Criteria for reliable entanglement quantification with finite data

We propose one and a half criteria for determining how many measurements are needed to quantify entanglement reliably. We base these criteria on Bayesian analysis of measurement results, and apply our methods to four-qubit entanglement, but generalizations to more qubits are straightforward.Comment: >4

Continuum and discrete models of dislocation pile-ups. I Pile-up at a lock

A mathematical methodology for analysing pile-ups of large numbers of dislocations is described. As an example, the pile-up of n identical screw or edge dislocations in a single slip pane under the action of an external force in the direction of a locked dislocation in that plane is considered. As $n \rightarrow \infty$ there is a well-known formula for the number density of the dislocations, but this density is singular at the lock and it cannot predict the stress field there or the force on the lock. This poses the interesting analytical and numerical problem of matching a local discrete model near the lock to the continuum model further away

Hydrogen hollow cathode ion source

A source of hydrogen ions is disclosed and includes a chamber having at one end a cathode which provides electrons and through which hydrogen gas flows into the chamber. Screen and accelerator grids are provided at the other end of the chamber. A baffle plate is disposed between the cathode and the grids and a cylindrical baffle is disposed coaxially with the cathode at the one end of the chamber. The cylindrical baffle is of greater diameter than the baffle plate to provide discharge impedance and also to protect the cathode from ion flux. An anode electrode draws the electrons away from the cathode. The hollow cathode includes a tubular insert of tungsten impregnated with a low work function material to provide ample electrons. A heater is provided around the hollow cathode to initiate electron emission from the low work function material

Ring-cusp ion thruster with shell anode

An improved ion thruster for low specific impulse operation in the 1500 sec to 6000 sec range has a multicusp boundary field provided by high strength magnets on an iron anode shell which lengthens the paths of electrons from a hollow cathode assembly. A downstream anode pole piece in the form of an iron ring supports a ring of magnets to provide a more uniform beam profile. A cylindrical cathode magnet can be moved selectively in an axial direction along a feed tube to produce the desired magnetic field at the cathode tip

Three-State Feshbach Resonances Mediated By Second-Order Couplings

We present an analytical study of three-state Feshbach resonances induced by second-order couplings. Such resonances arise when the scattering amplitude is modified by the interaction with a bound state that is not directly coupled to the scattering state containing incoming flux. Coupling occurs indirectly through an intermediate state. We consider two problems: (i) the intermediate state is a scattering state in a distinct open channel; (ii) the intermediate state is an off-resonant bound state in a distinct closed channel. The first problem is a model of electric-field-induced resonances in ultracold collisions of alkali metal atoms [Phys. Rev. A 75, 032709 (2007)] and the second problem is relevant for ultracold collisions of complex polyatomic molecules, chemical reaction dynamics, photoassociation of ultracold atoms, and electron - molecule scattering. Our analysis yields general expressions for the energy dependence of the T-matrix elements modified by three-state resonances and the dependence of the resonance positions and widths on coupling amplitudes for the weak-coupling limit. We show that the second problem can be generalized to describe resonances induced by indirect coupling through an arbitrary number of sequentially coupled off-resonant bound states and analyze the dependence of the resonance width on the number of the intermediate states.Comment: 27 pages, 4 figures; added a reference; journal reference/DOI refer to final published version, which is a shortened and modified version of this preprin

Initial radio-frequency gas heating experiments to simulate the thermal environment in a nuclear light bulb reactor

Initial radio frequency gas heating experiments to simulate thermal environment in nuclear light bulb reacto

Investigation of the vibration isolation of commercial jet transport pilots during turbulent air penetration

Electrohydraulic pilot seat isolation system of commercial transport pilots during turbulent air penetratio

px+ipyp_{x}+ip_{y} superfluid from s-wave interactions of fermionic cold atoms

Two-dimensional ($p_{x}+ip_{y}$) superfluids/superconductors offer a playground for studying intriguing physics such as quantum teleportation, non-Abelian statistics, and topological quantum computation. Creating such a superfluid in cold fermionic atom optical traps using p-wave Feshbach resonance is turning out to be challenging. Here we propose a method to create a $p_{x}+ip_{y}$ superfluid directly from an s-wave interaction making use of a topological Berry phase, which can be artificially generated. We discuss ways to detect the spontaneous Hall mass current, which acts as a diagnostic for the chiral p-wave superfluid.Comment: 4 pages, 1 figur

Calculation of model Hamiltonian parameters for LaMnO_3 using maximally localized Wannier functions

Maximally localized Wannier functions (MLWFs) based on Kohn-Sham band-structures provide a systematic way to construct realistic, materials specific tight-binding models for further theoretical analysis. Here, we construct MLWFs for the Mn e_g bands in LaMnO_3, and we monitor changes in the MLWF matrix elements induced by different magnetic configurations and structural distortions. From this we obtain values for the local Jahn-Teller and Hund's rule coupling strength, the hopping amplitudes between all nearest and further neighbors, and the corresponding reduction due to the GdFeO_3-type distortion. By comparing our results with commonly used model Hamiltonians for manganites, where electrons can hop between two "e_g-like" orbitals located on each Mn site, we find that the most crucial limitation of such models stems from neglecting changes in the underlying Mn(d)-O(p) hybridization.Comment: 15 pages, 11 figures, 3 table

Quantum annealing of the Traveling Salesman Problem

We propose a path-integral Monte Carlo quantum annealing scheme for the symmetric Traveling Salesman Problem, based on a highly constrained Ising-like representation, and we compare its performance against standard thermal Simulated Annealing. The Monte Carlo moves implemented are standard, and consist in restructuring a tour by exchanging two links (2-opt moves). The quantum annealing scheme, even with a drastically simple form of kinetic energy, appears definitely superior to the classical one, when tested on a 1002 city instance of the standard TSPLIB.Comment: 5 pages, 2 figure