  Quantum spatial search has been widely studied with most of the study
focusing on quantum walk algorithms. We show that quantum walk algorithms are
extremely sensitive to systematic errors. We present a recursive algorithm
which offers significant robustness to certain systematic errors. To search N
items, our recursive algorithm can tolerate errors of size O(1/\sqrt{\ln N})
which is exponentially better than quantum walk algorithms for which tolerable
error size is only O(\ln N/\sqrt{N}). Also, our algorithm does not need any
ancilla qubit. Thus our algorithm is much easier to implement experimentally
compared to quantum walk algorithms.
