Creation of Entanglement by Interaction with a Common Heat Bath

I show that entanglement between two qubits can be generated if the two qubits interact with a common heat bath in thermal equilibrium, but do not interact directly with each other. In most situations the entanglement is created for a very short time after the interaction with the heat bath is switched on, but depending on system, coupling, and heat bath, the entanglement may persist for arbitrarily long times. This mechanism sheds new light on the creation of entanglement. A particular example of two quantum dots in a closed cavity is discussed, where the heat bath is given by the blackbody radiation.Comment: 4 revtex pages, 1 eps figure; replaced with published version; short discussion on entanglement distillation adde

Hadron-nucleus scattering in the local reggeon model with pomeron loops for realistic nuclei

Contribution of simplest loops for hadron-nucleus scattering cross-sections is studied in the Local Reggeon Field Theory with a supercritical pomeron. It is shown that inside the nucleus the supercritical pomeron transforms into a subcritical one, so that perturbative treatment becomes possible. The pomeron intercept becomes complex, which leads to oscillations in the cross-sections.Comment: 13 pages, 6 figure

Testing Helioseismic-Holography Inversions for Supergranular Flows Using Synthetic Data

Supergranulation is one of the most visible length scales of solar convection and has been studied extensively by local helioseismology. We use synthetic data computed with the Seismic Propagation through Active Regions and Convection (SPARC) code to test regularized-least squares (RLS) inversions of helioseismic holography measurements for a supergranulation-like flow. The code simulates the acoustic wavefield by solving the linearized three-dimensional Euler equations in Cartesian geometry. We model a single supergranulation cell with a simple, axisymmetric, mass-conserving flow. The use of simulated data provides an opportunity for direct evaluation of the accuracy of measurement and inversion techniques. The RLS technique applied to helioseismic-holography measurements is generally successful in reproducing the structure of the horizontal flow field of the model supergranule cell. The errors are significant in horizontal-flow inversions near the top and bottom of the computational domain as well as in vertical-flow inversions throughout the domain. We show that the errors in the vertical velocity are due largely to cross talk from the horizontal velocity.Comment: 22 pages, 12 figues, accepted for publication in Solar Physic

Thermal equation of state of polarized fermions in one dimension via complex chemical potentials

We present a nonperturbative computation of the equation of state of polarized, attractively interacting, nonrelativistic fermions in one spatial dimension at finite temperature. We show results for the density, spin magnetization, magnetic susceptibility, and Tan's contact. We compare with the second-order virial expansion, a next-to-leading-order lattice perturbation theory calculation, and interpret our results in terms of pairing correlations. Our lattice Monte Carlo calculations implement an imaginary chemical potential difference to avoid the sign problem. The thermodynamic results on the imaginary side are analytically continued to obtain results on the real axis. We focus on an intermediate- to strong-coupling regime, and cover a wide range of temperatures and spin imbalances.Comment: 14 pages, 19 figures; published versio

Exclusive processes in position space and the pion distribution amplitude

We suggest to carry out lattice calculations of current correlators in position space, sandwiched between the vacuum and a hadron state (e.g. pion), in order to access hadronic light-cone distribution amplitudes (DAs). In this way the renormalization problem for composite lattice operators is avoided altogether, and the connection to the DA is done using perturbation theory in the continuum. As an example, the correlation function of two electromagnetic currents is calculated to the next-to-next-to-leading order accuracy in perturbation theory and including the twist-4 corrections. We argue that this strategy is fully competitive with direct lattice measurements of the moments of the DA, defined as matrix elements of local operators, and offers new insight in the space-time picture of hard exclusive reactions.Comment: 15 pages, 10 figure

Conditions driving chemical freeze-out

We propose the entropy density as the thermodynamic condition driving best the chemical freeze-out in heavy-ion collisions. Taking its value from lattice calculations at zero chemical potential, we find that it is excellent in reproducing the experimentally estimated freeze-out parameters. The two characteristic endpoints in the freeze-out diagram are reproduced as well.Comment: 8 pages, 5 eps figure

Simultaneous time-optimal control of the inversion of two spin 1/2 particles

We analyze the simultaneous time-optimal control of two-spin systems. The two non coupled spins which differ in the value of their chemical offsets are controlled by the same magnetic fields. Using an appropriate rotating frame, we restrict the study to the case of opposite shifts. We then show that the optimal solution of the inversion problem in a rotating frame is composed of a pulse sequence of maximum intensity and is similar to the optimal solution for inverting only one spin by using a non-resonant control field in the laboratory frame. An example is implemented experimentally using techniques of Nuclear Magnetic Resonance.Comment: 13 pages, 3 figure