Abstract
The EPR Hamiltonian is a family of 2-local quantum Hamiltonians introduced by King (arXiv:2209.02589). We introduce a polynomial time 1+√5/4≈ 0.809-approximation algorithm for the problem of computing the ground energy of the EPR Hamiltonian, improving upon the previous state of the art of 0.72 (arXiv:2410.15544). As a special case, this also implies a 1+√5/4-approximation for Quantum Max Cut on bipartite instances, improving upon the approximation ratio of 3/4 that one can infer in a relatively straightforward manner from the work of Lee and Parekh (arXiv:2401.03616).