598 research outputs found
The Effects of Symmetries on Quantum Fidelity Decay
We explore the effect of a system's symmetries on fidelity decay behavior.
Chaos-like exponential fidelity decay behavior occurs in non-chaotic systems
when the system possesses symmetries and the applied perturbation is not tied
to a classical parameter. Similar systems without symmetries exhibit
faster-than-exponential decay under the same type of perturbation. This
counter-intuitive result, that extra symmetries cause the system to behave in a
chaotic fashion, may have important ramifications for quantum error correction.Comment: 5 pages, 3 figures, to be published Phys. Rev. E Rapid Communicatio
Luttinger Liquid Instability in the One Dimensional t-J Model
We study the t-J model in one dimension by numerically projecting the true
ground state from a Luttinger liquid trial wave function. We find the model
exhibits Luttinger liquid behavior for most of the phase diagram in which
interaction strength and density are varied. However at small densities and
high interaction strengths a new phase with a gap to spin excitations and
enhanced superconducting correlations is found. We show this phase is a
Luther-Emery liquid and study its correlation functions.Comment: REVTEX, 11 pages. 4 Figures available on request from
[email protected]
Effect of nonmagnetic impurities on stripes in high-Tc cuprates
We perform the numerically exact diagonalization study of the t-J model with
nonmagnetic impurities to clarify the relation between Zn impurities and the
stripes. By examining the hole-hole correlation function for a two-hole
\sqrt{18}x\sqrt{18} cluster with a single impurity, we find that the impurity
has a tendency to stabilize vertical charge stripes. This tendency is caused by
the gain of the kinetic energy of holes moving along the stripes that are
formed avoiding the impurity.Comment: 3 pages including 2 figures. Proceedings for ISS2000 (Tokyo, October
2000). To be published in Physica
Neutrophil-mediated post-ischemic tubular leakage in the rat kidney
Neutrophil-mediated post-ischemic tubular leakage in the rat kidney. Neutropenia was induced in male Sprague-Dawley rats by administration of antineutrophil serum (ANS). A control group received an equal volume of inactive serum. After 45 minutes of unilateral complete renal ischemia the renal blood flow (RBF) was measured by an electromagnetic flow meter. The net filtration force (NFF) in glomerular capillaries, single nephron filtration rate (SNGFR) and frequency of tubular obstructions were estimated by a micropuncture technique. Tubular leakage was measured from the fractional recovery in the normal contralateral kidney of 3H- or 14C-inulin injected into surface proximal and distal tubules of the post-ischemic kidney. Neither ANS nor inactive serum had any influence on inulin clearance (CIn) in the normal kidney. In the post-ischemic kidney, CIn was four times higher in ANS-treated than in control animals. There was no difference in RBF, NFF, SNGFR or the frequency of tubular obstructions between neutrophil-depleted and control animals. The transtubular leakage of inulin injected into proximal tubules was substantially less in the ANS-treated than in the control group (11.3 ± 1.5% vs. 35.1 ± 6.5%; P < 0.01). But distal tubular leakage was equal in the two groups. The control group showed isosthenuria (350 ± 29mOsm · kg-1), while ANS-treated animals produced hyperosmolar urine (555 ± 60mOsm · kg-1; P < 0.05). It is concluded that neutrophil granulocytes mediate post-ischemic tubular leakage, which contributes to the depression in renal clearance parameters and the inability to produce hyperosmolar urine
Implementing Jastrow--Gutzwiller operators on a quantum computer using the cascaded variational quantum eigensolver algorithm
A Jastrow--Gutzwiller operator adds many-body correlations to a quantum
state. However, the operator is non-unitary, making it difficult to implement
directly on a quantum computer. We present a novel implementation of the
Jastrow--Gutzwiller operator using the cascaded variational quantum eigensolver
algorithm. We demonstrate the method on IBM Q Lagos for a Hubbard model
Cascaded variational quantum eigensolver algorithm
We present a cascaded variational quantum eigensolver algorithm that only
requires the execution of a set of quantum circuits once rather than at every
iteration during the parameter optimization process, thereby reducing the
number of needed circuit executions. This algorithm lets a quantum processing
unit probe all the needed probability mass functions and a classical processing
unit perform all the remaining calculations, including the variational
optimization. The ansatz form does not restrict the solution space and provide
full control over the parameter space, including the implementation of symmetry
and other physically motivated constraints.Comment: 5 pages, 2 figure
The breakdown of the Nagaoka phase in the 2D t-J model
In the limit of weak exchange, J, at low hole concentration, the ground state
of the 2D t-J model is believed to be ferromagnetic. We study the leading
instability of this Nagaoka state, which emerges with increasing J. Both exact
diagonalization of small clusters, and a semiclassical analytical calculation
of larger systems show that above a certain critical value of the exchange,
Nagaoka's state is unstable to phase separation. In a finite-size system a
bubble of antiferromagnetic Mott insulator appears in the ground state above
this threshold. The size of this bubble depends on the hole concentration and
scales as a power of the system size, N
Stripes due to the next-nearest neighbor exchange in high-Tc cuprates
We propose a possible mechanism of the charge stripe order due to the
next-nearest neighbor exchange interaction J' in the two-dimensional t-J model,
based on the concept of the phase separation. We also calculate some hole
correlation functions of the finite cluster of the model using the numerical
diagonalization, to examine the realization of the mechanism. It is also found
that the next-nearest neighbor hopping t' suppresses the stripe order induced
by the present mechanism for t'0.Comment: 4 pages, Revtex, with 5 eps figures, to appear in Phys. Rev. B Rapid
Communications (April 1, 2001
Limits on Phase Separation for Two-Dimensional Strongly Correlated Electrons
From calculations of the high temperature series for the free energy of the
two-dimensional t-J model we construct series for ratios of the free energy per
hole. The ratios can be extrapolated very accurately to low temperatures and
used to investigate phase separation. Our results confirm that phase separation
occurs only for J/t greater than 1.2. Also, the phase transition into the phase
separated state has Tc of approximately 0.25J for large J/t.Comment: 4 pages, 6 figure
Photoluminescence Spectroscopy of the Molecular Biexciton in Vertically Stacked Quantum Dot Pairs
We present photoluminescence studies of the molecular neutral
biexciton-exciton spectra of individual vertically stacked InAs/GaAs quantum
dot pairs. We tune either the hole or the electron levels of the two dots into
tunneling resonances. The spectra are described well within a few-level,
few-particle molecular model. Their properties can be modified broadly by an
electric field and by structural design, which makes them highly attractive for
controlling nonlinear optical properties.Comment: 4 pages, 5 figures, (v2, revision based on reviewers comments,
published
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