timestep. This model is in part motivated by the fact that decoherence times of qubits are
typically small, so it makes sense to parallelize quantum algorithms as much as possible.
We show tight bounds for a number of problems, specifically Θ ((n/p)^ 2/3) Θ ((n/p) 2/3) p-
parallel queries for element distinctness and Θ ((n/p)^ k/(k+ 1)) Θ ((n/p) k/(k+ 1)) for k k-sum.
Our upper bounds are obtained by parallelized quantum walk algorithms, and our lower …