Quantum computing using shortcuts through higher dimensions

TL;DR

This paper introduces a method leveraging higher-dimensional quantum systems to reduce the number of gates needed for quantum circuits, demonstrated by implementing complex gates in linear optics.

Contribution

It presents a novel technique using higher dimensions to simplify quantum circuit implementation, enabling the realization of complex gates with current technology.

Findings

Successfully implemented Toffoli and controlled-unitary gates

Reduced gate count for quantum circuits using higher-dimensional systems

Demonstrated feasibility in linear optical architecture

Abstract

Quantum computation offers the potential to solve fundamental yet otherwise intractable problems across a range of active fields of research. Recently, universal quantum-logic gate sets - the building blocks for a quantum computer - have been demonstrated in several physical architectures. A serious obstacle to a full-scale implementation is the sheer number of these gates required to implement even small quantum algorithms. Here we present and demonstrate a general technique that harnesses higher dimensions of quantum systems to significantly reduce this number, allowing the construction of key quantum circuits with existing technology. We are thereby able to present the first implementation of two key quantum circuits: the three-qubit Toffoli and the two-qubit controlled-unitary. The gates are realised in a linear optical architecture, which would otherwise be absolutely infeasible with current technology.