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Posted: Jun 09, 2011
Researchers discover method for direct measurement of the quantum wavefunction
(Nanowerk News) Scientists around the world now have a new tool to investigate the elementary units of nature. Until now, the quantum wavefunction was believed to be impossible to measure directly, since the very act of observing it would alter it.
The team of researchers include Jeff S. Lundeen, Charles Bamber, Brandon Sutherland, Aabid Patel and Corey Stewart from the National Research Council of Canada Institute for National Measurement Standards (NRC-INMS) in Ottawa. Their method was published in Nature ("Direct measurement of the quantum wavefunction").
"The wavefunction is probably the most complete description of a particle's state, yet it has been elusive to scientists since its inception" said Brandon Sutherland. We have brought clarity to the situation by showing for the first time how it can be directly observed and defined."
The team discovered that by measuring the position of the particle using what is known as "weak measurement," one can avoid the change normally inflicted on the particle. The catch is that one also gets very little information. But by performing the measurement over and over, one can eventually find the average result. This average is equal to the wavefunction itself.
The wavefunction is at the very heart of quantum mechanics. Every object in the universe has a quantum wavefunction that determines and predicts how it will react to other objects. It is used for everything from quantum cryptography, computing and metrology, to drug design and microelectronics. By knowing the measurement of the wavefunction, it is possible to calculate where a particle is most likely to be, or how fast it's likely to be moving.
"The wavefunction embodies the idea that every particle is also a wave" said Jeff S. Lundeen. "This wave is much like the set of ripples travelling out from a pebble dropped in a pool. A feature of the wavefunction is that, unlike a water wave, the very act of observing it changes it, making it a slippery object to measure."
The development of this direct measuring method could allow scientists to design better drugs and chemicals and build faster computer processors, in the decades to come. This discovery keeps Canada at the forefront of the development of quantum computers, which physicists around the world are currently competing to build first. Quantum computers would be able to solve problems that no regular computer ever could, including breaking encryption codes.