# Simons Collaboration on It From Qubit Annual Meeting

• Organized by
• Patrick Hayden, Ph.D.Stanford University
Date & Time

The interface of quantum information theory and high-energy theory has seen rapid progress over the last few years, with significant advances on topics such as scrambling and chaos in quantum systems; complexity and black holes; holography and quantum error correction; entropy and energy bounds in quantum field theories; and traversable wormholes and quantum teleportation in semiclassical quantum gravity. This progress has shifted the landscape of physics, changing our perspectives on the deepest problems in the two fields and blurring the boundary between them. The 2018 annual meeting of It from Qubit: Simons Collaboration on Quantum Fields, Gravity, and Information will be an opportunity to review progress, assess where we stand today and develop strategies to tackle the outstanding challenges as we see them now.

• Agenda

#### THURSDAY, DECEMBER 6

 8:30 AM CHECK-IN & BREAKFAST 9:30 AM Patrick Hayden | Holographic Quantum Error Correction: What, How and Why? 10:30 AM BREAK 11:00 AM Leonard Susskind | Complexity Behind the Horizon 12:00 PM LUNCH 1:00 PM Alexei Kitaev | The SYK Model and Black Holes 2:00 PM BREAK 2:30 PM Brian Swingle | Scrambling and Quantum Spacetime 3:30 PM BREAK 4:00 PM Mark Van Raamsdonk | Gravitational Physics from Quantum Information Constraint 5:00 PM DAY ONE CONCLUDES

#### FRIDAY, DECEMBER 7

 8:30 AM CHECK-IN & BREAKFAST 9:30 AM Horacio Casini | Entanglement Entropy in Quantum Field Theory: Recent Results and Future Prospects 10:30 AM BREAK 11:00 AM Dorit Aharonov | Minimizing Resources for Analog Quantum Simulations 12:00 PM LUNCH 1:00 PM Juan Maldacena | Traversable Wormholes 2:00 PM MEETING CONCLUDES
• Abstracts

Dorit Aharonov
Hebrew University

Minimizing Resources for Analog Quantum Simulations

The goal of analog quantum simulation, where a Hamiltonian $$H$$ is simulated by another Hamiltonian $$H’$$ that is simpler or more easily implemented, was identified by Feynman as a main motivation for quantum computers as early as 1981 and is considered to be one of the more practical and useful applications in the era of noisy intermediate-scale quantum technology (NISQ). The minimal resources required for such analog simulations will play a crucial role in such applications. We prove two results in this context: one, we prove that reducing the degree to a constant in analog simulations is, in general, impossible in the quantum world; this is due to the special nature of quantum correlations and stands in stark contrast to the classical world, where degree reduction is possible. Two, we significantly improve the requirements on the spatial dimension required for such analog simulations. Based on joint work with Leo Zhou.

Horacio Casini
Centro Atómico Bariloche

Entanglement Entropy in Quantum Field Theory: Recent Results and Future Prospects

Entanglement entropy offers a nonstandard view of quantum field theory where the focus is on the statistical properties of the state, rather than the ones of a particular set of operators — the traditional approach based on correlation functions. We will review the main recent results in this approach. In particular, we now have a unification of all theorems of irreversibility of the renormalization group for dimensions d=2, 3 and 4 (c, F and A theorems) based on the property of strong subadditivity of entanglement entropy. This proof offers, for the first time, a simple conceptual understanding of the quantum information theory meaning of these theorems and highlights the role of relativity. The Markovian property of the vacuum state, a new general property of relativistic quantum field theories, was discovered in this context. We will also discuss the quantum null energy condition that deepens our understanding of the relations between energy and entropy. We will end with an outlook of future possibilities.

Patrick Hayden
Stanford University

Holographic Quantum Error Correction: What, How and Why?

The bulk to boundary mapping in AdS/CFT has a surprising built-in redundancy: it is a quantum error-correcting code. That simple observation resolved a number of conceptual puzzles, including nonlinearities and redundancies in the correspondence. More recently, the algebra of error-correction property has provided the first detailed argument for the existence of localized quantum degrees of freedom in the bulk theory. In an even more striking advance, the proof of the entanglement wedge reconstruction hypothesis has illustrated how to extract information from beyond a horizon. In this talk, Hayden will summarize these and other advances, ending with a discussion of further challenges and opportunities. The talk will also contain a brief overview of the It from Qubit Simons Collaboration and its activities over the past three years.

Alexei Kitaev
California Institute of Technology

The SYK Model and Black Holes

Information scrambling in black holes is special because (up to stringy effects) it is operated by few collective degrees of freedom, ’t Hooft’s ‘shock waves.’ A similar situation occurs in the Sachdev-Ye-Kitaev model, where the relevant collective mode is described by the Schwarzian action. Kitaev will give a quick overview of the SYK model, including some recent developments. The main focus will be on mapping SYK observables, microstates, and more to the Schwarzian model, which is itself a consistent quantum theory.

Juan Maldacena

Traversable Wormholes

The full Schwarzschild solution describes two black holes joined by a nontraversable wormhole. In a theory of quantum gravity, this can be viewed as arising from two entangled black holes. If the two black holes are near each other, then interactions in the ambient space can make the wormhole traversable. We discuss this phenomenon in simple two-dimensional gravity models and quantum mechanical models of interacting Majorana fermions. Finally, we will show how the lessons for this model can lead to a traversable wormhole solution in four dimensions.

Brian Swingle
University of Maryland

Scrambling and Quantum Spacetime

Swingle will first review information scrambling and its relation to chaos and the geometry of space-time in the context of AdS/CFT. Scrambling can also be related to a kind of many-body spin echo, which opens a route to potentially measuring scrambling in the lab by effectively controlling the flow of time, as demonstrated in five preliminary experiments already carried out. Swingle will then comment on current directions, including a new definition of a spectrum of quantum Lyapunov exponents, a new universal structure for the spread of chaos in spatially extended systems, and the generation of macroscopic superpositions of space-times via quantum chaos. Swingle will close with a discussion of experiments to probe quantum space-time in toy universes and our own.

Leonard Susskind
Stanford University

Complexity Behind the Horizon

Susskind will explain aspects of the application of quantum complexity to the dynamics of the interiors of black holes. These will include the complexity-action correspondence and the importance of the second law of complexity to the evolution of the bulk geometry of black hole interiors.

Mark Van Raamsdonk
University of British Columbia

Gravitational Physics from Quantum Information Constraint

In this talk, Mark Van Raamsdonk will review some of the remarkable connections between gravitational physics and the physics of entanglement in conformal field theories. He will describe how the structure of entanglement in a conformal field theory can be captured by the geometry of an asymptotically Anti-de Sitter (AdS) space-time and how constraints on entanglement imply (at least to second order in perturbation theory around AdS) that this space-time must satisfy Einstein’s equations. Further quantum information-theoretic constraints suggest new results in classical gravity, including a family of positive energy theorems for gravitational subsystems.

• Travel

#### Air and Train

The foundation will arrange and pay for all air and train travel to the conference as well as reimburse local expenses. Please provide your travel specifications by clicking the registration link above.

#### Personal Car

For participants in Group A driving to Manhattan, The Roger Hotel offers valet parking. Please note there are no in-and-out privileges when using the hotel’s garage, therefore it is encouraged that participants walk or take public transportation to the Simons Foundation.
• Hotel

Participants who require accommodations are hosted by the foundation for a maximum of three nights at The Roger hotel. Any additional nights are at the attendee’s own expense.

The Roger New York
New York, NY 10016
(between 30th and 31st Streets)

• Contacts

#### Travel Assistance

Elise Volpe, Protravel
simons.foundation@protravelinc.com
516-465-1006

#### Registration, Hotel and General Meeting Assistance

Meghan Fazzi
Senior Executive Assistant, Simons Foundation
mfazzi@simonsfoundation.org
(212) 524-6080

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