# Optimal lower bounds for quantum automata and random access codes

@article{Nayak1999OptimalLB, title={Optimal lower bounds for quantum automata and random access codes}, author={Ashwin Nayak}, journal={40th Annual Symposium on Foundations of Computer Science (Cat. No.99CB37039)}, year={1999}, pages={369-376} }

Consider the finite regular language L/sub n/={w0|w/spl isin/{0,1}*,|w|/spl les/n}. A. Ambainis et al. (1999) showed that while this language is accepted by a deterministic finite automaton of size O(n), any one-way quantum finite automaton (QFA) for it has size 2/sup /spl Omega/(n/logn)/. This was based on the fact that the evolution of a QFA is required to be reversible. When arbitrary intermediate measurements are allowed, this intuition breaks down. Nonetheless, we show a 2/sup /spl Omega…

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