ABSTRACT
We study collective "free-space" radiation properties of two distant single-layer arrays of quantum emitters as two-level atoms. We show that this system can support a long-lived Bell superposition state of atomic excitations exhibiting strong subradiance, which corresponds to a nonlocal excitation of the two arrays. We describe the preparation of these states and their application in quantum information as a resource of nonlocal entanglement, including deterministic quantum state transfer with high fidelity between the arrays representing quantum memories. We discuss experimental realizations using cold atoms in optical trap arrays with subwavelength spacing, and analyze the role of imperfections.
ABSTRACT
Electromagnetically induced transparency (EIT) in a ladder system involving a Rydberg level is known to yield giant optical nonlinearities for the probe field, even in the few-photon regime. This enhancement is due to the strong dipole-dipole interactions between Rydberg atoms and the resulting excitation blockade phenomenon. In order to study such highly correlated media, ad hoc models or low-excitation assumptions are generally used to tackle their dynamical response to optical fields. Here, we study the behavior of a cavity Rydberg-EIT setup in the nonequilibrium quantum field formalism, and we obtain analytic expressions for elastic and inelastic components of the cavity transmission spectrum, valid up to higher excitation numbers than previously achieved. This allows us to identify and interpret a polaritonic resonance structure, to our knowledge unreported so far.
ABSTRACT
The aim of the study was to determine the cause of the high frequency of meniscal tear coexisting rupture of the anterior cruciate ligament of the knee joint and to establish an optimal timing of surgical stabilization of the knee joint. Medical records of 476 patients who had surgery at the clinic of the Kirov Military Traumatology and Orthopedics of Military Medical Academy were studied. In 82 patients operation on the reconstruction of the anterior cruciate ligament was perormed in the early period after injury (up to 6 weeks), 347 patients were operated within a period exceeding 6 weeks. It was revealed that the soldiers who had the operation in the period after 6 weeks from the date of injury, secondary damage of meniscus and articular cartilage occured twice as much as in surgery performed during the acute phase. Thus, the reconstruction of the anterior cruciate ligament should be carried out in a specialized epartment in the early stages after injury, when not yet any secondary damage to the meniscus and articular cartilage.