116 AUGUST 2019|COMPUTER SHOPPER|ISSUE 378
One such technology –the futuristic
sounding quantum computing, with its
potential foralmost unimaginable levels
of performance –isour subject here.
QUANTUM LEAPS
So how close are we to the current
developments in quantum computing
research starting to affect the real
world? With several major players in
computing involved, we might expect
that quantum computing could soon
come of age.But the reality is that it’s
still astonishing, unfathomable and
downright weird technology.
It’s hard to actually understand how
quantum computing works, in the
normal sense of the word; nobody does.
Instead, you’re going to have to take it
on face value,even though it’s totally
counter-intuitive.Even the eminent
Danish physicist Niels Bhor,one of the
pioneers of quantum
physics, admitted this.
“If you think you can
talk about quantum
theory without feeling
dizzy,you haven’t
understood the first thing
about it,”hefamously said.
Quantum physics is
concerned with the
behaviour of sub-atomic
particles, in contrast to
classical physics, which
deals with larger objects.
This is the primary reason
that we’re inclined to think of quantum
behaviour as strange,bizarre and even
downright impossible.Afterall, our
common-sense view of the world has
been conditioned from our observation
of large objects. By wayofcontrast,
we’ve never seen sub-atomic particles,
and this explains why their behaviour,
when it differs from that of everyday
objects, appears totally unbelievable.
First up in our tour of quantum
phenomena is the property known as
superposition. To saythat something
can only be in one place at one time,or
that an electronic circuit can only be in
one stateatonce –for example,the on
and off of atransistor that defines the
states of 0or1inadigital computer –
might seem obvious. Once we get down
to sub-atomic dimensions, however,this
isn’t guaranteed. Such particles can
indeed be in two places at once or in
two states at once; this is
called superposition. To
makethingsevenstranger,
you can never observe a
stateofsuperposition
because the very act of
observing it causes the
superposition to be
destroyed –aprocess
called decoherence.So,
forexample,ifanelectron
is in asuperposition of
the two states known as
spin-up and spin-down, as
soon as you observe it, it
willdecohereto revealeitherthespin-up
or the spin-down stateatrandom.
Next we come to aproperty of two
or more sub-atomic particles, which is
called entanglement. If two particles
are entangled, something that can be
brought about by some sort of
interaction between them, theyshare
properties so that neither particle can
be defined individually.Let’s consider
two superimposed electrons that are
entangled so that theyhaveopposite
spins. Initially,both particles are in a
stateofsuperposition, having an up and
adown spin simultaneously.Weknow
that observing the spin of either
electron will cause it to decohere and
therebyreveal either an up or down
spin. However,when we do observe
one electron and, in so doing, cause it
to decohere,the other particle will
decohere at exactly the same moment
and will exhibit the oppositespin. It was
predicted by theory,and confirmed by
experiment, that this takes place
instantaneously,however farapart the
two particles might be.Einstein called
this “spookyaction at adistance”
becauseitseemedtocontradictthelaws
of physics, which statethat nothing can
travel faster than the speed of light.
THEQUANTUM EDGE
So we’ve seen something of the
strangeness of quantum physics, but
how does any of this relateto
computing? In fact, we’ve already hinted
ABOVE:Ħub-atomic
particles might be
hard to visualise,
and theѻbehave in
totallѻ bi҄arre waѻs,
but their strange
behaviour could
unleash almost
unimaginable
computing power
BELOW:Lven some
oɋ the best minds
in phѻsics, such as
ãiels Bohr ̣leɗ̧
and lbert Linstein,
had to admit that
quantum behaviour
is downright strange
