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

 

Regular Seminar

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

Speaker: Rahul Sahay (Harvard)

Time: Thursday 2/29 11:00ET. 

Emergent Holographic Forces from Tensor Networks and Criticality

Rahul Sahay, Mikhail D. Lukin, Jordan Cotler

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
 
Abstract: Here we investigate the use of deep multiscale entanglement renormalization ansatz (DMERA) circuits as a variational ansatz. We use the exactly solvable one-dimensional critical transverse-field Ising model as a test bed. Numerically exact simulation of the quantum circuit ansatz can in this case be carried out to hundreds of qubits by exploiting efficient classical algorithms for simulating matchgate circuits. We find that, for this system, the DMERA strongly outperforms a standard quantum approximate optimization algorithm (QAOA)–style ansatz, and that a major source of systematic error in correlation functions approximated using the DMERA is the breaking of the translational and Kramers-Wannier symmetries of the transverse-field Ising model. We are able to reduce this error by up to four orders of magnitude by symmetry averaging, without incurring additional cost in qubits or circuit depth. We propose that this technique for mitigating systematic error could be applied to noisy intermediate-scale quantum (NISQ) simulations of physical systems with other symmetries.

3.  Speaker: Erik Gustafson, USRA, NASA

Time: Dec 5th (Tues) @ 1pm CT

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

Abstract:    Mechanisms for suppressing thermalization in disorder-free many-body systems, such as Hilbert space fragmentation and quantum many-body scars, have recently attracted much interest in foundations of quantum statistical physics and potential quantum information processing applications. However, their sensitivity to realistic effects such as finite temperature remains largely unexplored. Here, we have utilized IBM's Kolkata quantum processor to demonstrate an unexpected robustness of quantum many-body scars at finite temperatures when the system is prepared in a thermal Gibbs ensemble. We identify such robustness in the PXP model, which describes quantum many-body scars in experimental systems of Rydberg atom arrays and ultracold atoms in tilted Bose--Hubbard optical lattices. By contrast, other theoretical models which host exact quantum many-body scars are found to lack such robustness, and their scarring properties quickly decay with temperature. Our study sheds light on the important differences between scarred models in terms of their algebraic structures, which impacts their resilience to finite temperature.

 

4. Speaker: Bharath Sambasivam, Syracuse University

Time: 31st 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

QuEra

Lukin Lab

Linke Lab

Zeiher Lab

IBM Quantum Hub at NC State