980 research outputs found
Ultrastrong coupling few-photon scattering theory
We study the scattering of photons by a two-level system ultrastrongly
coupled to a one-dimensional waveguide. Using a combination of the polaron
transformation with scattering theory we can compute the one-photon scattering
properties of the qubit for a broad range of coupling strengths, estimating
resonance frequencies, lineshapes and linewidths. We validate numerically and
analytically the accuracy of this technique up to , close to the
Toulouse point , where inelastic scattering becomes relevant. These
methods model recent experiments with superconducting circuits [P.
Forn-D{\'\i}az et al., Nat. Phys. (2016)]
Mapping the spatial distribution of entanglement in optical lattices
We study the entangled states that can be generated using two species of
atoms trapped in independently movable, two-dimensional optical lattices. We
show that using two sets of measurements it is possible to measure a set of
entanglement witness operators distributed over arbitrarily large regions of
the lattice, and use these witnesses to produce two-dimensional plots of the
entanglement content of these states. We also discuss the influence of noise on
the states and on the witnesses, as well as connections to ongoing experiments.Comment: 2 figures, 6 page
Driven Spin-Boson Luttinger Liquids
We introduce a lattice model of interacting spins and bosons that leads to
Luttinger-liquid physics, and allows for quantitative tests of the theory of
bosonization by means of trapped-ion or superconducting-circuit experiments. By
using a variational bosonization ansatz, we calculate the power-law decay of
spin and boson correlation functions, and study their dependence on a single
tunable parameter, namely a bosonic driving. For small drivings,
Matrix-Product-States (MPS) numerical methods are shown to be efficient and
validate our ansatz. Conversely, even static MPS become inefficient for
large-driving regimes, such that the experiment can potentially outperform
classical numerics, achieving one of the goals of quantum simulations
Spin models and boson sampling
In this work we proof that boson sampling with particles in modes is
equivalent to short-time evolution with excitations in an XY model of
spins. This mapping is efficient whenever the boson bunching probability is
small, and errors can be efficiently postselected. This mapping opens the door
to boson sampling with quantum simulators or general purpose quantum computers,
and highlights the complexity of time-evolution with critical spin models, even
for very short times.Comment: Extended supplementary material; typos fixed in the proof equation
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