Our new preprint NPA Hierarchy for Quantum Isomorphism and Homomorphism Indistinguishability (with Prem Nigam Kar, David E. Roberson, and Peter Zeman) is now available on arXiv.

In this paper, we give a more elementary proof of the breakthrough result by Mančinska and Roberson [FOCS 2020] equating homomorphism indistinguishability over planar graphs and quantum isomorphism by characterising the feasibility of each level of the NPA semidefinite programming hierarchy for quantum isomorphism as a homomorphism indistinguishability relation over a suitable class of planar graphs of bounded treewidth.

Check it out!