Engineering the Dynamics of Effective Spin-Chain Models for Strongly Interacting Atomic Gases

We consider a one-dimensional gas of cold atoms with strong contact interactions and construct an effective spin-chain Hamiltonian for a two-component system. The resulting Heisenberg spin model can be engineered by manipulating the shape of the external confining potential of the atomic gas. We find that bosonic atoms offer more flexibility for tuning independently the parameters of the spin Hamiltonian through interatomic (intra-species) interaction which is absent for fermions due to the Pauli exclusion principle. Our formalism can have important implications for control and manipulation of the dynamics of few- and many-body quantum systems; as an illustrative example relevant to quantum computation and communication, we consider state transfer in the simplest non-trivial system of four particles representing exchange-coupled qubits.Comment: 10 pages including appendix, 3 figures, revised versio

Frustrated collisions and unconventional pairing on a quantum superlattice

We solve the problem of scattering and binding of two spin-1/2 fermions on a one-dimensional superlattice with a period of twice the lattice spacing analytically. We find the exact bound states and the scattering states, consisting of a generalized Bethe ansatz augmented with an extra scattering product due to "asymptotic" degeneracy. If a Bloch band is doubly occupied, the extra wave can be a bound state in the continuum corresponding to a single-particle interband transition. In all other cases, it corresponds to a quasi-momentum changing, frustrated collision.Comment: 4 pages, 2 figure

Minimally Invasive Urological Interventions in Outpatient Clinic on the Example of Prostate Biopsy

One of the main directions of improving medical care was the introduction of inpatient forms of medical care for patients who do not require round-the-clock supervision.Aim of the research: to prove the effectiveness and economic feasibility of minimally invasive procedures in outpatient conditions.Materials and methods. The study included 3524 patients in the period from 2010 to 2017, who underwent transrectal prostate biopsy on the basis of the Department of urology of polyclinic No. 195 of the Western district of Moscow. For comparison, the patients were taken, who underwent a biopsy of the prostate gland at the base hospital No. 31, No. 51, No. 17.Results. The average number of biopsies performed in hospital No. 31, No. 51 and No. 17 for the year amounted to 344 biopsies, and the average detectability of prostate cancer was 142 (41.3 %). The average number of biopsies per year in the urology department of the branch number 2 GP No. 195 amounted to 440.5, and the average detectability of prostate cancer – 152.8 (34.7 %). Thus, with comparable inpatient detection of prostate cancer in one large outpatient urology center, an average of 28 % more biopsies are performed (440.5 versus 344) than in 3 hospitals over a comparable period of time.Conclusions. Inpatient technologies can reduce the burden on hospitals. The development of hospital-replacing forms is determined by the need of the population and for efficient use of financial and technical resources of health care

Symmetric photon-photon coupling by atoms with Zeeman-split sublevels

We propose a simple scheme for highly efficient nonlinear interaction between two weak optical fields. The scheme is based on the attainment of electromagnetically induced transparency simultaneously for both fields via transitions between magnetically split F=1 atomic sublevels, in the presence of two driving fields. Thereby, equal slow group velocities and symmetric cross-coupling of the weak fields over long distances are achieved. By simply tuning the fields, this scheme can either yield giant cross-phase modulation or ultrasensitive two-photon switching.Comment: Modified scheme, 4 pages, 1 figur

Anomalous latent heat in non-equilibrium phase transitions

We study first-order phase transitions in a two-temperature system, where due to the time-scale separation all the basic thermodynamical quantities (free energy, entropy, etc) are well-defined. The sign of the latent heat is found to be counterintuitive: it is positive when going from the phase where the temperatures and the entropy are higher to the one where these quantities are lower. The effect exists only out of equilibrium and requires conflicting interactions. It is displayed on a lattice gas model of ferromagnetically interacting spin-1/2 particles.Comment: 4 pages, 2 figure

Microscopic dynamics and effective Landau-Zener transition in quasi-adiabatic preparation of spatially-ordered states of Rydberg excitations

We examine the adiabatic preparation of spatially-ordered Rydberg excitations of atoms in finite one-dimensional lattices by frequency-chirped laser pulses, as realized in a number of recent experiments simulating quantum Ising model. Our aims are to unravel the microscopic mechanism of the phase transition from the unexcited state of atoms to the antiferromagnetic-like state of Rydberg excitations by traversing an extended gapless phase, and to estimate the preparation fidelity of the target state in a moderately sized system amenable to detailed numerical analysis. We find that, in the basis of the bare atomic states, the system climbs the ladder of Rydberg excitations predominantly along the strongest-amplitude paths towards the final ordered state. We show that, despite its complexity, the interacting many-body system can be described as an effective two-level system involving a pair of lowest-energy instantaneous collective eigenstates of the time-dependent Hamiltonian. The final preparation fidelity of the target state can then be well approximated by the Landau-Zener formula, while the nonadiabatic population leakage during the passage can be estimated using a perturbative approach applied to the instantaneous collective eigenstates.Comment: revised m