Summary: Impossibility of Succinct Quantum Proofs for Collision­Freeness
Scott Aaronson #
Abstract
We show that any quantum algorithm to decide whether a function f : [n] # [n] is a
permutation or far from a permutation must
make# # n 1/3 /w # queries to f , even if the algorithm
is given a w­qubit quantum witness in support of f being a permutation. This implies that
there exists an oracle A such that SZK A
## QMA A , answering an eight­year­old open question
of the author. Indeed, we show that relative to some oracle, SZK is not in the counting class
A 0 PP defined by Vyalyi. The proof is a fairly simple extension of the quantum lower bound for
the collision problem.
1 Introduction
The collision problem is to decide whether a black­box function f : [n] # [n] is one­to­one (i.e.,
a permutation) or two­to­one function, promised that one of these is the case. Together with its
close variants, the collision problem is one of the central problems studied in quantum computing
theory; it abstractly models numerous other problems such as graph isomorphism and the breaking
of cryptographic hash functions.
In this paper, we will mostly deal with a slight generalization of the collision problem that we
call the Permutation Testing Problem, or PTP. This is a property testing problem, in which we

Source: Aaronson, Scott - Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology (MIT)

Collections: Physics; Computer Technologies and Information Sciences