Abstract
Consider a function which is defined on the integers from 1 to and takes the values and . The parity of is the product over all from 1 to of . With no further information about , to classically determine the parity of requires calls of the function . We show that any quantum algorithm capable of determining the parity of contains at least applications of the unitary operator which evaluates . Thus, for this problem, quantum computers cannot outperform classical computers.
- Received 19 February 1998
DOI:https://doi.org/10.1103/PhysRevLett.81.5442
©1998 American Physical Society