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Simultaneous continuous measurement of photon-counting and homodyne detection on a free photon field: dynamics of state reduction and mutual influence of measurement backaction  [PDF]
Yui Kuramochi,Yu Watanabe,Masahito Ueda
Physics , 2012, DOI: 10.1088/1751-8113/46/42/425303
Abstract: We analyze a simultaneous continuous measurement of photon-counting and homodyne detection. The stochastic master equation or stochastic Schr\"odinger equation describing the measurement process includes both jump-type and diffusive-type stochastic increments. Analytic expressions of the wave function conditioned on homodyne and photon-counting records are obtained, yielding the probability density distributions and generating functions of the measurement records. Formula for the expectation values of the homodyne records conditioned on a photon-counting event is also derived which quantitatively describes the measurement backaction of photon-counting on the homodyne output. The obtained results are applied to typical initial states --- coherent, number, thermal, and squeezed states. Monte Carlo simulations of the measurement processes are also presented to demonstrate the dynamics of the combined measurement process.
Coronal Magnetic Field Measurement from EUV Images made by the Solar Dynamics Observatory  [PDF]
Nat Gopalswamy,Nariaki Nitta,Sachiko Akiyama,Pertti M?kel?,Seiji Yashiro
Physics , 2011, DOI: 10.1088/0004-637X/744/1/72
Abstract: By measuring the geometrical properties of the coronal mass ejection (CME) flux rope and the leading shock observed on 2010 June 13 by the Solar Dynamics Observatory (SDO) mission's Atmospheric Imaging Assembly (AIA) we determine the Alfv\'en speed and the magnetic field strength in the inner corona at a heliocentric distance of ~ 1.4 Rs. The basic measurements are the shock standoff distance (deltaR) ahead of the CME flux rope, the radius of curvature of the flux rope (Rc), and the shock speed. We first derive the Alfv\'enic Mach number (M) using the relationship, deltaR/Rc = 0.81[(gamma-1) M^2 + 2]/[(gamma+1)(M^2-1)], where gamma is the only parameter that needed to be assumed. For gamma =4/3, the Mach number declined from 3.7 to 1.5 indicating shock weakening within the field of view of the imager. The shock formation coincided with the appearance of a type II radio burst at a frequency of ~300 MHz (harmonic component), providing an independent confirmation of the shock. The shock compression ratio derived from the radio dynamic spectrum was found to be consistent with that derived from the theory of fast mode MHD shocks. From the measured shock speed and the derived Mach number, we found the Alfv\'en speed to increase from ~140 km/s to 460 km/s over the distance range 1.2 to 1.5 Rs. By deriving the upstream plasma density from the emission frequency of the associated type II radio burst, we determined the coronal magnetic field to be in the range 1.3 to 1.5 G. The derived magnetic field values are consistent with other estimates in a similar distance range. This work demonstrates that the EUV imagers, in the presence of radio dynamic spectra, can be used as coronal magnetometers.
On quasi-free dynamics on the resolvent algebra  [PDF]
Hajime Moriya
Physics , 2014,
Abstract: The resolvent algebra is a new C*-algebra of the canonical commutation relations of a boson field given by Buchholz-Grundling. We study analytic properties of quasi-free dynamics on the resolvent algebra. Subsequently we consider a supersymmetric quasi-free dynamics on the graded C*-algebra made of a Clifford (fermion) algebra and a resolvent (boson) algebra. We establish an infinitesimal supersymmetry formula upon the GNS Hilbert space for any regular state satisfying some mild requirement which is standard in quantum field theory. We assert that the supersymmetric dynamics is given as a C*-dynamics.
Detection of Quasi-equilibrium using Jeener-Broekaert experiment combined with multiple-quantum coherence spectra measurement under spin-reversion dynamics  [PDF]
H H. Segnorile,C. E. González,R. C. Zamar
Physics , 2015,
Abstract: We present an NMR experiment to detect the evolution of a spin system during the transient to a quasi-equilibrium state. In this way, new evidence is presented in favor of irreversible decoherence as the mechanism which leads an initial out-of-equilibrium state to quasi-equilibrium. The results are obtained using a modified Jeener-Broekaert experiment where a spin reversion pulse sequence and a decode of coherence are included. The sequence also allows visualizing the evolution of the full spectra of the different coherences during the formation of the quasi-equilibrium. We use different reversion strategies on three nematic liquid crystal samples. We conclude that the eigen-selection observed as an evidence of irreversible decoherence is an indication that the spin system in liquid-crystal NMR experiments, conform actual quantum open systems, where the quasi-equilibrium is a rigorous description of their dynamics in a time-scale far earlier than thermal equilibrium.
Quantum dynamics in single spin measurement  [PDF]
Stefano Mancini,David Vitali,Hector Moya-Cessa
Physics , 2003, DOI: 10.1103/PhysRevB.71.054406
Abstract: We study the quantum dynamics of a model for the single-spin measurement in magnetic-resonance force microscopy. We consider an oscillating driven cantilever coupled with the magnetic moment of the sample. Then, the cantilever is damped through an external bath and its readout is provided by a radiation field. Conditions for reliable measurements will be discussed.
Quasi-equilibrium in glassy dynamics: an algebraic view  [PDF]
Silvio Franz,Giorgio Parisi
Physics , 2012, DOI: 10.1088/1742-5468/2013/02/P02003
Abstract: We study a chain of identical glassy systems in a constrained equilibrium where each bond of the chain is forced to remain at a preassigned distance to the previous one. We apply this description to Mean Field Glassy systems in the limit of long chain where each bond is close to the previous one. We show that in specific conditions this pseudo-dynamic process can formally describe real relaxational dynamics the long time. In particular, in mean field spin glass models we can recover in this way the equations of Langevin dynamics in the long time limit at the dynamical transition temperature and below. We interpret the formal identity as an evidence that in these situations the configuration space is explored in a quasi-equilibrium fashion. Our general formalism, that relates dynamics to equilibrium puts slow dynamics in a new perspective and opens the way to the computation of new dynamical quantities in glassy systems.
Anisotropy and Field-Dependence of the Spin-Density-Wave Dynamics in the Quasi One-Dimensional Conductor (TMTSF)_2PF_6  [PDF]
P. Zornoza,K. Petukhov,M. Dressel,N. Biskup,T. Vuletic,S. Tomic
Physics , 2004, DOI: 10.1140/epjb/e2005-00223-3
Abstract: The anisotropic and non-linear transport properties of the quasi one-dimensional organic conductor (TMTSF)_2PF_6 have been studied by dc, radiofrequency, and microwave methods. Microwave experiments along all three axes reveal that collective transport, which is considered to be the fingerprint of the spin-density-wave condensate, also occurs in the perpendicular b' direction. The pinned mode resonance is present in the $a$ and b'-axes response, but not along the least conducting c* direction. The ac-field threshold, above which the spin-density-wave response is non-linear, strongly decreases as the temperature drops below 4 K. With increasing strength of the microwave electric field and of the radiofrequency signal, the pinned mode and the screened phason loss-peak shift to lower frequencies. In the non-linear regime, in addition to the phason relaxation mode with Arrhenius-like resistive decay, an additional mode with very long and temperature-independent relaxation time appears below 4 K. We attribute the new process to short-wavelength spin-density-wave excitations associated with discommensurations in a random commensurate N=4 domain structure.
High-Field Low-Frequency Spin Dynamics  [PDF]
A. M. Farutin,V. I. Marchenko
Physics , 2005, DOI: 10.1134/S002136400606004X
Abstract: The theory of exchange symmetry of spin ordered states is extended to the case of high magnetic field. Low frequency spin dynamics equation for quasi-goldstone mode is derived for two cases of collinear and noncollinear antiferromagnets.
Physical dynamics of quasi-particles in nonlinear wave equations  [PDF]
Ivan Christov,C. I. Christov
Physics , 2006, DOI: 10.1016/j.physleta.2007.08.038
Abstract: By treating the centers of solitons as point particles and studying their discrete dynamics, we demonstrate a new approach to the quantization of the soliton solutions of the sine-Gordon equation, one of the first model nonlinear field equations. In particular, we show that a linear superposition of the non-interacting shapes of two solitons offers a qualitative (and to a good approximation quantitative) description of the true two-soliton solution, provided that the trajectories of the centers of the superimposed solitons are considered unknown. Via variational calculus, we establish that the dynamics of the quasi-particles obey a pseudo-Newtonian law, which includes cross-mass terms. The successful identification of the governing equations of the (discrete) quasi-particles from the (continuous) field equation shows that the proposed approach provides a basis for the passage from the continuous to a discrete description of the field.
Hamiltonian dynamics reveals the existence of quasi-stationary states for long-range systems in contact with a reservoir  [PDF]
Fulvio Baldovin,Enzo Orlandini
Physics , 2006, DOI: 10.1103/PhysRevLett.96.240602
Abstract: We introduce a Hamiltonian dynamics for the description of long-range interacting systems in contact with a thermal bath (i.e., in the canonical ensemble). The dynamics confirms statistical mechanics equilibrium predictions for the Hamiltonian Mean Field model and the equilibrium ensemble equivalence. We find that long-lasting quasi-stationary states persist in presence of the interaction with the environment. Our results indicate that quasi-stationary states are indeed reproducible in real physical experiments.
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