Experimental NMR implementation of a robust quantum search algorithm

TL;DR

This paper reports the experimental implementation of a modified quantum search algorithm using NMR, demonstrating increased robustness against systematic errors compared to Grover's original algorithm.

Contribution

First experimental validation of Tulsi's robust quantum search algorithm using NMR, showing improved error tolerance over Grover's algorithm.

Findings

Modified algorithm succeeds with systematic errors in NMR systems.

Experimental results match theoretical predictions.

Enhanced robustness demonstrated in practical NMR setup.

Abstract

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.