32 research outputs found
Symmetry reduction induced by anyon condensation: a tensor network approach
Topological ordered phases are related to changes in the properties of their
quasi-particle excitations (anyons). We study these relations in the framework
of projected entanglement pair states (\textsf{PEPS}) and show how condensing
and confining anyons reduces a local gauge symmetry to a global on-site
symmetry. We also study the action of this global symmetry over the
quasiparticle excitations. As a byproduct, we observe that this symmetry
reduction effect can be applied to one-dimensional systems as well, and brings
about appealing physical interpretations on the classification of phases with
symmetries using matrix product states (\textsf{MPS}). The case of
on-site symmetry is studied in detail.Comment: 21+5 pages, 15+3 figures. Introduction and conclusions enlarged,
references and figure added, minor typos corrected, appendix about dyons
adde
Mathematical open problems in Projected Entangled Pair States
Projected Entangled Pair States (PEPS) are used in practice as an efficient
parametrization of the set of ground states of quantum many body systems. The
aim of this paper is to present, for a broad mathematical audience, some
mathematical questions about PEPS.Comment: Notes associated to the Santal\'o Lecture 2017, Universidad
Complutense de Madrid (UCM), minor typos correcte
SimetrĂas en estados de redes tensoriales topolĂłgicas: clasificaciĂłn, construcciĂłn y detecciĂłn
Tesis inĂ©dita de la Universidad Complutense de Madrid, Facultad de Ciencias Matemáticas, Departamento de Análisis y Matemática Aplicada, leĂda el 10/01/2019The exotic properties which appear in the quantum setting, mainly manifested in strongly-correlated systems, oer potential applications in future technologies. For instance, high-precision measurementsor the new paradigm of a quantum computer. One of the most prominent features of quantum physics is entanglement: the correlationsbetween the parties of a system that cannot be described classically. This property is believed to be the one endowing quantum mechanics its complexity. Therefore, characterizing the entanglement properties of strongly-correlated systems plays a fundamental role for condensed-matter physics. However, this complexity comes hand in hand with a challenge: the number of parameters needed to describe a system grows exponentially with the number of parties in the system. This challengelies at the heart of the mathematical description of quantum mechanics. Such a situation happens naturally in many-body systems and in particular, in condensed-matter physics where the relevant physics appears when considering large systems. Then, how can we deal with this diculty? Thekey observation here is that realistic physical systems are the ones whose parties interact locally and this restricts the entanglement pattern in the low-energy sector (zero temperature). So thequestion is shifted to: Is there a framework that captures states with such entanglement pattern? The answer is yes: tensor network states...Las inusuales propiedades que surgen en la mecánica cuantica, manifestadas especialmente en sistemas fuertemente correlacionados, ofrecen aplicaciones potenciales a nuevas tecnologĂas. Por ejemplo, mediciones de alta precision o la creacion un nuevo modelo de computacion (el ordenador cuantico). Una de las propiedades mas destacadas de la fĂsica cuantica es el entrelazamiento: las correlaciones entre las partes de un sistema que no se pueden describir clasicamente. Se cree que esta propiedad es la que dota a la mecanica cuantica de su complejidad. Por lo tanto, caracterizar el entrelazamiento de sistemas fuertemente correlacionados desempeña un papel fundamental en la fĂsica de la materia condensada. Pero esta complejidad viene unida a una dificultad: el numero de parámetros necesario para describir un sistema crece exponencialmente con el numero de partes en el sistema. Este reto esta en el corazon de la descripcion matematica de la mecánica cuantica. Esto ocurre de forma natural en sistemas de muchos cuerpos y en particular, en fĂsica de la materia condensada, donde la fĂsica relevante aparece cuando el tamaño del sistema es grande. Entonces, Âżcomo podemos lidiar con esta dificultad? La observaciĂłn clave es que los sistemas fĂsicos reales son aquellos en los que las partes interaccionan localmente y esto restringe el patron de entrelazamiento en el sector de baja energĂa de los sistemas. Por lo que ahora la cuestion es: Âżhay un formalismo que capture los estados con ese tipo de patrĂłn de entrelazamiento? La respuesta es si: los estados de redes tensoriales...Depto. de Análisis Matemático y Matemática AplicadaFac. de Ciencias MatemáticasTRUEunpu
String order parameters for symmetry fractionalization in an enriched toric code
We study a simple model of symmetry-enriched topological order obtained by
decorating a toric code model with lower-dimensional symmetry-protected
topological states. We show that the symmetry fractionalization in this model
can be characterized by string order parameters, and that these signatures are
robust under the effects of external fields and interactions, up to the phase
transition point. This extends the recent proposal of [New Journal of Physics
21, 113016 (2019)] beyond the setting of fixed-point tensor network states, and
solidifies string order parameters as a useful tool to characterize and detect
symmetry fractionalization. In addition to this, we observe how the
condensation of an anyon that fractionalizes a symmetry forces that symmetry to
spontaneously break, and we give a proof of this in the framework of projected
entangled pair states. This phenomenon leads to a notable change in the phase
diagram of the toric code in parallel magnetic fields.Comment: Changes in title, astract and introdution. 11+7 pages, 7+3 figures, 2
table
Subsystem symmetry enriched topological order in three dimensions
We introduce a model of three-dimensional (3D) topological order enriched by
planar subsystem symmetries. The model is constructed starting from the 3D
toric code, whose ground state can be viewed as an equal-weight superposition
of two-dimensional (2D) membrane coverings. We then decorate those membranes
with 2D cluster states possessing symmetry-protected topological order under
line-like subsystem symmetries. This endows the decorated model with planar
subsystem symmetries under which the loop-like excitations of the toric code
fractionalize, resulting in an extensive degeneracy per unit length of the
excitation. We also show that the value of the topological entanglement entropy
is larger than that of the toric code for certain bipartitions due to the
subsystem symmetry enrichment. Our model can be obtained by gauging the global
symmetry of a short-range entangled model which has symmetry-protected
topological order coming from an interplay of global and subsystem symmetries.
We study the non-trivial action of the symmetries on boundary of this model,
uncovering a mixed boundary anomaly between global and subsystem symmetries. To
further study this interplay, we consider gauging several different subgroups
of the total symmetry. The resulting network of models, which includes models
with fracton topological order, showcases more of the possible types of
subsystem symmetry enrichment that can occur in 3D.Comment: 21 pages. v2: Published version. Updated Section IV with new figure
and tabl
Normal projected entangled pair states generating the same state
Tensor networks are generated by a set of small rank tensors and define
many-body quantum states in a succinct form. The corresponding map is not
one-to-one: different sets of tensors may generate the very same state. A
fundamental question in the study of tensor networks naturally arises: what is
then the relation between those sets? The answer to this question in one
dimensional setups has found several applications, like the characterization of
local and global symmetries, the classification of phases of matter and unitary
evolutions, or the determination of the fixed points of renormalization
procedures. Here we answer this question for projected entangled-pair states
(PEPS) in any dimension and lattice geometry, as long as the tensors generating
the states are normal, which constitute an important and generic class
Brca1 Alternative Splicing Landscape In Breast Tissue Samples
Background: BRCA1 is a key protein in cell network, involved in DNA repair pathways and cell cycle. Recently, the ENIGMA consortium has reported a high number of alternative splicing (AS) events at this locus in blood-derived samples. However, BRCA1 splicing pattern in breast tissue samples is unknown. Here, we provide an accurate description of BRCA1 splicing events distribution in breast tissue samples. Methods: BRCA1 splicing events were scanned in 70 breast tumor samples, 4 breast samples from healthy individuals and in 72 blood-derived samples by capillary electrophoresis (capillary EP). Molecular subtype was identified in all tumor samples. Splicing events were considered predominant if their relative expression level was at least the 10% of the full-length reference signal. Results: 54 BRCA1 AS events were identified, 27 of them were annotated as predominant in at least one sample. Delta 5q, Delta 13, Delta 9, Delta 5 and del 1aA were significantly more frequently annotated as predominant in breast tumor samples than in blood-derived samples. Predominant splicing events were, on average, more frequent in tumor samples than in normal breast tissue samples (P = 0.010). Similarly, likely inactivating splicing events (PTC-NMDs, Non-Coding, Delta 5 and Delta 18) were more frequently annotated as predominant in tumor than in normal breast samples (P = 0.020), whereas there were no significant differences for other splicing events (No-Fs) frequency distribution between tumor and normal breast samples (P = 0.689). Conclusions: Our results complement recent findings by the ENIGMA consortium, demonstrating that BRCA1 AS, despite its tremendous complexity, is similar in breast and blood samples, with no evidences for tissue specific AS events. Further on, we conclude that somatic inactivation of BRCA1 through spliciogenic mutations is, at best, a rare mechanism in breast carcinogenesis, albeit our data detects an excess of likely inactivating AS events in breast tumor samples