3,197 research outputs found
Coherent Imaging Spectroscopy of a Quantum Many-Body Spin System
Quantum simulators, in which well controlled quantum systems are used to
reproduce the dynamics of less understood ones, have the potential to explore
physics that is inaccessible to modeling with classical computers. However,
checking the results of such simulations will also become classically
intractable as system sizes increase. In this work, we introduce and implement
a coherent imaging spectroscopic technique to validate a quantum simulation,
much as magnetic resonance imaging exposes structure in condensed matter. We
use this method to determine the energy levels and interaction strengths of a
fully-connected quantum many-body system. Additionally, we directly measure the
size of the critical energy gap near a quantum phase transition. We expect this
general technique to become an important verification tool for quantum
simulators once experiments advance beyond proof-of-principle demonstrations
and exceed the resources of conventional computers
Zero-Point cooling and low heating of trapped 111Cd+ ions
We report on ground state laser cooling of single 111Cd+ ions confined in
radio-frequency (Paul) traps. Heating rates of trapped ion motion are measured
for two different trapping geometries and electrode materials, where no effort
was made to shield the electrodes from the atomic Cd source. The low measured
heating rates suggest that trapped 111Cd+ ions may be well-suited for
experiments involving quantum control of atomic motion, including applications
in quantum information science.Comment: 4 pages, 6 figures, Submitted to PR
Bell inequality violation with two remote atomic qubits
We observe violation of a Bell inequality between the quantum states of two
remote Yb ions separated by a distance of about one meter with the detection
loophole closed. The heralded entanglement of two ions is established via
interference and joint detection of two emitted photons, whose polarization is
entangled with each ion. The entanglement of remote qubits is also
characterized by full quantum state tomography.Comment: 4 pages, 4 figure
Quantum Computation and Spin Physics
A brief review is given of the physical implementation of quantum computation
within spin systems or other two-state quantum systems. The importance of the
controlled-NOT or quantum XOR gate as the fundamental primitive operation of
quantum logic is emphasized. Recent developments in the use of quantum
entanglement to built error-robust quantum states, and the simplest protocol
for quantum error correction, are discussed.Comment: 21 pages, Latex, 3 eps figures, prepared for the Proceedings of the
Annual MMM Meeting, November, 1996, to be published in J. Appl. Phy
Yang-Lee Zeros of the Q-state Potts Model on Recursive Lattices
The Yang-Lee zeros of the Q-state Potts model on recursive lattices are
studied for non-integer values of Q. Considering 1D lattice as a Bethe lattice
with coordination number equal to two, the location of Yang-Lee zeros of 1D
ferromagnetic and antiferromagnetic Potts models is completely analyzed in
terms of neutral periodical points. Three different regimes for Yang-Lee zeros
are found for Q>1 and 0<Q<1. An exact analytical formula for the equation of
phase transition points is derived for the 1D case. It is shown that Yang-Lee
zeros of the Q-state Potts model on a Bethe lattice are located on arcs of
circles with the radius depending on Q and temperature for Q>1. Complex
magnetic field metastability regions are studied for the Q>1 and 0<Q<1 cases.
The Yang-Lee edge singularity exponents are calculated for both 1D and Bethe
lattice Potts models. The dynamics of metastability regions for different
values of Q is studied numerically.Comment: 15 pages, 6 figures, with correction
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