56 research outputs found
A short note on spin pumping theory with Landau-Lifshitz-Gilbert equation under quantum fluctuation; necessity for quantization of localized spin
We would like to point out the blind spots of the approach combining the spin
pumping theory proposed by Tserkovnyak et al. with the Landau-Lifshitz-Gilbert
equation; this method has been widely used for interpreting vast experimental
results. The essence of the spin pumping effect is the quantum fluctuation.
Thus, localized spin degrees of freedom should be quantized, i.e. be treated as
magnons not as classical variables. Consequently, the precessing ferromagnet
can be regarded as a magnon battery. This point of view will be useful for
further progress of spintronics.Comment: 10pages, 1 figure. This article is closely related to the work by K.
N.; arXiv:1201.194
Quantum dynamics and statistics of two coupled down-conversion processes
In the framework of Heisenberg-Langevin theory the dynamical and statistical
effects arising from the linear interaction of two nondegenerate
down-conversion processes are investigated. Using the strong-pumping
approximation the analytical solution of equations of motion is calculated. The
phenomena reminiscent of Zeno and anti-Zeno effects are examined. The
possibility of phase-controlled and mismatch-controlled switching is
illustrated.Comment: 17 pages, 7 figure
Experimental test of strongly non-classical character of a noisy squeezed single-photon state
We experimentally verify the quantum non-Gaussian character of a
conditionally generated noisy squeezed single-photon state with positive Wigner
function. Employing an optimized witness based on probabilities of squeezed
vacuum and squeezed single-photon states we prove that the state cannot be
expressed as a mixture of Gaussian states. In our experiment, the non-Gaussian
state is generated by conditional subtraction of a single photon from squeezed
vacuum state. The state is probed with a homodyne detector and the witness is
determined by averaging a suitable pattern function over the measured homodyne
data. Our experimental results are in good agreement with a theoretical fit
obtained from a simple yet realistic model of the experimental setup.Comment: 10 pages, 8 figures, REVTeX
Relative entropy of entanglement of a kind of two qubit entangled states
We in this paper strictly prove that some block diagonalizable two qubit
entangled state with six none zero elements reaches its quantum relative
entropy entanglement by the a separable state having the same matrix structure.
The entangled state comprises local filtering result state as a special case.Comment: 5 page
Squeezing and entanglement in continous variable systems
Based on total variance of a pair of Einstein-Podolsky-Rosen (EPR) type
operators, the generalized EPR entangled states in continuous variable systems
are defined. We show that such entangled states must correspond with two-mode
squeezing states whether these states are Gaussian or not and whether they are
pure or not. With help of the relation between the total variance and the
entanglement, the degree of such entanglement is also defined. Through
analyzing some specific cases, we see that this method is very convenient and
easy in practical application. In addition, an entangled state with no
squeezing is studied, which reveals that there certainly exist something
unknown about entanglement in continuous variable systems.Comment: 5 page
- …