The Problem of Completeness

Alex Meiburg

A quantum constraint problem is a frustration-free Hamiltonian problem: given a collection of local operators, is there a state that is in the ground state of each operator simultaneously? It has previously been shown that these problems can be in P, NP-complete, MA-complete, or QMA_1-complete, but this list has not been shown to be exhaustive. We present three quantum constraint problems, that are (1) BQP_1-complete (also known as coRQP), (2) QCMA_1-complete and (3) coRP-complete. This provides the first natural complete problem for BQP_1. We also show that all quantum constraint problems can be realized on qubits, a trait not shared with classical constraint problems. These results suggest a significant diversity of complexity classes present in quantum constraint problems.

Jeffrey Bub

Dick J. Hoekzema

Sean Hallgren, Daniel Nagaj, S. Narayanaswami

The Local Hamiltonian problem is the problem of estimating the least eigenvalue of a local Hamiltonian, and is complete for the class QMA. The 1D problem on a chain of qubits has heuristics which work well, while the 13-state qudit case has been shown to be QMA-complete. We show that this problem remains QMA-complete when the dimensionality of the qudits is brought down to 8.

Sean Hallgren, Daniel Nagaj, S. Narayanaswami

The Local Hamiltonian problem is the problem of estimating the least eigenvalue of a local Hamiltonian, and is complete for the class QMA. The 1D problem on a chain of qubits has heuristics which work well, while the 13-state qudit case has been shown to be QMA-complete. We show that this problem remains QMA-complete when the dimensionality of the qudits is brought down to 8.

Jan Hamhalter