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MIT Technology Review

What Else We Don't Know

More questions driving MIT physicists

December 22, 2008

Particle physics and cosmology are keeping physicists plenty busy. But MIT researchers are asking other fundamental questions, too–and the answers should lead to new technologies in the areas of energy, medicine, and computing. Here are some examples:

Why are some ceramics superconductive at relatively high temperatures?

The powerful magnets used in magnetic resonance imaging make clinical MRI scanners large, power hungry, and expensive. The magnets are made of superconducting materials, which can carry electricity with no losses, but only when cooled to near absolute zero by liquid helium. In the mid-1980s, physicists discovered ceramics that become superconductive at about 100 K–still quite cold, but warm enough to allow the use of liquid nitrogen, a much cheaper and more abundant cooling material. After more than 20 years of research, physicists are still baffled by these so-called high-temperature superconductors. MIT associate professor Eric Hudson, an experimental physicist, and professor ­Patrick Lee, a theoretical physicist, are among those studying the question. They hope that an understanding of why these materials exhibit superconduc­tivity will lead to superconductors that either work at higher temperatures or have better material properties. (For ­example, materials less brittle than ceramic could be made into wires to make the electrical grid more efficient.) A long-term goal of the field is to develop materials that are superconductive at room temperature. Among other payoffs, that could mean cheap, portable MRI scanners.

How do you build small, efficient optical chips?

Optical fiber carries much of the world’s data. Engineers would like to use light not just to carry data but to process it: optical chips are much faster than chips that use electrical current. But making small, power-efficient optical processors has proved challenging. It’s difficult to get photons to interact with each other because they don’t have any charge. “The same thing that makes photons useful for transferring information–that is, they don’t interact much, which means they can propagate over long distances without being absorbed–makes them very hard to use to manipulate information,” explains Marin Soljacˇic ‘96, an assistant professor who’s working in the field of nanophotonics. He and others are developing artificial materials called photonic crystals that could be made into devices capable of carefully controlling the flow of light through chips. (Soljacˇic is also working on wireless power transmission. See “TR10: Wireless Power,” March/April 2008.)

How do you build a quantum computer?

According to physics professor Frank ­Wilczek, “Physics seems to suggest possibilities for new kinds of information processing you could do if you could control quantum behavior”–the behavior of matter and light at the scale of the atom and smaller. But, ­Wilczek says, “progress has been unimpressive.” MIT researchers are exploring quantum information through multidisciplinary research initiatives like the W. M. Keck Foundation Center for Extreme Quantum Information Theory. Mechanical-engineering professor Seth Lloyd, the center’s head, leads efforts to determine the capacities of quantum systems. Professor Edward Farhi, head of the Center for Theoretical Physics, and professor ­Jeffrey Goldstone are developing algorithms that take advantage of quantum mechanics to speed computation. Wilczek is investigating quantum effects at larger scales in objects called solitons, which he calls “beefed-up electrons” because they “combine the robustness of a large system with the richness of behavior of quantum-mechanical objects.”