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