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Photonic Quantum Computing

Periodic Reporting for period 3 - PQC (Photonic Quantum Computing)

Reporting period: 2018-06-01 to 2019-11-30

Quantum mechanics describes a microscopic world that is fundamentally probabilistic, where a single object can be in a superposition of two places at once, and where two far apart, entangled objects can instantaneously influence each other. The implications and interpretations of this theory have continued to be of tremendous research interest internationally since the development of quantum mechanics at the start of the last century. In recent times attention has also focused on the potential for harnessing these counterintuitive phenomena for dramatic increases in the power and functionality of information and communication tasks—quantum technologies. In particular, exponentially more powerful quantum computers promise to solve important problems in factoring, machine learning and the simulation of quantum systems—if they can be built—the key research question of this project.

The overall objectives of this grant were to develop an approach to large-scale photonic quantum computing, demonstrate a number of proof-of-principles, and begin to address the key issues of system integration, control and scale-up to large systems. Through this work, a path to the realisation of such a system could emerge. However, combining high-performance components into functional sub-systems that operate fault tolerantly on a large scale presents many research challenges —challenges that form the basis of this project.
This project has developed a whole-systems methodology to the implementation of a photonic quantum information processing approach. Previously activities in this area were concerned with the research surrounding the individually discrete components that might one day complete a photonic quantum computer. We have advanced beyond developing the individual components in and of themselves and dealt with the much wider challenges of systems engineering and combining the sub-components to realise a technology solution. We have examined all layers of a quantum photonic ‘stack’ from the combination of individual components into functional building blocks through to the implementation of logical processors. We have solved some of the major technological bottle-necks that beset the field and established roadmaps that address future requirements and anticipated challenges. We have tested our results in device specific applications (e.g. integrated detectors and high performance optical filtering on chip), combined our technologies with others in similar fields to test the broad-applicability of our approach, and demonstrated the validity of the work through implementations of simulation, learning and processing schemes.
Despite this project’s early termination, which is in part caused by a measure of its success, we have advanced the photonic platform for quantum information processing from disparate components to functional systems. The outcomes have not just established the building blocks for future approaches in this field but also mastered the compilation of problems which make the most of the unique capabilities of the platform. These will be taken forward as new projects.