Abstract
We seek to design experimentally feasible broadband, temporally multiplexed optical quantum memory with near-term applications to telecom bands. Specifically, we devise dispersion ...compensation (DC) for an impedance-matched narrow-band quantum memory by exploiting Raman processes over two three-level atomic subensembles, one for memory and the other for DC. DC provides impedance matching over more than a full cavity linewidth. Combined with 1 s spin-coherence lifetime the memory could be capable of power efficiency exceeding 90% leading to 10
6
modes for temporal multiplexing. Our design could lead to significant multiplexing enhancement for quantum repeaters to be used for telecom quantum networks.
We show that, under certain circumstances, an optical field in a two-mode squeezed vacuum (TMSV) state can propagate through a lossy atomic medium without degradation or evolution. Moreover, the ...losses give rise to that state when a different state is initially injected into the medium. Such a situation emerges in a Λ-type atomic system, in which both optical transitions are driven by strong laser fields that are two-photon resonant with the respective signal modes. Then the interactions of the two signal modes with the ground-state atomic coherence interfere destructively, thereby ensuring the preservation of the TMSV with a particular squeezing parameter. This mechanism permits unified interpretation of recent experimental results and predicts new phenomena.
Time-bin quantum RAM Moiseev, E. S.; Moiseev, S. A.
Journal of modern optics,
11/2016, Letnik:
63, Številka:
20
Journal Article
Recenzirano
Odprti dostop
We have proposed a compact scheme of quantum random access memory (qRAM) based on the impedance matched multi-qubit photon echo quantum memory incorporated with the control four-level atom in two ...coupled QED cavities. A set of matching conditions for basic physical parameters of the qRAM scheme that provides an efficient quantum control of the fast single photon storage and readout has been found. In particular, it has been discovered that the efficient qRAM operations are determined by the specific properties of the excited photonic molecule coupling the two QED cavities. Herein, the maximal efficiency of the qRAM is realized when the cooperativity parameter of the photonic molecule equals to unity that can be experimentally achievable. We have also elaborated upon the new quantum address scheme where the multi-time-bin photon state is used for the control of the four-level atom during the readout of the photonic qubits from the quantum memory. The scheme reduces the required number of logical elements to one. Experimental implementation by means of current quantum technologies in the optical and microwave domains is also discussed.
In mountainous regions, climate warming is expected to shift species' ranges to higher altitudes. Evidence for such shifts is still mostly from revisitations of historical sites. We present recent ...(2001 to 2008) changes in vascular plant species richness observed in a standardized monitoring network across Europe's major mountain ranges. Species have moved upslope on average. However, these shifts had opposite effects on the summit floras' spedes richness in boreal-temperate mountain regions (+3.9 species on average) and Mediterranean mountain regions (-1.4 species), probably because recent climatic trends have decreased the availability of water in the European south. Because Mediterranean mountains are particularly rich in endemic species, a continuation of these trends might shrink the European mountain flora, despite an average increase in summit species richness across the region.
To study demographic, clinical, serological and morphological features of interstitial pneumonia with autoimmune features (IPAF), compare survival in IPAF and interstitial lung disease in connective ...tissue diseases (CTD-ILD), and identify predictors of mortality and transformation to CTD in the IPAF group.
The IPAF group included 48 patients (75.0% women, median age 57.5 years), CTD-ILD - 49 patients (79.6% women, median age 60.0 years). The analysis of demographic, clinical, laboratory and instrumental data was performed, as well as comparison of survival with the Kaplan-Meier method and the log-rank test in the IPAF and CTD-ILD groups. In the IPAF group, predictors of mortality and the development of CTD were studied with multivariate regression analysis.
Duration of observation period did not differ significantly in the IPAF and CTD-ILD groups (40.0 and 37.0 months, respectively). Clinical criteria of IPAF were observed in 25 (52.1%) patients, serological - in 44 (91.7%), morphological - in 44 (91.7%). Mortality in the IPAF group was significantly higher than in the CTD-ILD group (29.2 and 6.1%, respectively;
=0.023). The presence of diabetes mellitus, CT-pattern of usual interstitial pneumonia, and an initial low forced vital capacity value were independent predictors of mortality in the IPAF group. During the observation period, the development of CTD was noted in 4 (8.3%) patients with IPAF. The independent predictor of the CTD development was the increased C-reactive protein level.
IPAF is characterized by a lower survival rate compared to CTD-ILD, and a relatively low risk of CTD transformation.
We report a theoretical analysis of a photonic quantum interface, which makes it possible to deterministically convert photonic qubits from subcarrier wave to polarization encoding. The interface ...provides unambiguous conversion of an arbitrary phase of the input signal into the corresponding polarization of the converted radiation. Possibilities of implementing this interface in an integrated optical design and its use in constructing a hybrid quantum network are discussed.
—The scanning Fabry–Perot interferometer (FPI) is the oldest method of optical 3D spectroscopy. It is still in use because of the high spectral resolution it provides over a large field of view. The ...history of the application of this method for the study of extended objects (nebulae and galaxies) and the technique of data reduction and analysis are discussed. The paper focuses on the performing observations with the scanning FPI on the 6-m telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences. The instrument is currently used as a part of the SCORPIO-2 multimode focal reducer. The results of studies of various galactic and extragalactic objects with the scanning FPI on the 6-m telescope—star-forming regions and young stellar objects, spiral, ring, dwarf and interacting galaxies, gas subsystems associated with the ionization cones of active galactic nuclei, galactic winds, etc. are briefly discussed. Further prospects for research with the scanning FPI of the Special Astrophysical Observatory of the Russian Academy of Sciences are discussed.
We have found a new hidden symmetry of time reversal light-atom interaction in the photon echo quantum memory with Raman atomic transition. The time-reversed quantum memory creates generalized ...conditions for the ideal compression decompression of time duration of the input light pulses and its wavelength. Based on a general analytical approach to this scheme, we have studied the optimal conditions for the light field compression decompression in resonant atomic systems characterized by realistic spectral properties. The demonstrated necessary conditions for the effective quantum conversion of the light waveform and wavelength are also discussed for various possible realizations of the quantum memory scheme. The performed study promises new capabilities for fundamental study of the light-atom interaction and deterministic quantum manipulation of the light field, significant for quantum communication and quantum computing.
ABSTRACT
The S254-258 star-forming complex is a place of massive star formation where five OB-stars have created H ii regions, visible as optical nebulae, and disrupted the parental molecular gas. In ...this work, we study the 3D structure of these H ii regions using optical spectroscopy and tunable-filter photometry with the 6- and 1-m telescopes of the Special Astrophysical Observatory of the Russian Academy of Sciences. We construct maps of the optical extinction and find that the H ii emission is attenuated by neutral material with 2 ≤ AV ≤ 5 mag. The typical electron density in S255, and S257 is ≈100 cm−3, with enhancements up to 200 cm−3 in their borders, and up to 400 cm−3 toward the dense molecular cloud between them, where active star formation is taking place. We show that either a model of a clumpy dense neutral shell, where UV photons penetrate through and ionize the gas, or a stellar wind, can explain the shell-like structure of the ionized gas. S255 is surrounded by neutral material from all sides, but S257 is situated on the border of a molecular cloud and does not have dense front and rear walls. The compact H ii regions S256 and S258 are deeply embedded in the molecular clouds.
PDF
