1,760,049 research outputs found
Information and communication in polygon theories
Generalized probabilistic theories (GPT) provide a framework in which one can
formulate physical theories that includes classical and quantum theories, but
also many other alternative theories. In order to compare different GPTs, we
advocate an approach in which one views a state in a GPT as a resource, and
quantifies the cost of interconverting between different such resources. We
illustrate this approach on polygon theories (Janotta et al. New J. Phys 13,
063024, 2011) that interpolate (as the number n of edges of the polygon
increases) between a classical trit (when n=3) and a real quantum bit (when
n=infinity). Our main results are that simulating the transmission of a single
n-gon state requires more than one qubit, or more than log(log(n)) bits, and
that n-gon states with n odd cannot be simulated by n'-gon states with n' even
(for all n,n'). These results are obtained by showing that the classical
capacity of a single n-gon state with n even is 1 bit, whereas it is larger
than 1 bit when n is odd; by showing that transmitting a single n-gon state
with n even violates information causality; and by showing studying the
communication complexity cost of the nondeterministic not equal function using
n-gon states.Comment: 18 page
Observational information for f(T) theories and Dark Torsion
In the present work we analyze and compare the information coming from
different observational data sets in the context of a sort of f(T) theories. We
perform a joint analysis with measurements of the most recent type Ia
supernovae (SNe Ia), Baryon Acoustic Oscillation (BAO), Cosmic Microwave
Background radiation (CMB), Gamma-Ray Bursts data (GRBs) and Hubble parameter
observations (OHD) to constraint the only new parameter these theories have. It
is shown that when the new combined BAO/CMB parameter is used to put
constraints, the result is different from previous works. We also show that
when we include Observational Hubble Data (OHD) the simpler LambdaCDM model is
excluded to one sigma level, leading the effective equation of state of these
theories to be of phantom type. Also, analyzing a tension criterion for SNe Ia
and other observational sets, we obtain more consistent and better suited data
sets to work with these theories.Comment: 8 pages, 4 figures. AIC criterion added. Version accepted in Phys.
Lett.
A note on information theoretic characterizations of physical theories
Clifton, Bub, and Halvorson [Foundations of Physics 33, 1561 (2003)] have
recently argued that quantum theory is characterized by its satisfaction of
three information-theoretic axioms. However, it is not difficult to construct
apparent counterexamples to the CBH characterization theorem. In this paper, we
discuss the limits of the characterization theorem, and we provide some
technical tools for checking whether a theory (specified in terms of the convex
structure of its state space) falls within these limits.Comment: 16 pages, LaTeX, Contribution to Rob Clifton memorial conferenc
Lattice gauge theories simulations in the quantum information era
The many-body problem is ubiquitous in the theoretical description of
physical phenomena, ranging from the behavior of elementary particles to the
physics of electrons in solids. Most of our understanding of many-body systems
comes from analyzing the symmetry properties of Hamiltonian and states: the
most striking example are gauge theories such as quantum electrodynamics, where
a local symmetry strongly constrains the microscopic dynamics. The physics of
such gauge theories is relevant for the understanding of a diverse set of
systems, including frustrated quantum magnets and the collective dynamics of
elementary particles within the standard model. In the last few years, several
approaches have been put forward to tackle the complex dynamics of gauge
theories using quantum information concepts. In particular, quantum simulation
platforms have been put forward for the realization of synthetic gauge
theories, and novel classical simulation algorithms based on quantum
information concepts have been formulated. In this review we present an
introduction to these approaches, illustrating the basics concepts and
highlighting the connections between apparently very different fields, and
report the recent developments in this new thriving field of research.Comment: Pedagogical review article. Originally submitted to Contemporary
Physics, the final version will appear soon on the on-line version of the
journal. 34 page
Classical Spacetimes as Amplified Information in Holographic Quantum Theories
We argue that classical spacetimes represent amplified information in the
holographic theory of quantum gravity. In general, classicalization of a
quantum system involves amplification of information at the cost of
exponentially reducing the number of observables. In quantum gravity, the
geometry of spacetime must be the analogously amplified information. Bulk local
semiclassical operators probe this information without disturbing it; these
correspond to logical operators acting on code subspaces of the holographic
theory. From this viewpoint, we study how bulk local operators may be realized
in a holographic theory of general spacetimes, which includes AdS/CFT as a
special case, and deduce its consequences. In the first half of the paper, we
ask what description of the bulk physics is provided by a holographic state
dual to a semiclassical spacetime. In particular, we analyze what portion of
the bulk can be reconstructed as spacetime in the holographic theory. The
analysis indicates that when a spacetime contains a quasi-static black hole
inside a holographic screen, the theory provides a description of physics as
viewed from the exterior (though the interior information is not absent). In
the second half, we study how and when a semiclassical description emerges in
the holographic theory. We find that states representing semiclassical
spacetimes are non-generic in the holographic Hilbert space. If there are a
maximal number of independent microstates, semiclassical operators must be
given state-dependently; we elucidate this point using the stabilizer formalism
and tensor network models. We also discuss possible implications of the present
picture for the black hole interior.Comment: 17 pages, 3 figures; v4: matches published versio
- …