Partition-function estimation: Quantum and quantum-inspired algorithms
Andrew Jackson, Theodoros Kapourniotis, Animesh Datta · Physical Review A · 2023
We present two algorithms, one quantum and one classical, for estimating partition functions of quantum spin Hamiltonians. The first is a DQC1 (deterministic quantum computation with one clean qubit) algorithm. The second, for real temperatures, achieves performance comparable to a state-of-the-art DQC1 algorithm [A. N. Chowdhury, R. D. Somma, and Y. Suba\ifmmode \mbox{\c{s}}\else \c{s}\fi{}i, Phys. Rev. A 103, 032422 (2021)]. Both our algorithms take as input the Hamiltonian decomposed as a linear combination Pauli operators. We show this decomposition to be DQC1-hard for a given Hamiltonian, providing insight into the hardness of estimating partition functions.