748 research outputs found
Hybrid quantum information processing
The development of quantum information processing has traditionally followed
two separate and not immediately connected lines of study. The main line has
focused on the implementation of quantum bit (qubit) based protocols whereas
the other line has been devoted to implementations based on high-dimensional
Gaussian states (such as coherent and squeezed states). The separation has been
driven by the experimental difficulty in interconnecting the standard
technologies of the two lines. However, in recent years, there has been a
significant experimental progress in refining and connecting the technologies
of the two fields which has resulted in the development and experimental
realization of numerous new hybrid protocols. In this Review, we summarize
these recent efforts on hybridizing the two types of schemes based on discrete
and continuous variables.Comment: 13 pages, 6 figure
Demonstration of three- and four-body interactions between trapped-ion spins
Quantum processors use the native interactions between effective spins to
simulate Hamiltonians or execute quantum gates. In most processors, the native
interactions are pairwise, limiting the efficiency of controlling entanglement
between many qubits. Here we experimentally demonstrate a new class of native
interactions between trapped-ion qubits, extending conventional pairwise
interactions to higher order. We realize three- and four-body spin interactions
as examples, showing that high-order spin polynomials may serve as a new
toolbox for quantum information applications
Universal quantum gates between nitrogen-vacancy centers in a levitated nanodiamond
We propose a scheme to realize universal quantum gates between
nitrogen-vacancy (NV) centers in an optically trapped nanodiamond, through
uniform magnetic field induced coupling between the NV centers and the
torsional mode of the levitated nanodiamond. The gates are tolerant to the
thermal noise of the torsional mode. By combining the scheme with dynamical
decoupling technology, it is found that the high fidelity quantum gates are
possible for the present experimental conditions. The proposed scheme is useful
for NV-center-based quantum network and distributed quantum computationComment: 7 pages, 6 figure
Coherent control of trapped ions using off-resonant lasers
In this paper we develop a unified framework to study the coherent control of
trapped ions subject to state-dependent forces. Taking different limits in our
theory, we can reproduce two different designs of a two-qubit quantum gate
--the pushing gate [1] and the fast gates based on laser pulses from Ref.
[2]--, and propose a new design based on continuous laser beams. We demonstrate
how to simulate Ising Hamiltonians in a many ions setup, and how to create
highly entangled states and induce squeezing. Finally, in a detailed analysis
we identify the physical limits of this technique and study the dependence of
errors on the temperature. [1] J.I. Cirac, P. Zoller, Nature, 404, 579, 2000.
[2] J.J. Garcia-Ripoll, P. Zoller, J.I. Cirac, PRL 67, 062318, 200
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