# 2023 Simons Collaboration on Ultra Quantum Matter Annual Meeting

Date & Time

Organizers:
Michael Hermele, University of Colorado, Boulder
Ashvin Vishwanath, Harvard University

Speakers:
Leon Balents, Kavli Institute for Theoretical Physics
John McGreevy, UC San Diego
Dam Thanh Son, University of Chicago
Ashvin Vishwanath, Harvard University
Monika Aidelsburger, Ludwig-Maximilians-Universität München
Ana Maria Rey, University of Colorado Boulder / NIST
Shu-Heng Shao, Stony Brook University
Mike Zaletel, UC Berkeley

Past Meetings:
2020
2021
2022

Meeting Goals:
The two overarching goals of the Simons Collaboration on Ultra Quantum Matter (UQM) are to develop the theory of highly entangled quantum matter and to work towards physical realization, particularly in synthetic matter systems. The collaboration’s 2023 annual meeting will include a mix of condensed matter, high-energy, quantum information and atomic physicists and will survey progress in constructing and understanding exotic quantum field theories of fracton phases, as well as recent developments in the theory of compressible gapless phases and other forms of UQM.

In addition, we will describe progress and prospects in realizing various forms of UQM in cold atomic systems as well as moiré materials. The interplay of entanglement and measurements, the development of nonlocal probes, and how to steer these developments towards more robust realizations of highly entangled states will be discussed. Mirroring the convergence of different communities in recent exciting developments, the meeting will bring together a wide spectrum of theoretical physicists cutting across traditional boundaries, aiming to plant the seeds for further progress.

• Agenda

#### THURSDAY, JANUARY 19

 8:30 AM CHECK-IN & BREAKFAST 9:30 AM Ashvin Vishwanath | Ultra Quantum Matter 10:30 AM BREAK & POSTER SESSION 11:00 AM Shu-Heng Shao | Harmony of Symmetries 12:00 PM LUNCH & POSTER SESSION 1:00 PM Dam Thanh Son | Nonlinear Bosonization of Fermi Surfaces: The Method of Coadjoint Orbits 2:00 PM BREAK & POSTER SESSION 2:30 PM Ana Maria Rey | Quantum Engineering of Pair Production Process in Spin Models in Multi- Layers: From Two- Mode Squeezing to Topological Kitaev Models 3:30 PM BREAK & POSTER SESSION 4:00 PM Leon Balents | Strong Correlation Physics of Mott and Wigner Crystals in Two-Dimensional Non-Graphene Moiré Systems 5:00 PM DAY ONE CONCLUDES

#### FRIDAY, JANUARY 20

 8:30 AM CHECK-IN & BREAKFAST 9:30 AM John McGreevy | Entanglement Bootstrap in Various Dimensions 10:30 AM BREAK & POSTER SESSION 11:00 AM Monika Aidelsburger | Quantum Simulation with Ultracold Atoms – From Hubbard Models to Gauge Theories 12:00 PM LUNCH & POSTER SESSION 1:00 PM Mike Zaletel | Local Detection of Symmetry Breaking in Magic Angle Graphene 2:00 PM MEETING CONCLUDES
• Abstracts

Monika Aidelsburger
Fakultät für Physik, Ludwig-Maximilians-Universität München &
Munich Center for Quantum Science and Technology (MCQST)

Quantum Simulation with Ultracold Atoms – From Hubbard Models to Gauge Theories

Well-controlled synthetic quantum systems, such as ultracold atoms in optical lattices, offer intriguing possibilities to study complex many-body problems in regimes that are beyond reach using state-of-the-art classical computations. The basic idea is to construct and use a well-controlled quantum many-body system in order to study its in- and out-of-equilibrium properties and potentially use it to develop more efficient tailored numerical methods that can then be applied to other systems that are not directly accessible with the simulator.

An important future quest concerns the development of novel experimental techniques that allow us to expand the range of models that can be accessed. Monika Aidelsburger will demonstrate this using the example of topological lattice models, which in general do not naturally appear in cold-atom experiments. Aidelsburger will show how the technique of periodic driving, also known as Floquet engineering, facilitates their realization and show how charge-neutral atoms in lattices can mimic the behavior of charged particles in the presence of an external magnetic field.

A key ingredient for quantum simulation is the degree of control one has over the individual particles and the microscopic parameters of the model. We have recently succeeded to not only use the technique of periodic driving to emulate physical systems that we know exist in nature, but to take this idea one step further and realize completely new topological regimes that do not have any static analog. Moreover, we are currently developing a novel hybrid optical lattice platform, where tightly focused optical tweezers are used to locally control the motion of the atoms in the lattice, paving the way towards quantum simulation of simplified lattice gauge theories, which play a fundamental role in a variety of research areas including high-energy physics and topological quantum computation.

Leon Balents
Kavli Institute for Theoretical Physics

Strong Correlation Physics of Mott and Wigner Crystals in Two-Dimensional Non-Graphene Moiré Systems

Moiré patterns provide realizations of interacting electron physics on a lattice in two-dimensional transition metal dichalcogenide structures. Leon Balents will discuss prospects to observe strong correlation physics and ultra-quantum phases of matter in this framework and will focus on phenomena beyond local mean field theories like Hartree–Fock, which are the de facto standard.

John McGreevy
University of California, San Diego

Entanglement Bootstrap in Various Dimensions

The Entanglement Bootstrap is a program to understand the universal properties of quantum matter starting from a representative density matrix on a ball. Much (perhaps all) of the structure of topological quantum field theory can be extracted starting from a state satisfying two axioms that implement the area law for entanglement. In this talk, based on work with Bowen Shi, Jin-Long Huang and Xiang Li, John McGreevy will describe how to use these methods to construct groundstates on a large class of manifolds. One important application of this construction is to demonstrate the property of remote detectability of topological excitations, an assumption of topological field theory. Another is to construct generalized symmetry algebras. These methods are also useful for understanding symmetry-enriched topological phases.

Ana Maria Rey
University of Colorado Boulder / NIST

Quantum Engineering of Pair Production Process in Spin Models in Multi-Layers: From Two-Mode Squeezing to Topological Kitaev Models

Understanding and controlling the growth and propagation of quantum correlations and entanglement is an emerging frontier in non-equilibrium many-body physics, and a crucial key step for unlocking the full advantage of quantum systems. In this talk, Ana Maria Rey will discuss how in multi-layer spin systems, currently accessible in a broad range of quantum platforms, such as arrays of neutral atoms, Rydberg atoms, magnetic atoms and polar molecules, spin interactions can be utilized to realize in a controllable manner a variety of correlated pair-production processes. In particular, Rey will describe how in bi-layer systems, the capability to select individual layers and prepare targeted initial states, can enable the generation of iconic two-mode squeezing models that feature exponential growth of entanglement and are relevant in many contexts ranging from the foundations of quantum mechanics, to parametric amplification in quantum optics, to the Schwinger effect in high-energy physics and Unruh thermal radiation in general relativity. In multi-layers Rey will show it is possible to engineer a chiral bosonic Kitaev model featuring chiral propagation of correlations. Overall in this talk, Rey will report how current single-layer addressing capabilities can allow shaping and controlling the temporal growth and spatial propagation of quantum correlations in a variety of spin systems relevant for quantum simulation.

Shu-Heng Shao
Stony Brook University

Harmony of Symmetries

We will discuss lattice and continuum models ranging from those related to fractons, to compact Lifshitz theory, and to tensor gauge theory. These models have exotic global symmetries, which are the underlying reasons why they defy a standard continuum limit. We also discuss the anomalies of these global symmetries and their realizations on the lattice. Finally, we present a class of lattice models that can be defined on general graphs, which include a robust stabilizer code with lineon excitations.

Dam Thanh Son
University of Chicago

Nonlinear Bosonization of Fermi Surfaces: The Method of Coadjoint Orbits

Dam Thanh Son and collaborators have developed a new method for bosonizing the Fermi surface based on the formalism of the coadjoint orbits. This allows one to parametrize the Fermi surface by a bosonic field that depends on the spacetime coordinates and on the position on the Fermi surface. The Wess–Zumino–Witten term in the effective action, governing the adiabatic phase acquired when the Fermi surface changes its shape, is given by the Kirillov–Kostant–Souriau symplectic form on the coadjoint orbit. Together with a Hamiltonian, the resulting local effective field theory captures both linear and nonlinear effects in Landau’s Fermi liquid theory. Extensions of the theory that incorporate spin degrees of freedom and the BCS order parameter are discussed.

Ashvin Vishwanath
Harvard University

Ultra Quantum Matter

The investigation of new states of matter made possible by long-range quantum entanglement represents a fundamental frontier of science that is seeing rapid progress. Ashvin Vishwanath will describe our collaboration’s efforts to classify such ultra quantum matter, to pinpoint their patterns of entanglement and physical properties and to realize and identify them in the laboratory. Promising future directions in the study of both gapped states, such as topological orders and fractons, as well as gapless states including novel metallic phases and the realization of such states particularly in synthetic quantum systems, will be outlined.

Mike Zaletel
University of California, Berkeley

Local Detection of Symmetry Breaking in Magic Angle Graphene

As the electron density is tuned through the flat bands of magic-angle graphene, numerous experiments indicate there is a “cascade” of symmetry-breaking transitions that reduce the degeneracy of the Fermi surface. Due to the combination of spin, valley and sub lattice degrees of freedom, there are many possible patterns of symmetry breaking, each with their own implications for superconductivity. Despite myriad theoretical predictions, to date there is no experimental detection of the order parameter. Mike Zaletel will present an analysis of recent local probe experiments which provide definitive detection of the order parameter of the $$\nu = \pm 2$$ insulator and its behavior upon doping.

• Participation & Funding

Participation in the meeting falls into the following four categories. An individual’s participation category is communicated via their letter of invitation.

Group A – PIs and Speakers
The foundation will arrange and pay for all air and train travel to the conference as well as hotel accommodations and reimbursement of local expenses.

Group B – Out-of-town Participants
The foundation will arrange and pay for all air and train travel to the conference as well as hotel accommodations and reimbursement of local expenses.

Group C – Local Participants
Individuals in Group C will not receive financial support, but are encouraged to enjoy all conference-hosted meals.

Group D – Remote Participants
Individuals in Group D will participate in the meeting remotely. Please register at the link above and a remote participation link will be sent to you approximately two weeks prior to the meeting.

• Travel & Hotel

Air and Train
The foundation will arrange and pay for all air and train travel to the conference for those in Groups A and B. 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.

Personal Car
For participants in Groups A & B driving to Manhattan, The James NoMad 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 in Groups A & B who require accommodations are hosted by the foundation for a maximum of three nights at The James NoMad Hotel. Any additional nights are at the attendee’s own expense. To arrange accommodations, please register at the link above.

22 E 29th St
New York, NY 10016
(between 28th and 29th Streets)

• COVID-19 Policy

ALL in-person meeting attendees must be vaccinated against the COVID-19 and wear a mask when not eating or drinking.

• Reimbursement

Individuals in Groups A & B will be reimbursed for meals not hosted by the Simons Foundation as well as local expenses, including ground transportation. Additional information in this regard will be emailed on the final day of the meeting.

• Contacts

Registration and Travel Assistance

Ovation Travel Group
sfnevents@ovationtravel.com
(917) 408-8384 (24-Hours)
www.ovationtravel.com

Meeting Questions and Assistance
Meghan Fazzi
Manager, Events and Administration, MPS, Simons Foundation
mfazzi@simonsfoundation.org
(212) 524-6080

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