Numerical simulations of a ballistic spin interferometer with the Rashba spin-orbital interaction

We numerically investigate the transport behavior of a quasi one-dimension (1D) square loop device containing the Rashba spin-orbital interaction in the presence of a magnetic flux. The conductance versus the magnetic field shows the Al'tshuler-Aronov-Spivak (AAS) and Aharonov-Bohm (AB) oscillations. We focus on the oscillatory amplitudes, and find that both of them are strongly dependent on the spin precession angle (i.e. the strength of the spin-orbit interaction) and exhibit no-periodic oscillations, which are well in agreement with a recent experiment by Koga et al. [cond-mat/0504743(unpublished)]. However, our numerical results for the ideal 1D square loop device for the node positions of the amplitudes of the AB and AAS oscillations are found to be of some discrepancies comparing with quasi-1D square loop with a finite width. In the presence of disorder and taking the disorder ensemble average, the AB oscillation in the conductance will disappear, while the time-reversal symmetric AAS oscillation still remains. Furthermore, the node positions of the AAS oscillatory amplitude remains the same.Comment: 6 pages, 7 figure

On the Conductance Sum Rule for the Hierarchical Edge States of the Fractional Quantum Hall Effect

The conductance sum rule for the hierarchical edge channel currents of a Fractional Quantum Hall Effect state is derived analytically within the Haldane-Halperin hierarchy scheme. We provide also an intuitive interpretation for the hierarchical drift velocities of the edge excitations.Comment: 11 pages, no figure, Revtex 3.0, IC/93/329, ASITP-93-5

Detecting the inseparability and distillability of continuous variable states in Fock space

The partial transposition(PT) operation is an effecient tool in detecting the inseparability of a mixed state. We give an explicit formula for the PT operation for the continuous variable states in Fock space. We then give the necessary and sufficient condition for the positivity of Gaussian operators. Based on this, a number of creterions on the inseparability and distillability for the multimode Gaussian states are naturally drawn. We finally give an explicit formula for the state in a subspace of a global Gaussian state. This formula, together with the known results for Gaussian states, gives the criterions for the inseparability and distillability in a subspace of the global Gaussian state.Comment: 8 pages, no figure, some typing errors correcte

A Unified Quantum NOT Gate

We study the feasibility of implementing a quantum NOT gate (approximate) when the quantum state lies between two latitudes on the Bloch's sphere and present an analytical formula for the optimized 1-to-$M$ quantum NOT gate. Our result generalizes previous results concerning quantum NOT gate for a quantum state distributed uniformly on the whole Bloch sphere as well as the phase covariant quantum state. We have also shown that such 1-to-$M$ optimized NOT gate can be implemented using a sequential generation scheme via matrix product states (MPS)

Fermi Surface Evolution, Pseudo Gap and Stagger Gauge Field Fluctuation in Underdoped Cuprates

In the context of t-J model we show that in underdoped regime,beside the usual long wave length gauge field fluctuation, an additional low energy fluctuation, staggered gauge field fluctuation plays a crucial role in the evolution of Fermi surface(FS) as well as the line shape of spectral function for the cuprates. By including the staggered gauge field fluctuation we calculate the spectral function of the electrons by RPA(random phase approximation). The line shape of the spectral function near $(\pi,0)$ is very broad in underdoped case and is quite sharp in overdoped case. For the spectral function near $(0.5\pi,0.5\pi)$, the quasiparticle peaks are always very sharp in both underdoped and overdoped case. The temperature dependence of the spectral function is also discussed in our present calculation. These results fit well with the recent ARPES experiments. We also calculate the FS crossover from a small four segment like FS to a large continuous FS. The reason of such kind of FS crossover is ascribed to the staggered gauge field fluctuation which is strong in underdoped regime and becomes much weaker in overdoped regime. The pseudo gap extracted from the ARPES data can be also interpreted by the calculation.Comment: 4 pages,6 eps figures include

Control the entanglement of two atoms in an optical cavity via white noise

Two two-level atoms within a leaky optical cavity is driven by two independent external optical white noise fields. We investigate how entanglement between two atoms arises in such a situation. The steady state entanglement of two atoms is also investigated. A stochastic-resonance-like behavior of entanglement is revealed. Finally, the Bell violation between atoms is discussed.Comment: 10 pages, 9 figure

GlobSim (v1.0): Deriving meteorological time series for point locations from multiple global reanalyses

Simulations of land-surface processes and phenomena often require driving time series of meteorological variables. Corresponding observations, however, are unavailable in most locations, even more so, when considering the duration, continuity and data quality required. Atmospheric reanalyses provide glo