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Trapped and Coupled Trapped single atoms are ideal for storing and manipulating quantum information. Thompson et al. (p. 1202 , published online 25 April; see the Perspective by Keller ) were able to control single atoms interacting coherently with a field mode of a photonic crystal cavity. An optical tweezer was used to trap the single atom, which enabled positioning of the atom in close proximity to the photonic crystal waveguide, coupling the atom to the optical mode of the cavity. Such coupling should prove useful in quantum measurement, sensing, and information processing.

The number of laser cooled and trapped thulium atoms in a magneto-optical trap is increased by a factor of 3 using a two-dimensional optical molasses which collimated the atomic beam before entering a Zeeman slower. A diode laser operating at 410.6 nm was employed to form optical molasses: The laser was heated to 70 Degree-Sign C by a two-step temperature stabilisation system. The laser system consisting of a master oscillator and an injection-locked amplifier emitted more than 100 mW at 410 nm and had a spectral linewidth of 0.6 MHz. (extreme light fields and their applications)

Review: emphasis on processes that are essential in terms of photovoltaic and photocatlytic cells; 655 refs.

Understanding the optical properties of quantum emitters is the cornerstone of many phenomena in nanophotonics. Spontaneous emission from quantum emitters can be modified when they are placed in resonators, for example, near plasmonic or dielectric nanoantennas. We numerically study the Purcell factor of the emitter inside a nanodiamond placed near the resonant silicon nanoparticle. We show that in this system the 11-fold enhancement can be achieved for a specific orientation of the dipole moment of the emitter. The obtained results are of particular importance for nanophotonic applications which aim to control optical properties of quantum light sources.

Nitrogen-vacancy centers in diamond allow coherent spin state manipulation and optical readout at room temperature, which has powerful applications in nanoscale sensing. Nanophotonic structures such as plasmonic waveguides, nanoantennae, metamaterials, and metasurfaces can enhance the detected fluorescence rate from such broadband emitters. The fluorescence of the coupled emitter is directed into confined plasmonic modes with high photonic density of states. However, an accurate spin readout requires both high photon counts and a strong contrast between the spin states, both of which can be influenced by the Purcell effect. We introduce a novel method for measuring the spin contrast in large nitrogen-vacancy ensembles. We use this method to study how the photonic density of states must be engineered in order to minimize the uncertainty of spin readout in dense NV ensembles. We describe these results using a kinetic model of the nitrogen-vacancy's internal dynamics.

Here we present the design of a dielectric resonator antenna for spin manipulation of large volume ensemble of nitrogen-vacancy centers in a bulk diamond. The proposed antenna design is based on a high permittivity hollow dielectric resonator excited by a symmetric microstrip loop. We present the result of numerical simulation of the magnetic field excited at the TE01δ mode of the dielectric resonator. We analyze the uniformity of the magnetic field in volume and discuss the possibility to use the antenna for efficient excitation of nitrogen-vacancy centers in whole commercially available sample.

This work presents a nonadiabatic molecular dynamics methodology that relies on the use of fragment molecular orbitals computed using tight-binding Hamiltonians. The approach aims to model charge and energy transfer in large systems via quantum-classical trajectory-based approaches. The technique relies on a chemically motivated fragmentation of the overall system into arbitrary fragments. Several types of fragment molecular orbitals (FMO) can be constructed and used in nonadiabatic simulations, comprising quasidiabatic, adiabatic, and Lowdin-transformed ones. The adiabatic FMOs are found to be most suitable for modeling nonadiabatic dynamics in complex molecular systems. The overall algorithm shows advantageous scaling properties, making it possible to model long time scale charge transfer processes in large systems with many hundreds of atoms. The approach is applied to study charge transfer in subphtalocyanine(SubPc)/C60 heterojunction. The computational results emphasize the importance of decoherence ...

Understanding the dynamics of electron–ion energy transfer in warm dense (WD) matter is important to the measurement of equation of state (EOS) properties and for understanding the energy balance in dynamic simulations. In this work, we present a comprehensive investigation of nonadiabatic electron relaxation and thermal excitation dynamics in aluminum under high pressure and temperature. Using quantum–classical trajectory surface hopping approaches, we examine the role of nonadiabatic couplings and electronic decoherence in electron-nuclear energy transfer in WD aluminum. The computed timescales range from 400 fs to 4.0 ps and are consistent with existing experimental studies. We have derived general scaling relationships between macroscopic parameters of WD systems such as temperature or mass density and the timescales of energy redistribution between quantum and classical degrees of freedom. The scaling laws are supported by computational results. We show that electronic decoherence plays essential role and can change the functional dependencies qualitatively. The established scaling relationships can be of use in modelling of WD matter.

Metamaterials and metasurfaces can be seen as a novel approach for constructing practical quantum photonic systems. In this talk, we present our recent advances in controlling single-photon emission from nitrogen-vacancy (NV) color centers in nanodiamonds using CMOS-compatible hyperbolic metamaterials. Further, we discuss how an increased photonic density of states affects the optical readout of the NV center spin-state. These results can be useful for engineering on-chip room-temperature quantum registers.

Nonadiabatic molecular dynamics (NA-MD) is an extremely useful approach to model electron transfer dynamics in molecular and solid state systems. The performance of NA-MD simulations depends critically on the accuracy of the underlying electronic structure properties, such as state energies and nonadiabatic couplings (NAC). Practical NA-MD modeling relies extensively on computationally efficient pure density functionals, despite the known intrinsic problems of the latter. A reliable solution to the problems presented by the use of pure density functionals, is the use of hybrid functionals, however hybrid functionals are significantly more expensive. In this work, we investigate how the choice of the density functional can affect the NAC magnitudes for small silicon clusters and silicon hydrides. We find that pure functionals can significantly overestimate NAC magnitudes in comparison to those obtained with hybrid functionals. The ratio of the two magnitudes increases with the system size and differs by an order of magnitude even for small Si

Integration of solid-state quantum emitters such as NV center in diamond with tapered optical fiber is demanded by number of applications ranging from sensing and imaging to quantum communications and computations. Nevertheless, utilization of a single NV center coupled with an optical fiber meets significant challenge of fiber fluorescence that can considerably mask emission of the quantum object. In this paper, we analyze main sources of such fluorescence for the case of NV center coupled to tapered single mode optical fiber and discuss possible ways of improving signal to noise ratio in this case.

NV center in diamond is attracting a lot of attention in quantum information processing community [1]. Been spin system in clean and well-controlled environment of diamond it shows outstanding performance as quantum memory even at room temperature, spin control with single shot optical readout and possibility to build up quantum registers even on single NV center. Moreover, NV centers could be used as high-resolution sensitive elements of detectors of magnetic or electric field, temperature, tension, force or rotation. For all of these applications collection of the light emitted by NV center is crucial point. There were number of approaches suggested to address this issue, proposing use of surface plasmoms [2], manufacturing structures in diamond [3] etc. One of the key feature of any practically important interface is compatibility with the fiber technology. Several groups attacking this problem using various approaches. One of them is placing of nanodiamonds in the holes of photonic crystal fiber [4], another is utilization of AFM to pick and place nanodiamond on the tapered fiber[5]. We have developed a novel technique of placing a nanodiamond with single NV center on the tapered fiber by controlled transfer of a nanodiamond from one “donor” tapered fiber to the “target” clean tapered fiber. We verify our ability to transfer only single color centers by means of measurement of second order correlation function. With this technique, we were able to double collection efficiency of confocal microscope. The majority of the factors limiting the collection of photons via optical fiber are technical and may be removed allowing order of magnitude improved in collection. We also discuss number of extensions of this technique to all fiber excitation and integration with nanostructures. References: [1] Marcus W. Doherty, Neil B. Manson, Paul Delaney, Fedor Jelezko, Jorg Wrachtrup, Lloyd C.L. Hollenberg , " The nitrogen-vacancy colour centre in diamond," Physics Reports, vol. 528, no. 1, p. 1–45, 2013. [2] A.V. Akimov, A. Mukherjee, C.L. Yu, D.E. Chang, A.S. Zibrov, P.R. Hemmer, H. Park and M.D. Lukin, "Generation of single optical plasmons in metallic nanowires coupled to quantum dots," Nature, vol. 450, p. 402–406, 2007. [3] Michael J. Burek , Yiwen Chu, Madelaine S.Z. Liddy, Parth Patel, Jake Rochman , Srujan Meesala, Wooyoung Hong, Qimin Quan, Mikhail D. Lukin and Marko Loncar High quality-factor optical nanocavities in bulk single-crystal diamond, Nature communications 6718 (2014) [4] Tim Schroder, Andreas W. Schell, Gunter Kewes, Thomas Aichele, and Oliver Benson Fiber-Integrated Diamond-Based Single Photon Source, Nano Lett. 2011, 11, 198-202 [5]Lars Liebermeister, et. al. “Tapered fiber coupling of single photons emitted by a deterministically positioned single nitrogen vacancy center”, Appl. Phys. Lett. 104, 031101 (2014)

The nitrogen-vacancy (NV) center in diamond is attracting a lot of attention in quantum information processing community. A spin system in the NV center is positioned in a clean and well-controlled environment. As a result, it shows outstanding performance as quantum memory, even at room temperature, allows for spin control with a single shot optical readout, and offers a possibility of building quantum registers on a single NV center. At low temperature, the NV centers have narrow optical transitions, which enable interfacing between optical photons and the NV center spin states. Recently, the entanglement of two independent NV centers has been demonstrated. This makes the NV center a promising candidate for realization of quantum repeaters. Moreover, the NV centers could be used as sensitive elements of detectors of magnetic or electric fields, temperature etc‥ For all of these applications collection of the light emitted by the NV center is a crucial point. Recent developments in the field of metamaterials allowed creating hyperbolic metamaterials which may provide an efficient interface for coupling light into and out of the NV centers and, in particular, enable a single photon source based on NV. In this work, I will present our work on using CMOS-compatible hyperbolic metamaterials and optical fibers to construct efficient single photon sources and sensing elements using NV centers in diamond.

Laser cooling and trapping became powerful tool enabling number of research activities and applications such as quantum simulation [1], quantum information processing [2], control of light propagation and switching of optical pulses [3] including single photon gates [4], metrology and testing drift of fundamental constants [5]. Recently rare earth elements attracted considerable attention due to the high orbital and magnetic moments. Such a systems allow low-field Feshabach resonances [6] enabling tunable in wide range interactions, relatively large dipole-dipole interactions. In particular, thulium atom has one hole in 4f shell therefore having orbital moment of 3 in the ground state, magnetic moment of 4 Bohr magnetons in ground state. While magnetic moment of the thulium atom is less than that of Erbium or Dysprosium [7, 8] simpler level structure, possibility to capture thulium atoms and the dipole trap at 532nm [9] make thulium atom an extremely attractive subject for quantum simulations and quantum information processing. In this contribution, I will present our efforts toward brining thulium atom to ultracold temperatures and quantum degeneracy as well as our study of collisional proprieties of thulium atom.

Understanding microscopic mechanisms of motion of artificial molecular machines is fundamentally important for scientific and technological progress. It is known that electric field might strongly influence structures and dynamic properties of molecules at the nanoscale level. Specifically, it is possible to induce conformational changes and the directional motion in many surface-bound molecules by electric field in scanning tunneling microscopy (STM) experiments. Utilizing a recently developed theoretical method to describe charge transfer phenomena for fullerenes near metal surfaces, in this work we theoretically investigated dynamics of fullerene-based nanocars in the presence of external electric field. Our approach is based on classical rigid-body molecular dynamics simulations that allow us to fully analyze dynamics of nanocars on gold surfaces. Theoretical calculations predict that it is possible to drive nonpolar nanocars unidirectionally with the help of external electric field. It is shown also ...

It is widely believed that the dynamics of surface-bound fullerene molecules is not fully understood because current theoretical analyses do not include charge-transfer phenomena. A new theoretical approach to describe charge transfer and chemisorption processes for fullerenes on gold surfaces has been developed. The method is based on extensive semiempirical calculations that provide a consistent description of charge transfer and adsorption phenomena. Our theoretical approach is applied for analyzing complex dynamics of fullerene-based molecular machines, known as nanocars. It is found that the charge transfer makes the rolling of nanocars' wheels a preferable mode for translational motion because of the complex interactions with the metal surfaces. The physical-chemical aspects of the rolling mechanism are discussed.

We demonstrated laser cooling and trapping of thulium atoms at sub-Doppler temperatures in a magneto-optical trap (MOT). Up to 3 × 106 thulium atoms were trapped in the MOT at temperatures down to 25(5) μK which is approximately 10 times lower than the Doppler limit. The lifetime of atoms in the MOT varied between 0.3–1.5 s and was restricted mostly by optical leaks from the upper cooling level. The lower limit for the leaking rate was estimated to be 22(6) s−1. Due to a big magnetic moment of Tm atoms, a part of them were trapped in a magnetic trap from the quadrupole field of the MOT. We observed about 3 × 104 purely magnetically trapped atoms at temperature of 25 μK with a lifetime in the trap of 0.5 s. Also we set up a “dark” MOT consisting of six crossed hollow beams which increased the number of trapped atoms by a factor of 5 leading to 1.5 × 107 atoms at the expense of higher temperature.

Molecular dynamics computer simulation methods are very important for understanding mechanisms of chemical, physical, and biological processes. The reliability of molecular dynamics simulations strongly depends on the integration schemes used in the simulations. In this work, we developed new rigid body integration schemes for molecular dynamics simulations. Our approach is based on a numerically exact solution to the free rigid body problem, which is used in the classical propagator splitting scheme. We use the Taylor series expansion of rotational dynamical variables in conjunction with the recursive solution for higher order derivatives of these variables. Such an approach is computationally very efficient, robust, and easy to implement, and it does not employ Jacobi elliptic functions, while still providing the numerically exact solution of the free rigid body problem. Our studies showed that the new integration methods have long-time stability and accuracy properties which are comparable to those of existing symplectic integrators. The extension to the case of a canonical ensemble is also developed, allowing one to perform simulations at constant temperatures.

For the first time ultra-cold thulium atoms were trapped in a magnetic quadrupole trap with a small field gradient (20 Gs cm-1). The atoms were loaded from a cloud containing 4×105 atoms that were preliminarily cooled in a magneto-optical trap to the sub-Doppler temperature of 80 μK. As many as 4×104 atoms were trapped in the magnetic trap at the temperature of 40 μK. By the character of trap population decay the lifetime of atoms was determined (0.5 s) and an upper estimate was obtained for the rate constant of inelastic binary collisions for spin-polarised thulium atoms in the ground state (gin < 10-11cm3 s-1).

The conditions necessary to implement a single-photon pulse source using quantum filtering based on the coherent population trapping phenomenon in N-systems of atomic levels are determined. The dependences of dark resonance characteristics on laser field intensities are experimentally measured in Rb vapor. These dependences define optimum intensity ratios and pulse durations of used laser beams, at which the system can efficiently operate as a single-photon quantum filter.

In recent years molecular rotors have attracted the attention of many research groups for possible applications as new nanoscale devices and materials with controlled chemical, physical, and mechanical properties. One of the most unique systems with molecular rotations is amphidynamic molecular crystals, also known as crystalline molecular gyroscopes. This system can be viewed as a solid-state assembly of molecules that cannot move translationally but show internal rotations. Recent experiments on amphidynamic crystals indicate importance of rotational symmetry for describing their dynamics. However, mechanisms and rotational dynamic properties of molecular gyroscopes are still not well understood. We present here a theoretical investigation of amphidynamic crystals by utilizing extensive rigid-body molecular dynamics simulations and simple phenomenological arguments. Theoretical analysis suggests that intramolecular interactions within stator and rotator segments of molecular rotors as well as their flex...

The sensitivity of magnetic and electric field sensors based on nitrogen-vacancy (NV) center in diamond strongly depends on the available concentration of NV and their coherence properties. Achieving high coherence times simultaneously with high concentration is a challenging experimental task. Here, we demonstrate that by using a temperature gradient method of high-pressure, high-temperature growing technique, one can achieve nearly maximally possible dephasing times, limited only by carbon nuclear spins at low nitrogen concentrations or nitrogen electron spin at high nitrogen concentrations. Hahn-echo T 2 coherence times were also investigated and found to demonstrate reasonable values. Thus, the high-pressure, high-temperature technique is a strong contender to the popular chemical vapor deposition method in the development of high-sensitivity, diamond-based sensors.

Color centers in diamonds have shown promising potential for luminescent thermometry. So far, the nitrogen-vacancy (NV) color center has demonstrated a high sensitivity for optical temperature monitoring in biological systems. However, the NV center requires microwave excitation which can cause unwanted heating, and the NV is also sensitive to non-axial magnetic fields, both of which can result in inaccurate temperature measurements. To overcome this drawback, the silicon-vacancy (SiV) and germanium-vacancy (GeV) color centers in diamonds have recently been explored and have shown good optical temperature sensitivity owing to the temperature dependent wavelength optical zero-phonon line. Here, we report optical temperature measurements using the recently discovered tin-vacancy (SnV) color center in diamond and show sensitivity better than 0.2 K in 10 s integration time. Also, we compare the relative merits of SnV with respect to SiV and GeV for luminescent thermometry. These results illustrate that there are likely to be many future options for nanoscale thermometry using diamonds.

A simple and robust methodology, dubbed Entangled Trajectories Hamiltonian Dynamics (ETHD), is developed to capture quantum nuclear effects such as tunneling and zero-point energy through the coupling of multiple classical trajectories. The approach reformulates the classically mapped second-order Quantized Hamiltonian Dynamics (QHD-2) in terms of coupled classical trajectories. The method partially enforces the uncertainty principle and facilitates tunneling. The applicability of the method is demonstrated by studying the dynamics in symmetric double well and cubic metastable state potentials. The methodology is validated using exact quantum simulations and is compared to QHD-2. We illustrate its relationship to the rigorous Bohmian quantum potential approach, from which ETHD can be derived. Our simulations show a remarkable agreement of the ETHD calculation with the quantum results, suggesting that ETHD may be a simple and inexpensive way of including quantum nuclear effects in molecular dynamics simulations.

The level splitting appearing upon cascade excitation of the 5D5/2 and 5D3/2 levels of the 87Rb atom in a magnetooptical trap is studied experimentally. The 5S5/2 and 5P3/2 levels are coupled by a cooling laser field, the Rabi frequency being comparable with the rate of spontaneous decay of the 5P3/2 level. The experimental spectral profiles are compared with a theoretical model.

The resonant interaction of 87Rb atoms in a magneto-optical trap with femtosecond laser radiation in the spectral range 760–820 nm has been investigated experimentally. It has been demonstrated that femtosecond laser radiation with a spectral width of 10 nm interacts with an atomic ensemble as a set of spectrally narrow modes and as an ionizing laser field simultaneously. The dynamics of trap loading in the presence of ionization by femtosecond radiation has been studied, and the 5D5/2 level population produced by an additional weak laser field has been measured.

The influence of noises of the frequency and phase difference of an exciting bichromatic field on the parameters of coherent population trapping resonances is studied experimentally. When the phase difference fluctuates within a limited interval near its average value with a short correlation time, the resonance contrast decreases proportionally to exp(2rms), where 2rms is the phase dispersion (in rad2). In this case, the spectral width of the resonance remains constant. In another limiting case, when the phase noise has a long correlation time, the resonance contour broadens, the area under the contour being invariable. Experiments were performed with the Zeeman sublevels of the ground state of 87Rb by exciting rubidium vapour in a glass cell at the resonance wavelength of 795 nm.

Recent single-molecule experiments indicated that thioethers (dialkyl sulfides) on gold surfaces act as thermally- or mechanically activated molecular rotors, although the mechanisms for these phenomena are not yet clearly understood. Here we present theoretical and experimental investigations of the rotational dynamics of these thioether molecules. Single-molecule studies utilizing low-temperature scanning tunneling microscopy allowed us to determine rotational rates and activation energies for the rotation of symmetric dialkyl sulfides. It was found that the rotational energy barriers increased as a function of alkyl chain length but then quickly saturated. Molecular dynamics simulations have also been performed in order to understand the molecular rotations of thioethers, and our theoretical calculations agree well with experimental observations. It is argued that the observed rotational dynamics of dialkyl sulfides are determined by the effective interactions with the surface and the flexibility of th...

The results of frequency-modulation (FM) spec- troscopy of coherent dark resonances from the Zeeman sub- levels of the transition F = 2 ↔ F = 1o fD1 line in absorp- tion of 87 Rb atoms are presented and discussed in detail. By contrast with the conventional spectroscopy of coherent dark resonances employing two laser beams, relative frequency of which can be varied, these data has been obtained with the help of a single frequency-modulated laser field. Varia- tion of the modulation frequency plays then a similar role as the variation of the relative frequency in conventional spec- troscopy. Experimental data are fit to the theoretical calcu- lations, which are based on the theory of FM spectroscopy of coherent dark resonances recently developed by us. Fea- sibility of using such experimental technique for accurate measurements of magnetic fields is also discussed.

The possibility of the use of the F = 2↔F = 1 transition of the D1 absorption line of the 87Rb atom for creating of a single-photon quantum filter based on coherent population trapping (CPT) has been analyzed. It has been shown that the external magnetic field is necessary for ensuring the creation of the quantum filter on boson isotopes of alkali atoms. The field strength should be enough for the manifestation of the splitting of the Zeeman CPT resonances that is much larger than their spectral widths. The splittings of the CPT resonances, which characterize the nonlinearity of the Zeeman effect, have been measured for the 87Rb atom and the possibility of the use of this system for the quantum filter is concluded.

The possibility of laser cooling of thulium atoms is considered. The hyperfine structure of almost cyclic 4f136s2 (Jg = 7/2) ↔ 4f125d3/26s2 (Je = 9/2) and 4f136s2 (Jg = 7/2) ↔ 4f125d5/26s2 (Je = 9/2) transitions at 410.6 and 420.4 nm, respectively, is studied by the method of sub-Doppler saturation spectroscopy in counterpropagating laser beams. The hyperfine splitting of excited levels involved in these transitions is measured and the natural linewidths of these transitions are determined. The structure of the neighbouring 4f136s6p (Je = 5/2) and 4f125d5/26s2 (Je = 7/2) levels is studied for the first time by this method. The decay probabilities of the Je = 9/2 levels via channels removing atoms from the cooling cycle are calculated. It is found that the branching ratio for the strong transition at 410.6 nm (A = 6×107 s-1) is smaller than 2×10-5, which makes this transition most promising for laser cooling. The laser cooling of atoms in a Zeeman cooler at this transition is simulated. The possibility of using a laser-cooled cloud of thulium atoms to study the metrological transition at 1.14 μm is discussed.

We consider the effect of the noise difference phase of a bichromatic field upon coherent population trapping resonances in the simplest three-level system in Λ configuration. The quasi-stationary solution of Bloch optical equations, which was found with some assumptions, shows that the presence of exciting short-correlated fluctuations of the phase of radiation reduces the contrast of the resonance line without affecting its spectral width. For the Gaussian phase noise the contrast suppression factor is χ = exp[−ϕ rms 2 ], where ϕ rms 2 is phase dispersion. The experimental results obtained earlier by our group are analyzed.

We developed molecular models describing the thermally initiated motion of nanocars, nanosized vehicles composed of two to four spherical fullerene wheels chemically coupled to a planar chassis, on a metal surface. The simulations were aimed at reproducing qualitative features of the experimentally observed migration of nanocars over gold crystals as determined by scanning tunneling microscopy. Coarse-grained-type molecular dynamics simulations were carried out for the species "Trimer" and "Nanotruck", the simplified versions of the experimentally studied nanomachines. Toward this goal, we developed a version of the rigid body molecular dynamics based on the symplectic quaternion scheme in conjunction with the Nose-Poincare thermostat approach. Interactions between rigid fragments were described by using the corrected CHARMM force field parameters, while several empirical models were introduced for interactions of nanocars with gold crystals. With the single adjusted potential parameter, the computed trajectories are consistent with the qualitative features of the thermally activated migration of the nanocars: the primary pivoting motion of Trimer and the two-dimensional combination of translations and pivoting of Nanotruck. This work presents a first attempt at a theoretical analysis of nanocars' dynamics on a surface by providing a computationally minimalist approach.

We report ab initio time-domain simulations of nonradiative electron-hole recombination and electronic dephasing in ideal and defect-containing monolayer black phosphorus (MBP). Our calculations predict that the presence of phosphorus divacancy in MBP (MBP-DV) substantially reduces the nonradiative recombination rate, with time scales on the order of 1.57 ns. The luminescence line width in ideal MBP of 150 meV is 2.5 times larger than MBP-DV at room temperature, and is in excellent agreement with experiment. We find that the electron-hole recombination in ideal MBP is driven by the 450 cm(-1) vibrational mode, whereas the recombination in the MBP-DV system is driven by a broad range of vibrational modes. The reduced electron-phonon coupling and increased bandgap in MBP-DV rationalize slower recombination in this material, suggesting that electron-phonon energy losses in MBP can be minimized by creating suitable defects in semiconductor device material.

We demonstrated a simple and reliable technique of coupling diamond nanocrystal containing NV center to tapered optical fiber. The NV center emission was collected by the fiber via nearfield interaction between NV center and the tapered portion of the fiber. Single photon statistics was demonstrated at the fiber end as well as up to 3 times improvement in collection efficiency with respect to our confocal microscope. Also, we carefully studied fluorescence of the fiber itself and were able to suppress it to the level lower than single photon emission from the NV center.

The "methodology discovery" library for quantum and classical dynamics simulations is presented. One of the major foci of the code is on nonadiabatic molecular dynamics simulations with model and atomistic Hamiltonians treated on the same footing. The essential aspects of the methodology, design philosophy, and implementation are discussed. The code capabilities are demonstrated on a number of model and atomistic test cases. It is demonstrated how the library can be used to study methodologies for quantum and classical dynamics, as well as a tool for performing detailed atomistic studies of nonadiabatic processes in molecular systems. The source code and additional information are available on the Web at http://www.acsu.buffalo.edu/~alexeyak/libra/index.html. © 2016 Wiley Periodicals, Inc.

In our previous work [J. Chem. Theory Comput. 2013, 9, 4959], we introduced the PYXAID program, developed for the purpose of performing nonadiabatic molecular dynamics simulations in large-scale condensed matter systems. The methodological aspects and the basic capabilities of the program have been extensively discussed. In the present work, we perform a thorough investigation of advanced capabilities of the program, namely, the advanced integration techniques for the time-dependent Schrodinger equation (TD-SE), the decoherence corrections via decoherence-induced surface hopping, the use of multiexciton basis configurations, and the direct simulation of photoexcitation via explicit light-matter interaction. We demonstrate the importance of the mentioned features by studying the electronic dynamics in a variety of systems. In particular, we demonstrate that the advanced integration techniques for solving TD-SE may lead to a significant speedup of the calculations and provide more stable solutions. We show that decoherence is necessary for accurate description of slow relaxation processes such as electron-hole recombination in solid C60. By using multiexciton configurations and direct, nonperturbative treatment of field-matter interactions, we found nontrivial optimality conditions for the multiple exciton generation in a small silicon cluster.

Efficient generation of single photons is essential for the development of photonic quantum technologies. We have demonstrated that coupling a nanodiamond nitrogen-vacancy (NV) center to CMOS-compatible nanophotonic structures results in significant reduction of the excited state lifetime, increase in the collected single–photon emission, and modification of radiation pattern. In addition, we studied the effect of increased photonic density of states on spin dependent fluorescence contrast.

We experimentally studied the narrow resonances of coherent population trapping (CPT) in a rubidium vapor cell with the help of a phase-coherent bichromatic light source based on a mode-locked femtosecond laser. We investigated the dependence of the contrast and the width of CPT resonance on the light power, as well as the sensitivity of the shape of the resonance to a magnetic field. Prospects of using the novel bichromatic source for phase-coherent Raman spectroscopy of CPT resonances in atomic systems with a large energy separation of the lower levels are discussed. Copyright © 2006 John Wiley & Sons, Ltd.

We propose a new approach to the study of coherent population trapping (CPT) resonances using a phase-coherent bichromatic light source based on a mode-locked femtosecond laser as an intermediate frequency coupler. The source consists of two diode lasers tuned to the rubidium D2 line (780 nm) which are phase locked to different longitudinal modes of a femtosecond laser MIRA-900F with 75 MHz repetition rate. Using this bichromatic source with a stable differential frequency, we excited and investigated the CPT resonances in the three-level system 5s S1/2 (F = 2) ↔ 5s P3/2 (F = 2) ↔ 5s S1/2 (F = 3) of the 85Rb atom. Potentially, this method opens up the possibility of coherently exciting Raman transitions with differential frequencies up to hundreds of terahertz. Copyright © 2005 John Wiley & Sons, Ltd.

A new source of the bichromatic laser field with a stable mean value of the difference frequency is used to study coherent population trapping (CPT). A high stability of the difference phase of the fields of the radiation source is achieved by phase locking the radiation frequency of two semiconductor lasers to longitudinal modes of a femtosecond laser. The first experimental results on the spectroscopy of CPT resonances in rubidium are presented. The possibility of using the new method for spectroscopy of CPT resonances in rare-earth atom vapours is discussed.

A technique for creating the source of a bichromatic laser field with a stable mean value of the difference frequency is realized. The spectral characteristics of a femtosecond passive mode-locked laser are used in this technique. Such a source operating in the region of 780 nm is created. The possibility of using the phenomenon of coherent population trapping (CPT) in three-level systems of the rare-earth atoms for the development of secondary frequency standards in the optical range is considered. The contributions of the processes affecting the width and contrast of the CPT resonances and defining their attainable Q factors are studied. The prospects of using the experimental technique developed for the spectroscopy of the CPT resonances in samarium and thulium vapors are discussed.

A universal theory for calculating coherent population trapping resonances in multilevel atoms is suggested. The theory allows arbitrary schemes of multilevel atoms and their excitations to be calculated tak- ing into account the influence of relaxation effects in atoms, applied magnetic field, and the Doppler effect. The experimental data obtained by high-precision diode spectroscopy of coherent dark resonances in samar- ium vapor are systematically analyzed using the suggested theory. In the absence of a magnetic field, the model of samarium is based on consideration of a degenerate Λ system of the 4 f 6 6 s 2 ( 7 F 0 ) 4 f 6 ( 7 F )6 s 6 p ( 3 P 0 ) 9 4 f 6 6 s 2 ( 7 F 1 ) active transitions. If the fourth 4 f 6 6 s 2 ( 7 F 2 ) level is taken into account, this Λ system becomes open. Numerical simulation of coherent population trapping resonances shows that the open character of the system decreases the contrast of resonance curves in absorption spectra without changing resonance widths. The system under applied external longitudinal and transverse magnetic fields is correctly described by 7- and 12-level models of atomic transitions, respectively. © 2003 MAIK "Nauka/Interperiodica".

Dark resonances in the 154Sm Λ-system 4f66s2(7F0) ↔ 4f66s6p(9F10) ↔ 4f6s2(7F1) are observed alongside the velocity selective optical pumping. The shape of the resulting spectra strongly depended on the buffer gas (He, Ar) pressure due to velocity-changing collisions (VCC): the sign of the effect could be reversed from the “dark” to the “bright” resonance. The observed spectra are interpreted within the framework of the hard-sphere collision model. The role of VCC in the formation of the “dark state” in the Λ-system is discussed.