Physics

Galaxy mergers are a standard aspect of galaxy formation and evolution, and most (likely all) large galaxies contain supermassive black holes. As part of the merging process, the supermassive black holes should in-spiral together and eventually merge, generating both continuous gravitational waves and a background of gravitational radiation in the nanohertz to microhertz regime.  An array of precisely timed pulsars spread across the sky can form a galactic-scale gravitational wave detector in the nanohertz band. I describe the current efforts to develop and extend the pulsar timing array concept, together with recent limits which have emerged from international efforts to constrain astrophysical phenomena at the heart of supermassive black hole mergers.

The spectral action functional of noncommutative geometry provides a model of Euclidean (modified) gravity, possibly coupled to matter. The terms in the large energy asymptotic expansion of the spectral action can be computed via pseudodifferential calculus. In the case of highly symmetric spacetimes, like Robertson-Walker metrics and Bianchi IX gravitational instantons, there is a richer arithmetic structure in the spectral action, and the terms in the asymptotic expansion are expressiblein terms of periods of motives and of modular forms. This reveals a new occurrence of interesting periods and motives in high-energy physics.

The Hubble Space Telescope has completely revolutionized our understanding of the universe, and has become a beloved icon of popular culture. As revolutionary as Hubble has been, we have pushed it to its scientific limits in many ways. Hubble’s successor, the James Webb Space Telescope, has been in the works for almost two decades and is scheduled to launch in late 2018. It will be 100 times more powerful than Hubble. In her Perimeter Public Lecture, Dr. Amber Straughn will provide an update on the progress of building the world’s largest-yet space telescope, and will give an overview of the astronomical questions we hope to answer with Webb. These questions get to the heart of what it means to be human: Where did we come from? How did we get here? Are we alone?

By a celebrated theorem of Jacob Lurie, an extended TQFT is entirely determined by what it assigns to a point. It is natural to ask whether this theorem applies to TQFTs of physical interest. And, if yes, what do these theories assign to a point? In this talk, I will propose an answer for the case of 3-dimensional Chern-Simons theory. I will then
explore the relation to line defects in chiral WZW models, and boundary conditions for full WZW models. At last, I will present a conjectural classification of the above mentioned line defects and boundary conditions.

Quantum Field Theories are interacting quantum systems described by an infinite number of degrees of freedom, necessarily living on an infinite-dimensional Hilbert space. Hence, many concepts from Quantum Information Theory have to be adapted before they can be applied to this setting. However, the task is worthwhile as we obtain new tools to understand the entanglement structure of theories describing the fundamental forces of nature. I will outline two approaches along this route, one bottom-down and one bottom-up strategy. First, general Lorentz invariant quantum fields are studied from a quantum information perspective. Second, I discuss the use of tensor networks to model the entanglement structure of quantum fields. The combination of both approaches yields new insights into Quantum Field Theory from an information theoretic point of view. I will end my talk by giving an outlook into future research directions.

It is commonly believed that quantum information is not lost in a black hole. Instead, it is encoded into non-local degrees of freedom in some clever way; like a quantum error-correcting code. In this talk, I will discuss recent attempts to resolve some paradoxes in quantum gravity by using the theory of quantum error-correction. First, I will introduce a simple toy model of the AdS/CFT correspondence based on tensor networks and demonstrate that the correspondence between the AdS gravity and CFT is indeed a realization of quantum codes. I will then show that the butterfly effect in black holes can be interpreted as non-local encoding of quantum information and can be quantitatively measured by out-of-time ordered correlations. Finally, I will discuss how out-of-time ordered correlations, measured outside the black hole horizon, may probe smoothness of the geometry across the horizon.

Laser-cooled trapped ions are among the most versatile experimental platforms for exploring quantum information. In this talk, I will give a brief overview of this system and its capabilities to simulate non-trivial interacting quantum models. Internal states of these ions, such as hyperfine states, constitute well isolated qubit (or spin-1/2) states, with quantum coherence demonstrated up to fifteen minutes. Individual qubits states can be detected by laser beams with near perfection. Quantum logic gates and interacting spin Hamiltonians are engineered by coupling internal states of multiple ions to their collective vibrational modes using optical forces. By suitably tailoring these spin-phonon couplings, interactions between ion-spins can be tuned in magnitude, range, and sign. The laboratory for Quantum Information with Trapped Ions at IQC aims to build a highly flexible quantum simulator with dozens of spins, and explore problems in quantum information and many-body physics in a regime that is intractable with classical computers.