Optical Quantum Information

Quantum optics provides a very natural system for realizing quantum communications protocols over long and short distances. Light is mobile, easy to manipulate, and can be measured with very low noise. These same properties make optics a strong platform for realizing a quantum computer. The aim of this program is to understand the underlying science behind, and develop optical techniques for, the implementation of key quantum communications and computation protocols.

Quantum communications offers the promise of secure cryptography over long distances – enabled by quantum key distribution (QKD) – and secure distributed processing. One of the challenges in QKD is the present difficulty in distributing keys over long distances because of signal attenuation. An important goal of CQC2T is the development of a quantum repeater, a device which can extend the range of quantum communications by establishing shared entanglement between remote parties or by noiselessly amplifying quantum signals in a nondeterministic but heralded way.

The Optical Quantum Information Program will contribute to the development of quantum repeater technology by pursuing the science and technology of heralded noiseless amplification and by developing sources of quantum entanglement compatible with the Centre’s optical quantum memory platforms. These components will play an important role in the development of practical quantum repeater technology.

Quantum computers have the potential to revolutionise the future. Possessing processing power unmatchable by any classical device, applications are already known in codebreaking, database searching, mathematics, and quantum simulation. Optical quantum computing is particularly promising – not only is light relatively immune from noisy interactions with the environment, it is also a natural information carrier, making optical quantum computers easy to interface with a larger quantum information network. In optics, as with other approaches to quantum computing, we need to overcome significant physical challenges – the fragility of quantum systems, the difficulty in individually preparing and controlling large numbers of quantum systems, the substantial resources needed to make them all interact, the problem of high-efficiency measurement.

The Optical Quantum Information Program will address these issues by investigating the use of novel entangled states for increasing the scale of medium-sized quantum processing circuits, simplifying circuit structure. This will allow the demonstration of new protocols with larger numbers of qubits. Additionally, efficient error encodings will be investigated for protection against loss and other forms of quantum computational error. These schemes will be pursued in collaboration with Centre theory teams.

One of the strengths of CQC2T is the joint approach of optics and solid-state/atomic systems. By bringing these different platforms together the Centre can draw on the strengths of each. The Optical Quantum Information Program will play a central role in this collaboration by investigating the propagation of light in solid-state systems and utilizing these techniques for enhancing optical quantum circuitry. Additionally, the Program will contribute to the development of systems that combine hybrid optical and solid-state quantum components, by providing custom quantum optical states, manipulation techniques for the optics side of the collaboration, as well as developing measurement and characterization techniques for states, protocols and devices.