Portland, Ore. -- Quantum mechanics predicts that measurements motivate mass--that the act of observing can affect the observed. Now a former National Security Agency scientist turned physics professor has demonstrated that motion can be elicited and quelled by quantum-level observations.
Indeed, observations alone changed not only the physical motion of a device but also the motion's thermal consequence, Cornell University professor Keith Schwab said. His report documents the largest device in which quantum mechanical effects have been observed.
"Our measurements were so strongly coupled to the device that by looking at it, we made it move," said Schwab. "We actually pulled energy out of it too, lowering its temperature with observations."
The device was an aluminum-on-silicon nitride resonating bar measuring 8.7 microns long by 200 nanometers wide, pinned down at both ends but allowed to vibrate from the middle. A superconducting single-electron transistor measured changes in the bar's position.
Schwab created the device to determine the dividing line between the quantum mechanical world, where observations affect the observed, and the classical world, where objects stay put. The Heisenberg Uncertainty Principle states that you can't observe both position and velocity with precision; the observations will be limited by a quantifiable amount.
Schwab's team attempted to measure both the position and velocity of the resonating bar. The results show that quantum effects can result from objects that contain many atoms--the bar contained 10 trillion.
Schwab likened his observation process to the "Doppler cooling" technique, through which lasers are used to quell the motion and thereby lower the temperature of atomic vapors. This is the first time that the phenomenon has been seen in condensed matter, he said.