A5102005674- Physics of Superconductivity and Magnetism
- Quantum Information and Cryptography
- Quantum Computing Algorithms and Architecture
- Magnetic properties of thin films
- Quantum optics and atomic interactions
- Advanced Condensed Matter Physics
- Magnetic and transport properties of perovskites and related materials
- Quantum and electron transport phenomena
- Quantum Mechanics and Applications
- Superconductivity in MgB2 and Alloys
- Mechanical and Optical Resonators
- Theoretical and Computational Physics
- Iron-based superconductors research
- Quantum many-body systems
- Quantum Electrodynamics and Casimir Effect
- Neural Networks and Reservoir Computing
- Acoustic Wave Resonator Technologies
- Advanced Thermodynamics and Statistical Mechanics
- Laser-Matter Interactions and Applications
- Superconducting Materials and Applications
- Magnetic confinement fusion research
- Cold Atom Physics and Bose-Einstein Condensates
- Electrical Contact Performance and Analysis
- Chemical and Physical Properties of Materials
- Security and Verification in Computing
All Russia Research Institute of Automatics
2015-2023
St Petersburg University
2023
Moscow Engineering Physics Institute
2015-2020
Lomonosov Moscow State University
1991-2004
Imperial College London
1992-2002
The novel experimental realization of three-level optical quantum systems is presented. We use the polarization state biphotons to generate a specific sequence states that are used in extended version BB84 protocol. experimentally verify orthogonality basis and demonstrate ability easily switch between them. tomography procedure employed reconstruct density matrices generated states.
The influence of the oxygen stoichiometry on magnetization and relaxation R${\mathrm{Ba}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7\mathrm{\ensuremath{-}}\mathrm{\ensuremath{\delta}}}$ (R=Y,Tm) single crystals was studied for 0\ensuremath{\le}\ensuremath{\delta}\ensuremath{\le}0.55. field dependences shielding currents ${\mathit{j}}_{\mathit{s}}$(H) flux creep rates S(H) were analyzed. Three different kinds behavior can be seen in highly oxygenated samples (\ensuremath{\delta}0.1). (i) At high...
We discuss a procedure of measurement followed by the reproduction quantum state three-level optical system - frequency- and spatially degenerate two-photon field. The method statistical estimation based on solving likelihood equation analyzing properties obtained estimates is developed. Using root approach estimating states, initial vector reproduced from measured fourth moments in field . developed applied to states reconstruction amplitudes mutually complementary processes. Classical...
A natural atom placed into a cavity with time-dependent parameters can be parametrically excited due to the interaction quantized photon mode. One of channels such process is dynamical Lamb effect, induced by nonadiabatic modulation atomic level shift. However, in experiments atoms it quite difficult isolate this effect from other mechanisms excitation. We point out that transmission line coupled superconducting qubit (artificial macroscopic atom) provides unique platform for observation...
In recent years, there has been a significant progress in the development of digital quantum processors. The state-of-the-art devices are imperfect, and fully-algorithmic fault-tolerant computing is matter future. Until technology develops to state with practical error correction, computational approaches other than standard one can be used avoid execution most noisy operations. We demonstrate how hybrid digital-analog approach allows simulating dynamics transverse-field Ising model without...
Variational quantum algorithms are a promising tool for solving partial differential equations. The standard approach its numerical solution is finite-difference schemes, which can be reduced to the linear algebra problem. We consider three approaches solve heat equation on computer. Using direct variational method we minimize expectation value of Hamiltonian with ground state being problem under study. Typically, an exponential number Pauli products in decomposition does not allow speedup...
Superconducting circuits provide a new platform for study of nonstationary cavity QED phenomena. An example such phenomenon is the dynamical Lamb effect, which parametric excitation an atom due to nonadiabatic modulation its shift. This effect was initially introduced natural in varying cavity, while we suggest realization superconducting qubit-cavity system with dynamically tunable coupling. In present paper, interplay between and energy dissipation, unavoidable realistic systems. We find...
In this paper we present the results of measurements microwave surface impedance a powder sample and two films MgB2. The has Tc = 39 K have 29 38 K. These samples show different temperature dependences field penetration depth. Over period six months, film with degraded to 35 We compare on all data obtained elsewhere discuss implications as far is possible at stage.
The microwave power and frequency dependence of the surface resistance MgB2 films powder samples were studied. Sample quality is relatively easy to identify by breakdown in ω2 law for poor-quality at all temperatures. performance 10 GHz 21 K was compared directly with that high-quality YBCO films. found be approximately three times higher low showed an onset nonlinearity fields ten lower than film. It clear are not yet optimized applications.
The peak effect in ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7\mathrm{\ensuremath{-}}\mathrm{\ensuremath{\delta}}}$ single crystals is observed by transport-current measurements. Comparison with the shielding current from magnetization shows good agreement between results, which exclude granularity as being necessarily involved origin of effect. behavior current-voltage characteristics a wide voltage range (${10}^{\mathrm{\ensuremath{-}}9}$E${10}^{\mathrm{\ensuremath{-}}4}$ V/cm)...
We consider a dissipative evolution of parametrically-driven qubits-cavity system under the periodical modulation coupling energy between two subsystems, which leads to amplification counterrotating processes. reveal very rich dynamical behavior this hybrid system. In particular, we find that dissipation in one subsystems can enhance quantum effects another subsystem. For instance, optimal cavity decay assists stabilize entanglement and correlations qubits even steady state compensate finite...
Measurements of the temperature dependence surface resistance at 3 GHz 100 micron size fragments MgB2 separated powder are presented and discussed. The microwave data compared to experimental results Nb, Bi2Sr2CaCu2O8+δ (BSCCO) theoretical predictions s-wave weak coupling electron-phonon theory (BCS).
We consider the dynamics of a disordered ensemble qubits interacting with single-mode photon field, which is described by an exactly solvable inhomogeneous Dicke model. In particular, we concentrate on crossover from few-qubit systems to system many and analyze how collective behavior coupled qubit-cavity emerges despite broadening. show that quantum interference effects survive in mesoscopic regime---the entangled Bell state encoded into qubit subsystem remains highly sensitive symmetry...
We propose and discuss a specific scheme allowing realization of quantum cryptography qutrit protocol. This protocol exploits the polarization properties single-frequency single-spatial-mode biphotons.
A model-independent analysis of magnetization loop scaling is used to study the vortex behavior in a set ${\mathrm{RBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7\mathrm{\ensuremath{-}}\mathrm{\ensuremath{\delta}}}$ (RBCO, R=Y, Tm) single crystals differing oxygen content (0.10.5). Throughout range studied, qualitative dynamics remains same, and characterized by two power law exponents m n relating magnetic field dependences current scale ${\mathrm{J}}_{0}$(B,T,\ensuremath{\delta}) an energy...