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Thursday, 20 January, 2000, 17:46 GMT
Scientists probe the quantum world




By BBC News Online Science Editor Dr David Whitehouse

Physicists say they have managed to nudge atoms between our everyday world and the strange microscopic quantum realm where objects can paradoxically be in two places at the same time.

Confused? Well confusion is all part of the quantum world where everyday laws of matter do not apply. Some have speculated that command of the quantum realm could result in incredibly fast quantum computers able to crack even the toughest encryption codes used by conventional computers today.

Quantum theory was developed in the first third of the 20th Century by such figures as Max Planck, Albert Einstein, Niels Bohr and Werner Heisenberg. Dealing with the fundamental nature of matter and energy, it radically changed how scientists viewed the Universe.

Quantum theory says that energy and matter, which are really different aspects of the same thing, come in discrete units or "quanta". One of the central tenets of the theory is that particles on the sub-atomic level can simultaneously be in two places and have two energy states.

In an experiment reported in the journal Nature, scientists have now been able to move atoms into and out of quantum states with more precision than has ever been achieved before.

Quantum Cat

Perhaps the most well-know and peculiar aspect of the quantum world was described by Austrian physicist Erwin Schroedinger, who proposed his now famous cat paradox in the early 20th Century.

He described the hypothetical situation of a cat in a box with vial of cyanide gas capped by a decaying radioactive atom, which would release the poison once it decayed.

Under quantum theory, the atom could be in both states, that is decayed and non-decayed, meaning the cat is both dead and alive at the same time. Only if you looked into the box would you know if it was alive. If you did not look, then you could not know and would have to consider it both dead and alive.

The experiment is hypothetical, as such strange quantum effects do not occur in large systems comprising countless billions of atoms. Individual atoms are, however, a different matter.

The researchers from National Institute of Standards and Technology (NIST) in Colorado, US, say they were able to keep a beryllium ion in a Schrodinger's cat-like state for as long as 100 millionths of a second.

Outside world

To achieve this, the beryllium atom was cooled to close to absolute zero and isolated from all types of radiation and energy sources.

The team then used lasers to force the atom's single electron into two states of spin, which also forced the atom to be in two places at the same time.

The researchers then caused the situation to break down by deliberately introducing contact to the outside world via an electrical field. Then, in some cases, they were able to reverse the process. The experiments helped the scientists determine what causes a quantum state to collapse.

Such control is necessary if scientists are to come up with practical devices that employ quantum principles.

For example, a quantum computer could store process information in the quantum states of atoms or molecules simultaneously. This would dramatically improve the power of computers. But for such a development to come about, scientists would have to be able to block the outside forces that can cause a quantum state to collapse.

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See also:
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