What is a Quantum Mirage?

Bill Jennings

Today, MP3 players that are smaller than a book of matches can hold two gigabytes of information — enough space for about 500 songs. When it comes to the capabilities, power, speed and energy efficiency that are possible to pack into a cell phone, or a laptop, a phenomenon called quantum mirage portends that the surface may have only been scratched so far. Essentially, quantum mirage is a phenomenon that suggests that data can be transferred without conventional wires.

Stringing a necklace of atoms together takes a lot of time and energy.
Stringing a necklace of atoms together takes a lot of time and energy.

In 1993, IBM scientists discovered the concept of quantum mirage. That discovery may be regarded as a turning point in the history of nanotechnology, even as integrated circuits approach their limit in miniaturization. As advanced as this technology has become, it depends on something invented in the 19th century — wires. Eventually, wires become too small for the efficient flow of electrons and the connection fizzles out.

These scientists at IBM believe quantum mirage may lead to the creation of circuits on an atomic scale. Instead of flowing through wires, information in this atomic circuit rides a wave in a sea of electrons.

A team at IBM, led by Don Eigler, set up an experiment to demonstrate quantum mirage in action. Using a scanning, tunneling microscope, they assembled an ellipse with a diameter 5,000 times smaller than that of a human hair. The ellipse was formed by a necklace of 36 cobalt atoms on the surface of a copper crystal cooled to four degrees above absolute zero.

They used an ellipse because, as a geometric shape, it has what are called focus points at each end of its long axis. If you draw a line from one focus point to any point on the ellipse, then over to the opposite focus point, the distance will always be the same.

They used copper because it’s non-magnetic and cobalt atoms are magnetic. They put the copper in a deep freeze because when it’s that cold, the electrons in the copper produces a resonance called the Kondo effect when a cobalt atom comes in contact with them. The Kondo effect is the notion that electrical resistance diverges when the temperature is near 0 Kelvin.

The ellipse of cobalt atoms formed a corral containing electrons from the copper crystal. As expected, when the IBM scientists used the scanning, tunneling microscope to position an atom within the ellipse they saw the Kondo effect. But, when they moved the cobalt atom to one of the focus points on the ellipse, the Kondo effect appeared at the other focus point.

In essence, the resonance created by the magnetic cobalt atom interacting with the non-magnetic copper electrons rode a wave through the electrons contained within the cobalt necklace to the other focus point. All this despite the fact that an atom was not there. The scientists dubbed this effect quantum mirage.

IBM scientists theorize that quantum mirage may be operated in ways similar to focusing light with lenses, or sound with parabolic reflectors. But the technology has a long way to go. Stringing together a necklace of atoms with a scanning, tunneling microscope takes a lot of time and energy. But if the process can be accelerated and refined, just imagine, one day people may be able to store 10,000 songs within a microscopic MP3 player implanted in the inner ear. Why not? With phenomena like quantum mirage existing in the universe, anything is possible.

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