30. A Device at the Cutting Edge
Keith Schwab
Keith C. Schwab, Physics, created a device that approaches quantum mechanical limits of measurement. Quantum mechanics requires that a measurement of something cannot be made without perturbing it, but the researchers managed to make measurements that are very close to the uncertainty principle. According to the Heisenberg uncertainty principle, the precision of simultaneous measurements of position and velocity of a particle is limited by a quantifiable amount. The researchers created a sliver of aluminum on silicon nitride—8.7 microns long and 200 nanometers wide—pinned it down on both ends, and allowed it to vibrate in the middle. They coupled this device to a superconducting single electron transistor (SSET). They were able to get closer than ever to the theoretical limit with their measurement, detecting minuscule changes in the sliver’s position. They also observed the sliver move through the phenomenon known as quantum back-action, where the act of observing something gives it a nudge of momentum. When the researchers applied certain voltages to the transistor, they saw the system’s temperature decrease. They believe that, just by looking at the device, they can pull energy away from it. This is the first time that quantum back-action has been observed in a condensed matter context. The results could have implications for areas such as quantum computing and cooling engineering. Research into the quantum mechanics principle of superimposition, which holds that a particle can simultaneously be in two places, is next for Schwab and his colleagues.