Analog computations with feedback (Science)

[From Bill Powers (2003.02.03.1352 MST)]

See the Persectives section of Science _299_m 525-527. Shaped femtosecond
laser pulses are used to favor one ionization reaction over alternatives.
To find the right pulse shape, the experimenters used a closed-loop method.
From the diagram caption: "(A) the molecule is subjected to trial laser
pulse shapes. Signals from the molecule are used to direct a laser pulse
shaper until the desired transformation is achieved."

The text says "[A] digital computational bottleneck is exactly the
impediment that has generally prevented the a priori design of shaped
control laser pulses. The closed-loop procedure ... circumvents this
difficulty by using the molecule as a very efficient analog computer."


Bill P.