TY  - JOUR
AU  - Bazavov, Alexei
AU  - Henke, Brandon
AU  - Hostetler, Leon
AU  - Lee, Dean
AU  - Lin, Huey-Wen
AU  - Pederiva, Giovanni
AU  - Shindler, Andrea
TI  - Efficient state preparation for the Schwinger model with a theta term
JO  - Physical review / D
VL  - 111
IS  - 7
SN  - 2470-0010
CY  - Ridge, NY
PB  - American Physical Society
M1  - FZJ-2025-05297
SP  - 074515
PY  - 2025
AB  - We present a comparison of different quantum state preparation algorithms and their overall efficiency for the Schwinger model with a theta term. While adiabatic state preparation is proved to be effective, in practice it leads to large cnot gate counts to prepare the ground state. The quantum approximate optimization algorithm (QAOA) provides excellent results while keeping the cnot counts small by design, at the cost of an expensive classical minimization process. We introduce a “blocked” modification of the Schwinger Hamiltonian to be used in the QAOA that further decreases the length of the algorithms as the size of the problem is increased. The rodeo algorithm (RA) provides a powerful tool to efficiently prepare any eigenstate of the Hamiltonian, as long as its overlap with the initial guess is large enough. We obtain the best results when combining the blocked QAOA ansatz and the RA, as this provides an excellent initial state with a relatively short algorithm without the need to perform any classical steps for large problem sizes.
LB  - PUB:(DE-HGF)16
DO  - DOI:10.1103/PhysRevD.111.074515
UR  - https://juser.fz-juelich.de/record/1049489
ER  -