Undergraduate Studies Quantum Optics in the Lab

Thursday, October 7, 2010

Yu-Po “Ken” Wong, a junior physics major from Taiwan, has spent the last two summers working in Prof. Dan Gauthier’s optics lab. He’s studying the spontaneous down conversion, which is when a photon going through a crystal is changed into two lower frequency photons. The research has implications for high-speed quantum communication.

“This kind of optics experiment is very fun to me. I’m learning a lot of stuff from a lot of areas of physics,” Wong says.

“At the end of my freshman year, I thought it’s time for me to learn to do some research so I emailed Dan and asked if there is an opportunity for me to do some research in his lab,” Wong says. Dan said yes, and Wong received a Deans’ Summer Research Fellowship to do so. Wong first worked to duplicate an experiment done at another university. In setting up the lenses and lasers, every piece of equipment needs to be located precisely in relation to all the other pieces. Making sure every lens is in the correct position is a “very painful and long job,” he says. “The alignment process takes about two days, and it takes me 30 minutes to align stuff if we modified something in the setup.” This past summer, Wong was joined in the lab by graduate student Hannah Guilbert. In the process of duplicating the original experiment, Wong, Guilbert and Gauthier discovered something interesting. The down conversion in this experimental setup is known to produce a circular ring of light, but they discovered the circle is actually an elliptical ring. Wong is doing an independent study this semester working with Gauthier to understand the theory that explains the ellipse. He’s also doing an experimental independent study using a turbulence cell, built by Bill Ebenstein, a research scientist in the department, to see what happens when the down conversion ring goes through turbulence. The work has implications for the emerging field of quantum communication. Traditional electronic communication uses two states—zeros and ones. Quantum communication uses many more than two states, so there is a potential to transmit more information in a shorter period of time. Furthermore, quantum communication adds an extra element of security because the act of eavesdropping changes the quantum states in such a way that leaves a mark. The turbulence question is relevant because quantum communication traveling long distances would go through turbulence in the atmosphere. In late October, Wong is going to the annual meeting of the Optical Society in Rochester, New York, to present last summer’s work in a special session for undergraduates. Gauthier is also attending the conference and will be giving a talk titled, “Toward Single-Photon Nonlinear Optics via Self-Assembled Ultracold Atoms.”