  Can one considerably shorten a proof for a quantum problem by using a
protocol with a constant number of unentangled provers? We consider a
frustration-free variant of the QCMA-complete Ground State Connectivity (GSCON)
problem for a system of size n with a proof of superlinear-size. We show that
we can shorten this proof in QMA(2): there exists a two-copy, unentangled proof
with length of order n, up to logarithmic factors, while the
completeness-soundness gap of the new protocol becomes a small inverse
polynomial in n.
