Activities

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:

Towards preparation of scattering wave packets of hadrons on a quantum computer

Abstract:

Hamiltonian simulation of lattice gauge theories (LGTs) is a non-perturbative method of numerically solving gauge theories that offers novel avenues for studying scattering processes in gauge theories. With the advent of quantum computers, Hamiltonian simulation of LGTs has become a reality. Simulating scattering on quantum computers requires the preparation of initial scattering states in the interacting theory on the quantum hardware. Current state preparation methods involve bridging the scattering states in the free theory to the ones in the interacting theory adiabatically. Such quantum algorithms have limitations when applied to LGTs, and they tend to be computational resource intensive, rendering their implementation a challenge on the noisy intermediate-scale quantum (NISQ) era devices. In this work, we propose a wave packet state preparation algorithm for a 1+1D Z2 LGT coupled to dynamical matter. We show how this algorithm circumvents the adiabatic process by building and implementing the wave packet creation operators directly in the interacting theory using an optimized ansatz consisting of hadronic degrees of freedom in the confined Z2 LGT. Moreover, we numerically confirm the validity of this ansatz for a U(1) LGT in 1+1D. Finally, we demonstrate the viability of our algorithm for NISQ devices by comparing the classical simulation with the results obtained using the Quantinuum H1-1 quantum computer upon a simple symmetry-based noise mitigation technique.

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

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 5^th (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: 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

IBM Quantum Hub at NC State