A team of Australian engineers and physicists
have claimed a world first, the creation of a single atom
quantum bit in a silicone chip.
The work, published in Nature Magazine, is the fundamental requirement
for a revolutionary piece of hardware, the quantum computer.
Team leaders, Doctor Andrea Morello and Professor Andrew Dzurak
and the main experimental author, Jared Pla, are based at
The University of New South Wales in Sydney.
Modern computers store information as bits which can be
either zero or one to create a binary code.
These bits are realised
using transistors or other devices on a silicone chip.
Now the power of modern computing comes from the fact that
over the last fifty years, it's been possible to cram
more and more of these silicone transistors so there's now over a billion
of these on a single square centimetre of silicone on a chip.
Now imagine you can make a bit
that can be in the zero and the one state at the same time.
That's called a quantum bit, or qubit,
and the simplest example in nature would be just a single electron.
It has a magnetic dye pool
called the spin which is like the needle of a compass,
but because it's a quantum needle, it can be pointing up and down
at the same time.
If you can make a computer that uses that,
then you can program it in a completely different way
and you can solve certain problems that are otherwise impossible to solve
on normal computers.
For example, simulating and understanding
molecules and complicated drugs for instance.
So you can actually design them on a computer
instead of having to find them by trial and error.
So to build a large scale
functioning quantum computer, you need four basic elements.
First you need to be able to read information on the quantum bit,
then write information on a qubit, then to take pairs of qubits
and perform operations between them, and finally, transport information
around the quantum processor to perform complex calculations.
To build a qubit, you must first insert a single phosphorus atom
into a silicone chip, then build tiny electrodes
just thirty nanometres wide above it.
Each wire is three thousand times smaller than the width of a human hair.
Adding a small voltage
to the electrode above the phosphorus ion forces an electron to cross the gap
and orbit the phosphorus.
That's the initialisation stage
and the qubit is in a logic zero state.
What we do to write information on the electron spin is to
radiate it with microwaves.
The spin absorbs these microwaves
and then begins to rotate around this sphere from down to up.
It can't stay tied to the phosphorus atom at spin up
so it drops back into the electron pool.
This switches the transistor on
which corresponds to reading a logic one state.
What we've done now is to demonstrate the first two steps
for a quantum computer, to read and to write information on
a single quantum bit represented by an electron spin but this is still
done with the same technology used for normal silicone chips.
The electron is attached to an atom
that's implanted in the silicone a nd the quantum information encoded on it
is read out with a silicone transistor j ust fabricated next to the electron.
Silicone microelectronics and nano-electronics underpins all
of the information age at the moment and if you can make a quantum computer
using silicone, then you've got a fantastic advantage in terms of
manufacturability.
So the fact that we've now demonstrated a quantum bit
in a system that uses effectively silicone transistors
to read it out, is a remarkable step.
And it is going to very significantly
accelerate the work in silicone.
I'm truly amazed every day that I step into the lab
I mean, on a daily basis I get to interact with this
single electron which belongs to a single atom.
We really are controlling nature at its most fundamental level
and being able to demonstrate the potential of the system
for quantum computing, to me it's just icing on the cake.