Better control of building blocks for quantum computer

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Delft University of Technology. "Better control of
building blocks for quantum computer."
ScienceDaily. ScienceDaily, 23 December 2010.
<www.sciencedaily.com/
releases/2010/12/101223083759.htm>.
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Scanning electron image of the nanowire device
with gate electrodes used to electrically control
qubits, and source and drain electrodes used to
probe qubit states.
cientists from the Kavli Institute of
Nanoscience at Delft University of
Technology and Eindhoven University of
Technology have succeeded in controlling
the building blocks of a future super-fast
quantum computer. They are now able to
manipulate these building blocks (qubits) with
electrical rather than magnetic fields, as has been
the common practice up till now. They have also
been able to embed these qubits into
semiconductor nanowires.
The scientists' findings have been published in
the current issue of the journal Nature (Dec. 23).
A qubit is the building block of a possible, future
quantum computer, which would far outstrip
current computers in terms of speed. One way to
make a qubit is to trap a single electron in
semiconductor material. A qubit can, just like a
normal computer bit, adopt the states '0' and '1'.
This is achieved by using the spin of an electron,
which is generated by spinning the electron on its
axis. The electron can spin in two directions
(representing the '0' state and the '1' state).
Until now, the spin of an electron has been
controlled by magnetic fields. However, these field
are extremely difficult to generate on a chip. The
electron spin in the qubits that are currently being
generated by the Dutch scientists can be
controlled by a charge or an electric field, rather
than by magnetic fields. This form of control has
major advantages, as Leo Kouwenhoven, scientist
at the Kavli Institute of Nanoscience at TU Delft,
points out. "These spin-orbit qubits combine the
best of both worlds. They employ the advantages
of both electronic control and information storage
in the electron spin," he says.
There is another important new development in
the Dutch research: the scientists have been able
to embed the qubits (two) into nanowires made
of a semiconductor material (indium arsenide).
These wires are of the order of nanometres in
diameter and micrometres in length. "These
nanowires are being increasingly used as
convenient building blocks in nanoelectronics.
Nanowires are an excellent platform for quantum
information processing, among other
applications," says Kouwenhoven.