Photon-mediated interactions between quantum systems are essential for realizing quantum networks and scalable quantum information processing. We demonstrate such interactions between pairs of ...silicon-vacancy (SiV) color centers strongly coupled to a diamond nanophotonic cavity. When the optical transitions of the two color centers are tuned into resonance, the coupling to the common cavity mode results in a coherent interaction between them, leading to spectrally-resolved superradiant and subradiant states. We use the electronic spin degrees of freedom of the SiV centers to control these optically-mediated interactions. Our experiments pave the way for implementation of cavity-mediated quantum gates between spin qubits and for realization of scalable quantum network nodes.
The high-pressure synthesis of boron doped diamonds from boron-containing organics has proven effective. This work is devoted to the study of the synthesis under high pressure of diamond and graphite ...doped with boron, both materials being in demand in high-tech applications. At 8 GPa and 1700 °C, graphite is obtained from adamantane C10H16, whereas microcrystals of boron-doped diamond (2 ÷ 2.5 at.% of boron) are synthesized from a mixture of adamantane and ortho-carborane C2B10H12 (atomic ratio B:C = 5:95). This result indicates the promotional activity of boron in the synthesis of diamond under high pressure. At pressures lower than 7 GPa, only graphite is synthesized from the adamantane and carborane mixture. Graphitization starts at quite low temperatures (below 1400 °C) and an increase in temperature simultaneously increases boron content and the quality of the graphite crystal lattice. Extensive study of the material structure allows us to assume that the substitutional boron atoms are distributed periodically and equidistantly from each other in the graphite layers at boron concentrations above ∼1 at.%. The theoretical arguments and model ab initio calculations confirm this assumption and explain the experimentally observed boron concentrations.
Display omitted
Abstract
The recent theoretical prediction of a new compound, WB
5
, has spurred the interest in tungsten borides and their possible implementation in industry. In this research, the experimental ...synthesis and structural description of a boron‐rich tungsten boride and measurements of its mechanical properties are performed. The ab initio calculations of the structural energies corresponding to different local structures make it possible to formulate the rules determining the likely local motifs in the disordered versions of the WB
5
structure, all of which involve boron deficit. The generated disordered WB
4.18
and WB
4.86
models both perfectly match the experimental data, but the former is the most energetically preferable. The precise crystal structure, elastic constants, hardness, and fracture toughness of this phase are calculated, and these results agree with the experimental findings. Because of the compositional and structural similarity with predicted WB
5
, this phase is denoted as WB
5−
x
. Previously incorrectly referred to as “WB
4
,” it is distinct from earlier theoretically suggested WB
4
, a phase with a different crystal structure that has not yet been synthesized and is predicted to be thermodynamically stable at pressures above 1 GPa. Mild synthesis conditions (enabling a scalable synthesis) and excellent mechanical properties make WB
5−
x
a very promising material for drilling technology.
We review our recent experiments demonstrating a hollow-core photonic-crystal fiber loaded with laser-cooled atomic vapor as a system for all-optical switching with pulses containing few hundred ...photons. Additionally, we discuss the outlooks for improving the efficiency of this switching scheme and present preliminary results geared toward using the system as a photon-number resolving detector.
We demonstrate that silicon-vacancy (SiV) centers in diamond can be used to efficiently generate coherent optical photons with excellent spectral properties. We show that these features are due to ...the inversion symmetry associated with SiV centers, and demonstrate generation of indistinguishable single photons from separate emitters in a Hong-Ou-Mandel (HOM) interference experiment.Prospects for realizing efficient quantum network nodes using SiV centers are discussed.
Quantum entanglement involving coherent superpositions of macroscopically distinct states is among the most striking features of quantum theory, but its realization is challenging, since such states ...are extremely fragile. Using a programmable quantum simulator based on neutral atom arrays with interactions mediated by Rydberg states, we demonstrate the deterministic generation of 'Schr\"odinger cat' states of the Greenberger-Horne-Zeilinger (GHZ) type with up to 20 qubits. Our approach is based on engineering the energy spectrum and using optimal control of the many-body system. We further demonstrate entanglement manipulation by using GHZ states to distribute entanglement to distant sites in the array, establishing important ingredients for quantum information processing and quantum metrology.
The article presents the current trends in the recomposed work stand and the terminology used. Technical solutions were considered in order to optimize the use of this system type. Intermodular ...element of locating and fixing - multi-tiered was proposed. This device contains automatic plug-in units, layout - multi-tiered. Tiered layout does not always meet the requirements of the technical process. Industrial robot for automatic replacement of nodes was proposed.
Pis'ma v ZhETF 82, 124-128 (2005); JEPT Lett. 82, 110-114 (2005) We present experimental study of polarization quantum noise of laser
radiation passed through optically think vapor of Rb87. We ...observe a step-like
noise spectrum. We discuss various factor which may result in such noise
spectrum and prevent observation of squeezing of quantum fluctuations predicted
in Matsko et al. PRA 63, 043814 (2001).
PDF
