The Theoretical Idea of writing information on Atoms

In a most circuitous web-path I came across this remarkable page from, I guess, 1999:

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Writing Words on an Atom

This computer simulation of a hydrogen atom shows an electron cloud sculpted to read the word "optics," a feat that is within the realm of possibility in the near future by using lasers to manipulate electrons within atoms.

According to quantum mechanics, electrons often don't occupy a single definite position but a cloud of possible positions around the nucleus. Only until the act of measurement does the electron assume a definite position. Until then, each point on the cloud represents a place where you might find the electron after measurement.

Shining an ultrashort UV laser pulse and lower-frequency electromagnetic waves on an atom can send one of its electrons to a high-lying "Rydberg state," in which it no longer exists as a cloud of charge enshrouding the nucleus but instead becomes a "wavepacket" that circles the atomic nucleus like a planet around a sun. Applying a series of pulses can create a set of wavepackets that combine with each other like water waves and cancel each other out at specific places to form patterns around the atom, such as the word "optics," in which points on each letter correspond to possible places for finding the electron after measurement.

Although neither this feat, nor the act of accurately measuring such spatial patterns, can yet be achieved technologically, Carlos Stroud of the University of Rochester and Michael Noel of University of Virginia point out that an electron in an n=50 Rydberg state (49 energy levels higher than the lowest state) has 2,500 possible states of angular momentum, and have shown that the states can be combined in many ways.

In recent computer simulations, researchers formed the word "optics" by calculating the electron cloud for a specially prepared n=50 state. In the image above, the intensity of the letters represents the relative probability for finding the electron at that place, and the color denotes the phase (relative point in the cycle) of the electron wave associated with that point in the cloud. (Image courtesy Carlos Stroud, University of Rochester, and Michael Noel.) This research is described by Carlos Stroud and Michael Noel in the April 1999 issue of Optics and Photonics News.

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• Link to related Physics News Update item
  
• Link to the Carlos Stroud group's Wavepackets Home Page, with images, tutorials, and animations.