Search results for "Tunne"
showing 10 items of 739 documents
Detection of the optical magnetic field by circular symmetry plasmons
2000
We report on the influence of coating a sharpened optical fiber tip with Au when observing nanofabricated dielectric structures with a Photon Scanning Tunneling Microscope (PSTM) in constant-height mode. For well-defined incident wavelengths and coating thicknesses, we found that such tips detect the distribution of the magnetic field associated with the optical wave in the near-field zone. A simple tip model indicates that this phenomenon is related to the excitation of circular symmetry plasmons in Au coated tips.
Coherent control via weak measurements in P31 single-atom electron and nuclear spin qubits
2018
The understanding of weak measurements and interaction-free measurements has greatly expanded the conceptual and experimental toolbox to explore the quantum world. Here we demonstrate single-shot variable-strength weak measurements of the electron and nuclear spin states of a P31 single-atom donor in silicon. We first show how the partial collapse of the nuclear spin due to measurement can be used to coherently rotate the spin to a desired pure state. We explicitly demonstrate that phase coherence is preserved with high fidelity throughout multiple sequential single-shot weak measurements and that the partial state collapse can be reversed. Second, we use the relation between measurement st…
Simultaneous observation of light localization and confinement in near-field optics
2001
We report on the observation, in direct space, of both light localization and confinement effects near lithographically designed structures. The sample is observed in the optical near-field zone with a Photon Scanning Tunneling Microscope (PSTM). Several patterns composed of a few periods of TiO2 dots, arranged as a hexagonal lattice, have been investigated. When the central dot of the pattern is removed, a phenomenon of light localization above the vacancy can be observed in the PSTM image. The occurrence of this phenomenon can be related to the variation of the electromagnetic local density of state.
One and two dimensional tunnel junction arrays in weak Coulomb blockade regime-absolute accuracy in thermometry
1999
We have investigated one and two dimensional (1D and 2D) arrays of tunnel junctions in partial Coulomb blockade regime. The absolute accuracy of the Coulomb blockade thermometer is influenced by the external impedance of the array, which is not the same in the different topologies of 1D and 2D arrays. We demonstrate, both by experiment and by theoretical calculations in simple geometries, that the 1D structures are better in this respect. Yet in both 1D and 2D, the influence of the environment can be made arbitrarily small by making the array sufficiently large.
Influence effect of an external electric field and dissipative tunneling on intracenter optical transitions in quantum molecules with D2- states
2020
In the zero-range potential model and in the effective mass approximation, dispersion equations have been obtained, that describe dependence of the average binding energies of the quasistationary g- and u-states of the D − 2 - center in the QD, as well as the widths of energy levels on the magnitude of the external electric field and the parameters of 1D-dissipative tunneling. Dips in the field dependences of the binding energies average values for quasi-stationary g- and u-states have been revealed. It is shown that the field dependences of the energy level widths for the g- and u- states of the D − 2 -center have a resonance structure at the external electric field strengths corresponding…
ELECTROMAGNETIC CONTROL OF DYNAMICAL LOCALIZATION CONDITIONS IN 1D LATTICES WITH LONG-RANGE INTERSITE INTERACTIONS
2009
In this paper we investigate the possibility of controlling dynamical localization conditions for a charged particle confined in a 1D lattice biased with a dc-bichromatic field and long-range intersite interactions. We derive the quasi-energy spectrum of the system proving that the tunneling dynamics of the particle can be destroyed provided that the parameters of the external irradiating electric field are properly chosen.
Classical-to-quantum crossover in electron on-demand emission
2017
Emergence of a classical particle trajectory concept from the full quantum description is a key feature of quantum mechanics. Recent progress of solid state on-demand sources has brought single-electron manipulation into the quantum regime, however, the quantum-to-classical crossover remains unprobed. Here we describe theoretically a mechanism for generating single-electron wave packets by tunneling from a driven localized state, and show how to tune the degree of quantumness. Applying our theory to existing on-demand sources, we demonstrate the feasibility of an experimental investigation of quantum-to-classical crossover for single electrons, and open up yet unexplored potential for few-e…
Resonant effects in a SQUID qubit subjected to nonadiabatic changes
2013
By quickly modifying the shape of the effective potential of a double SQUID flux qubit from a single-well to a double-well condition, we experimentally observe an anomalous behavior, namely an alternance of resonance peaks, in the probability to find the qubit in a given flux state. The occurrence of Landau-Zener transitions as well as resonant tunneling between degenerate levels in the two wells may be invoked to partially justify the experimental results. A quantum simulation of the time evolution of the system indeed suggests that the observed anomalous behavior can be imputable to quantum coherence effects. The interplay among all these mechanisms has a practical implication for quantum…
Microwave-induced coupling of superconducting qubits
2008
We investigate the quantum dynamics of a system of two coupled superconducting qubits under microwave irradiation. We find that, with the qubits operated at the charge co-degeneracy point, the quantum evolution of the system can be described by a new effective Hamiltonian which has the form of two coupled qubits with tunable coupling between them. This Hamiltonian can be used for experimental tests on macroscopic entanglement and for implementing quantum gates.
Scale-free relaxation of a wave packet in a quantum well with power-law tails
2013
We propose a setup for which a power-law decay is predicted to be observable for generic and realistic conditions. The system we study is very simple: A quantum wave packet initially prepared in a potential well with (i) tails asymptotically decaying like ~ x^{-2} and (ii) an eigenvalues spectrum that shows a continuous part attached to the ground or equilibrium state. We analytically derive the asymptotic decay law from the spectral properties for generic, confined initial states. Our findings are supported by realistic numerical simulations for state-of-the-art expansion experiments with cold atoms.