1,632 research outputs found
Probabilistic quantum phase-space simulation of Bell violations and their dynamical evolution
Quantum simulations of Bell inequality violations are numerically obtained
using probabilistic phase space methods, namely the positive P-representation.
In this approach the moments of quantum observables are evaluated as moments of
variables that have values outside the normal eigenvalue range. There is thus a
parallel with quantum weak measurements and weak values. Nevertheless, the
representation is exactly equivalent to quantum mechanics. A number of states
violating Bell inequalities are sampled, demonstrating that these quantum
paradoxes can be treated with probabilistic methods. We treat quantum dynamics
by simulating the time evolution of the Bell state formed via parametric
down-conversion, and discuss multi-mode generalizations
Probabilistic simulation of mesoscopic "Schr\"odinger cat" states
We carry out probabilistic phase-space sampling of mesoscopic Schr\"odinger
cat quantum states, demonstrating multipartite Bell violations for up to 60
qubits. We use states similar to those generated in photonic and ion-trap
experiments. These results show that mesoscopic quantum superpositions are
directly accessible to probabilistic sampling, and we analyze the properties of
sampling errors. We also demonstrate dynamical simulation of super-decoherence
in ion traps. Our computer simulations can be either exponentially faster or
slower than experiment, depending on the correlations measured
Quantum probabilistic sampling of multipartite 60-qubit Bell inequality violations
We show that violation of genuine multipartite Bell inequalities can be
obtained with sampled, probabilistic phase space methods. These genuine Bell
violations cannot be replicated if any part of the system is described by a
local hidden variable theory. The Bell violations are simulated
probabilistically using quantum phase-space representations. We treat
mesoscopically large Greenberger-Horne-Zeilinger (GHZ) states having up to 60
qubits, using both a multipartite SU(2) Q-representation and the positive
P-representation. Surprisingly, we find that sampling with phase-space
distributions can be exponentially faster than experiment. This is due to the
classical parallelism inherent in the simulation of quantum measurements using
phase-space methods. Our probabilistic sampling method predicts a contradiction
with local realism of "Schr\"odinger-cat" states that can be realized as a GHZ
spin state, either in ion traps or with photonic qubits. We also present a
quantum simulation of the observed super-decoherence of the ion-trap "cat"
state, using a phenomenological noise model
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