Google claims it has reached a key milestone:
using a quantum computer 
to complete a task
that a classical computer 
couldn’t manage,
achieving what they call ‘quantum supremacy’.
This would be the first time that a quantum
computer has definitively beaten
the best conventional computer.
But it’s something that physicists 
have been trying to do for years.
Although not everyone is convinced
that a normal computer would find
 this particular task impossible,
it certainly seems like the
quantum processor solves it faster.
The task is a calculation 
that is not very useful.
It was designed just to 
demonstrate quantum supremacy
and was made to be especially
difficult for normal computers to handle.
Google’s quantum computer 
is called Sycamore.
It has just 53 qubits,
quantum versions of the ‘bits’ 
that encode information in a computer.
These behave completely differently to 
regular bits, and are very hard to manipulate.
But in theory they should allow the computer
to carry out certain kinds of calculations
way faster than a classical machine.
The calculation in this test was to figure 
out the probability distribution
of all the possible outcomes from a
quantum random number generator.
Because the generator creates random 
numbers using quantum operations,
simulating this distribution on a classical 
computer is extremely tough.
But Google’s machine only needed 
to set itself up like the generator,
and then run those operations 
a bunch of times.
Sycamore produced an answer in 
just 3 minutes and 20 seconds.
But proving quantum supremacy, means facing
off against classical competition.
For that, researchers borrowed 
the supercomputing might
of the Summit supercomputer at 
Oak Ridge National Laboratory in Tennessee.
By breaking up the problem into 
smaller chunks and then extrapolating,
they estimate that Summit would take 10,000
years to finish the same calculation.
If true, this means a quantum computer can
do something that is, in practice,
impossible on a classical machine:
Quantum supremacy.
But not everyone agrees.
IBM has released a paper claiming that the
Summit supercomputer could actually complete
the task in just 2.5 days by using a 
slightly different technique.
Scientists will now scrutinize 
both camps’ calculations.
But even if IBM is right,
it's still significant that Sycamore was so much
faster than the supercomputer.
It's the first time that this kind of 
quantum speed up has ever been shown.
It wouldn't be the standard 
definition of quantum supremacy,
but physicists
think it’s a big deal.
And although we’re still decades from harnessing
the full potential of quantum computers,
and maybe years from even doing 
anything particularly useful at all,
this achievement tells us 
that quantum computing
is edging ever closer to
those goals.
