During 2023–24, the CMSA will host a seminar on Quantum Matter in Mathematics and Physics, organized by Juven Wang. This seminar will take place on Fridays at 10:00–11:30 am (Eastern Time). To learn how to attend this seminar, please fill out this form. The schedule will be updated as talks are confirmed. Videos are available at the Quantum Matter in Mathematics and Physics Youtube Playlist

CMSA COVID-19 Policies



  • December 15, 2023 10:00 AM
Speaker: Aleksey Cherman
Title: Exact lattice chiral symmetry in 2d gauge theory
Venue: virtual

Quantum Matter Seminar Speaker: Aleksey Cherman (UMN) Title: Exact lattice chiral symmetry in 2d gauge theory Abstract: Preserving the symmetries of massless fermions is a well-known challenge in lattice field theory.  I’ll discuss symmetry-preserving lattice regularizations of 2d QED with one and two flavors of Dirac fermions, as well as the `3450′ chiral gauge theory. The construction leverages bosonization and recently-proposed modifications of Villain-type lattice actions. The internal global symmetries act just as locally on the lattice as they do in the continuum, the anomalies are reproduced at finite lattice spacing, and in each case we’ve found a sign-problem-free dual formulation.

  • December 08, 2023 02:30 PM
Speaker: Da-Chuan Lu
Title: Fermi surface symmetric mass generation and its application in nickelate superconductor
Venue: CMSA Room G10

Joint Quantum Matter in Mathematics and Physics & Topological Quantum Matter Seminar Speaker: Da-Chuan Lu (UCSD) Title: Fermi surface symmetric mass generation and its application in nickelate superconductor Abstract: Symmetric mass generation (SMG) is a novel interaction-driven mechanism that generates fermion mass without breaking symmetry, unlike the standard Anderson-Higgs mechanism. SMG can occur in the fermion system without quantum anomalies. In this talk, I will focus on the SMG for the systems with finite fermion density, i.e., the Fermi surface. I will discuss the Fermi surface anomaly and Fermi surface SMG. Lastly, I will talk about its application in the newly found nickelate superconductors, where the superconductivity emerges without a nearby spontaneous symmetry-breaking phase.

  • November 22, 2023 04:00 PM
Speaker: Guilherme Delfino Silva
Title: Modulated Gauge Theories and Fracton Behavior in 2D
Venue: CMSA Room G10

Quantum Matter Seminar Speaker: Guilherme Delfino Silva (Boston University) Title: Modulated Gauge Theories and Fracton Behavior in 2D Abstract: In this talk we investigate deconfined phases of two-dimensional ZN lattice gauge theories associated to spatially modulated symmetries. In order to study the low-energy physics of such modulated gauge theories we propose and explore exactly solvable gapped Hamiltonians, which allow us to fully characterize their low-energy properties at zero temperature. We provide explicit examples and discuss how non-polynomial symmetries, as exponential symmetries, are powerful enough to fully constrain the mobility of isolated excitations.

  • November 07, 2023 04:30 PM
Speaker: Cameron Krulewski (MIT) and Leon Liu (Harvard)
Title:  A Long Exact Sequence in Symmetry Breaking
Venue: CMSA Room G10

Quantum Matter Seminar Speaker: Cameron Krulewski (MIT) and Leon Liu (Harvard) Title: A Long Exact Sequence in Symmetry Breaking Abstract: We study defects in symmetry breaking phases, such as domain walls, vortices, and hedgehogs. In particular, we focus on the localized gapless excitations that sometimes occur at the cores of these objects. These are topologically protected by an ’t Hooft anomaly. We classify different symmetry breaking phases in terms of the anomalies of these defects and relate them to the anomaly of the broken symmetry by an anomaly-matching formula. We also derive the obstruction to the existence of a symmetry breaking phase with a local defect. We obtain these results using a long exact sequence of groups of invertible field theories, which we call the “symmetry…

  • November 03, 2023 10:00 AM
Speaker: Meng Cheng
Title: Symmetry and many-body topology in mixed states
Venue: CMSA Room G10

Quantum Matter Seminar Speaker: Meng Cheng (Yale) Title: Symmetry and many-body topology in mixed states Abstract: It is by now well-understood that gapped ground states of local Hamiltonians can be classified topologically, and the nontrivial states exhibit many interesting topological phenomena. In this talk I’ll discuss recent developments in generalizing the topological classification to mixed states. Global symmetry plays a key role in understanding phases in pure states. For mixed states, certain “weak” symmetries may hold “on average” for the entire ensemble, in contrast to “strong” symmetries respected by each state in the ensemble. I will show that the interplay between these two kinds of symmetries lead to a rich landscape of symmetry-protected mixed states, and can also be used…

  • November 02, 2023 04:30 PM
Speaker: Liujun Zou
Title: Landscape of quantum phases in quantum materials
Venue: CMSA Room G10

Joint Quantum Matter in Mathematics and Physics and Topological Quantum Matter Seminar Speaker: Liujun Zou (Perimeter Institute) Title: Landscape of quantum phases in quantum materials Abstract: A central goal of condensed matter physics is to understand which quantum phases of matter can emerge in a quantum material. For this purpose, one should be able to not only describe the quantum phases using some effective field theories, but also capture the important microscopic information of the material via mathematical formulation. In this talk, I will present a framework to classify quantum phases in quantum materials, where the microscopic information of a material is encoded in its quantum anomaly. I will talk about the application of this framework to classify various…

  • October 20, 2023 10:00 AM
Speaker: Cheryne Jonay
Title: A Physical Theory of Two-stage Thermalization
Venue: CMSA Room G10

Quantum Matter Seminar Speaker: Cheryne Jonay (Stanford) Title: A Physical Theory of Two-stage Thermalization Abstract: One indication of thermalization time is subsystem entanglement reaching thermal values. Recent studies on local quantum circuits reveal two exponential stages with decay rates $r_1$ and $r_2$ of the purity before and after thermalization. We provide an entanglement membrane theory interpretation, with $r_1$ corresponding to the domain wall free energy. Circuit geometry can lead to $r_1 < r_2$, producing a “phantom eigenvalue”. Competition between the domain wall and magnon leads to $r_2 < r_1$ when the magnon prevails. However, when the domain wall wins, this mechanism provides a practical approach for measuring entanglement growth through local correlation functions.

  • October 11, 2023 04:30 PM
Speaker: Seth Koren
Title: Non-invertible symmetries, leptons, quarks, and why multiple generations
Venue: CMSA Room G10

Quantum Matter Seminar Speaker: Seth Koren (Notre Dame) Title: Non-invertible symmetries, leptons, quarks, and why multiple generations Abstract: Generalized global symmetries are present in theories of particle physics, and understanding their structure can give insight into these theories and UV completions thereof.  After discussing the generalized symmetries of the Standard Model, we will go Beyond and show that the identification of a non-invertible symmetry of Z’ models of L_µ – L_τ reveals the existence of non-Abelian horizontal gauge theories which naturally produce exponentially small Dirac neutrino masses. Next we will uncover a subtler non-invertible symmetry in horizontal gauge theories of the quark sector which will lead us to a massless down-type quarks solution to strong CP in color-flavor unification. Intriguingly,…

  • October 06, 2023 10:00 AM
Speaker: Nat Tantivasadakarn
Title: From wave-function collapse and Galois solvability to the realization of non-Abelian topological order on a quantum device
Venue: CMSA Room G10

Quantum Matter Seminar Speaker: Nat Tantivasadakarn (Caltech) Title: From wave-function collapse and Galois solvability to the realization of non-Abelian topological order on a quantum device Abstract: I will review our recent set of theoretical works on efficiently preparing long range quantum entanglement with adaptive quantum circuits: the combination of measurements with unitary gates whose choice can depend on previous measurement outcomes. I will show that this additional ingredient can be leveraged to prepare the long sought-after non-Abelian topological phases with a circuit depth that is independent of system size. Using this framework, we uncover a complexity hierarchy of long-range entangled states based on the minimal number of measurement layers required to create the state. Moreover, we find that…

  • September 28, 2023 04:30 PM
Speaker: Cenke Xu
Title: Quantum field theory approach to quantum information
Venue: CMSA Room G10

Quantum Matter Seminar Speaker: Cenke Xu (UCSB) Title: Quantum field theory approach to quantum information Abstract: We apply the formalism of quantum field theory and Euclidean space-time path integral to investigate a class of quantum information problems. In particular, we investigate quantum many-body systems under weak-measurement and decoherence. The Euclidean space-time path integral allows us to map this problem to a quantum field theory with (temporal) boundary or defects. We therefore investigate two types of quantum many-body systems with nontrivial boundary physics: quantum critical points, and states with nontrivial topology, such as Chern insulator and symmetry protected topological states. For example, we demonstrate that a Wilson-Fisher quantum critical point can be driven into an “extraordinary-log” phase after weak-measurement….

  • September 22, 2023 10:00 AM
Speaker: Margarita Davydova
Title: Floquet codes, automorphisms, and quantum computation
Venue: CMSA Room G10

Quantum Matter Seminar Speaker: Margarita Davydova (MIT) Title: Floquet codes, automorphisms, and quantum computation Abstract: In this talk, I will introduce a new kind of measurement-based quantum computation inspired by Floquet codes. In this model, the quantum logical gates are implemented by short sequences of low-weight measurements which simultaneously encode logical information and enable error correction.  We introduce a new class of quantum error-correcting codes generalizing Floquet codes that achieve this, which we call dynamic automorphism (DA) codes. As in Floquet codes, the instantaneous codespace of a DA code at any fixed point in time is that of a topological code. In this case, the quantum computation can be viewed as a sequence of time-like domain walls implementing automorphisms of the topological order,…

  • September 13, 2023 04:30 PM
Speaker: Clay Córdova
Title: Anomalies of Non-Invertible Symmetries
Venue: CMSA Room G10

Quantum Matter Seminar Speaker: Clay Córdova (U Chicago) Title: Anomalies of Non-Invertible Symmetries

  • September 08, 2023 10:00 AM
Speaker: Xiao-Gang Wen
Title: A 6-year journey: from gravitational anomaly to a unified theory of generalized symmetry
Venue: CMSA Room G10

Quantum Matter Seminar Speaker: Xiao-Gang Wen (MIT) Title: A 6-year journey: from gravitational anomaly to a unified theory of generalized symmetry Abstract: Emergent symmetry can be generalized symmetry beyond (higher) group description and/or can be anomalous. I will describe a unified theory for generalized symmetry based on symmetry/topological-order correspondence. I will also discuss some applications of emergent generalized symmetry.

  • August 24, 2023 10:00 AM
Speaker: John Baez
Title: Two of my favorite numbers: 8 and 24
Venue: virtual

Quantum Matter Seminar Speaker: John Baez (University of California, Riverside) Title: Two of my favorite numbers: 8 and 24 Abstract: The numbers 8 and 24 play special roles in mathematics. The number 8 is special because of Bott periodicity, the octonions and the E8 lattice, while 24 is special for many reasons, including the binary tetrahedral group, the 3rd stable homotopy group of spheres, and the Leech lattice. The number 8 does for superstring theory what the number 24 does for bosonic string theory. In this talk, which is intended to be entertaining, I will overview these matters and also some connections between the numbers 8 and 24.

  • June 30, 2023 10:00 AM
Speaker: Marieke Van Beest
Title: Monopoles, Scattering, and Generalized Symmetries
Venue: virtual

Quantum Matter Seminar Speaker: Marieke Van Beest (SCGP) Title: Monopoles, Scattering, and Generalized Symmetries Abstract: In this talk, we will discuss the problem of electrically charged, massless fermions scattering off magnetic monopoles. The interpretation of the outgoing states has long been a puzzle, as they can carry fractional quantum numbers. We argue that such outgoing particles live in the twisted sector of a topological co-dimension 1 surface, which ends topologically on the monopole. This symmetry defect is often non-invertible, and as such the outgoing radiation not only carries unconventional flavor quantum numbers, but is often trailed by a topological field theory, which is a new prediction.

  • June 26, 2023 10:00 AM
Speaker: Philip Boyle Smith
Title: Chiral fermionic CFTs of central charge ≤ 16
Venue: virtual

Quantum Matter Seminar Title: Chiral fermionic CFTs of central charge ≤ 16 Abstract: We classified all chiral fermionic CFTs of central charge ≤ 16 using Kac’s theorem and bosonization/fermionization. This talk will discuss the derivation of this result, its application to the classification of non-supersymmetric heterotic string theories, and along the way we’ll address some oft-overlooked subtleties of bosonization from the point of view of anomalies and topological phases.

  • June 13, 2023 10:00 AM
Speaker: Brandon C. Rayhaun
Title: Small Bosonic CFTs, Chiral Fermionization, and Symmetry/Subalgebra Duality
Venue: virtual

Quantum Matter Seminar Speaker: Brandon C. Rayhaun (C. N. Yang ITP, Stony Brook University) Title: Small Bosonic CFTs, Chiral Fermionization, and Symmetry/Subalgebra Duality Abstract: Conformal field theories in (1+1)D are key actors in many dramas of physics and mathematics. Their classification has therefore been an important and long-standing problem. In this talk, I will explain the main ideas behind the classification of (most) “small” bosonic CFTs. Here, I use the adjective “small” informally to refer to theories with low central charge (less than 24) and few primary operators (less than 5). Time and attention permitting, I will highlight two applications of this result. First, I will describe how it can be used in tandem with bosonization and fermionization techniques…

  • June 09, 2023 10:00 AM
Speaker: Gerald Höhn (Kansas State University) & Sven Möller (University of Hamburg)
Title: Classification of Self-Dual Vertex Operator Superalgebras of Central Charge at Most 24
Venue: virtual

Quantum Matter Seminar Speakers: Gerald Höhn (Kansas State University) & Sven Möller (University of Hamburg) Title: Classification of Self-Dual Vertex Operator Superalgebras of Central Charge at Most 24 Abstract: We discuss the classfication of self-dual vertex operator superalgebras (SVOAs) of central charge 24, or in physics parlance the purely chiral 2-dimensional fermionic conformal field theories with just one primary field. There are exactly 969 such SVOAs under suitable regularity assumptions and the assumption that the shorter moonshine module VB^# is the unique self-dual SVOA of central charge 23.5 whose weight-1/2 and weight-1 spaces vanish. We construct and classify the self-dual SVOAs by determining the 2-neighbourhood graph of the self-dual (purely bosonic) VOAs of central charge 24 and also…

  • May 12, 2023 10:00 AM
Speaker: Carolyn Zhang
Title: Anomalies of (1+1)D categorical symmetries
Venue: virtual

Quantum Matter Seminar Speaker: Carolyn Zhang (U Chicago) Title: Anomalies of (1+1)D categorical symmetries Abstract: We present a general approach for detecting when a fusion category symmetry is anomalous, based on the existence of a special kind of Lagrangian algebra of the corresponding Drinfeld center. The Drinfeld center of a fusion category $A$ describes a $(2+1)D$ topological order whose gapped boundaries enumerate all $(1+1)D$ gapped phases with the fusion category symmetry, which may be spontaneously broken. There always exists a gapped boundary, given by the \emph{electric} Lagrangian algebra, that describes a phase with $A$ fully spontaneously broken. The symmetry defects of this boundary can be identified with the objects in $A$. We observe that if there exists a…

  • May 05, 2023 10:00 AM
Speaker: Sona Najafi
Title: Detecting central charge in a superconducting quantum processor
Venue: Hybrid- G10

Quantum Matter Seminar Speaker: Sona Najafi (IBM Quantum) Title: Detecting central charge in a superconducting quantum processor Abstract: Physical systems at the continuous phase transition point exhibit conformal symmetry rendering local scaling invariance. In two dimensions, the conformal group possesses infinite generators described by Virasoro algebra with an essential parameter known as a central charge. While the central charge manifests itself in a variety of quantities, its detection in experimental setup remains elusive. In this work, we utilize Shannon-Renyi entropy on a local basis of a one-dimensional quantum spin chain at a critical point. We first use a simulated variational quantum eigen solver to prepare the ground state of the critical transfer field Ising model and XXZ model with…