Exponentially Localized Magnetic Fields for Single-Spin Quantum Logic Gates

An infinite array of parallel current-carrying wires is known, from the field of neutral particle optics, to produce an exponentially localized magnetic field when the current direction is antiparallel in adjacent wires. We show that a finite array of several tens of superconducting Nb nanowires can produce a peak magnetic field of 10mT that decays by a factor of 10^4 over a length scale of 500nm. Such an array is readily manufacturable with current technology, and is compatible with both semiconductor and superconducting quantum computer architectures. A series of such arrays can be used to individually address single single-spin or flux qubits spaced as little as 100nm apart, and can lead to quantum logic gate times of 5ns.Comment: 5 pages, incl. 4 figure

Sinus-preserving modification of eversional carotid endarterectomy: early and late results

Universitatea de Stat de Medicină de Sud Ural, Spitalul Clinic Regional, Celiabinsk, Federația Rusă, Al XIII-lea Congres al Asociației Chirurgilor „Nicolae Anestiadi” și al III-lea Congres al Societății de Endoscopie, Chirurgie miniminvazivă și Ultrasonografie ”V.M.Guțu” din Republica MoldovaIntroducere: Endarterectomia carotidiană (EAEC) și-a demonstrat avantajul în tratamentul stenozelor hemodinamic semnificative ale arterei carotide interne (ACI). Tehnica prin eversiune este cea mai populară, însă în versiunea sa standard se asociază cu traumatizarea frecventă a sinusului carotidian, cu impact negativ asupra reglării vegetative a tonusului vascular și hemodinamicii. Scopul: Evaluarea eficacității EAEC prin eversiune cu prezervarea nervilor sinusului carotid, comparând rezultatele precoce și la distanță cu cele ale unui lot de control. Material și metode: Studiul a inclus 375 pacienți supuși tratamentului chirurgical în Spitalul Clinic Regional Celiabinsk în perioada anilor 2012-2018. În lotul I (208 bolnavi) EAEC prin eversiune s-a efectuat conform tehnicii standard. În lotul II (167 pacienți) s-a practicat EAEC modificată, cu prezervarea sinusului. Loturile au fost comparabile în funcție de vârstă, gen, statutul neurologic și hipertensiv inițial, utilizarea șuntului temporar, timpul de clampaj al ACI și gradul leziunii arteriale carotidiene contralaterale. Pe lângă înregistrarea parametrilor hemodinamici comuni, a fost evaluată și activitatea vegetativă în baza analizei prospective a variabilității frecvenței cardiace utilizând ritmocardiografia. La etapa de follow-up, parametrii hemodinamici au fost evaluați la 103 pacienți: cu păstrarea nervilor sinusului carotidian (39) și după secționarea acestora (64). Rezultate: În prima zi atât presiunea sistolică, diastolică, cât și presiunea pulsului, precum și frecvența cardiacă au fost mai reduse la bolnavii după EAEC cu prezervarea sinusului în comparație cu lotul de control. În plus, diminuarea influenței simpatice asupra ritmului conform ritmocardiografiei a fost notabilă. La pacienții operați cu prezervarea nervilor sinusului carotidian elevarea tensiunii arteriale s-a atestat mai rar, iar doza necesară de remedii antihipertensive a fost mai mică. Concluzii: S-au constatat diferențe semnificative dintre parametrii, evaluați precoce și la distanță, ai hemodinamicii arteriale postoperatorii și reglării vegetative a tonusului vascular, în funcție de prezervarea nervilor sinusului carotidian. Practicarea EAEC prin eversiune cu prezervarea sinusului carotid reduce riscul complicațiilor postoperatorii cauzate de dereglările vegetative.Introduction: Carotid endarterectomy (CEAE) has proven its advantage in correcting hemodynamically significant stenoses of the internal carotid arteries (ICA). The eversion technique is the most popular, but with its standard procedure, traumatization of carotid sinus nerves occurs, which has a negative effect on the vegetative regulation of vascular tonus and hemodynamics. Aim: To evaluate the effectiveness of eversional CEAE with preservation of carotid sinus nerves, by comparing of early and long-term results with a control group of patients. Materials and methods: The study included 375 patients treated surgically at the Chelyabinsk Regional Clinical Hospital from 2012 to 2018. In the first group (208 patients), eversional CEAE was performed according to standard technique. In the second group (167 patients), a sinus-preserving modification of CEAE was applied. The groups were comparable by age, sex, baseline neurological status, baseline hypertension, use of a temporary shunt, ICA cross-clamping time, and degree of contralateral lesion of the carotid arteries. In addition to common hemodynamic parameters, mediator vegetative activity evaluated based on a prospective analysis of heart rate variability using rhythmocardiography. In the follow-up period, hemodynamic parameters assessed in 103 patients: with preservation of the carotid sinus nerves (39) and after their transection (64). Results: On the 1st day, systolic, diastolic and pulse blood pressure, as well as a heart rate were lower in patients after sinuspreserving CEAE as compared with the control group. In addition, a decrease in sympathetic pressure effect on the rhythm according to rhythmocardiography was noticeable. In patients operated with the preservation of carotid sinus nerves, an increased blood pressure is less common and they require a lower dosage of antihypertensive drugs. Conclusions: There are significant differences between early and distant parameters of postoperative arterial hemodynamics and vegetative regulation of vascular tonus, depending on preservation of the carotid sinus nerves. Practical application of sinus- preserving eversional CEAE reduces the risk of postoperative complications due to vegetative dysregulation

Spin Hall effect of Photons in a Static Gravitational Field

Starting from a Hamiltonian description of the photon within the set of Bargmann-Wigner equations we derive new semiclassical equations of motion for the photon propagating in static gravitational field. These equations which are obtained in the representation diagonalizing the Hamiltonian at the order $\hbar$, present the first order corrections to the geometrical optics. The photon Hamiltonian shows a new kind of helicity-magnetotorsion coupling. However, even for a torsionless space-time, photons do not follow the usual null geodesic as a consequence of an anomalous velocity term. This term is responsible for the gravitational birefringence phenomenon: photons with distinct helicity follow different geodesics in a static gravitational field.Comment: 6 page

Paraxial propagation in amorphous optical media with screw dislocation

We study paraxial beam propagation parallel to the screw axis of a dislocated amorphous medium that is optically weakly inhomogeneous and isotropic. The effect of the screw dislocation on the beam's orbital angular momentum is shown to change the optical vortex strength, rendering vortex annihilation or generation possible. Furthermore, the dislocation is shown to induce a weak \textit{biaxial} anisotropy in the medium due to the elasto-optic effect, which changes the beam's spin angular momentum as well as causing precession of the polarization. We derive the equations of motion of the beam and demonstrate the optical Hall effect in the dislocated medium. Its application with regard to determining the Burgers vector as well as the elasto-optic coefficients of the medium is explained

Transverse Shifts in Paraxial Spinoptics

The paraxial approximation of a classical spinning photon is shown to yield an "exotic particle" in the plane transverse to the propagation. The previously proposed and observed position shift between media with different refractive indices is modified when the interface is curved, and there also appears a novel, momentum [direction] shift. The laws of thin lenses are modified accordingly.Comment: 3 pages, no figures. One detail clarified, some misprints corrected and references adde

Writhing Photons and Berry Phases in Diffusive Wave Scattering

We study theoretically the polarization state of light in multiple scattering media in the limit of weak gradients in refractive index. Linearly polarized photons are randomly rotated due to the Berry phase associated with the scattering path. For circularly polarized light independent speckle patterns are found for the two helical states. The statistics of the geometric phase is related to the writhe distribution of semiflexible polymers such as DNA.Comment: 4 pages, 1 figur

Influence of the atomic-wall collision elasticity on the coherent population trapping resonance shape

We studied theoretically a coherent population trapping resonance formation in cylindrical cell without buffer gas irradiated by a narrow laser beam. We take into account non-zero probabilities of elastic ("specular") and inelastic ("sticking") collision between the atom and the cell wall. We have developed a theoretical model based on averaging over the random Ramsey pulse sequences of times that atom spent in and out of the beam. It is shown that the shape of coherent population trapping resonance line depends on the probability of elastic collision.Comment: 18 pages, 5 figure

Coriolis Effect in Optics: Unified Geometric Phase and Spin-Hall Effect

We examine the spin-orbit coupling effects that appear when a wave carrying intrinsic angular momentum interacts with a medium. The Berry phase is shown to be a manifestation of the Coriolis effect in a non-inertial reference frame attached to the wave. In the most general case, when both the direction of propagation and the state of the wave are varied, the phase is given by a simple expression that unifies the spin redirection Berry phase and the Pancharatnam--Berry phase. The theory is supported by the experiment demonstrating the spin-orbit coupling of electromagnetic waves via a surface plasmon nano-structure. The measurements verify the unified geometric phase, demonstrated by the observed polarization-dependent shift (spin-Hall effect) of the waves.Comment: 4 pages, 3 figure

Topological spin transport of photons: "magnetic monopole" gauge field in Maxwell equations and polarization splitting of rays in periodically inhomogeneous media

Topological spin transport of electromagnetic waves (photons) in stationary smoothly inhomogeneous isotropic medium is studied. By diagonalizing photon kinetic energy in Maxwell equations we derive the non-Abelian pure gauge potential in the momentum space, which in adiabatic approximation for transverse waves takes the form of two Abelian U(1) potentials corresponding to magnetic monopole-type fields. These fields act on circularly polarized waves resulting in the topological spin transport of photons. We deduce general semiclassical (geometrical optics) ray equations that take into account a Lorentz-type force of the magnetic-monopole-like gauge field. Detailed analysis of rays in 3D medium with 2D periodic inhomogeneity is presented. It is shown that rays located initially in the inhomogeneity plane experience topological deflections or splitting that move them out from this plane. The dependence of the rays' deflection on the parameters of the medium and on the direction of propagation is studied.Comment: 16 pages, 3 figure

Guiding Neutral Atoms with a Wire

We demonstrate guiding of cold neutral atoms along a current carrying wire. Atoms either move in Kepler-like orbits around the wire or are guided in a potential tube on the side of the wire which is created by applying an additional homogeneous bias field. These atom guides are very versatile and promising for applications in atom optics.Comment: 4 pages, 6 figures, submitted to PR