1,767 research outputs found
Multiphoton antiresonance
We show that nonlinear response of a quantum oscillator displays antiresonant
dips and resonant peaks with varying frequency of the driving field. The effect
is a consequence of special symmetry and is related to resonant multiphoton
mixing of several pairs of oscillator states at a time. We discuss the
possibility to observe the antiresonance and the associated multiphoton Rabi
oscillations in Josephson junctions.Comment: 4 pages, 3 figures; corrected referenc
Scaling in activated escape of underdamped systems
Noise-induced escape from a metastable state of a dynamical system is studied
close to a saddle-node bifurcation point, but in the region where the system
remains underdamped. The activation energy of escape scales as a power of the
distance to the bifurcation point. We find two types of scaling and the
corresponding critical exponents.Comment: 9 page
Qubit state detection using the quantum Duffing oscillator
We introduce a detection scheme for the state of a qubit, which is based on
resonant few-photon transitions in a driven nonlinear resonator. The latter is
parametrically coupled to the qubit and is used as its detector. Close to the
fundamental resonator frequency, the nonlinear resonator shows sharp resonant
few-photon transitions. Depending on the qubit state, these few-photon
resonances are shifted to different driving frequencies. We show that this
detection scheme offers the advantage of small back action, a large
discrimination power with an enhanced read-out fidelity, and a sufficiently
large measurement efficiency. A realization of this scheme in the form of a
persistent current qubit inductively coupled to a driven SQUID detector in its
nonlinear regime is discussed.Comment: 10 pages, 6 figures. To appear in Phys. Rev.
Quantum interference in the classically forbidden region: a parametric oscillator
We study tunneling between period two states of a parametrically modulated
oscillator. The tunneling matrix element is shown to oscillate with the varying
frequency of the modulating field. The effect is due to spatial oscillations of
the wave function and the related interference in the classically forbidden
region. The oscillations emerge already in the ground state of the oscillator
Hamiltonian in the rotating frame, which is quartic in the momentum.Comment: Submitted to PR
Properties of discrete breathers in graphane from ab initio simulations
A density functional theory (DFT) study of the discrete breathers (DBs) in
graphane (fully hydrogenated graphene) was performed. To the best of our
knowledge, this is the first demonstration of the existence of DBs in a
crystalline body from the first-principle simulations. It is found that the DB
is a robust, highly localized vibrational mode with one hydrogen atom
oscillating with a large amplitude along the direction normal to the graphane
plane with all neighboring atoms having much smaller vibration amplitudes. DB
frequency decreases with increase in its amplitude, and it can take any value
within the phonon gap and can even enter the low-frequency phonon band. The
concept of DB is then used to propose an explanation to the recent experimental
results on the nontrivial kinetics of graphane dehydrogenation at elevated
temperatures.Comment: 20.07.14 Submitted to PhysRev
- …