  Grover's quantum search algorithm, involving a large number of qubits, is
highly sensitive to errors in the physical implementation of the unitary
operators. This poses an intrinsic limitation to the size of the database that
can be practically searched. The lack of robustness of Grover's algorithm for a
large number of qubits is due to quite stringent "phase-matching" condition. To
overcome this limitation, Tulsi suggested a modified search algorithm [PRA 78,
022332] which succeeds as long as the errors are reproducible and reversible
while Grover's algorithm fails. Such systematic errors arise often from
imperfections in apparatus setup e.g. the errors arising from imperfect pulse
calibration and offset effect in NMR systems. In this paper, we report the
experimental NMR implementation of the modified search algorithm and its
comparison with the original Grover's algorithm. We experimentally validate the
theoretical predictions made by Tulsi.
