Hermitian conjugate measurement

We propose a new class of probabilistic reversing operations on the state of a system that was disturbed by a weak measurement. It can approximately recover the original state from the disturbed state especially with an additional information gain using the Hermitian conjugate of the measurement operator. We illustrate the general scheme by considering a quantum measurement consisting of spin systems with an experimentally feasible interaction and show that the reversing operation simultaneously increases both the fidelity to the original state and the information gain with such a high probability of success that their average values increase simultaneously.Comment: 26 pages, 4 figures; a paragraph is added in the introductio

Magnetic properties of Fe/Cu multilayers prepared using pulsed-current electrodeposition

[Fe (tFe) nm/Cu (tCu) nm]N multilayer films were prepared using pulsed-current electrodeposition method. The role of the pulsed-current deposition and Fe and Cu layer thicknesses on the magnetic properties was investigated. The microstructure of the multilayer films is dependent on the thicknesses of both the Fe and Cu layers. The saturation magnetization of the multilayers strongly correlated with the crystalline structure of Fe at the interface of Fe and Cu layers. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/2488

The dynamics of condensate shells: collective modes and expansion

We explore the physics of three-dimensional shell-shaped condensates, relevant to cold atoms in "bubble traps" and to Mott insulator-superfluid systems in optical lattices. We study the ground state of the condensate wavefunction, spherically-symmetric collective modes, and expansion properties of such a shell using a combination of analytical and numerical techniques. We find two breathing-type modes with frequencies that are distinct from that of the filled spherical condensate. Upon trap release and subsequent expansion, we find that the system displays self-interference fringes. We estimate characteristic time scales, degree of mass accumulation, three-body loss, and kinetic energy release during expansion for a typical system of Rb87

Staggered magnetism in LiV2_2O4_4 at low temperatures probed by the muon Knight shift

We report on the muon Knight shift measurement in single crystals of LiV2O4. Contrary to what is anticipated for the heavy-fermion state based on the Kondo mechanism, the presence of inhomogeneous local magnetic moments is demonstrated by the broad distribution of the Knight shift at temperatures well below the presumed "Kondo temperature" ($T^*\simeq 30$ K). Moreover, a significant fraction ($\simeq10$ %) of the specimen gives rise to a second component which is virtually non-magnetic. These observations strongly suggest that the anomalous properties of LiV2O4 originates from frustration of local magnetic moments.Comment: 11 pages, 5 figures, sbmitted to J. Phys.: Cond. Mat

Precision Measurements Using Squeezed Spin States via Two-axis Counter-twisting Interactions

We show that the two-axis counter twisting interaction squeezes a coherent spin state into three states of interest in quantum information, namely, the twin-Fock state, the equally-weighted superposition state, and the state that achieves the Heisenberg limit of optimal sensitivity defined by the Cramer-Rao inequality in addition to the well-known Heisenberg-limited state of spin fluctuations.Comment: 5 pages, 3 figure

Diagnostics for the ground state phase of a spin-2 Bose-Einstein condensate

We propose a method to determine the singlet-pair energy of a spin-2 Bose-Einstein condensate (BEC). By preparing the initial populations in the magnetic sublevels 0, 2, -2 with appropriate relative phases, we can obtain the coefficient of the spin singlet-pair term from the spin exchange dynamics. This method is suitable for hyperfine states with short lifetimes, since only the initial change in the population of each magnetic sublevel is needed. This method therefore enables the determination of the ground state phase of a spin-2 87Rb BEC at zero magnetic field, which is considered to lie in the immediate vicinity of the boundary between the antiferromagnetic and cyclic phases. We also show that the initial state in which relative phases are controlled can be prepared by Raman processes.Comment: 12 pages, 6 figure

Magnetic field-induced phase transitions in a weakly coupled s = 1/2 quantum spin dimer system Ba3_{3}Cr2_{2}O8_{8}

By using bulk magnetization, electron spin resonance (ESR), heat capacity, and neutron scattering techniques, we characterize the thermodynamic and quantum phase diagrams of Ba$_3$Cr$_2$O$_8$. Our ESR measurements indicate that the low field paramagnetic ground state is a mixed state of the singlet and the S$_z$ = 0 triplet for $H \perp c$. This suggests the presence of an intra-dimer Dzyaloshinsky-Moriya (DM) interaction with a DM vector perpendicular to the c-axis