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On a flat surface, an optical vortex looks like a ring of light, with a dark hole in the centre |
The helical (or spiral) wavefront structure of a vortex beam |
An optical vortex is a beam of light the phase of which varies in a corkscrew-like manner along the beam's direction of propagation. On a flat surface, an optical vortex looks like a ring of light, with a dark hole in the centre. This corkscrew of light, with darkness at the centre, is called an optical vortex. CSIR National Laser Centre researchers Angela Dudley and Melanie Mclaren, led by Dr Andrew Forbes, and academics from the University of KwaZulu-Natal, have started on an ambitious project to investigate quantum entanglement using vortex beams. Quantum entanglement also has applications in telecommunications and secure data transfer.
Quantum physics deals with atomic and subatomic systems. It is a result of the discovery that waves have discrete energy packets (called quanta) that behave in a manner similar to particles. Dudley says, "Quantum entanglement is a vital resource in quantum information technology such as quantum computation and quantum cryptography. The idea is simply to entangle quantum states for secure information transfer, so that the cryptography is based on quantum physics and not man-made codes, which can be broken. Quantum cryptography makes use of quantum entanglement in the transmitting of information (a key) in quantum states. This communication system is able to detect 'eavesdropping'; it involves two communicating users who share information that can be used as a 'key' to encrypt and decrypt messages. Quantum cryptography is only used in producing and distributing the key."
However, Dudley says, "challenges arise in using quantum states to carry data; for example, quantum noise and quantum decoherence are introduced in optical fibres resulting in the entanglement gradually being destroyed. Müstecaplioglu in his paper titled 'Quantum Entanglement in Optical Fibre' says "generating useful quantum entanglement is like creating a butterfly: you make a beautiful correlation of colours, but the result is fragile and short lived." Tackling this problem is the basis of the CSIR's collaboration with the University of KwaZulu-Natal.
Should the research project prove successful, it will have ground-breaking implications for the study of quantum cryptography.
Enquiries: CSIR Communications
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