June 8, 2010
By Robin Donovan

Mauricio Garrido will earn his Ph.D. this spring and has accepted a postdoctoral position at Columbia University.

Today’s technology industry is always looking for new ways to make smaller cell phones, sleeker laptops and ever-thinner television screens. Mauricio Garrido, a physics doctoral candidate, is helping researchers develop new tools to take tech to the quantum level.

Garrido works with quantum dots, tiny semiconductors that may provide a foundation for quantum computing in the future. “Quantum dots behave almost like an atom, so you can engineer the spaces between the energy levels. They’re designer atoms, if you like,” he said.

Garrido’s dissertation, “Quantum Optics and Coupled Quantum Dots,” includes his work with photoluminescence excitation and time-correlated experiments dealing with quantum entanglement.

Photoluminescence excitation is the process of creating excitons, which occur when a charged electron leaps from a low valence energy level to a higher conduction level, leaving behind a positively charged “hole.” An exciton is made up of the electron at a low energy level and the “hole,” which are bound together. When the charged electron returns to the valence level, it releases energy in the form of a photon.

When two electrons and two “holes” are bound together and recombine, the two resulting photons may be entangled. Entanglement, a phenomenon Einstein believed would invalidate quantum mechanics, is not yet physically understood. Garrido’s dissertation research will help other scientists study quantum dots that display this quirky trait.

Entangled photons are mathematically related even when physically separated. Despite the distance between them, they still depend on each other; if one is measured, the other “knows” this instantaneously. Garrido, with Professor Eric Stinaff, is developing a way to create this entanglement reliably. So far, they found a way to map energy levels in quantum dots and shift them using only light. This may allow future researchers to manipulate quantum dots without the costly, clunky machinery currently needed to manipulate electric fields during the super-short lifespan of excitons.

Originally from Bogotá, Garrido can appreciate what lowering the price of experimental physics might mean. Economic conditions in Colombia mean funding for physics research is limited, but lower-cost methods could help nations unable to fund expensive projects.

After graduating this spring, Garrido will venture into astrophysics. Originally drawn to physics by the hope of building a time machine as a kid, he defined a new goal after realizing that time travel would be difficult and impractical. “I’ve been focusing on technology for the sake of technology, but the most important aspect, which is life--my life, people’s lives--I’m totally neglecting,” he said.

His new position, a postdoctoral job at Columbia University in New York may not be the Colombia of his childhood, but promises a step toward understanding humanity a bit more. Garrido will join Dr. Daniel Savin’s research group, studying the ways that inorganic matter could become organic in an interstellar medium using merged ion beams.