Expansion testing aims to decide whether an n-node graph has expansion at least Φ, or is far from any such graph. We propose a quantum expansion tester with complexity eO(n1/3Φ-1). This accelerates the eO (n1/2Φ-2) classical tester by Goldreich and Ron [Algorithmica '02], and combines the eO (n1/3Φ-2) and eO(n1/2Φ-1) quantum speedups by Ambainis, Childs and Liu [RANDOM '11] and Apers and Sarlette [QIC '19], respectively. The latter approach builds on a quantum fast-forwarding scheme, which we improve upon by initially growing a seed set in the graph. To grow this seed set we use a so-called evolving set process from the graph clustering literature, which allows to grow an appropriately local seed set.

Quantum algorithms and applications
Centrum Wiskunde & Informatica, Amsterdam (CWI), The Netherlands

Apers, S. (2020). Expansion testing using quantum fast-forwarding and seed sets. Quantum, 4. doi:10.22331/Q-2020-09-16-323