



01380nas a2200145   4500008004100000245006200041210006100103260001500164300001200179490000600191520095800197100002301155700001901178856003701197       2011                        eng d00aQuantum query complexity of minor-closed graph properties0 aQuantum query complexity of minorclosed graph properties  c2011/01/01  a661-6720 v93 a  We study the quantum query complexity of minor-closed graph properties, which
include such problems as determining whether an $n$-vertex graph is planar, is
a forest, or does not contain a path of a given length. We show that most
minor-closed properties---those that cannot be characterized by a finite set of
forbidden subgraphs---have quantum query complexity \Theta(n^{3/2}). To
establish this, we prove an adversary lower bound using a detailed analysis of
the structure of minor-closed properties with respect to forbidden topological
minors and forbidden subgraphs. On the other hand, we show that minor-closed
properties (and more generally, sparse graph properties) that can be
characterized by finitely many forbidden subgraphs can be solved strictly
faster, in o(n^{3/2}) queries. Our algorithms are a novel application of the
quantum walk search framework and give improved upper bounds for several
subgraph-finding problems.
1 aChilds, Andrew, M.1 aKothari, Robin  uhttp://arxiv.org/abs/1011.1443v2