**QuLAT Annual meeting 2022**

Annual Collaboration meeting. June 15-17 2022, Iowa City

**Schedule**

**Wednesday morning: **discrete hyperbolic spaces, quantum gravity (BU/Syracuse/UCSB).**Wednesday afternoon:** lattice bosons, bootstrap, digitized anharmonic oscillators, O(2) breaking (UCSB/MSU/Iowa)**Thursday morning:** Universal quantum computers: state preparation, Gross-Neveu, error mitigation, open systems (Maryland, Syracuse, Iowa, ...)**Thursday afternoon:** Rydberg arrays, Quera, gauge simulators and fragmentation ..... (Quera, BU, Iowa, ....)**Friday: **External speakers and discussions

**Upcoming Seminars**

Everyone at QuLat Collaboration are welcome to join the regular seminars. Please keep an eye on the website for the upcoming talks.

**Speaker: **Saurabh Kadam, U of Washington

**Time: **May 28th (Tues) at 3.30 pm CT.

**Title:**

**Abstract:**

### Previous Seminars

**Speaker:**Marc Illa, U of Washington**Time:**May 14, 3.30 pm CT**Title:**Quantum Simulations of the Schwinger Model using 100+ qubits**Abstract:**Quantum electrodynamics in 1+1 dimensions (the Schwinger model) exhibits a number of features similar to quantum chromodynamics in 3+1D, including confinement and a fermion condensate, making it the perfect sandbox during the NISQ era. In this talk, I will present new scalable algorithms that use the symmetries and hierarchy of length scales in the Schwinger model (and generally applicable to other confining theories) for simulating the real-time dynamics of hadrons on a quantum computer, and their realization on a 56-site lattice (112 qubits) using IBM’s quantum computers. Essential to the success of these simulations is the multiple error mitigation techniques used to recover the results from the noisy quantum machines, where circuits with up to 13,858 CNOT gates were executed.

**Speaker:**Rahul Sahay (Harvard)**Time:**Thursday 2/29 11:00ET.**Title:**Emergent Holographic Forces from Tensor Networks and Criticality

Rahul Sahay, Mikhail D. Lukin, Jordan Cotler

**Abstract: **The AdS/CFT correspondence stipulates a duality between conformal field theories and certain theories of quantum gravity in one higher spatial dimension. However, probing this conjecture on contemporary classical or quantum computers is challenging. We formulate an efficiently implementable multi-scale entanglement renormalization ansatz (MERA) model of AdS/CFT providing a mapping between a (1+1)-dimensional critical spin system and a (2+1)-dimensional bulk theory. Using a combination of numerics and analytics, we show that the bulk theory arising from this optimized tensor network furnishes excitations with attractive interactions. Remarkably, these excitations have one- and two-particle energies matching the predictions for matter coupled to AdS gravity at long distances, thus displaying key features of AdS physics. We show that these potentials arise as a direct consequence of entanglement renormalization and discuss how this approach can be used to efficiently simulate bulk dynamics using realistic quantum devices.

**Junior Seminar**

Junior seminar series is arranged in every 3 weeks during Fall and the Spring semester. The seminar is organized for the postdocs, graduate and undergraduate students of the collaboration with an intention to increase collaborative effort among researchers at different research institutes. We are always looking for new speakers. If you have a suggestion on speakers, contact Muhammad Asaduzzaman, at masaduzzamanATuiowa.edu.

**Upcoming seminar**

**0. Speaker: Raghav Govind Jha, Jefferson Lab.**

**Time: Apr 16 (Tuesday), 3.45 CT**

**Title: Approaches to universal quantum computing for spin (and gauge) models **

**Abstract:** I will discuss two different approaches to universal quantum computing, discrete

variable (DV) and continuous variable (CV) quantum computing. As an example of both approaches, we show their application to models such as O(3) sigma model and all-to-all SYK model.

**Recent Seminars**

**1. Speaker: ****Wanqiang Liu****, **graduate student, University of Chicago.

**Time: Jan 30, 2024: Tues @ 1pm CT**

**Title: Lattice gauge symmetry as quantum error correction codes**

In the quantum simulation of lattice gauge theories, gauge symmetry can be either fixed or encoded as a redundancy of the Hilbert space. While gauge-fixing reduces the number of qubits, keeping the gauge redundancy can provide space to mitigate and correct quantum errors by checking and restoring Gauss's law. In this talk, I will treat the gauge redundancy as approximate error correction codes, discuss the correctable errors for generic finite gauge groups and the quantum circuits to detect and correct them. Noise thresholds are obtained below which the gauge-redundant digitization combined with error correction has better fidelity than the gauge-fixed digitization.

2. **Speaker: Troy Sewell, University of Maryland**

**Time: Jan 16, 2024: @ 1pm CT**

**Title: Variational quantum simulation of the critical Ising model with symmetry averaging**

3

**. Speaker: Erik Gustafson, USRA, NASA**

**Time: Dec 5 ^{th} (Tues) @ 1pm CT**

**Title: Robust Finite-Temperature Many-Body Scarring on a Quantum Computer**

4. **Speaker: ****Bharath Sambasivam,** Syracuse University

**Time: 31**

^{st}Oct, 1pm -2pm**Title**: **Quantum simulation of open systems **

**Abstract**: Open quantum systems are ubiquitous in several areas of physics. They are at times well described or approximated by non-Hermitian effective Hamiltonians. In this talk, I will motivate such Hamiltonians using examples from high energy particle physics, discuss their interesting features like exceptional points, and present algorithms based on the Quantum Channels formalism that we developed. I will then show recent results implementing one of these algorithms on IBM quantum hardware for the 1D Ising chain with an imaginary longitudinal magnetic field. I will also comment on the resilience of the exceptional points of non-Hermitian Hamiltonians to hardware noise.

**Collaborations**

QuLat collaboration has developed strong connection to different research organizations and labs through collaboration. Here is an incomplete list of the major labs and computing resources that we are working with