41 research outputs found
Avoided crossing resonances: structural and dynamical aspects
We examine structural and dynamical properties of quantum resonances
associated with an avoided crossing and identify the parameter shifts where
these properties attain maximal or extreme values, first at a general level,
and then for a two-level system coupled to a harmonic oscillator, of the type
commonly found in quantum optics. Finally the results obtained are exemplified
and applied to optimize the fidelity and speed of quantum gates in trapped
ions.Comment: 4 pages, 1 figur
Deep Strong Coupling Regime of the Jaynes-Cummings model
We study the quantum dynamics of a two-level system interacting with a
quantized harmonic oscillator in the deep strong coupling regime (DSC) of the
Jaynes-Cummings model, that is, when the coupling strength g is comparable or
larger than the oscillator frequency w (g/w > 1). In this case, the
rotating-wave approximation cannot be applied or treated perturbatively in
general. We propose an intuitive and predictive physical frame to describe the
DSC regime where photon number wavepackets bounce back and forth along parity
chains of the Hilbert space, while producing collapse and revivals of the
initial population. We exemplify our physical frame with numerical and
analytical considerations in the qubit population, photon statistics, and
Wigner phase space.Comment: Published version, note change of title: DSC regime of the JC mode
Motional frequency shifts of trapped ions in the Lamb-Dicke regime
First order Doppler effects are usually ignored in laser driven trapped ions
when the recoil frequency is much smaller than the trapping frequency
(Lamb-Dicke regime). This means that the central, carrier excitation band is
supposed to be unaffected by vibronic transitions in which the vibrational
number changes. While this is strictly true in the Lamb-Dicke limit (infinitely
tight confinement), the vibronic transitions do play a role in the Lamb-Dicke
regime. In this paper we quantify the asymptotic behaviour of their effect with
respect to the Lamb-Dicke parameter. In particular, we give analytical
expressions for the frequency shift, ``pulling'' or ``pushing'', produced in
the carrier absorption band by the vibronic transitions both for Rabi and
Ramsey schemes. This shift is shown to be independent of the initial
vibrational state.Comment: 9 pages, 6 figure
Structural and dynamical aspects of avoided-crossing resonances in a -level system
In a recent publication [Phys. Rev. A 79, 065602 (2009)] it was shown that an
avoided-crossing resonance can be defined in different ways, according to
level-structural or dynamical aspects, which do not coincide in general. Here a
simple -level system in a configuration is discussed, where the
difference between both definitions of the resonance may be observed. We also
discuss the details of a proposed experiment to observe this difference, using
microwave fields coupling hyperfine magnetic sublevels in alkali atoms.Comment: 7 pages, 5 figure
Circuit Quantum Electrodynamics with a Superconducting Quantum Point Contact
We consider a superconducting quantum point contact in a circuit quantum
electrodynamics setup. We study three different configurations, attainable with
current technology, where a quantum point contact is coupled galvanically to a
coplanar waveguide resonator. Furthermore, we demonstrate that the strong and
ultrastrong coupling regimes can be achieved with realistic parameters,
allowing the coherent exchange between a superconducting quantum point contact
and a quantized intracavity field.Comment: 5 pages, 4 figures. Updated version, accepted for publication as a
Rapid Communication in Physical Review