A quantum laser pointer.

Treps, Nicolas; Grosse, Nicolai; Bowen, Warwick P; Fabre, Claude; Bachor, Hans-A; Lam, Ping Koy · Science · 2003

basic_science · Level V

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Abstract

The measurement sensitivity of the pointing direction of a laser beam is ultimately limited by the quantum nature of light. To reduce this limit, we have experimentally produced a quantum laser pointer, a beam of light whose direction is measured with a precision greater than that possible for a usual laser beam. The laser pointer is generated by combining three different beams in three orthogonal transverse modes, two of them in a squeezed-vacuum state and one in an intense coherent field. The result provides a demonstration of multichannel spatial squeezing, along with its application to the improvement of beam positioning sensitivity and, more generally, to imaging.