Multimode theory of measurement-induced non-Gaussian operation on wideband squeezed light

We present a multimode theory of non-Gaussian operation induced by an imperfect on/off-type photon detector on a splitted beam from a wideband squeezed light. The events are defined for finite time duration $T$ in the time domain. The non-Gaussian output state is measured by the homodyne detector with finite bandwidh $B$. Under this time- and band-limitation to the quantm states, we develop a formalism to evaluate the frequency mode matching between the on/off trigger channel and the conditional signal beam in the homodyne channel. Our formalism is applied to the CW and pulsed schemes. We explicitly calculate the Wigner function of the conditional non-Gaussian output state in a realistic situation. Good mode matching is achieved for BT\alt1, where the discreteness of modes becomes prominant, and only a few modes become dominant both in the on/off and the homodyne channels. If the trigger beam is projected nearly onto the single photon state in the most dominant mode in this regime, the most striking non-classical effect will be observed in the homodyne statistics. The increase of $BT$ and the dark counts degrades the non-classical effect.Comment: 20 pages, 14 figures, submitted to Phys. Rev.

Equilibrium magnetization in the vicinity of the first order phase transition in the mixed state of high-Tc superconductors

We present the results of a scaling analysis of isothermal magnetization M(H) curves measured in the mixed state of high-Tc superconductors in the vicinity of the established first order phase transition. The most surprising result of our analysis is that the difference between the magnetization above and below the transition may have either sign, depending on the particular chosen sample. We argue that this observation, based on M(H) data available in the literature, is inconsistent with the interpretation that the well known first order phase transition in the mixed state of high-Tc superconductors always represents the melting transition in the vortex system.Comment: 4 pages, 5 figure

A Quantum-Gravity Perspective on Semiclassical vs. Strong-Quantum Duality

It has been argued that, underlying M-theoretic dualities, there should exist a symmetry relating the semiclassical and the strong-quantum regimes of a given action integral. On the other hand, a field-theoretic exchange between long and short distances (similar in nature to the T-duality of strings) has been shown to provide a starting point for quantum gravity, in that this exchange enforces the existence of a fundamental length scale on spacetime. In this letter we prove that the above semiclassical vs. strong-quantum symmetry is equivalent to the exchange of long and short distances. Hence the former symmetry, as much as the latter, also enforces the existence of a length scale. We apply these facts in order to classify all possible duality groups of a given action integral on spacetime, regardless of its specific nature and of its degrees of freedom.Comment: 10 page

Elastic Behavior of a Two-dimensional Crystal near Melting

Using positional data from video-microscopy we determine the elastic moduli of two-dimensional colloidal crystals as a function of temperature. The moduli are extracted from the wave-vector-dependent normal mode spring constants in the limit $q\to 0$ and are compared to the renormalized Young's modulus of the KTHNY theory. An essential element of this theory is the universal prediction that Young's modulus must approach $16 \pi$ at the melting temperature. This is indeed observed in our experiment.Comment: 4 pages, 3 figure

Resonance Damping in Ferromagnets and Ferroelectrics

The phenomenological equations of motion for the relaxation of ordered phases of magnetized and polarized crystal phases can be developed in close analogy with one another. For the case of magnetized systems, the driving magnetic field intensity toward relaxation was developed by Gilbert. For the case of polarized systems, the driving electric field intensity toward relaxation was developed by Khalatnikov. The transport times for relaxation into thermal equilibrium can be attributed to viscous sound wave damping via magnetostriction for the magnetic case and electrostriction for the polarization case.Comment: 5 pages no figures ReVTeX

Theoretical study of electronic transport through a small quantum dot with a magnetic impurity

We model a small quantum dot with a magnetic impurity by the Anderson Hamiltonian with a supplementary exchange interaction term. The transport calculations are performed by means of the Green functions within the equation of motion scheme, in which two decoupling procedures are proposed, for high and low temperatures, respectively. The paper focuses on the charge fluctuations for such a system, aspect not addressed before, as well as on the Kondo resonance. We show a specific role of the excited state, which can be observed in transport and in spin-spin correlations. Our studies show on a new many-body feature of the phase shift of transmitted electrons, which is manifested in a specific dip. In the Kondo regime, our calculations complement existing theoretical results. The system shows three Kondo peaks in the density of states: one at the Fermi energy and two side peaks, at a distance corresponding to the singlet-triplet level spacing. The existence of the central peak is conditioned by a degenerate state (the triplet) below the Fermi energy.Comment: 12 pages, 4 figure