Quantum computers are all over the news, but what are they
and how do they differ from conventional computing?
If they can be built economically and at scale
quantum computers will harness properties
that extend beyond the limits of classical physics
to offer us exponential gains in computing power.
Classical computers are made of bits, a unit of information
that can either be a 0 or a 1.
But in a quantum computer, the basic unit, known as a qubit,
can represent both 0 and 1 at the same time, a state known
as superposition.
By stringing together qubits the number
of states that they could represent
rises exponentially, enabling it to compute
millions of possibilities instantaneously.
The applications of this type of machine
could revolutionise fields from cryptography to chemistry,
ranging from materials science, agriculture,
and pharmaceuticals, not to mention artificial intelligence
and energy.
So far, the challenge has been to scale up
the number of qubits to perform useful calculations
while reducing the number of errors
that the qubits are prone to.
This week Google has published a landmark paper
in the scientific journal Nature.
It claims to have built a processor that
can perform a very specific calculation in 200 seconds that
would take today's most powerful computer 10,000
years to complete.
This demonstration is known as quantum supremacy.
This is just the first step towards creating
a useful quantum computer.
Next, scientists will have to build a scaled-up version that
can perform real world, useful calculations, thus achieving
the promise of quantum computing.