117 research outputs found
Simulating Quantum Magnetism with Correlated Non-Neutral Ion Plasmas
By employing forces that depend on the internal electronic state (or spin) of
an atomic ion, the Coulomb potential energy of a strongly coupled array of ions
can be modified in a spin-dependent way to mimic effective quantum spin
Hamiltonians. Both ferromagnetic and antiferromagnetic interactions can be
implemented. We use simple models to explain how the effective spin
interactions are engineered with trapped-ion crystals. We summarize the type of
effective spin interactions that can be readily generated, and discuss an
experimental implementation using single-plane ion crystals in a Penning trap.Comment: 10 pages, 5 figures, to be published in the Proceedings of 10th
International Workshop on Non-Neutral Plasma
Many Body Physics with Coupled Transmission Line Resonators
We present the Josephson junction intersected superconducting transmission
line resonator. In contrast to the Josephson parametric amplifier, Josephson
bifurcation amplifier and Josephson parametric converter we consider the regime
of few microwave photons. We review the derivation of eigenmode frequencies and
zero point fluctuations of the nonlinear transmission line resonator and the
derivation of the eigenmode Kerr nonlinearities. Remarkably these
nonlinearities can reach values comparable to Transmon qubits rendering the
device ideal for accessing the strongly correlated regime. This is particularly
interesting for investigation of quantum many-body dynamics of interacting
particles under the influence of drive and dissipation. We provide current
profiles for the device modes and investigate the coupling between resonators
in a network of nonlinear transmission line resonators.Comment: submitted to the proceedings of the CEWQO 2012 conferenc
Large-scale photonic Ising machine by spatial light modulation
Quantum and classical physics can be used for mathematical computations that
are hard to tackle by conventional electronics. Very recently, optical Ising
machines have been demonstrated for computing the minima of spin Hamiltonians,
paving the way to new ultra-fast hardware for machine learning. However, the
proposed systems are either tricky to scale or involve a limited number of
spins. We design and experimentally demonstrate a large-scale optical Ising
machine based on a simple setup with a spatial light modulator. By encoding the
spin variables in a binary phase modulation of the field, we show that light
propagation can be tailored to minimize an Ising Hamiltonian with spin
couplings set by input amplitude modulation and a feedback scheme. We realize
configurations with thousands of spins that settle in the ground state in a
low-temperature ferromagnetic-like phase with all-to-all and tunable pairwise
interactions. Our results open the route to classical and quantum photonic
Ising machines that exploit light spatial degrees of freedom for parallel
processing of a vast number of spins with programmable couplings.Comment: https://journals.aps.org/prl/accepted/7007eYb7N091546c41ad4108828a97d5f92006df
Topological Schr\"odinger cats: Non-local quantum superpositions of topological defects
Topological defects (such as monopoles, vortex lines, or domain walls) mark
locations where disparate choices of a broken symmetry vacuum elsewhere in the
system lead to irreconcilable differences. They are energetically costly (the
energy density in their core reaches that of the prior symmetric vacuum) but
topologically stable (the whole manifold would have to be rearranged to get rid
of the defect). We show how, in a paradigmatic model of a quantum phase
transition, a topological defect can be put in a non-local superposition, so
that - in a region large compared to the size of its core - the order parameter
of the system is "undecided" by being in a quantum superposition of conflicting
choices of the broken symmetry. We demonstrate how to exhibit such a
"Schr\"odinger kink" by devising a version of a double-slit experiment suitable
for topological defects. Coherence detectable in such experiments will be
suppressed as a consequence of interaction with the environment. We analyze
environment-induced decoherence and discuss its role in symmetry breaking.Comment: 7 pages, 4 figure
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