Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Quantum engines must break down

26.06.2013
Our present understanding of thermodynamics is fundamentally incorrect if applied to small systems and need to be modified, according to new research from University College London and the University of Gdansk

Our present understanding of thermodynamics is fundamentally incorrect if applied to small systems and needs to be modified, according to new research from University College London (UCL) and the University of Gdañsk. The work establishes new laws in the rapidly emerging field of quantum thermodynamics.

The findings, published today in Nature Communications, have wide applications in small systems, from nanoscale engines and quantum technologies, to biological motors and systems found in the body.

The laws of thermodynamics govern much of the world around us – they tell us that a hot cup of tea in a cold room will cool down rather than heat up; they tell us that unless we are vigilant, our houses will become untidy rather than spontaneously tidy; they tell us how efficient the best heat engines can be.

The current laws of thermodynamics only apply to large objects, when many particles are involved. The laws of thermodynamics for smaller systems are not well understood but will have implications for the construction of molecular motors and quantum computers, and might even determine how efficient energy extracting processes such as photosynthesis can be.

In this study researchers used results from quantum information theory to adapt the laws of thermodynamics for small systems, such as microscopic motors, nanoscale devices and quantum technologies.

Small systems behave very differently to large systems composed of many particles. And when systems are very small, then quantum effects come into play. The researchers found a set of laws which determine what happens to such microscopic systems when we heat them up or cool them down. An important consequence of their laws is that there is more fundamental irreversibility in small systems, and this means that microscopic heat engines can not be as efficient as their larger counterparts.

"We see that nature imposes fundamental limitations to extracting energy from microscopic systems and heat engines. A quantum heat engine is not as efficient as a macroscopic one, and will sometimes fail," said Professor Oppenheim, a Royal Society University Research Fellow at UCL's Department of Physics and Astronomy and one of the authors of the research. "The limitations are due to both finite size effects, and to quantum effects."

The researchers investigated the efficiency of microscopic heat engines and found that one of the basic quantities in thermodynamics, the free energy, does not determine what can happen in small systems, and especially in quantum mechanical systems. Instead, several new free energies govern the behaviour of these microscopic systems.

In large systems, if you put pure energy into a system, then you can recover all this energy back to use to power an engine which can perform work (such as lifting a heavy weight). But the researchers found that this was not the case for microscopic systems. If you put work into a quantum system you generally cannot get it all back.

Professor Michal Horodecki of the University of Gdansk, and co-author of the paper, said: "Thermodynamics at the microscopic scale is fundamentally irreversible. This is dramatically different to larger systems where all thermodynamic processes can be made reversible if we change systems slowly enough."

Notes for Editors

1. For more information or to speak to the authors, please contact Rosie Waldron in the UCL Media Relations Office on tel: +44 (0)20 7679 9041, out of hours +44 (0)7917 271 364, e-mail: r.waldron@ucl.ac.uk. Please note Rosie will be out of the office on Wednesday 26 June, in her absence please contact Clare Ryan tel: +44 (0)20 3108 3846 email: clare.ryan@ucl.ac.uk.

2. 'Fundamental limitations for quantum and nanoscale thermodynamics' is published in the journal Nature Communications on Wednesday 26 June. For copies of the paper please contact UCL Media Relations.

About UCL (University College London)

Founded in 1826, UCL was the first English university established after Oxford and Cambridge, the first to admit students regardless of race, class, religion or gender and the first to provide systematic teaching of law, architecture and medicine.

We are among the world's top universities, as reflected by our performance in a range of international rankings and tables. According to the Thomson Scientific Citation Index, UCL is the second most highly cited European university and the 15th most highly cited in the world.

UCL has nearly 25,000 students from 150 countries and more than 9,000 employees, of whom one third are from outside the UK. The university is based in Bloomsbury in the heart of London, but also has two international campuses – UCL Australia and UCL Qatar. Our annual income is more than £800 million.

Rosie Waldron | EurekAlert!
Further information:
http://www.ucl.ac.uk

More articles from Physics and Astronomy:

nachricht Black hole spin cranks-up radio volume
15.01.2018 | National Institutes of Natural Sciences

nachricht The universe up close
15.01.2018 | Georg-August-Universität Göttingen

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Scientists decipher key principle behind reaction of metalloenzymes

So-called pre-distorted states accelerate photochemical reactions too

What enables electrons to be transferred swiftly, for example during photosynthesis? An interdisciplinary team of researchers has worked out the details of how...

Im Focus: The first precise measurement of a single molecule's effective charge

For the first time, scientists have precisely measured the effective electrical charge of a single molecule in solution. This fundamental insight of an SNSF Professor could also pave the way for future medical diagnostics.

Electrical charge is one of the key properties that allows molecules to interact. Life itself depends on this phenomenon: many biological processes involve...

Im Focus: Paradigm shift in Paris: Encouraging an holistic view of laser machining

At the JEC World Composite Show in Paris in March 2018, the Fraunhofer Institute for Laser Technology ILT will be focusing on the latest trends and innovations in laser machining of composites. Among other things, researchers at the booth shared with the Aachen Center for Integrative Lightweight Production (AZL) will demonstrate how lasers can be used for joining, structuring, cutting and drilling composite materials.

No other industry has attracted as much public attention to composite materials as the automotive industry, which along with the aerospace industry is a driver...

Im Focus: Room-temperature multiferroic thin films and their properties

Scientists at Tokyo Institute of Technology (Tokyo Tech) and Tohoku University have developed high-quality GFO epitaxial films and systematically investigated their ferroelectric and ferromagnetic properties. They also demonstrated the room-temperature magnetocapacitance effects of these GFO thin films.

Multiferroic materials show magnetically driven ferroelectricity. They are attracting increasing attention because of their fascinating properties such as...

Im Focus: A thermometer for the oceans

Measurement of noble gases in Antarctic ice cores

The oceans are the largest global heat reservoir. As a result of man-made global warming, the temperature in the global climate system increases; around 90% of...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

10th International Symposium: “Advanced Battery Power – Kraftwerk Batterie” Münster, 10-11 April 2018

08.01.2018 | Event News

See, understand and experience the work of the future

11.12.2017 | Event News

Innovative strategies to tackle parasitic worms

08.12.2017 | Event News

 
Latest News

White graphene makes ceramics multifunctional

16.01.2018 | Materials Sciences

Breaking bad metals with neutrons

16.01.2018 | Materials Sciences

ISFH-CalTeC is “designated test centre” for the confirmation of solar cell world records

16.01.2018 | Power and Electrical Engineering

VideoLinks
B2B-VideoLinks
More VideoLinks >>>