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Edward Flagg
Department of Physics and Astronomy

Quantum Dots

Schematic diagram of quantum dot band structure

QDs are sometimes called “artificial atoms” because they have discrete electronic energy levels in a manner similar to isolated atoms. A quantum dot is a semiconductor heterostructure that confines charge carriers (electrons and holes) in a volume on the order of the particles’ quantum mechanical wavelength. Confinement at this scale results in discrete energy levels just like electrons confined to orbit an atomic nucleus have discrete energies. A hole is the absence of an electron in the material, and the collective behavior of the nearby electrons makes the hole appear to be a particle unto itself. When an electron and a hole are simultaneously confined in a quantum dot, they may recombine and emit their energy as a photon. The quantum mechanical state of the charge carriers trapped in the dot can be coherently manipulated by interactions with externally-applied laser beams, and electric and magnetic fields. Therefore, a quantum dot with an electron confined inside it is potentially suitable as a quantum bit, or qubit, in a future quantum computer.

Introduction to Quantum Dots

Photoluminescence from a single quantum dot

If you want to learn more details about quantum dots, what they are, how they work, and why they are interesting physical systems to study, below are links to several review articles. They are listed in approximate order of most general to most specific. If you open the links from a WVU computer, you can access the articles freely.

An overview of the physics underlying quantum dots and how a certain kind of quantum dot (colloidal nanocrystals) are made:

Murphy, C. J. and Coffer, J. L. “Quantum Dots: A Primer Applied Spectroscopy 56, no. 1 (2002): 16A–27A. doi:10.1366/0003702021954214

An overview of a quantum computing scheme that is the reason for interest in sources of indistinguishable single photons:

Kok, P. “Linear Optical Quantum Computing with Photonic QubitsReviews of Modern Physics 79, no. 1 (2007): 135–174. doi:10.1103/RevModPhys.79.135

An overview of how the quantum mechanical spin of electrons or holes could be used as the quantum bits in a quantum computer:

Kloeffel, C. and Loss, D. “Prospects for Spin-Based Quantum Computing in Quantum DotsAnnual Review of Condensed Matter Physics 4, no. 1 (2013): 51–81. doi:10.1146/annurev-conmatphys-030212-184248

An overview of recent research in spin control and measurement in quantum dots like those used in our work:

Warburton, R. J. “Single Spins in Self-Assembled Quantum DotsNature Materials 12, no. 6 (2013): 483–493. doi:10.1038/nmat3585

An overview of recent efforts to make spin-photon interfaces: 

Gao, W. B., Imamoglu, A., Bernien, H., and Hanson, R. “Coherent Manipulation, Measurement and Entanglement of Individual Solid-State Spins Using Optical FieldsNature Photonics 9, no. 6 (2015): 363–373. doi:10.1038/nphoton.2015.58

An excellent introductory book on quantum optics - the science of light at the level of single photons - is the one by Mark Fox. A digital version is available in the WVU library.

Mark Fox. "Quantum Optics: An Introduction," Oxford University Press (2012)