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.
