Focus on quantum thermodynamics

By Rebecca Gillan on August 30, 2017

The interface between quantum information and thermodynamics is currently a very active area and the topical review The role of quantum information in thermodynamics — a topical review, published in Journal of Physics A: Mathematical and Theoretical is the most highly cited article in the journal from 2016. Here we talk to one of the authors of the review, Marcus Huber, from Institute for Quantum Optics and Quantum Information Vienna, to discover why this field is so active and where he thinks it’s heading.

What is your review about?

We review contemporary efforts in understanding the interplay of quantum information and thermodynamics. There have been several research lines that have been pursued in parallel and we wanted to amalgamate the communities working along them. We start by discussing pure state statistical mechanics, which investigates the very origin of equilibration and thermalisation in quantum systems. Once one takes the fact that most systems thermalize for granted, one can start building a resource theory with thermal states as free resources. Resource theories allow for an exact derivation of thermodynamic laws from microscopic principles, which is our second chapter. However, beyond classic thermodyamic figures of merit, one may be interested in genuinely quantum tasks with no classical equivalent, which is the third part of our review: The interplay of correlations and entanglement with thermodynamic notions. Then we move our attention to practical design of quantum machines as open quantum systems and the role that genuine quantum features have in their performance. Finally, we discuss the basics of fluctuating energies that are inevitable in every practical thermodynamic protocol, how they can be characterized and how they impact definitions of work and heat at the quantum scale.

The Huber group at IQOQI

What attracted you to this field?

The fact that there even some of the most basic notions are still in large parts open: What are appropriate notions of heat and work at the quantum scale? How do entanglement and other quantum features influence the workings of machines? Why is thermodynamics so effective and the notion of thermal states so ubiquitously applicable if all fundamental dynamics is unitary? Could there be a “quantum advantage”, similar to other fields, by harnessing quantum features?

Why is this area so active at the moment?

I think that the recent influx in activity also has to do with the fact there are different communities that have slowly developed a common language and are willing to learn from each other. This has led to some great results that have inspired more people to apply their expertise to some of the challenges in the field.

Where do you see the field going?

I think that part of the future will inevitably be an increased focus on experiments. Thermodynamics can be said to have been born out of the practical need to understand the limitations of the first engines being built. The first proof-of-principle quantum engines have recently been built and I believe that if useful quantum machines are actually being built and used, that this would create a clear set of questions to pursue going forward.

What discoveries would you most like to see?

Well, apart from answering the foundational questions and the experimental progress I mentioned before, I think that there may still be discoveries that I couldn’t possibly anticipate and I look forward to seeing them.

What are you working on now?

My background and many active projects are actually in the realm of quantum optics/information theory. In the past years, however, I have been slowly expanding my own research to all of the above topics. Currently I am working on more detailed proposals for experimental realizations of quantum refrigerators. But I also still pursue foundational questions, such as e.g. the thermodynamic origin of the arrow of time or the emergence of of classical features from complex quantum dynamics. I am also lucky to have an amazing team of postdocs and PhD students to explore these questions with and that I can learn from to guide future research.

We thank Marcus for publishing in the journal and taking the time to answer our questions.

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