7,071 research outputs found
Ballistic Thermal Transistor of Dielectric Four-terminal Nanostructures
We report a theoretical model for a thermal transistor in dielectric
four-terminal nanostructures based on mesoscopic ballistic phonon transport, in
which a steady thermal flow condition of system is obtained to set up the
temperature field effect of gate. In the environment, thermal flow shows the
transisting behaviors at low temperatures: saturation, asymmetry, and
rectification. The phenomena can be explained reasonably by the nonlinear
variation of the temperature dependence of propagating phonon modes in
terminals. The results suggest the possibility of the novel nano-thermal
transistor fabrication
A Study of Fermi-LAT GeV gamma-ray Emission towards the Magnetar-harboring Supernova Remnant Kesteven 73 and Its Molecular Environment
We report our independent GeV gamma-ray study of the young shell-type
supernova remnant (SNR) Kes 73 which harbors a central magnetar, and CO-line
millimeter observations toward the SNR. Using 7.6 years of Fermi-LAT
observation data, we detected an extended gamma-ray source ("source A") with
the centroid on the west of the SNR, with a significance of 21.6 sigma in
0.1-300 GeV and an error circle of 5.4 arcminute in angular radius. The
gamma-ray spectrum cannot be reproduced by a pure leptonic emission or a pure
emission from the magnetar, and thus a hadronic emission component is needed.
The CO-line observations reveal a molecular cloud (MC) at V_LSR~90 km/s, which
demonstrates morphological correspondence with the western boundary of the SNR
brightened in multiwavelength. The 12CO (J=2-1)/12CO (J=1-0) ratio in the left
(blue) wing 85-88 km/s is prominently elevated to ~1.1 along the northwestern
boundary, providing kinematic evidence of the SNR-MC interaction. This SNR-MC
association yields a kinematic distance 9 kpc to Kes 73. The MC is shown to be
capable of accounting for the hadronic gamma-ray emission component. The
gamma-ray spectrum can be interpreted with a pure hadronic emission or a
magnetar+hadronic hybrid emission. In the case of pure hadronic emission, the
spectral index of the protons is 2.4, very similar to that of the
radio-emitting electrons, essentially consistent with the diffusive shock
acceleration theory. In the case of magnetar+hadronic hybrid emission, a
magnetic field decay rate >= 10^36 erg/s is needed to power the magnetar's
curvature radiation.Comment: 7 figures, published in Ap
Quantum logical gates with four-level SQUIDs coupled to a superconducting resonator
We propose a way for realizing a two-qubit controlled phase gate with
superconducting quantum interference devices (SQUIDs) coupled to a
superconducting resonator. In this proposal, the two lowest levels of each
SQUID serve as the logical states and two intermediate levels of each SQUID are
used for the gate realization. We show that neither adjustment of SQUID level
spacings during the gate operation nor uniformity in SQUID parameters is
required by this proposal. In addition, this proposal does not require the
adiabatic passage or a second-order detuning and thus the gate is much faster.Comment: 6 pages, 3 figure
- …