 figure
Josephson dynamics of a spin-orbit coupled Bose-Einstein condensate in a double well potential
We investigate the quantum dynamics of an experimentally realized spin-orbit
coupled Bose-Einstein condensate in a double well potential. The spin-orbit
coupling can significantly enhance the atomic inter-well tunneling. We find the
coexistence of internal and external Josephson effects in the system, which are
moreover inherently coupled in a complicated form even in the absence of
interatomic interactions. Moreover, we show that the spin-dependent tunneling
between two wells can induce a net atomic spin current referred as spin
Josephson effects. Such novel spin Josephson effects can be observable for
realistically experimental conditions.Comment: 8 page
Assisted optimal state discrimination without entanglement
A fundamental problem in quantum information is to explore the roles of
different quantum correlations in a quantum information procedure. Recent work
[Phys. Rev. Lett., 107 (2011) 080401] shows that the protocol for assisted
optimal state discrimination (AOSD) may be implemented successfully without
entanglement, but with another correlation, quantum dissonance. However, both
the original work and the extension to discrimination of states [Phys. Rev.
A, 85 (2012) 022328] have only proved that entanglement can be absent in the
case with equal a \emph{priori} probabilities. By improving the protocol in
[Sci. Rep., 3 (2013) 2134], we investigate this topic in a simple case to
discriminate three nonorthogonal states of a qutrit, with positive real
overlaps. In our procedure, the entanglement between the qutrit and an
auxiliary qubit is found to be completely unnecessary. This result shows that
the quantum dissonance may play as a key role in optimal state discrimination
assisted by a qubit for more general cases.Comment: 6 pages, 3 figures. Accepted by EPL. We extended the protocol for
assisted optimal state discrimination to the case with positive real
overlaps, and presented a proof for the absence of entanglemen
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