Intermittent quakes and record dynamics in the thermoremanent magnetization of a spin-glass

A novel method for analyzing the intermittent behavior of linear response data in aging systems is presented and applied to spin-glass thermoremanent magnetization (TRM) (Rodriguez et al. Phys. Rev. Lett. 91, 037203, 2003). The probability density function (PDF) of magnetic fluctuations is shown to have an asymmetric exponential tail, demonstrating that the demagnetization process is carried by intermittent, significant, spin rearrangements or \emph{quakes}. These quakes are most pronounced shortly after the field removal, $t/t_w \approx 1$ and in the non-equilibrium aging regime $t/t_w >>1$. For a broad temperature range, we study the dependence of the TRM decay rate on $t$, the time since the initial quench and on $t_w$, the time at which the magnetic field is cut. The $t$ and $t_w$ dependence of the rate is extracted numerically from the data and described analytically using the assumption that the linear response is subordinated to the intermittent process which spasmodically release the initial imbalances created by the quench.Comment: 8 pages, 9 figures. The paper has been expanded and restructured, the figures have been enlarged and improved. Final version, to appear in Phy. Rev.

Submicrosecond comparisons of time standards via the Navigation Technology Satellites (NTS)

An interim demonstration was performed of the time transfer capability of the NAVSTAR GPS system using a single NTS satellite. Measurements of time difference (pseudo-range) are made from the NTS tracking network and at the participating observatories. The NTS network measurements are used to compute the NTS orbit trajectory. The central NTS tracking station has a time link to the Naval Observatory UTC (USNO,MC1) master clock. Measurements are used with the NTS receiver at the remote observatory, the time transfer value UTC (USNO,MC1)-UTC (REMOTE, VIA NTS) is calculated. Intercomparisons were computed using predicted values of satellite clock offset and ephemeus

Entanglement between two superconducting qubits via interaction with non-classical radiation

We propose a scheme to physically interface superconducting nano-circuits and quantum optics. We address the transfer of quantum information between systems having different physical natures and defined in Hilbert spaces of different dimensions. In particular, we investigate the transfer of the entanglement initially in a non-classical state of a continuous-variable system to a pair of superconducting charge qubits. This set-up is able to drive an initially separable state of the qubits into an almost pure, highly entangled state suitable for quantum information processing.Comment: 4 pages, RevTeX; revised versio

Intermittency of glassy relaxation and the emergence of a non-equilibrium spontaneous measure in the aging regime

We consider heat exchange processes between non-equilibrium aging systems (in their activated regime) and the thermal bath in contact. We discuss a scenario where two different heat exchange processes concur in the overall heat dissipation: a stimulated fast process determined by the temperature of the bath and a spontaneous intermittent process determined by the fact that the system has been prepared in a non-equilibrium state. The latter is described by a probability distribution function (PDF) that has an exponential tail of width given by a parameter $\lambda$, and satisfies a fluctuation theorem (FT) governed by that parameter. The value of $\lambda$ is proportional to the so-called effective temperature, thereby providing a practical way to experimentally measure it by analyzing the PDF of intermittent events.Comment: Latex file, 8 pages + 5 postscript figure

Effect of the boundary condition on the vortex patterns in mesoscopic three-dimensional superconductors - disk and sphere

The vortex state of mesoscopic three-dimensional superconductors is determined using a minimization procedure of the Ginzburg-Landau free energy. We obtain the vortex pattern for a mesoscopic superconducting sphere and find that vortex lines are naturally bent and are closest to each other at the equatorial plane. For a superconducting disk with finite height, and under an applied magnetic field perpendicular to its major surface, we find that our method gives results consistent with previous calculations. The matching fields, the magnetization and $H_{c3}$, are obtained for models that differ according to their boundary properties. A change of the Ginzburg-Landau parameters near the surface can substantially enhance $H_{c3}$ as shown here.Comment: 7 pages, 4 figures (low resolution