444 research outputs found
The concept of auralising and trace in a formalized grammar of music
This paper tries to give a cognitive insight of the "chord transformation figure", one of the rules discussed in the book by M.Baroni-R.Dalmonte-C.Jacoboni, "A computer aided inquiry on music communication". After emphasising the physical nature of the affinity between the notes of the triadic chord, the papaer takes into consideration the transcultural constraints and the intracultural rules of music. More recent studies in the field of psychology of music are discussed
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
Non-topological parafermions in a one-dimensional fermionic model with even multiplet pairing
We discuss a one-dimensional fermionic model with a generalized
even multiplet pairing extending Kitaev
chain. The system shares many features with models believed to host localized
edge parafermions, the most prominent being a similar bosonized Hamiltonian and
a symmetry enforcing an -fold degenerate ground state
robust to certain disorder. Interestingly, we show that the system supports a
pair of parafermions but they are non-local instead of being boundary
operators. As a result, the degeneracy of the ground state is only partly
topological and coexists with spontaneous symmetry breaking by a (two-particle)
pairing field. Each symmetry-breaking sector is shown to possess a pair of
Majorana edge modes encoding the topological twofold degeneracy. Surrounded by
two band insulators, the model exhibits for the dual of an
fractional Josephson effect highlighting the presence of parafermions.Comment: 12 pages, 3 figure
Floquet time crystal in the Lipkin-Meshkov-Glick model
In this work we discuss the existence of time-translation symmetry breaking
in a kicked infinite-range-interacting clean spin system described by the
Lipkin-Meshkov-Glick model. This Floquet time crystal is robust under
perturbations of the kicking protocol, its existence being intimately linked to
the underlying symmetry breaking of the time-independent model.
We show that the model being infinite-range and having an extensive amount of
symmetry breaking eigenstates is essential for having the time-crystal
behaviour. In particular we discuss the properties of the Floquet spectrum, and
show the existence of doublets of Floquet states which are respectively even
and odd superposition of symmetry broken states and have quasi-energies
differing of half the driving frequencies, a key essence of Floquet time
crystals. Remarkably, the stability of the time-crystal phase can be directly
analysed in the limit of infinite size, discussing the properties of the
corresponding classical phase space. Through a detailed analysis of the
robustness of the time crystal to various perturbations we are able to map the
corresponding phase diagram. We finally discuss the possibility of an
experimental implementation by means of trapped ions.Comment: 14 pages, 12 figure
Many-body localization dynamics from gauge invariance
We show how lattice gauge theories can display many-body localization
dynamics in the absence of disorder. Our starting point is the observation
that, for some generic translationally invariant states, Gauss law effectively
induces a dynamics which can be described as a disorder average over gauge
super-selection sectors. We carry out extensive exact simulations on the
real-time dynamics of a lattice Schwinger model, describing the coupling
between U(1) gauge fields and staggered fermions. Our results show how memory
effects and slow entanglement growth are present in a broad regime of
parameters - in particular, for sufficiently large interactions. These findings
are immediately relevant to cold atoms and trapped ions experiments realizing
dynamical gauge fields, and suggest a new and universal link between
confinement and entanglement dynamics in the many-body localized phase of
lattice models.Comment: 5Pages + appendices; V2: updated discussion in page 2, more numerical
results, added reference
Measuring von Neumann entanglement entropies without wave functions
We present a method to measure the von Neumann entanglement entropy of ground
states of quantum many-body systems which does not require access to the system
wave function. The technique is based on a direct thermodynamic study of
entanglement Hamiltonians, whose functional form is available from field
theoretical insights. The method is applicable to classical simulations such as
quantum Monte Carlo methods, and to experiments that allow for thermodynamic
measurements such as the density of states, accessible via quantum quenches. We
benchmark our technique on critical quantum spin chains, and apply it to
several two-dimensional quantum magnets, where we are able to unambiguously
determine the onset of area law in the entanglement entropy, the number of
Goldstone bosons, and to check a recent conjecture on geometric entanglement
contribution at critical points described by strongly coupled field theories
Entanglement guided search for parent Hamiltonians
We introduce a method for the search of parent Hamiltonians of input
wave-functions based on the structure of their reduced density matrix. The two
key elements of our recipe are an ansatz on the relation between reduced
density matrix and parent Hamiltonian that is exact at the field theory level,
and a minimization procedure on the space of relative entropies, which is
particularly convenient due to its convexity. As examples, we show how our
method correctly reconstructs the parent Hamiltonian correspondent to several
non-trivial ground state wave functions, including conformal and
symmetry-protected-topological phases, and quantum critical points of
two-dimensional antiferromagnets described by strongly coupled field theories.
Our results show the entanglement structure of ground state wave-functions
considerably simplifies the search for parent Hamiltonians.Comment: 5 pages, 5 figures, supplementary materia
- …