195 research outputs found
Scalable solid-state quantum computation in decoherence-free subspaces with trapped ions
We propose a decoherence-free subspaces (DFS) scheme to realize scalable
quantum computation with trapped ions. The spin-dependent Coulomb interaction
is exploited, and the universal set of unconventional geometric quantum gates
is achieved in encoded subspaces that are immune from decoherence by collective
dephasing. The scalability of the scheme for the ion array system is
demonstrated, either by an adiabatic way of switching on and off the
interactions, or by a fast gate scheme with comprehensive DFS encoding and
noise decoupling techniques.Comment: 4 pages, 1 figur
Trapped ion chain as a neural network
We demonstrate the possibility of realizing a neural network in a chain of
trapped ions with induced long range interactions. Such models permit to store
information distributed over the whole system. The storage capacity of such
network, which depends on the phonon spectrum of the system, can be controlled
by changing the external trapping potential and/or by applying longitudinal
local magnetic fields. The system properties suggest the possibility of
implementing robust distributed realizations of quantum logic.Comment: 4 pages, 3 figure
Dynamic entanglement in oscillating molecules and potential biological implications
We demonstrate that entanglement can persistently recur in an oscillating
two-spin molecule that is coupled to a hot and noisy environment, in which no
static entanglement can survive. The system represents a non-equilibrium
quantum system which, driven through the oscillatory motion, is prevented from
reaching its (separable) thermal equilibrium state. Environmental noise,
together with the driven motion, plays a constructive role by periodically
resetting the system, even though it will destroy entanglement as usual. As a
building block, the present simple mechanism supports the perspective that
entanglement can exist also in systems which are exposed to a hot environment
and to high levels of de-coherence, which we expect e.g. for biological
systems. Our results furthermore suggest that entanglement plays a role in the
heat exchange between molecular machines and environment. Experimental
simulation of our model with trapped ions is within reach of the current
state-of-the-art quantum technologies.Comment: Extended version, including supplementary information. 9 pages, 8
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Simultaneous cooling of axial vibrational modes in a linear ion trap
In order to use a collection of trapped ions for experiments where a well-defined preparation of vibrational states is necessary, all vibrational modes have to be cooled to ensure precise and repeatable manipulation of the ions quantum states. A method for simultaneous sideband cooling of all axial vibrational modes is proposed. By application of a magnetic field gradient the absorption spectrum of each ion is modified such that sideband resonances of different vibrational modes coincide. The ion string is then irradiated with monochromatic electromagnetic radiation, in the optical or microwave regime, for sideband excitation. This cooling scheme is investigated in detailed numerical studies. Its application for initializing ion strings for quantum information processing is extensively discussed
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