Physical Review Letters

Blanchard, Ph

doi: 10.1103/PhysRevLett.92.120601pmid: 15089658

In the continuous space and time limit, we show that the probability density to find the quantum random walk (QRW) driven by the Hadamard “coin” solves a hyperbolic evolution equation similar to the one obtained for a random two-velocity evolution with spatially inhomogeneous transition rates between the velocity states. In spite of the presence of a nonlinear drift term, it is remarkable that the QRW position can easily be described in simple analytical terms. This allows us to derive the quadratic time dependence of the variance typical for the QRW.

Allahverdyan, A. E; Balian, R. E; Nieuwenhuizen, Th. M

doi: 10.1103/PhysRevLett.92.120402pmid: 15089654

The unknown state ρ ^ of a quantum system S is determined by letting it interact with an auxiliary system A , the initial state of which is known. A one-to-one mapping can thus be realized between the density matrix ρ ^ and the probabilities of the occurrence of the eigenvalues of a single and factorized observable of S + A , so that ρ ^ can be determined by repeated measurements using a single apparatus. If S and A are spins, it suffices to measure simultaneously their z components after a controlled interaction. The most robust setups are determined in this case for an initially pure or a completely disordered state of A . They involve an Ising or anisotropic Heisenberg coupling and an external field.

Craig, Walter L; Danworaphong, Sorasak L; Diebold, Gerald J

doi: 10.1103/PhysRevLett.92.125901pmid: 15089688

Separation of liquid mixtures in a thermal gradient, known as the Ludwig-Soret effect or thermal diffusion, is governed by a nonlinear, partial differential equation. It is shown here that the nonlinear differential equation for a binary mixture can be reduced to a Hamiltonian system of equations and that a solution can be obtained for the linear problem. The calculation gives a closed form expression for the space and time dependence of the concentration profile of the mixture, valid at short times.

Aubert, B; Barate, R; Boutigny, D; Couderc, F; Gaillard, J.-M; Hicheur, A; Karyotakis, Y; Lees, J. P; Tisserand, V. P; Zghiche, A. P; Palano, A. P; Pompili, A. P; Chen, J. C; Qi, N. D; Rong, G. D; Wang, P. D; Zhu, Y. S;

Bastea, Marina

doi: 10.1103/PhysRevLett.92.129601pmid: 15089716

A Comment on the Letter by R. Chau , Phys. Rev. Lett. PRLTAO 0031-9007 90 , 245501 ( 2003 ) . The authors of the Letter offer a Reply.

Krive, I. V; Romanovsky, I. A; Bogachek, E. N; Landman, Uzi N

doi: 10.1103/PhysRevLett.92.126802pmid: 15089697

The emergence of superconductivity-induced phase-controlled forces in the ( 10 - 2 – 10 - 1 ) nN range and of magnetization oscillations in nanowire junctions is discussed. A giant magnetic response to applied weak magnetic fields is predicted in the ballistic Josephson junction formed by a superconducting tip and a surface, bridged by a normal-metal nanowire where Andreev states form.

Yamakawa, K; Akahane, Y; Fukuda, Y; Aoyama, M; Inoue, N; Ueda, H; Utsumi, T

doi: 10.1103/PhysRevLett.92.123001pmid: 15089668

We report on detailed investigations of ionization dynamics of a Xe atom exposed to intense 800-nm pulses of 20-fs duration in the extensive intensity range from 10 13 – 10 18 W / cm 2 . Ion yields of Xe + – Xe 20 + were observed as a function of laser intensity and compared with the results from a single active electron based Ammosov-Delone-Krainov model. Unexpected ionization probabilities for lower charge states and no interplay between the inner and outer shells by screening are inferred. Suppression of nonsequential ionization towards higher intensity and few optical cycle regimes is also proved.

Mega, M. S; Allegrini, P. S; Grigolini, P. S; Latora, V. S; Palatella, L. S; Rapisarda, A. S; Vinciguerra, S. S

doi: 10.1103/PhysRevLett.92.129802pmid: N/A

A Reply to the Comment by A. Helmstetter and D. Sornette.

Prellberg, Thomas ; Krawczyk, Jarosław

doi: 10.1103/PhysRevLett.92.120602pmid: 15089659

In this Letter we present a flat histogram algorithm based on the pruned and enriched Rosenbluth method. This algorithm incorporates in a straightforward manner microcanonical reweighting techniques, leading to “flat histogram” sampling in the chosen parameter space. As an additional benefit, our algorithm is completely parameter free and, hence, easy to implement. We apply this algorithm to interacting self-avoiding walks, the generic lattice model of polymer collapse.

Ribeiro, E; Govorov, A. O; Carvalho, W. O; Medeiros-Ribeiro, G. O

doi: 10.1103/PhysRevLett.92.126402pmid: 15089692

The Aharonov-Bohm effect is commonly believed to be a typical feature of the motion of a charged particle interacting with the electromagnetic vector potential. Here we present a magnetophotoluminescence study of type-II InP / GaAs self-assembled quantum dots, revealing the Aharonov-Bohm–type oscillations for neutral excitons when the hole ground state changes its angular momentum from ℓ h = 0 to ℓ h = 1 , 2, and 3. The hole-ring parameters derived from a simple model are in excellent agreement with the structural parameters for this system.