90 research outputs found
Simulating Nonlinear Spin Models in an Ion Trap
We show how a conditional displacement of the vibrational mode of trapped ions can be used to simulate nonlinear collective and interacting spin systems including nonlinear tops and Ising models (a universal two qubit gate), independent of the vibrational state of the ion. Thus cooling to the vibrational ground state is unnecessary provided the heating rate is not too large
Communicating continuous quantum variables between different Lorentz frames
We show how to communicate Heisenberg-limited continuous (quantum) variables
between Alice and Bob in the case where they occupy two inertial reference
frames that differ by an unknown Lorentz boost. There are two effects that need
to be overcome: the Doppler shift and the absence of synchronized clocks.
Furthermore, we show how Alice and Bob can share Doppler-invariant
entanglement, and we demonstrate that the protocol is robust under photon loss.Comment: 4 pages, 1 figur
Simulating quantum effects of cosmological expansion using a static ion trap
We propose a new experimental testbed that uses ions in the collective ground
state of a static trap for studying the analog of quantum-field effects in
cosmological spacetimes, including the Gibbons-Hawking effect for a single
detector in de Sitter spacetime, as well as the possibility of modeling
inflationary structure formation and the entanglement signature of de Sitter
spacetime. To date, proposals for using trapped ions in analog gravity
experiments have simulated the effect of gravity on the field modes by directly
manipulating the ions' motion. In contrast, by associating laboratory time with
conformal time in the simulated universe, we can encode the full effect of
curvature in the modulation of the laser used to couple the ions' vibrational
motion and electronic states. This model simplifies the experimental
requirements for modeling the analog of an expanding universe using trapped
ions and enlarges the validity of the ion-trap analogy to a wide range of
interesting cases.Comment: (v2) revisions based on referee comments, figure added for clarity;
(v1) 17 pages, no figure
Characterizing GHZ Correlations in Nondegenerate Parametric Oscillation via Phase Measurements
We present a potential realization of the Greenberger, Horne and Zeilinger ALL or NOTHING contradiction of quantum mechanics with local realism using phase measurement techniques in a simple photon number triplet. Such a triplet could be generated using nondegenerate parametric oscillation
Quantum Measurements With a Quantum Computer
We present a scheme in which an ion trap quantum computer can be used to make arbitrarily accurate measurements of the quadrature phase variables for the collective vibrational motion of the ion. The electronic states of the ion become the 'apparatus', and the method is based on regarding the 'apparatus' as a quantum computer register which can be prepared in appropriate states by running a Fourier transform algorithm on the data stored within it. The resolution of the measurement rises exponentially with the number of ions used
Heuristic for estimation of multiqubit genuine multipartite entanglement
For every N-qubit density matrix written in the computational basis, an
associated "X-density matrix" can be obtained by vanishing all entries out of
the main- and anti-diagonals. It is very simple to compute the genuine
multipartite (GM) concurrence of this associated N-qubit X-state, which,
moreover, lower bounds the GM-concurrence of the original (non-X) state. In
this paper, we rely on these facts to introduce and benchmark a heuristic for
estimating the GM-concurrence of an arbitrary multiqubit mixed state. By
explicitly considering two classes of mixed states, we illustrate that our
estimates are usually very close to the standard lower bound on the
GM-concurrence, being significantly easier to compute. In addition, while
evaluating the performance of our proposed heuristic, we provide the first
characterization of GM-entanglement in the steady states of the driven Dicke
model at zero temperature.Comment: 19 pages, 5 figure
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