Workshop on the sign problem in QCD and beyond

Session

Tuesday morning

21 Jan 2025, 08:30

Lecture Hall 099 (ExWi Building) (University of Bern)

22. Complex instanton gas approximation for the Hubbard model away of half-filling

Maksim Ulybyshev (University of Wuerzburg)

21/01/2025, 08:30

talk

We present recent advancements towards the alleviation of the sign problem for the Hubbard model away of half filling. We couple the thimble decomposition approach with certain approximations, which allow us to predict the structure of the thimble decomposition in advance, before actual Quantum Monte Carlo simulations.

First, we show that the saddle points for the Hubbard model with...

20. Convex methods for sign problems

Scott Lawrence (Los Alamos National Laboratory)

21/01/2025, 09:15

talk

Quantum mechanical theories have an underlying convex geometry defined by the fact that the Hilbert-space norm is positive definite. Positivity is a surprisingly strong constraint, which when combined with other information (such as lattice data, Schwinger-Dyson relations, or equations of motion), allows one to establish qualitatively tight bounds on the behavior of many quantum systems,...

12. Phase Diagram of the Schwinger Model by Adiabatic Preparation of States on a Quantum Simulator

Dr Oleg Kaikov (Université Paris-Saclay, CEA-List)

21/01/2025, 10:45

talk

We demonstrate a method to study the phase diagram of a quantum system on quantum devices via adiabatic preparation of states. The method is a direct application of the adiabatic theorem due to M. Born and V. Fock, Z. Phys. 51, 165 (1928). The key idea of the method is to individually evolve the ground state and the first-excited state using a Hamiltonian whose parameters are time-dependent....

9. BBGKY hierarchy for zero noise extrapolation in quantum error mitigation

Theo Saporiti (Université Paris-Saclay)

21/01/2025, 11:30

talk

The phase diagram of QCD at finite densities remains numerically inaccessible by classical computations. Quantum computers, with their potential for exponential speedup, could overcome this challenge. However, their current physical implementations are affected by quantum noise. In this contribution, I will introduce a novel quantum error mitigation technique based on a BBGKY-like hierarchy,...