This is a key concept in the very new field of quantum computing. The aim is to produce a device which is the quantum equivalent of the digital computer. The qubit (pronounced exactly the same was as the Old Testament measurement, the cubit) is a “quantum bit”, the analogue at quantum dimensions of the ordinary computer’s 1 or 0, on or off, heads or tails binary digit or bit. Unlike such digital representations, a qubit remains in an indeterminate state until it is observed, like a tossed coin that is still spinning. It was shown recently that in theory a quantum computer could solve certain mathematical problems, such as factoring large numbers, much faster than conventional ones, and so could be used, for example, in codebreaking. It might even be possible to employ the “action at a distance” properties of quantum mechanics to transport information instantaneously over great distances without loss. This may all sound like SF, but the first two-bit quantum logic gates were actually demonstrated at the end of 1995. If this field takes off, we shall probably see a whole series of new portmanteau words beginning in “qu”. Anyone for “quanputer”?

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