In solid-state physics, a band gap, also called an energy gap, is an energy range in a solid where no electronic states can exist. In graphs of the electronic band structure of solids, the band gap generally refers to the energy difference between the top of the valence band and the bottom of the conduction band in insulators and semiconductors. It is the energy required to promote a valence electron bound to an atom to become a conduction electron, which is free to move within the crystal lattice and serve as a charge carrier to conduct electric current. It is closely related to the HOMO/LUMO gap in chemistry. If the valence band is completely full and the conduction band is completely empty, then electrons cannot move in the solid; however, if some electrons transfer from the valence to the conduction band, then current can flow. Therefore, the band gap is a major factor determining the electrical conductivity of a solid. Substances with large band gaps are generally insulators, those with smaller band gaps are semiconductors, while conductors either have very small band gaps or none, because the valence and conduction bands overlap.
A photonic crystal is a periodic optical nanostructure that affects the motion of photons in much the same way that ionic lattices affect electrons in solids. Photonic crystals occur in nature in the form of structural coloration and animal reflectors, and, in different forms, promise to be useful in a range of applications.
Artur Konrad Ekert FRS is a Polish-born British professor of quantum physics at the Mathematical Institute, University of Oxford, professorial fellow in quantum physics and cryptography at Merton College, Oxford, Lee Kong Chian Centennial Professor at the National University of Singapore and the founding director of the Centre for Quantum Technologies (CQT). His research interests extend over most aspects of information processing in quantum-mechanical systems, with a focus on quantum communication and quantum computation. He is best known as one of the pioneers of quantum cryptography.
An optical microcavity or microresonator is a structure formed by reflecting faces on the two sides of a spacer layer or optical medium, or by wrapping a waveguide in a circular fashion to form a ring. The former type is a standing wave cavity, and the latter is a traveling wave cavity. The name microcavity stems from the fact that it is often only a few micrometers thick, the spacer layer sometimes even in the nanometer range. As with common lasers this forms an optical cavity or optical resonator, allowing a standing wave to form inside the spacer layer, or a traveling wave that goes around in the ring.
A NOON state is a quantum-mechanical many-body entangled state:
Daniel Frank Walls FRS was a New Zealand theoretical physicist specialising in quantum optics.
Jonathan P. Dowling was an Irish-American researcher and professor in theoretical physics, known for his work on quantum technology, particularly for exploiting quantum entanglement for applications to quantum metrology, quantum sensing, and quantum imaging.
Dipankar Home is an Indian theoretical physicist at Bose Institute, Kolkata. He works on the fundamental aspects of quantum mechanics, including quantum entanglement and Quantum communication. He is co-author with Partha Ghose of the popular book Riddles in your Teacup - Fun with Everyday Scientific Puzzles.
The International Conference on Physics of Light–Matter Coupling in Nanostructures (PLMCN) is a yearly academic conference on various topics of semiconductor science and nanophotonics.
Yoshihisa Yamamoto is an applied physicist and the director of Physics & Informatics Laboratories, NTT Research, Inc. He is also Professor (Emeritus) at Stanford University and National Institute of Informatics (Tokyo).
Jeremy O'Brien is a physicist who researches in quantum optics, optical quantum metrology and quantum information science. As of 2010, he is Professorial Research Fellow in Physics and Electrical Engineering at the University of Bristol, and director of its Centre for Quantum Photonics.
The Purcell effect is the enhancement of a quantum system's spontaneous emission rate by its environment. In the 1940s Edward Mills Purcell discovered the enhancement of spontaneous emission rates of atoms when they are incorporated into a resonant cavity.
Exciton-polariton is a type of polariton; a hybrid light and matter quasiparticle arising from the strong coupling of the electromagnetic dipolar oscillations of excitons and photons.
Photonic molecules are a theoretical natural form of matter which can also be made artificially in which photons bind together to form "molecules". They were first predicted in 2007. Photonic molecules are formed when individual (massless) photons "interact with each other so strongly that they act as though they have mass". In an alternative definition, photons confined to two or more coupled optical cavities also reproduce the physics of interacting atomic energy levels, and have been termed as photonic molecules.
Yasuhiko Arakawa is a Japanese physicist.
Nicolas Gisin is a Swiss physicist and professor at the University of Geneva working on quantum information and communication, as well as on the foundations of quantum mechanics. His work includes both experimental and theoretical physics. He contributed significant work on the fields of experimental quantum cryptography and long distance quantum communication in standard telecom optical fibres. As a theoretician, Gisin brought deep insights into quantum mechanics. He is also the first to develop quantum information technology to such a level that it was for the first time possible to take it out of the lab and into the commercial world: he co-founded ID Quantique, a spin-off company which quickly developed into one of the world leaders in the field of quantum information and communication technologies.
Igor Aharonovich is an Australian physicist and materials engineer. He is a professor at the School of Mathematical and Physical Sciences at the University of Technology Sydney (UTS). Igor researchers optically active defects in solids, with an overarching goal to identify new generation of ultra-bright solid state quantum emitters. His main contributions include discovery of new color centers in diamond and hexagonal boron nitride as well as development of new methodologies to engineer nanophotonic devices from these materials.
Thomas Jennewein is an Austrian physicist who conducts research in quantum communication and quantum key distribution. He has taught as an associate professor at the University of Waterloo and the Institute for Quantum Computing in Waterloo, Canada since 2009. He earned his PhD under Anton Zeilinger at the University of Vienna in 2002, during which time he performed experiments on Bell's inequality and cryptography with entangled photons. His current work at the Institute for Quantum Computing focuses on satellite-based free space quantum key distribution, with the goal of creating a global quantum network.
Jeremy John Baumberg, is Professor of Nanoscience in the Cavendish Laboratory at the University of Cambridge, a Fellow of Jesus College, Cambridge and Director of the NanoPhotonics Centre.
A quantum dot single-photon source is based on a single quantum dot placed in an optical cavity. It is an on-demand single-photon source. A laser pulse can excite a pair of carriers known as an exciton in the quantum dot. The decay of a single exciton due to spontaneous emission leads to the emission of a single photon. Due to interactions between excitons, the emission when the quantum dot contains a single exciton is energetically distinct from that when the quantum dot contains more than one exciton. Therefore, a single exciton can be deterministically created by a laser pulse and the quantum dot becomes a nonclassical light source that emits photons one by one and thus shows photon antibunching. The emission of single photons can be proven by measuring the second order intensity correlation function. The spontaneous emission rate of the emitted photons can be enhanced by integrating the quantum dot in an optical cavity. Additionally, the cavity leads to emission in a well-defined optical mode increasing the efficiency of the photon source.
