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Search Results: 1 - 10 of 347 matches for " Serguei Vorojtsov "
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The description of an arbitrary configuration evolution in the Conway's Game Life in terms of the elementary configurations evolution in the first generation
Serguei Vorojtsov
Physics , 2001,
Abstract: The connection between the evolution of an arbitrary configuration and the evolution of its parts in the first generation is established. The equivalence of Conway's evolution rules to the elementary configurations' (containing one, two, three, and four pieces) evolution laws in the first generation has been proved.
Coulomb Blockade Oscillations of Conductance at Finite Energy Level Spacing in a Quantum Dot
Serguei Vorojtsov
Physics , 2002, DOI: 10.1142/S0217979204026706
Abstract: We find an analytical expression for the conductance of a single electron transistor in the regime when temperature, level spacing, and charging energy of a grain are all of the same order. We consider the model of equidistant energy levels in a grain in the sequential tunneling approximation. In the case of spinless electrons our theory describes transport through a dot in the quantum Hall regime. In the case of spin-1/2 electrons we analyze the line shape of a peak, shift in the position of the peak's maximum as a function of temperature, and the values of the conductance in the odd and even valleys.
Quantum Dots: Coulomb Blockade, Mesoscopic Fluctuations, and Qubit Decoherence
Serguei Vorojtsov
Physics , 2006,
Abstract: In this thesis I find an analytic expression for the conductance of a single electron transistor in the regime when temperature, level spacing, and charging energy of an island are all of the same order. I also study the correction to the spacing between Coulomb blockade peaks due to finite dot-lead tunnel couplings. I find analytic expressions for both correction to the spacing averaged over mesoscopic fluctuations and the rms of the correction fluctuations. In the second part of the thesis I discuss the feasibility of quantum dot based spin- and charge-qubits. Firstly, I study the effect of mesoscopic fluctuations on the magnitude of errors that can occur in exchange operations on quantum dot spin-qubits. Mid-size double quantum dots, with an odd number of electrons in the range of a few tens in each dot, are investigated through the constant interaction model using realistic parameters. It is found that the number of independent parameters per dot that one should tune depends on the configuration and ranges from one to four. Then, I study decoherence of a quantum dot charge qubit due to coupling to piezoelectric acoustic phonons in the Born-Markov approximation. After including appropriate form factors, I find that phonon decoherence rates are one to two orders of magnitude weaker than was previously predicted. My results suggest that mechanisms other than phonon decoherence play a more significant role in current experimental setups.
Coulomb Blockade Peak Spacings: Interplay of Spin and Dot-Lead Coupling
Serguei Vorojtsov,Harold U. Baranger
Physics , 2005, DOI: 10.1103/PhysRevB.72.165349
Abstract: For Coulomb blockade peaks in the linear conductance of a quantum dot, we study the correction to the spacing between the peaks due to dot-lead coupling. This coupling can affect measurements in which Coulomb blockade phenomena are used as a tool to probe the energy level structure of quantum dots. The electron-electron interactions in the quantum dot are described by the constant exchange and interaction (CEI) model while the single-particle properties are described by random matrix theory. We find analytic expressions for both the average and rms mesoscopic fluctuation of the correction. For a realistic value of the exchange interaction constant J_s, the ensemble average correction to the peak spacing is two to three times smaller than that at J_s = 0. As a function of J_s, the average correction to the peak spacing for an even valley decreases monotonically, nonetheless staying positive. The rms fluctuation is of the same order as the average and weakly depends on J_s. For a small fraction of quantum dots in the ensemble, therefore, the correction to the peak spacing for the even valley is negative. The correction to the spacing in the odd valleys is opposite in sign to that in the even valleys and equal in magnitude. These results are robust with respect to the choice of the random matrix ensemble or change in parameters such as charging energy, mean level spacing, or temperature.
Spin Qubits in Multi-Electron Quantum Dots
Serguei Vorojtsov,Eduardo R. Mucciolo,Harold U. Baranger
Physics , 2003, DOI: 10.1103/PhysRevB.69.115329
Abstract: We study the effect of mesoscopic fluctuations on the magnitude of errors that can occur in exchange operations on quantum dot spin-qubits. Mid-size double quantum dots, with an odd number of electrons in the range of a few tens in each dot, are investigated through the constant interaction model using realistic parameters. It is found that the constraint of having short pulses and small errors implies keeping accurate control, at the few percent level, of several electrode voltages. In practice, the number of independent parameters per dot that one should tune depends on the configuration and ranges from one to four.
Phonon Decoherence of a Double Quantum Dot Charge Qubit
Serguei Vorojtsov,Eduardo R. Mucciolo,Harold U. Baranger
Physics , 2004, DOI: 10.1103/PhysRevB.71.205322
Abstract: We study decoherence of a quantum dot charge qubit due to coupling to piezoelectric acoustic phonons in the Born-Markov approximation. After including appropriate form factors, we find that phonon decoherence rates are one to two orders of magnitude weaker than was previously predicted. We calculate the dependence of the Q-factor on lattice temperature, quantum dot size, and interdot coupling. Our results suggest that mechanisms other than phonon decoherence play a more significant role in current experimental setups.
The Underwater Historical Cultural Heritage of Russia Research and Preservation
Serguei Fazlullin
Journal of Cultural Research , 2012,
Abstract: he author analyses the current state of affairs in the study and preservation of the underwater historical and cultural heritage in the Russian Federation and proposes recommendations for harmonising attitudes of the society and the State towards objects of the underwater historical and cultural heritage and rising public awareness.
An Approach to Balancing the Positive and Negative Effects of Elevated Nitrogen Oxides in the Lower Atmosphere on Terrestrial Plants
Serguei Semenov
The Scientific World Journal , 2001, DOI: 10.1100/tsw.2001.87
Abstract:
The Impact of Discoveries of Ferroelectricity and Charge Disproportionation in Organic Conductors
Serguei Brazovskii
Physics , 2003,
Abstract: Discoveries of the Ferroelectric anomaly (Nad, Monceau, et al) and of the related charge disproportionation (Brown et al) call for a revaluation of the phase diagram of the (TMTTF)2X compounds and return the attention to the interplay of electronic and structural properties. We shall describe a concept of the Combined Mott-Hubbard state as the source for the ferroelectricity. We shall demonstrate the existence of two types of spinless solitons: pi- solitons, the holons, are observed via the activated conductivity; the noninteger alpha- solitons are responsible for the depolarization of the FE order. We propose that the (anti) ferroelectricity does exists hiddenly even in the Se subfamily, giving rise to the unexplained yet optical peak. We remind then the abandoned theory by the author and Yakovenko for the universal phase diagram which we contrast with the recent one.
Inclusive Search for the SM Higgs Boson in the H->gammagamma channel at the LHC
Serguei Ganjour
Physics , 2008, DOI: 10.1063/1.3051903
Abstract: A prospective for the inclusive search of the Standard Model Higgs boson in the decay channel H->gammagamm is presented with the CMS experiment at the LHC. The analysis relies on a strategy to determine the background characteristics and systematics from data. The strategy is applied to a Monte Model of the QCD background, with full simulation of the detector response. The discrimination between signal and background exploits information on photon isolation and kinematics. The resolution for the reconstructed Higgs boson mass profits from the excellent energy resolution of the CMS crystal calorimeter. A discovery significance above 5 sigma is expected at integrated LHC luminosities below 30 inverse femtobarn for Higgs boson masses below 140 GeV/c^2.
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