Chaos and the quantum mechanical behaviour of classically chaotic systems have been attracting increasing attention. Initially, there was perhaps more emphasis on the theoretical side, but this is now being backed up by experimental work to an increasing extent. The words 'Quantum Chaos' are often used these days, usually with an undertone of unease, the reason being that, in contrast to classical chaos, quantum chaos is ill defined; some authors say it is non-existent. So, why is it that an increasing number of physicists are devoting their efforts to a subject so fuzzily defined?.
