8,158 research outputs found
Quantum Noise of Kramers-Kronig Receiver
Abstrac--Kramers-Kronig (KK) receiver, which is equivalent to heterodyne
detection with one single photodetector, provides an efficient method to
reconstruct the complex-valued optical field by means of intensity detection
given a minimum-phase signal. In this paper, quantum noise of the KK receiver
is derived analytically and compared with that of the balanced heterodyne
detection. We show that the quantum noise of the KK receiver keeps the radical
fluctuation of the measured signal the same as that of the balanced heterodyne
detection, while compressing the tangential noise to 1/3 times the radical one
using the information provided by the Hilbert transform. In consequence, the KK
receiver has 3/2 times the signal-to-noise ratio of balanced heterodyne
detection while presenting an asymmetric distribution of fluctuations, which is
also different from that of the latter. More interestingly, the projected
in-phase and quadrature field operators of the retrieved signal after down
conversion have a time dependent quantum noise distribution depending on the
time-varying phase. This property provides a feasible scheme for controlling
the fluctuation distribution according to the requirements of measurement
accuracy in the specific direction. Under the condition of strong carrier wave,
the fluctuations of the component requiring to be measured more accurately can
be compressed to 1 / 6, which is even lower than 1/4 by measuring a coherent
state. Finally, we prove the analytic conclusions by simulation results
Comment on Reparametrization Invariance of Quark-Lepton Complementarity
We study the complementarity between quark and lepton mixing angles (QLC),
the sum of an angle in quark mixing and the corresponding angle in lepton
mixing is . Experimentally in the standard PDG parametrization, two such
relations exist approximately. These QLC relations are accidental which only
manifest themselves in the PDG parametrization. We propose reparametrization
invariant expressions for the complementarity relations in terms of the
magnitude of the elements in the quark and lepton mixing matrices. In the exact
QLC limit, it is found that and . Expressions with deviations
from exact complementarity are obtained. Implications of these relations are
also discussed.Comment: 5 pages and 1 figure. Implications for recent Daya-Bay neutrino data
on theta_{13} discusse
Large Water Management Projects and Schistosomiasis Control, Dongting Lake Region, China
Two large water projects will likely extend the range of snail habitats and increase schistosome transmission
Role of dimensional crossover on spin-orbit torque efficiency in magnetic insulator thin films
Magnetic insulators (MIs) attract tremendous interest for spintronic
applications due to low Gilbert damping and absence of Ohmic loss. Magnetic
order of MIs can be manipulated and even switched by spin-orbit torques (SOTs)
generated through spin Hall effect and Rashba-Edelstein effect in heavy
metal/MI bilayers. SOTs on MIs are more intriguing than magnetic metals since
SOTs cannot be transferred to MIs through direct injection of electron spins.
Understanding of SOTs on MIs remains elusive, especially how SOTs scale with
the film thickness. Here, we observe the critical role of dimensionality on the
SOT efficiency by systematically studying the MI layer thickness dependent SOT
efficiency in tungsten/thulium iron garnet (W/TmIG) bilayers. We first show
that the TmIG thin film evolves from two-dimensional to three-dimensional
magnetic phase transitions as the thickness increases, due to the suppression
of long-wavelength thermal fluctuation. Then, we report the significant
enhancement of the measured SOT efficiency as the thickness increases. We
attribute this effect to the increase of the magnetic moment density in concert
with the suppression of thermal fluctuations. At last, we demonstrate the
current-induced SOT switching in the W/TmIG bilayers with a TmIG thickness up
to 15 nm. The switching current density is comparable with those of heavy
metal/ferromagnetic metal cases. Our findings shed light on the understanding
of SOTs in MIs, which is important for the future development of ultrathin
MI-based low-power spintronics
Facile synthesis of composition-tuned ZnO/Zn x Cd1-xSe nanowires for photovoltaic applications
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