Among
the strange features of quantum mechanics is the phenomenon known as quantum
tunneling, where a subatomic particle overcomes a barrier that would be
impassable in other sorts of physics. Generations of physics students have been
taught this phenomenon with analogies like objects passing through solid walls,
but the time this process takes has always been a mystery. A new study has set
an upper bound on the time it takes, one so short the process may be
instantaneous, in which case these particles would be exceeding the speed of
light.
Tunneling
certainly happens so quickly it is hard to measure. Recent efforts have used
heavier atoms, necessitating indirect measurements. Dr Igor Litvinyuk
of Griffith University told IFLScience the Australian Attosecond Science
Facility is the only place in the world with all three types of equipment
required to measure the time it takes electrons to tunnel from the grip of
hydrogen atoms.
Litvinyuk
helped put that combination to use, reporting in Nature that
the process takes no more than 1.8 attoseconds. An attosecond is 10-18
or a billionth of a billionth of a second. “It’s hard to appreciate how short
that is, but it takes an electron about a hundred attoseconds to orbit a
nucleus in an atom,” said co-author Professor Robert Sang
in a statement.
Tunneling
time sets a limit on how fast transistors could theoretically switch, so having
such a short time makes ultra-fast computers more realistic.
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