241,765 research outputs found
Fast entanglement of two charge-phase qubits through nonadiabatic coupling to a large junction
We propose a theoretical protocol for quantum logic gates between two
Josephson junction charge-phase qubits through the control of their coupling to
a large junction. In the low excitation limit of the large junction when
, it behaves effectively as a quantum data-bus mode of a
harmonic oscillator. Our protocol is efficient and fast. In addition, it does
not require the data-bus to stay adiabatically in its ground state, as such it
can be implemented over a wide parameter regime independent of the data-bus
quantum state.Comment: 5 pages, 1 figur
Quantum storage and information transfer with superconducting qubits
We design theoretically a new device to realize the general quantum storage
based on dcSQUID charge qubits. The distinct advantages of our scheme are
analyzed in comparison with existing storage scenarios. More arrestingly, the
controllable XY-model spin interaction has been realized for the first time in
superconducting qubits, which may have more potential applications besides
those in quantum information processing. The experimental feasibility is also
elaborated.Comment: 4 pages, 2 figure
Coronal magnetic topology and the production of solar impulsive energetic electrons
We investigate two candidate solar sources or active regions (ARs) in
association with a solar impulsive energetic electron (SIEE) event on 2002
October 20. The solar particle release (SPR) times of SIEEs are derived by
using their velocity dispersion with consideration of the instrumental effect.
It is found that there are double electron injections at the Sun. The
low-energy (<13 keV) electron injection coincides with a C6.6 flare in AR10154
and is accompanied with prominent type III radio bursts rather than a stronger
M1.8 flare in AR10160. The M1.8 flare produces, however, faint type III radio
bursts. Whereas electrons of 25 to 300 keV are released 9 min later when a
jet-like CME travels to 2.6 solar radii. We further examine the coronal
magnetic configurations above the two ARs based on the potential field source
surface (PFSS) model. It is found that open field lines, rooted in AR10154 and
well connected to the Earth, provide escaping channels for energetic electrons.
Only a small portion of magnetic fields are opened above AR10160, being
responsible for the faint type III radio bursts. These lines are, however, not
well connected, making it impossible for SIEEs detection by near-Earth
spacecraft. The results appear to establish a physical link between coronal
magnetic topology, formation of type III radio bursts, and production of SIEEs.Comment: A&A Letters, accepte
- …