- Organized by
Patrick Hayden, Ph.D.Stanford University
Matthew Headrick, Ph.D.Brandeis University
This is the second annual meeting of the Simons Collaboration on It from Qubit.
Thursday, December 7
8:00 AM Check-in & breakfast 9:00 AM Patrick Hayden | Approximate Quantum Error Correction Revisited 10:00 AM Posters | New IFQ Fellows 11:30 AM Brian Swingle | Tensor Networks and Early Quantum Devices 12:30 PM Lunch 2:00 PM Daniel Harlow | Lorentzian vs. Euclidean Quantum Gravity in 1+1 Dimensions 3:00 PM Break 3:30 PM John Preskill | Quantum Computing in the NISQ Era and Beyond 4:30 PM Day one concludes
Friday, December 8
8:00 AM Check-in & breakfast 9:00 AM Alexei Kitaev | Efficient Decoding for the Hayden-Preskill Protocol 10:00 AM Posters | General Session 11:30 AM Scott Aaronson | An Armory of Assumptions 12:30 PM Lunch 1:30 PM Juan Maldacena | How to Make a Wormhole 2:30 PM Meeting concludes
Approximate Quantum Error Correction Revisited
Patrick Hayden, Stanford University
The theory of quantum error correction has been firmly established as a key feature of the AdS/CFT correspondence. Mapping observables from the quantum gravitational bulk theory to the boundary conformal field theory is mathematically a problem of decoding quantum error correcting codes. This insight has led to new formulas for the mapping in cases where it wasn’t understood how to accomplish it previously, as well as resolved conceptual puzzles like how entropy, a nonlinear function of the state, can be identified with area, an observable. Hayden will describe a new theory of approximate quantum error correction appropriate for mapping observables behind a black hole horizon to the boundary. That theory is full of new surprises from the quantum information point of view, including way to squeeze two qubits into one asymptotically.
Tensor Networks and Early Quantum Devices
Brian Swingle, University of Maryland
It is interesting to ask how “it from qubit” differs from “it from bit”, for example, from the point of view of computational hardness. Swingle will present two tensor network results, one in equilibrium and one out of equilibrium, that bear on the question of classical versus quantum computational hardness in physics. He will then discuss a result with Isaac Kim showing that certain renormalization group inspired tensor networks can be efficiently contracted on a small quantum device even in the presence of noise. Finally, Swingle will discuss work with Shenglong Xu showing how quantum scrambling physics can be computed using classical tensor network methods.
Lorentzian vs. Euclidean Quantum Gravity in 1+1 Dimensions
Daniel Harlow, Massachusetts Institute of Technology
Daniel Harlow will describe the canonical quantization of Jackiw-Teitelboim gravity in 1+1 dimensions, taking care to extract all physical degrees of freedom. He will then use the resulting quantum gravity theory to re-interpret some existing Euclidean results in a novel way. There will be nary a Schwarzian in sight.
Quantum Computing in the NISQ Era and Beyond
John Preskill, California Institute of Technology
Noisy Intermediate-Scale Quantum (NISQ) technology will be available in the near future. Quantum computers with 50-100 qubits may be able to perform tasks which surpass the capabilities of today’s classical digital computers, but noise in quantum gates will limit the size of quantum circuits that can be executed reliably. NISQ devices will be useful tools for exploring many-body quantum physics, and may have other useful applications, but the 100-qubit quantum computer will not change the world right away — we should regard it as a significant step toward the more powerful quantum technologies of the future. Quantum technologists should continue to strive for more accurate quantum gates and, eventually, fully fault-tolerant quantum computing.
Efficient Decoding for the Hayden-Preskill Protocol
Alexei Kitaev, California Institute of Technology
We present two procedures for reconstructing a quantum state from the Hawking radiation in the Hayden-Preskill thought experiment. We work in an idealized setting and represent the black hole and its entangled partner by n EPR pairs. The first procedure teleports the state thrown into the black hole to an outside observer by post-selecting on the condition that a sufficient number of EPR pairs remain undisturbed. The probability of this favorable event scales as 1/dA², where dA is the Hilbert space dimension for the input state. The second procedure is deterministic and combines the previous idea with Grover’s search. The decoding complexity is O(dA C) where C is the size of the quantum circuit implementing the unitary evolution operator U of the black hole. (Based on joint work with Beni Yoshida.)
An Armory of Assumptions
Scott Aaronson, University of Texas, Austin
Scott Aaronson will provide an overview of assumptions about computational hardness and what kinds of assumptions are necessary and sufficient to derive various conclusions of interest for quantum gravity.
Aaronson will focus on the relationships among the following:
- “Traditional” hardness assumptions (like PSPACE not in PP/poly, or the existence of one-way functions)
- Assumptions about the hardness of preparing certain states (like the end result of applying a CFT Hamiltonian for exponential time)
- Assumptions about the hardness of applying certain unitary transformations (like that needed to decode the Hawking radiation in the firewall problem)
Aaronson will also discuss the “Unitary Synthesis Problem,” a problem posed by Greg Kuperberg and Aaronson a decade ago that asks whether there’s any hope to justify assumptions of type (3) without needing to justify (1) or (2). Aaronson will also discuss connections to other topics, including the security of quantum money schemes. The goal of this talk is to help It from Qubit participants who might need to deploy complexity assumptions in their own work.
How to Make a Wormhole
Juan Maldacena, Institute for Advanced Study
Juan Maldacena will review aspects of wormholes, thermofield double states and traversable wormholes in nearly AdS₂ spacetimes. He will then discuss a way to produce a state close to the thermofield double state in the SYK model.
Air and Train
- Group A
The foundation will arrange and pay for all air and train travel to the conference for those in Group A. Please provide your travel specifications by clicking the registration link above. If you are unsure of your group, please refer to your invitation sent via email.
- Group B
Individuals in Group B will not receive travel or hotel support. Please register at the link above so we can capture your dietary requirements. If you are unsure of your group, please refer to your invitation sent via email.
- 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.
- Group A
Participants in Group A 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
131 Madison Avenue
New York, NY 10016
(between 30th and 31st Streets)
To arrange accommodations, please register at the link above.
For driving directions to The Roger, please click here.