| 2005 - 2007
| Controlling Quantum Technologies |
| | We are on the verge of a Quantum Technology revolution, where quantum physics is driving otherwise impossible technological advances. To date, quantum technologies have made little use of the monitoring and feedback that is ubiquitous in everyday industry, keeping planes in the air and robots welding accurately. This project is concerned with learning to actively control finite-size quantum systems and processes, by studying the control of photons - single particles of light. Our experimental and theoretical research will advance the new science of quantum control and have immediate application to quantum technologies such as absolutely secure communication and ultrahigh precision measurement. |
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| Quantum Holography: encoding quantum information in optical patterns |
| | Quantum information applies concepts from quantum mechanics to information tasks such as communication and computation. The fundamental units of quantum information are multi-level quantum systems known as qudits Ñ to date, most experiments have realised only their simplest two-level incarnation, the qubit. In principle, tasks such as quantum cryptography, secret sharing, and dense coding, all benefit from using qudits larger than the qubit. We propose a scheme to realise qudits in practice by encoding them into optical patterns (the transverse spatial modes of the field); to manipulate these qudits via holographic techniques; and to make entangling gates using linear optics and measurement. We will explore a range of quantum phenomena and information protocols that are only accessible with qudits. |
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| Optical Quantum Computing |
| | One of the earliest proposals for implementing quantum computation was based on encoding qubits in optical modes, each containing exactly one photon. However it is extremely difficult to couple optical modes containing very few photons. Knill , Laflamme and Milburn (KLM) have proposed a way to circumvent this restriction and implement efficient quantum computation using only passive linear optics, photodetectors, and single photon sources. This efficient optical quantum computing is distinct from all other linear optical schemes which are not efficiently scalable. The objective of this project is to produce a prototype two qubit gate for photons using linear optics, and to develop a blue-print for a multiple qubit device that might be implemented over a longer time scale.proposed an efficient linear optical quantum computing distinct from all other linear optical schemes which are not efficiently scalable. The objective of this project is to produce a prototype two qubit gate for photons using linear optics, and to develop a blueprint for a multiple qubit device that might be implemented over a longer time scale. |
| Keywords: | Linear Optics Quantum Computing |
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| Quantum State Engineering |
| | Production of non-classically correlated quantum states - entangled states - is now an issue of urgent practical importance. Communication using such states can achieve outcomes impossible with classical systems, such as absolutely secure messaging. We are interested in optically engineering arbitrary quantum states via novel twin-photon sources, and analysing these states via quantum tomography. |
| Keywords: | Quantum State Engineering |
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| High-efficiency Quantum Interrogation |
| | (Also known as "interaction-free" measurement). Using the complementary wave- and particle-like natures of photons, the basic particles of light, it is possible to make measurements where the presence of an object can be unambiguously determined without the photons ever interacting with the object. Previous detectors have achieved this with efficiencies of < 80%. In this project we aim to develop a high-efficiency IFM detector, one with efficiencies of 90% or better. Such a detector has great potential for imaging delicate objects, such as biological cells, or quantum systems. An old, but still illuminating, discussion of such measurements can be found here. |
| Keywords: | Quantum Interrogation |
