125 research outputs found
Wigner Functions for Arbitrary Quantum Systems
The possibility of constructing a complete, continuous Wigner function for
any quantum system has been a subject of investigation for over 50 years. A key
system that has served to illustrate the difficulties of this problem has been
an ensemble of spins. Here we present a general and consistent framework for
constructing Wigner functions exploiting the underlying symmetries in the
physical system at hand. The Wigner function can be used to fully describe any
quantum system of arbitrary dimension or ensemble size.Comment: 5 pages, 3 figure
Observing quantum chaos with noisy measurements and highly mixed states
A fundamental requirement for the emergence of classical behavior from an
underlying quantum description is that certain observed quantum systems make a
transition to chaotic dynamics as their action is increased relative to
. While experiments have demonstrated some aspects of this transition,
the emergence of quantum trajectories with a positive Lyapunov exponent has
never been observed directly. Here, we remove a major obstacle to achieving
this goal by showing that, for the Duffing oscillator, the transition to a
positive Lyapunov exponent can be resolved clearly from observed trajectories
even with measurement efficiencies as low as 20%. We also find that the
positive Lyapunov exponent is robust to highly mixed, low purity states and to
variations in the parameters of the system.Comment: 3 figures, 5 pages, updated after comment
Charged Higgs bosons from the 3-3-1 models and the anomalies
Several anomalies in the semileptonic B-meson decays such as
have been reported by , Belle, and LHCb
collaborations recently. In this paper, we investigate the contributions of the
charged Higgs bosons from the 3-3-1 models to the
anomalies. We find that, in a wide range of parameter space, the 3-3-1 models
might give reasonable explanations to the anomalies and
other analogous anomalies of the B meson's semileptonic decays.Comment: Accpeted by Physical Review
On the quantum-to-classical transition of a particle in a box
The exact formulation of the correspondence principle and in particular understanding the quantum-to-classical transition remains an open problem in quantum mechanics. In
this paper we present our investigation into the quantumto-classical transition of the most trivial of quantum systems — a particle in a box. Whilst it is perhaps surprising,
even this example can produce new physical insight into these fundamental problems. With modern fabrication techniques of nano-mechanical systems we will be able to experimentally investigate these results and directly observe the quantum-to-classical transition. This will enable us to build technologies that probe the fundamental questions of quantum mechanics, such as the maximum size of a quantum object
Photonic architecture for scalable quantum information processing in NV-diamond
Physics and information are intimately connected, and the ultimate
information processing devices will be those that harness the principles of
quantum mechanics. Many physical systems have been identified as candidates for
quantum information processing, but none of them are immune from errors. The
challenge remains to find a path from the experiments of today to a reliable
and scalable quantum computer. Here, we develop an architecture based on a
simple module comprising an optical cavity containing a single
negatively-charged nitrogen vacancy centre in diamond. Modules are connected by
photons propagating in a fiber-optical network and collectively used to
generate a topological cluster state, a robust substrate for quantum
information processing. In principle, all processes in the architecture can be
deterministic, but current limitations lead to processes that are probabilistic
but heralded. We find that the architecture enables large-scale quantum
information processing with existing technology.Comment: 24 pages, 14 Figures. Comment welcom
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