Arne Laucht is a
Research Fellow at the School of Electrical Engineering &
Telecommunications at the University of New South Wales, in Australia, and the lead
author of a paper documenting a breakthrough experiment that involved
maintaining “quantum superposition” of an electron spin for ten times longer than ever achieved
previously, thereby making it easier to preserve and work with information on
the quantum level for longer periods and to use it to perform more calculations
using capabilities generated and supported by quantum effects..
You can
learn more about this work in “Quantum computers: 10-fold boost in stability achieved." The work shows how qubits “dressed” with an oscillating electromagnetic field
are more stable than “undressed” qubits without one. “Qubits” are the basic building blocks of
quantum computing, and can perform multiple calculations simultaneously, due to
the probabilistic nature of atomic structure at the quantum level.
As Laucht
says in this article:
“We have now
implemented a new way to encode the information: we have subjected the atom to
a very strong, continuously oscillating electromagnetic field at microwave
frequencies, and thus we have ‘redefined’ the quantum bit as the orientation of
the spin with respect to the microwave field.”
Dr. Laucht
was kind enough to provide Etopia News
with a statement comparing the work being done with quantum computing technology
in his lab with related work being done by the Sandia-Harvard team reported on
recently by Etopia News here and here.
Here’s what
he had to say:
“The
work done by the Sandia-Harvard team is a very nice demonstration of an
all-optical switch using a single SiV [silicon vacancy] centre in diamond integrated in a
photonic crystal nanobeam cavity, and the entanglement of two SiV centres via
the cavity. Aspects of these experiments have already been demonstrated in other
materials using other quantum systems, so the real novelty is the demonstration
of all of that within a single chip, with the potential to scale the system to
multiple colour centres.
“The physical system that was used by the
Sandia-Harvard team is completely different to the one that we are using. They
are using excitonic qubits while we are using spin qubits. Their qubits couple
directly to the electric field component of light, while our qubits couple to
the magnetic field component of microwaves. In principle, it would be possible
to demonstrate the entanglement of two spin qubits via a microwave cavity
(which would correspond to the measurements from the Sandia-Harvard team in our
physical system), however we would have to use special tricks to get the
coupling strengths large enough to see these effects. This could possibly be
done using the dressed qubits that we have demonstrated, or alternatively using
the flip-flop states of the phosphorus donor (see https://arxiv.org/abs/1509.08538 ).
“I hope that helps to clarify the connection between
the different experiments.”
Separated as they are by thousands of miles of
physical space, these quantum researchers are nevertheless still “entangled” in
their efforts to discover and apply quantum mechanical principles that could
transform computing and the world. It’s
almost “spooky action at a distance,” in which physically-separated-but-entangled
quantum states can function as a single, unitary entity.