Spin-orbit correlation energy in neutron matter

We study the relevance of the energy correlation produced by the two-body spin-orbit coupling present in realistic nucleon-nucleon potentials. To this purpose, the neutron matter Equation of State (EoS) is calculated with the realistic two-body Argonne $v_8'$ potential. The shift occuring in the EoS when spin-orbit terms are removed is taken as an estimate of the spin-orbit correlation energy. Results obtained within the Bethe-Brueckner-Goldstone expansion, extended up to three hole-line diagrams, are compared with other many-body calculations recently presented in the literature. In particular, excellent agreement is found with the Green's function Monte-Carlo method. This agreement indicates the present theoretical accuracy in the calculation of the neutron matter EoS.Comment: 5 pages, 2 figures, 2 tables; to appear in Phys. Rev.

Attacking quantum key distribution with single-photon two-qubit quantum logic

The Fuchs-Peres-Brandt (FPB) probe realizes the most powerful individual attack on Bennett-Brassard 1984 quantum key distribution (BB84 QKD) by means of a single controlled-NOT (CNOT) gate. This paper describes a complete physical simulation of the FPB-probe attack on polarization-based BB84 QKD using a deterministic CNOT constructed from single-photon two-qubit quantum logic. Adding polarization-preserving quantum nondemolition measurements of photon number to this configuration converts the physical simulation into a true deterministic realization of the FPB attack.Comment: 8 pages, 9 figures; references added, 1 new figure, appendix expanded; accepted for publication in Phys. Rev.

Critical phenomena at the threshold of black hole formation for collisionless matter in spherical symmetry

We perform a numerical study of the critical regime at the threshold of black hole formation in the spherically symmetric, general relativistic collapse of collisionless matter. The coupled Einstein-Vlasov equations are solved using a particle-mesh method in which the evolution of the phase-space distribution function is approximated by a set of particles (or, more precisely, infinitesimally thin shells) moving along geodesics of the spacetime. Individual particles may have non-zero angular momenta, but spherical symmetry dictates that the total angular momentum of the matter distribution vanish. In accord with previous work by Rein et al, our results indicate that the critical behavior in this model is Type I; that is, the smallest black hole in each parametrized family has a finite mass. We present evidence that the critical solutions are characterized by unstable, static spacetimes, with non-trivial distributions of radial momenta for the particles. As expected for Type I solutions, we also find power-law scaling relations for the lifetimes of near-critical configurations as a function of parameter-space distance from criticality.Comment: 32 pages, 10 figure

Applications to Earth physics: Very-long-baseline interferometry and data analysis

A range of very long baseline interferometry experiments applied to Earth physics are covered

Analysis of the Capability and Limitations of Relativistic Gravity Measurements Using Radio Astronomy Methods

The uses of radar observations of planets and very-long-baseline radio interferometric observations of extragalactic objects to test theories of gravitation are described in detail with special emphasis on sources of error. The accuracy achievable in these tests with data already obtained, can be summarized in terms of: retardation of signal propagation (radar), deflection of radio waves (interferometry), advance of planetary perihelia (radar), gravitational quadrupole moment of sun (radar), and time variation of gravitational constant (radar). The analyses completed to date have yielded no significant disagreement with the predictions of general relativity

Piecewise adiabatic population transfer in a molecule via a wave packet

We propose a class of schemes for robust population transfer between quantum states that utilize trains of coherent pulses and represent a generalized adiabatic passage via a wave packet. We study piecewise Stimulated Raman Adiabatic Passage with pulse-to-pulse amplitude variation, and piecewise chirped Raman passage with pulse-to-pulse phase variation, implemented with an optical frequency comb. In the context of production of ultracold ground-state molecules, we show that with almost no knowledge of the excited potential, robust high-efficiency transfer is possibleComment: 4 pages, 5 figures. Submitted to Phys. Rev. Let