Optics, QKD and Plasmonics

Quantum Information Science is a transdisciplinary area of research that capitalizes on the abstract power of quantum physics to revolutionize Information and Communication Technology, as we know it currently. Quantum key distribution (QKD) provides an expanded framework that limits the manipulation of information by only the laws of physics. Exploiting some of the fundamental features of the quantum world. QKD enables new and exciting possibilities that will transform the very essence of communication and related technology.

QKD effectively addresses the challenges confronting conventional encryption approaches, by providing a provably secure cryptographic building block for remote parties to share cryptographic keys. It is primarily an optical technology which has the ability to automate the delivery of information security between any two points or a network that share an optical link. This is advantageous given the growth of optical communication networks. QKD has the potential to replace or augment existing conventional technologies for secure transmission of encryption keys.

This shifts the paradigm away from a mathematical approach towards a physical approach of ensuring the security of information. Furthermore there is a current drive towards industry 4.0 and the emphasis of the global quantum technology trend to develop a quantum internet which is strongly dependent on a secure quantum network.

Fibre based QKD links

During the 2010 Fifa World Cup the Quantum Research Group implemented the Quantum City and Quantum Stadium Project. Which was the first fibre based quantum link in South Africa. The Quantum City link was established between the Westville municipality and Westville Civic Hall. This was extended to the Quantum Stadium Project establishing a secure link between the Moses Mabhida Stadium and the main hub during the 2010 Fifa World Cup

Selected publications


Long range free-space QKD links

Selected Publications



Quantum Optics

On-chip single photon source: Our team are also experimenting using quantum dots as a possible on-chip single photon source. Of recent, a lot of progress has been made integrating quantum dots with dielectrics metallic waveguides, nanowires, plasmonic waveguides. If these were made, it will enable on-demand generation of single photons for on-chip quantum communication.

Selected Publications


Quantum Plasmonics

Plasmonics forms a major part of the fascinating field of nanophotonics, which explores how electromagnetic fields can be confined over dimensions on the order of or smaller than the wavelength. It is based on interaction processes between electromagnetic field and free electrons at metallic interfaces or in small metallic nanostructures, leading to an enhanced optical near field of sub-wavelength dimension. Research in plasmonics has shown how a distinct and often exotic behavior can occur if sub-wavelength structure is imposed. Plasmonics as a research field is made up of two major areas: surface plasmon polaritons (SPPs) and localized surface polaritons (LSPs). SPPs are electromagnetic waves that travel along a metal–dielectric or metal–air interface at visible or infrared frequency. LSPs are the electromagnetic waves due to the confinement of a surface plasmon in a nanoparticle of size comparable to or smaller than the wavelength of light the plasmon incident light. Of recent, quantum plasmonic has open up new exciting ways of controlling and manipulating light at the quantum level, which is central to quantum communication. Our research under quantum plasmonic is focus on

  1. Fundamental and applied quantum plasmonic (plasmonic waveguides, plasmonic gratings etc) for quantum communication.

  2. Integrated surface plasmon polariton for on-chip quantum communication

  3. Study of photon-photon interaction at the nanoscale

Quantum Metamaterials

Metamaterials are artificially engineered materials of nanoscale whose unit cells are arranged periodically possessing exotic optical properties that are not found in conventional materials. Metamaterial properties depend on the constituents and how the unit cells are designed. The exotic materials are designed to have an electromagnetic response, that is, effective electric permittivity and magnetic permeability µ that can be positive, negative or simultaneously negative. These electromagnetic properties make them useful materials that can be used to control the propagation of electromagnetic waves in matter. For example, metamaterials have been used to bend light below the diffraction limit leading to exciting applications such as super-resolution imaging, enabling quantum state engineering, electromagnetic cloak of invisibility, sensing etc.

Also, integrating plasmonic metamaterials with plasmonic waveguides and some photonic crystals may lead to the realization of on-chip device for quantum communication. Our team is looking at the interesting aspects of the fundamental and applications of quantum metamaterials to quantum communication. We aim to explore further how to take the advantage of the strong light confinement in plasmonic metamaterials to realize quantum control devices (on-chip) for quantum communication. The complementary expertise of the academic group members and the state of our labs enable us to investigate these topics at quantum optics with applications to quantum communication.

Selected Publications