DMFT-QE Symposium: April 20th

Name: DMFT-QE Symposium: April 20th
Start: 2026-04-20T09:30:00-04:00
End: 2026-04-20T11:00:00-04:00
Location: Virtual

Monday April 20, 2026
9:30 - 11:00 a.m.

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Virtual

Invitation Only

Talk 1:

The Ghost Gutzwiller Approximation and its connection to Dynamical Mean-Field Theory

Nicola Lanata, RIT

I will give a pedagogical introduction to the ghost Gutzwiller approximation (ghost-GA), a variational quantum-embedding framework that extends the Gutzwiller approximation by introducing auxiliary ghost orbitals and provides a systematic route toward higher accuracy. I will then discuss recent work proving that ghost-GA, which also admits a density-matrix-matching formulation known as ghost-DMET, becomes strictly equivalent to dynamical mean-field theory (DMFT) in the limit of infinitely many auxiliary bath modes. This result shows that the full local dynamical information of the Green’s function can be encoded in static variational parameters and yields a principled finite-temperature extension of ghost-GA. More broadly, it clarifies the relation between ghost-GA, ghost-DMET, and DMFT as complementary formulations of the same quantum-embedding structure, and opens a route to more efficient simulations of strongly correlated materials.

Talk 2:

Quantum Assisted Ghost Gutzwiller Ansatz

Fedor Šimkovic, IQM

The ghost Gutzwiller ansatz (gGut) embedding technique was shown to achieve comparable accuracy to the dynamical mean-field theory method for materials, but at much lower cost. Despite this, gGut is limited by the bottleneck of computing the density matrix of the embedding model, which must converge within a self-consistent loop. We develop a hybrid quantum-classical gGut technique that computes embedding-Hamiltonian ground states using the quantum-selected configuration interaction (QSCI) algorithm. We study SCI-based methods for density-of-states calculations in Anderson impurity models within gGut and find that the ground states become sparse in the CI basis as the number of ghost orbitals increases. We investigate QSCI with LUCJ states and circuit cutting on IQM quantum hardware for up to 11 ghost orbitals (24 qubits). We report converged gGut calculations that capture the metal-to-insulator transition in the Bethe-lattice Fermi-Hubbard model using quantum samples to build an SCI basis with as little as 1% of the CI basis.