752 research outputs found
A tunable rf SQUID manipulated as flux and phase qubit
We report on two different manipulation procedures of a tunable rf SQUID.
First, we operate this system as a flux qubit, where the coherent evolution
between the two flux states is induced by a rapid change of the energy
potential, turning it from a double well into a single well. The measured
coherent Larmor-like oscillation of the retrapping probability in one of the
wells has a frequency ranging from 6 to 20 GHz, with a theoretically expected
upper limit of 40 GHz. Furthermore, here we also report a manipulation of the
same device as a phase qubit. In the phase regime, the manipulation of the
energy states is realized by applying a resonant microwave drive. In spite of
the conceptual difference between these two manipulation procedures, the
measured decay times of Larmor oscillation and microwave-driven Rabi
oscillation are rather similar. Due to the higher frequency of the Larmor
oscillations, the microwave-free qubit manipulation allows for much faster
coherent operations.Comment: Proceedings of Nobel Symposium "Qubits for future quantum computers",
Goeteborg, Sweden, May 25-28, 2009; to appear in Physica Script
Tunable Flux Qubit manipulated by fast pulses: operating requirements, dissipation and decoherence
A double SQUID manipulated by fast magnetic flux pulses can be used as a
tunable flux qubit. In this paper we study the requirements for the qubit
operation, and evaluate dissipation and decoherence due to the manipulation for
a typical system. Furthermore, we discuss the possibility to use an integrated
Rapid Single Flux Quantum logic for the qubit control.Comment: 6 pages, 4 figure
Dynamical Behavior of a Squid Ring Coupled to a Quantized Electromagnetic Field
In this paper we investigate the dynamical behavior of a SQUID ring coupled
to a quantized single-mode electromagnetic field. We have calculated the
eigenstates of the combined fully quantum mechanical SQUID-field system.
Interesting phenomena occur when the energy difference between the usual
symmetric and anti-symmetric SQUID states equals the field energy . We find the
low-energy lying entangled stationary states of the system and demonstrate that
its dynamics is dominated by coherent Rabi oscillations.Comment: 6 pages, 2 figures. to be published on International Journal of
Modern Physics
Fujita modified exponent for scale invariant damped semilinear wave equations
The aim of this paper is to prove a blow-up result of the solution for a semilinear scale invariant damped wave equation under a suitable decay condition on radial initial data. The admissible range for the power of the nonlinear term depends both on the damping coefficient and on the pointwise decay order of the initial data. In addition, we give an upper bound estimate for the lifespan of the solution. It depends not only on the exponent of the nonlinear term and not only on the damping coefficient but also on the size of the decay rate of the initial data
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