Teleportation: from probability distributions to quantum states

The role of the off-diagonal density matrix elements of the entangled pair is investigated in quantum teleportation of a qbit. The dependence between them and the off-diagonal elements of the teleported density matrix is shown to be linear. In this way the ideal quantum teleportation is related to an entirely classical communication protocol: the one-time pad cypher. The latter can be regarded as the classical counterpart of Bennett's quantum teleportation scheme. The quantum-to-classical transition is demonstrated on the statistics of a gedankenexperiment.Comment: 11 pages, 1 figure, accepted for publication in J. Phys. A (Math. Gen.

Device-spectroscopy of magnetic field effects in a polyfluorene organic light-emitting diode

We perform charge-induced absorption and electroluminescence spectroscopy in a polyfluorene organic magnetoresistive device. Our experiments allow us to measure the singlet exciton, triplet exciton and polaron densities in a live device under an applied magnetic field, and to distinguish between three different models that were proposed to explain organic magnetoresistance. These models are based on different spin-dependent interactions, namely exciton formation, triplet exciton-polaron quenching and bipolaron formation. We show that the singlet exciton, triplet exciton and polaron densities and conductivity all increase with increasing magnetic field. Our data are inconsistent with the exciton formation and triplet-exciton polaron quenching models.Comment: 4 pages, two figure

Transport in the XX chain at zero temperature: Emergence of flat magnetization profiles

We study the connection between magnetization transport and magnetization profiles in zero-temperature XX chains. The time evolution of the transverse magnetization, m(x,t), is calculated using an inhomogeneous initial state that is the ground state at fixed magnetization but with m reversed from -m_0 for x0. In the long-time limit, the magnetization evolves into a scaling form m(x,t)=P(x/t) and the profile develops a flat part (m=P=0) in the |x/t|1/2 while it expands with the maximum velocity, c_0=1, for m_0->0. The states emerging in the scaling limit are compared to those of a homogeneous system where the same magnetization current is driven by a bulk field, and we find that the expectation values of various quantities (energy, occupation number in the fermionic representation) agree in the two systems.Comment: RevTex, 8 pages, 3 ps figure

Study of Magnetic Excitation in Singlet-Ground-State Magnets CsFeCl3_3 and RbFeCl3_3 by Nuclear Magnetic Relaxation

The temperature dependences of spin-lattice relaxation time $T_1$ of $^{133}$Cs in CsFeCl$_3$ and $^{87}$Rb in RbFeCl$_3$ were measured in the temperature range between 1.5 K and 22 K, at various fields up to 7 T applied parallel (or perpendicular) to the c-axis, and the analysis was made on the basis of the DCEFA. The mechanism of the nuclear magnetic relaxation is interpreted in terms of the magnetic fluctuations which are characterized by the singlet ground state system. In the field region where the phase transition occurs, $T_1^{-1}$ exhibited the tendency of divergence near $T_{\rm N}$, and this feature was ascribed to the transverse spin fluctuation associated with the mode softening at the $K$-point. It was found that the damping constant of the soft mode is remarkably affected by the occurrence of the magnetic ordering at lower temperature, and increases largely in the field region where the phase transition occurs.Comment: 12 pages, 18 figures, submitted to J. Phys. Soc. Jp

Weiterer Kariesrückgang bei Schweizer Rekruten von 1996 bis 2006

Rekruten der Rekrutenschule Thun (N = 606) wurden im Jahr 2006 mit einer standardisierten Methode zahnmedizinisch untersucht. Die Resultate wurden mit denjenigen aus früheren Erhebungen (1985 und 1996) verglichen. Der DM6FT-Wert betrug im Jahr 2006 im Durchschnitt 3,11; im Jahr 1996 lag er noch deutlich höher (4,95). Dies entspricht einem Kariesrückgang von 37%. Der beobachtete Kariesrückgang konnte nur zum Teil erklärt werden. Rekruten, die rauchten, zeigten einen erhöhten Kariesbefall. Rekruten aus der Deutschschweiz, die in Kindergarten und Primarschule von Schulzahnpflege- Instruktorinnen betreut worden waren, unterschieden sich im Kariesbefall nicht von den Rekruten aus der Romandie

Further caries decline in Swiss recruits from 1996 to 2006

Swiss army recruits (N = 606) from the army base at Thun were dentally examined with a standardized method in the year 2006. The results were compared with those of previous surveys (1985 and 1996). The mean DM6FT-value in the year 2006 was 3.11, whereas in 1996 it had been clearly higher (4.95). This corresponds to a caries decline of 37%. The observed caries decline can only partly be explained. Recruits, who were smokers, showed an increased caries experience. Recruits of the German-speaking part of Switzerland who had profited from oral health lessons by oral health instructors in Kindergarten and primary schools did not differ in caries experience from recruits of the French-speaking part of Switzerland