Electromagnetics

NIST Solving a Mystery Among Electrons

When it comes to sleuthing in science, few are better than the intrepid investigators at the National Institute of Standards and Technology (NIST). For example, take the “Case of the Stray Electrons.”

NIST researchers have created nanoscale devices that manipulate electrons in order to count them one at a time. Such counting is critical to the development of new fundamental electrical standards. When two electrons are bound in pairs (called Cooper pairs) in a superconductor, they can be manipulated much faster, providing larger currents that can be measured more accurately. Manipulation of Cooper pairs also is important in several schemes to develop quantum computers. Past attempts at manipulation, however, have been thwarted by the existence of a small number of unpaired electrons rambling around in the superconducting state. Avoiding these unpaired electrons is the mystery that NIST is now helping solve.

NIST researchers have uncovered an important clue by showing that a previously unappreciated factor has a strong effect on the number of unpaired electrons in Cooper pair devices. Electron counting devices are made from two layers of aluminum, where the strengths of the bonds pairing electrons in each layer can be different. This slight difference originally was thought to be unimportant. However, a study of more than a dozen devices in which this difference was varied in a controlled way and indepen-dently measured in each device, shows the
difference does affect device performance directly.

Space Exploration

NIST Micro-Positioner May Help Send Messages from the Stars

Phoning home from 93 billion miles away—only E.T. and other science fiction characters can do that. But with the help of National Institute of Standards and Technology (NIST) know-how, reality soon may catch up with imagination.

Conceptual designs for a “realistic interstellar explorer,” or RISE—a highly autonomous craft that would travel far beyond this solar system to collect scien-tific data—call for a laser-based communications link to Earth that relies in part on a recent NIST invention called a Parallel Cantilever Bi-axial Micro-Positioner. The prototype NIST device acts as a mechanical filter that generates very straight lines by screening out all other motions. Primarily intended for use in the delicate assembly and alignment of optoelectronic devices and applications in micro- and nano-manufacturing, the micro-positioner in a different application offers a promising means for meeting the demanding range, mass and power requirements for the RISE.

In its interstellar role, the micro-positioner would be used to position a lens that steers a laser beam communication link toward Earth. The beam must be pointed precisely because the distances would be, well, astronomical. The RISE is envisioned as having a range up to 1,000 Astronomical Units (AU)—1,000 times the distance from the Earth to the sun, or 93 billion miles.

A recent paper by researchers at NIST and Johns Hopkins University Applied Physics Laboratory (which is designing the RISE) concluded that an optical communications downlink spanning 1,000 AU is technically feasible in the next decade if these new technologies can be sufficiently refined. For example, the current range of the NIST micro-positioner would have to be improved by a factor of nearly 10.