Distributed exact multi-objective quantum search algorithm

TL;DR

This paper introduces two distributed multi-objective quantum search algorithms that improve qubit efficiency and exactness over existing methods, potentially aiding practical quantum computing in the NISQ era.

Contribution

The paper proposes novel distributed iterated operators leading to two new distributed Grover's algorithms with fewer qubits and one being exact, advancing multi-objective quantum search methods.

Findings

Require fewer qubits than previous algorithms

One algorithm is exact, improving accuracy

Potential advantages in NISQ-era quantum realizability

Abstract

Multi-objective search means searching for any one of several objectives in an unstructured database. Grover's algorithm has quadratic acceleration in multi-objection search than classical ones. Iterated operator in Grover's algorithm is a key element and plays an important role in amplitude amplification. In this paper, we design two distributed iterated operators and therefore two new distributed Grover's algorithms are obtained with the following advantages: (1) Compared to Grover's algorithm and the modified Grover's algorithm by Long, our distributed algorithms require fewer qubits; (2) Compared to the distributed Grover's algorithm proposed by Qiu et al., one of our distributed algorithms is exact. Of course, both our distributed algorithms require quite quantum communication and involve a number of more complicated unitary operators as cost, but there still may have certain advantage of physical realizability in the Noisy Intermediate-Scale Quantum (NISQ) era.