Quantum machine learning with small-scale devices: Implementing a distance-based classifier with a quantum interference circuit

Abstract

Lately, much attention has been given to quantum algorithms that solve pattern recognition tasks in machine learning. Many of these quantum machine learning algorithms try to implement classical models on large-scale universal quantum computers that have access to non-trivial subroutines such as Hamiltonian simulation, amplitude amplification and phase estimation. We approach the problem from the opposite direction and analyse a distance-based classifier that is realised by a simple quantum interference circuit. After state preparation, the circuit only consists of a Hadamard gate as well as two single-qubit measurements and can be implemented with small-scale setups available today. We demonstrate this using the IBM Quantum Experience and analyse the classifier with numerical simulations.