Macroscopic Object Placed in a Mixed Quantum State

Physicists at the University of California in Santa Barbara (UCSB) recently managed an exceptional achievement, when they instilled a mixed quantum state on an object that is visible to the unaided eye. This is a momentous achievement, given that until now only nanoscale objects could be placed into such states, and even then with great effort. What makes the group's work so important is the fact that they managed to condition quantum physics principles into the largest object ever. No other research team managed to do the same for macroscopic object, let alone at this size, Nature News reports.

The UCSB group, led by expert physicist Andrew Cleland, used a small metal paddle for their experiments. They cooled the object down until they achieved something known as the quantum mechanical “ground state”. What this means is that the metal paddle was in the lowest-energy state permitted theoretically by quantum mechanics. Then they used the peculiar rules that govern the interaction of elementary particles to set the paddle moving, while at the same time observing it as it stands still. This principle, called superposition, was thus far not demonstrated in such large objects. The paddle itself was 30 micrometers long.

“No one has shown to date that if you take a big object, with trillions of atoms in it, that quantum mechanics applies to its motion,” the team leader says. Details of this amazing feat were published in the March 17 online issue of the respected scientific journal Nature, and were also presented in Portland, Oregon, at a meeting of the American Physical Society (APS). The thing about designing quantum states is that they are extremely sensitive to external influences, which means that they can be easily destroyed by outside factors. The real accomplishment of the team was to keep superposition “alive” at this level of complexity.

“The environment is this huge, complex thing. It's that interaction with this incredibly complex system that makes the quantum coherence vanish,” Cleland explains. He adds that future research in making ever-larger objects take on quantum states could reveal more clues as to how quantum mechanics and gravity interact. This could be especially useful for designing unified field theories that would bind Newtonian physics and quantum mechanics in a single explanation of the Universe.