Aberystwyth University scientist proposes a new mechanism for building quantum computers

A new mechanism for building quantum computers has been proposed by an international team of scientists led by Dr Daniel Klaus Burgarth at Aberystwyth University.
Writing in the scientific journal Nature Communications (http://www.nature.com/ncomms/index.html), Dr Burgarth et al describe how the frequent observation of a basic building block of a quantum system, known as a qubit, could lead to the creation of far more powerful computers.
The paper, Exponential rise of dynamic complexity in quantum computing through projections http://www.nature.com/ncomms/2014/141010/ncomms6173/full/ncomms6173.html is published today, Friday 10 October 2014.
While the possibility of using quantum effects to develop a new type of computer has been known for over 30 years, only small “quantum computers” have been built until now.
Scientists are now engaged in a world wide effort to build large quantum computers which will be able perform some very complex computations in a very short time, tasks that would take the most powerful computers currently in use many thousands of years.
Dr Burgarth said: “Essentially our result is in the realm of theoretical physics, more specifically quantum computing.”
“What we show is that the act of measuring a quantum system can change its dynamics substantially, to the extent that the not-measured system is very simple while the measured one is a quantum computer.”
Besides potential practical applications, the result sheds new light on the role of measurements in quantum mechanics. While in our day-to-day life things appear independent of our observations, it is a perplexing but long known fact that this is no longer the case in the quantum world. The work of Dr Burgarth et al demonstrates this in the strongest possible way.
Dr Burgarth is a Senior Lecturer at the Institute of Mathematics, Physics and Computer Science at Aberystwyth University. Originally from Hamburg in Germany, he graduated in Physics at Freiburg University and was awarded his PhD from University College London.
As a researcher he has worked at ETH Zurich, Oxford University and Imperial College London.
His area of research is Quantum Physics and he works closely with physicists, mathematicians and computer scientists. He joined Aberystwyth University in 2011.

Notes:

Exponential rise of dynamical complexity in quantum computing through projections
http://www.nature.com/ncomms/2014/141010/ncomms6173/full/ncomms6173.html
Daniel Klaus Burgarth1, Paolo Facchi2,3, Vittorio Giovannetti4, Hiromichi Nakazato5,
Saverio Pascazio2,3 & Kazuya Yuasa5

Synopsis
The ability of quantum systems to host exponentially complex dynamics has the potential to revolutionize science and technology. Therefore, much effort has been devoted to developing of protocols for computation, communication and metrology, which exploit this scaling, despite formidable technical difficulties. Here we show that the mere frequent observation of a small part of a quantum system can turn its dynamics from a very simple one into an exponentially complex one, capable of universal quantum computation. After discussing examples, we go on to show that this effect is generally to be expected: almost any quantum dynamics becomes universal once ‘observed’ as outlined above. Conversely, we show that any complex quantum dynamics can be ‘purified’ into a simpler one in larger dimensions. We conclude by demonstrating that even local noise can lead to an exponentially complex dynamics.

1 Institute of Mathematics, Physics and Computer Science, Aberystwyth University, Aberystwyth. 2 Dipartimento di Fisica and MECENAS, Universita di Bari, Italy. 3 INFN, Sezione di Bari, Italy. 4 NEST, Scuola Normale Superiore and Istituto Nanoscienze-CNR, Pisa, Italy. 5 Department of Physics, Waseda University, Tokyo, Japan.