Researchers gain information advantage from surprising quantum source

August 06, 2012

New research lends hope that a phenomenon called quantum discord could be harnessed to bring quantum technologies within easier reach than expected. The work, by an international team, is published 5 August in Nature Physics.

Up until a few years ago, researchers thought that realising quantum technologies would mean harnessing the most difficult-to-tame properties of the quantum world. For example, 'entanglement', the phenomenon referred to by Einstein as spooky-action-at-a-distance, was thought to be a resource required to run a quantum computer. This presents a challenge. In a laboratory setting, entanglement can be protected with near ideal conditions. Outside the lab, however, entanglement is fragile and transient.

But now researchers realise that entanglement may not always be necessary. In the past few years, scientists have discovered examples of technologies that seem to gain a quantum advantage without entanglement. Researchers are left with the question, where does the quantum power come from?

The new research by the National University of Singapore (NUS), The Australian National University (ANU), the University of Queensland and the University of Oxford identifies that quantum discord, a more robust and easy to access phenomenon than entanglement, can also deliver a quantum advantage.

The team in Singapore discovered a direct link between quantum power and quantum discord. "We've shown that quantum discord is a resource that we can tap with the right quantum tools," said Mile Gu, a Research Fellow of the Centre for Quantum Technologies at NUS.

The ANU team encoded information onto laser light to demonstrate the unlocking of this quantum resource. In their experiment, they show that they can retrieve more information by using quantum discord than if the discord is not accessed.

Ping Koy Lam, Professor at ANU, said "The experiment is analogous to decoding music from a AM/FM radio simulcast that is badly affected by static."

They found that discord is similar to shared quantum static and that more 'music' can be extracted from this simulcast with the right quantum tools. Quantum discord has been shown to be present in many systems, and might previously have been characterised as unwanted noise. This has made some scientists sceptical that it could be useful. The new results suggest otherwise. The experiment demonstrated isn't considered a quantum computation, but it shows that discord has potential that can be unlocked for quantum technologies.

Researchers are now looking for other tasks that may be enhanced by quantum discord. The hope is that discord could prove an easier path to future quantum technologies than entanglement. With a scientist's caution, Lam said "Our work hints towards the possibility that the requirements on certain quantum technologies could be relaxed."
-end-
For details of the work, see M. Gu et al, "Observing the operational significance of discord consumption", Nature Physics, doi:10.1038/NPHYS2376. http://dx.doi.org/10.1038/NPHYS2376

A preprint is available at arXiv:1203.0011. http://arxiv.org/abs/1203.0011

Researcher Contacts

Mile Gu
Research Fellow
Centre for Quantum Technologies
National University of Singapore
Email: cqtmileg@nus.edu.sg
Tel: +65 94599507

Ping Koy Lam
Professor
Centre for Quantum Computation and Communication Technology
The Australian National University
Email: Ping.Lam@anu.edu.au
Tel: + 61 (0)2 6125 8378 and +61 (0) 414 839 612

About National University of Singapore (NUS)

A leading global university centred in Asia, the National University of Singapore (NUS) is Singapore's flagship university which offers a global approach to education and research, with a focus on Asian perspectives and expertise.

NUS has 16 faculties and schools across three campuses. Its transformative education includes a broad-based curriculum underscored by multi-disciplinary courses and cross-faculty enrichment. Over 37,000 students from 100 countries enrich the community with their diverse social and cultural perspectives.

NUS has three Research Centres of Excellence (RCE) and 22 university-level research institutes and centres. It is also a partner in Singapore's 5th RCE. NUS shares a close affiliation with 16 national-level research institutes and centres. Research activities are strategic and robust, and NUS is well-known for its research strengths in engineering, life sciences and biomedicine, social sciences and natural sciences. It also strives to create a supportive and innovative environment to promote creative enterprise within its community.

For more information, please visit www.nus.edu.sg

About Centre for Quantum Technologies at the National University of Singapore

The Centre for Quantum Technologies (CQT) was established as Singapore's inaugural Research Centre of Excellence in December 2007. It brings together quantum physicists and computer scientists to explore the quantum nature of reality and quantum possibilities in information processing. CQT is funded by Singapore's National Research Foundation and Ministry of Education and is hosted by the National University of Singapore (NUS). More at www.quantumlah.org.

About The Australian National University The Australian National University (ANU) is one of Australia's premier universities and ranked amongst the best in the world. It was created by Federal Parliament in 1946 to drive the nation forward and advance Australia's international standing through research and education of the highest quality. ANU is distinctive because of its national mission, international focus and impressive record of success in research and education for undergraduate and postgraduate students. Our leading researchers drive our educational programs and shape the ANU learning experience. www.anu.edu.au

Centre for Quantum Technologies at the National University of Singapore

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