In a new quantum theory breakthrough, researchers have finally proven the idea that a system can't change while you're watching it.
This new research could open the door for the creation of new sensors and even bring us closer to quantum computing by allowing us to control and manipulate the quantum states of atoms, Cornell University reported. The phenomenon has been compared to the weeping angels from the popular television show "Dr. Who." The characters are strange beings that appear as statues when observed but are able to move when nobody is watching, similar to what occurs in the atoms of a quantum system.
To make their findings, a team of researchers cooled a gas of about a billion Rubidium atoms inside a vacuum chamber and suspended the mass between laser beams. This arranged the atoms into a lattice that resembles what one would see in a crystalline solid, but the extremely low temperatures allowed the atoms to "tunnel" around the structure. The Heisenberg uncertainty principle states "position and velocity of a particle are related and cannot be simultaneously measured precisely." Temperature is a measure of a particle's motion, and under these frigid temperatures the velocity is at almost zero. This means there is ample flexibility in position, and when observed, these atoms are just as likely to be in one place as the other.
The researchers discovered they were able to halt quantum tunneling by simply observing the atoms. This "Quantum Zeno effect" comes from a proposal made in 1977 by E.C. George Sudarshan and Baidyanath Misra at the University of Texas, Austin, that suggests nature of quantum measurements allows for a quantum system to be "frozen" by repeated measurements. Past experiments have demonstrated the Zeno effect in the "spins" of subatomic particles.
"This is the first observation of the Quantum Zeno effect by real space measurement of atomic motion," said Mukund Vengalattore, assistant professor of physics at Cornell. "Also, due to the high degree of control we've been able to demonstrate in our experiments, we can gradually 'tune' the manner in which we observe these atoms. Using this tuning, we've also been able to demonstrate an effect called 'emergent classicality' in this quantum system."
In this new study, the researchers observed the atoms under a microscope by illuminating them with a separate imaging laser. The imaging laser triggered fluorescence in the atoms, which the researchers were then able to detect. When the laser was off the atoms were able to move freely, but when the beam was gradually brightened and more measurements were taken the tunneling was dramatically reduced.
These findings suggest scientists could one-day control quantum systems atom-by-atom. Atoms in this state are incredibly sensitive to outside forces, so the findings could have implications for the development of new sensors.
The findings were published in a recent edition of the journal Physical Review Letters.
