# A Quantum Algorithm for Finding Common Matches Between Databases with Reliable Behavior

## TL;DR

This paper introduces a quantum algorithm that efficiently finds common entries across multiple unstructured databases using amplitude amplification, requiring fewer queries than classical methods.

## Contribution

It presents a novel quantum algorithm that constructs an oracle for common entries and employs a reliable amplitude amplification technique for improved success probability.

## Key findings

- Requires O(κ√N) queries to find common entries.
- Constructs an oracle to mark common entries.
- Uses a variation of amplitude amplification with reliable behavior.

## Abstract

Given $\kappa$ databases of unstructured entries, we propose a quantum algorithm to find the common entries between those databases. The proposed algorithm requires $\mathcal{O}(\kappa \sqrt{N})$ queries to find the common entries, where $N$ is the number of records for each database. The proposed algorithm constructs an oracle to mark common entries, and then uses a variation of amplitude amplification technique with reliable behavior to increase the success probability of finding them.