Search results for "TUNNEL"
showing 10 items of 576 documents
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.
<title>Low-frequency excitation of double quantum dots</title>
2008
We address theoretically adiabatic regime of charge transport for a model of two tunnel-coupled quantum dots connected in series. The energy levels of the two dots are harmonically modulated by an external potential with a constant phase shift between the two. Motivated by recent experiments with surface-acoustic-wave excitation, we consider two situations: (a) pure pumping in the absence of external voltage (also at finite temperature), and (b) adiabatic modulation of the current driven by large external bias. In both cases we derive results consistent with published experimental data. For the case (b) we explicitly derive the adiabatic limit of Tien-Gordon formula for photon-assisted tunn…
Electron magneto-tunneling through single self-assembled InAs quantum dashes
2014
We have investigated electron magneto-tunneling through single self-assembled InAs quantum dashes (QDHs) coupled to metal nanogap electrodes. The samples operate as single electron transistors and exhibit clear shell structures, reflecting the anisotropic shape of the QDHs. In high magnetic fields, the samples exhibit strongly orbital-dependent large diamagnetic shifts and large electron g-factors in the range |g| ~ 3–11. The strong level-to-level fluctuation of the g-factors implies the presence of strong spin–orbit interaction in this system. These properties suggest that InAs QDHs are promising for the manipulation of single-electron orbital/spin states by external electric/magnetic fiel…
Experiments on tunnelling in small normal-metal junctions influenced by dissipative environment: Critical comparison to the theories of quantum fluct…
1998
We report on experiments of charging in small normal metal tunnel junctions attached to well-defined resistive impedances. Our experiments are in very good agreement with the phase-correlation (PC) theory but not with the simplified voltage fluctuation (VF) model. The strong tunnelling corrections to the PC theory make the agreement with our results even better in the case of junctions with low resistance.
A signal processing scheme based on high-frequency electromechanical oscillations in nanostructures
2009
We explore the characteristics of a new signal processing scheme based on the high-frequency electromechanical oscillations of a nanostructure formed by an oscillating metallic nanoparticle connected to the left and right electrodes by soft links. Because this system shows resonant behavior when the frequency of the applied electric potential is close to the characteristic natural frequency of the oscillating nanoparticle, a parallel arrangement of nanostructures with different frequencies can be excited selectively by an external time-dependent electrical signal with the appropriate resonant frequencies. The highly nonlinear system response makes it possible to devise a signal processing s…