Displaying 3097 - 3108 of 5085
Format results
-
-
-
-
Defects: A new window into topological quantum matter
Maissam Barkeshli University of California, Santa Barbara
PIRSA:14100048 -
Irreversibility and Entanglement Spectrum Statistics in Quantum Circuits
Eduardo Mucciolo University of Central Florida
-
-
3d Gravity, Universality and Poincare Series
PIRSA:14090005 -
ADMX: The Axion Dark Matter Experiment
Gray Rybka University of Washington
-
-
Fault-tolerant logical gates in quantum error-correcting codes
Beni Yoshida Perimeter Institute for Theoretical Physics
-
Lifshitz Field Theories, Anomalies and Hydrodynamics
Shira Chapman University of Amsterdam
PIRSA:14090083 -
Algebraic characterization of entanglement classes
Markus Grassl Max Planck Institute for the Science of Light
-
Computer Algebra for Theoretical Physics
Edgardo Cheb-Terrab Maplesoft
PIRSA:14100068Generally speaking, physicists still experience that computing with paper and pencil is in most cases simpler than computing on a Computer Algebra worksheet. On the other hand, recent developments in the Maple system implemented most of the mathematical objects and mathematics used in theoretical physics computations, and dramatically approximated the notation used in the computer to the one used in paper and pencil, diminishing the learning gap and computer-syntax distraction to a strict minimum. In connection, in this talk the Physics project at Maplesoft is presented and the resulting Physics package illustrated tackling problems in classical and quantum mechanics, general relativity and field theory. In addition to the 10 a.m lecture, there will be a hands-on workshop at 1pm in the Alice Room. Feel free to join! -
Probing (beyond) general relativity with compact binaries and gravitational waves
Leo Stein Cornell University
General relativity enjoys phenomenal success in agreeing with experiments and observations, but it must break down at some point. Astrophysics can give guidance for what type of theory may correct general relativity, if we know which phenomenology to look for. I will discuss the possible corrections to the structure of compact objects, the binary problem, and observations with pulsar timing and gravitational wave detection. These corrections are computed in specific effective theories, such as Einstein-dilaton-Gauss-Bonnet (EdGB) and dynamical Chern-Simons (dCS) gravity, and we may further generalize the common aspects of these theories to build a parametrized framework which captures a large number of effective field theories. -
The Effective Field Theory of Cosmological Large Scale Structures
Leonardo Senatore ETH Zurich
The Effective Filed Theory of Large Scale Structures provides a novel framework to analytically compute the clustering of the Large Scale Structures in the weakly non-linear regime in a consistent and reliable way. The theory that describes the long wavelength fluctuations is obtained after integrating out the short distance modes and adding suitable operators that allow to correctly reconstruct the effect of short distance fluctuations at long distances. A few observables have been computed so far, and the results are extremely promising. I will discuss the formalism and the main results so far. -
Defects: A new window into topological quantum matter
Maissam Barkeshli University of California, Santa Barbara
PIRSA:14100048Topologically ordered states, such as the fractional quantum Hall (FQH) states, are quantum states of matter with various exotic properties, including quasiparticles with fractional quantum numbers and fractional statistics, and robust topology-dependent ground state degeneracies. In this talk, I will describe a new aspect of topological states: their extrinsic defects. These include extrinsically imposed point-like or line-like defects that couple to the topological properties of the state in non-trivial ways. The extrinsic point defects localize topologically protected "parafermion" zero modes, which generalize the notion of Majorana fermion zero modes, and provide a new direction for realizing non-Abelian quantum statistics and topological quantum computation. The line defects allow direct quantum mechanical coupling between electrons and fractionalized anyons, leading to new ways to probe fractionalization. After describing the conceptual framework, I will focus on a specific set of experimental proposals, using conventional bilayer FQH states, to detect parafermion zero modes and to directly observe the long-predicted topological ground state degeneracy of FQH states. In the end I will comment on other ways in which extrinsic defects provide a new window into fractionalization. -
Irreversibility and Entanglement Spectrum Statistics in Quantum Circuits
Eduardo Mucciolo University of Central Florida
We show that for a system evolving unitarily under a stochastic quantum circuit, the notions of irreversibility, universality of computation, and entanglement are closely related. As the state of the system evolves from an initial product state, it becomes increasingly entangled until entanglement reaches a maximum. We define irreversibility as the failure to find a circuit that disentangles a maximally entangled state. We show that irreversibility occurs when maximally entangled states are generated with a quantum circuit formed by gates from a universal quantum computation set. We find that irreversibility is also associated to a Wigner-Dyson statistics in the fluctuations of spacings between adjacent eigenvalues of the system’s reduced density matrix. In contrast, when the system is evolved with a non-universal set of gates, the statistics of the entanglement spacing deviates from Wigner-Dyson and the disentangling algorithm succeeds. We discuss how these findings open a new way to characterize non-integrability in quantum systems. -
The Topology of Information Flow
Jamie Vicary University of Oxford
PIRSA:14090076I will outline a new topological foundation for computation, and show how it gives rise to a unified treatment of classical encryption and quantum teleportation, and a strong classical model for many quantum phenomena. This work connects to some other interesting topics, including quantum field theory, classical combinatorics, thermodynamics, Morse theory and higher category theory, which I will introduce in an elementary way. -
3d Gravity, Universality and Poincare Series
PIRSA:14090005Modular invariance plays an important role in the AdS3/CFT2 correspondence. Using modular invariance, I discuss under what conditions a 2d CFT shows a Hawking-Page phase transition in the large c limit, and what this implies for the range of validity of the Cardy formula and the universality of its spectrum. I will also discuss partition functions obtained by summing over the modular group, how their properties are compatible with their gravity interpretation, and briefly touch on implications for the existence of pure gravity. -
ADMX: The Axion Dark Matter Experiment
Gray Rybka University of Washington
Axions are an exceptionally well-motivated dark matter candidate in addition to being a consequence of the Peccei-Quinn solution to the strong CP problem. ADMX (Axion Dark Matter eXperiment) has recently been selected as the axion search for the US DOE Second-Generation Dark Matter Program. I will discuss the imminent upgrade of ADMX to a definitive search for micro-eV mass dark matter axions as well as the ongoing research and development of new technologies to expand the reach of ADMX to the entire plausible dark matter axion mass range. -
From Black Holes to Big Bang, and Back
Niayesh Afshordi University of Waterloo
PIRSA:14090088By now, both black hole astrophysics and big bang cosmology are empirically well-established disciplines of physics and astronomy. They are also the only circumstances in nature where Einstein's general relativity can be seen in its full glory, and yet contain within them, its eventual and inevitable folly. Here, I will outline subtle lines evidence for why a phenomenologically successful description of big bang cosmology and black hole horizons may be intimately connected. These lines include a holographic description of big bang, thermal tachyacoustic cosmology, and the firewall controversy. Astrophysical observations, ranging from CMB and dark energy probes, to astrophysical neutrinos could shed further light on these potential connections. -
Fault-tolerant logical gates in quantum error-correcting codes
Beni Yoshida Perimeter Institute for Theoretical Physics
Recently, Bravyi and Koenig have shown that there is a tradeoff between fault-tolerantly implementable logical gates and geometric locality of stabilizer codes. They consider locality-preserving operations which are implemented by a constant depth geometrically local circuit and are thus fault-tolerant by construction. In particular, they shown that, for local stabilizer codes in D spatial dimensions, locality preserving gates are restricted to a set of unitary gates known as the D-th level of the Clifford hierarchy. In this paper, we elaborate this idea and provide several extensions and applications of their characterization in various directions. First, we present a new no-go theorem for self-correcting quantum memory. Namely, we prove that a three-dimensional stabilizer Hamiltonian with a locality-preserving implementation of a non-Clifford gate cannot have a macroscopic energy barrier. Second, we prove that the code distance of a D-dimensional local stabilizer code with non-trivial locality-preserving m-th level Clifford logical gate is upper bounded by L^{D+1-m}. For codes with non-Clifford gates (m>2), this improves the previous best bound by Bravyi and Terhal. Third we prove that a qubit loss threshold of codes with non-trivial transversal m-th level Clifford logical gate is upper bounded by 1/m. As such, no family of fault-tolerant codes with transversal gates in increasing level of the Clifford hierarchy may exist. This result applies to arbitrary stabilizer and subsystem codes, and is not restricted to geometrically-local codes. Fourth we extend the result of Bravyi and Koenig to subsystem codes. A technical difficulty is that, unlike stabilizer codes, the so-called union lemma does not apply to subsystem codes. This problem is avoided by assuming the presence of error threshold in a subsystem code, and the same conclusion as Bravyi-Koenig is recovered. This is a joint work with Fernando Pastawski. arXiv:1408.1720 -
Lifshitz Field Theories, Anomalies and Hydrodynamics
Shira Chapman University of Amsterdam
PIRSA:14090083I will review various aspects of field theories that posses a Lifshitz scaling symmetry. I will detail our study of the cohomological structure of anisotropic Weyl anomalies (the equivalent of trace anomalies in relativistic scale invariant field theories). I will also analyze the hydrodynamics of Lifshitz field theories and in particular of Lifshitz superfluids which may give insights into the physics of high temperature superconductors. -
Algebraic characterization of entanglement classes
Markus Grassl Max Planck Institute for the Science of Light
Entanglement is a key feature of composite quantum system which is directly related to the potential power of quantum computers. In most computational models, it is assumed that local operations are relatively easy to implement. Therefore, quantum states that are related by local operations form a single entanglement class. In the case of local unitary operations, a finite set of polynomial invariants provides a complete characterization of the entanglement classes. Unfortunately, one faces the problem of combinatorial explosion so that computing such a complete set of invariants becomes difficult already for quite small system. The two main problems in this context are to compute invariants and to decide completeness, i.e., whether a given set of invariants generates the full invariant ring. Important tools are both univariate and multivariate Hilbert series which are already difficult to compute. We will also address computational aspects of these problems and techniques for showing completeness of a set of invariants.