Theoretical physicists discover a deep connection between quantum entanglement and thermalization

Theoretical physicists at Trinity have found a deep connection between one of the most striking features of quantum mechanics – quantum entanglement – ​​and thermalization, which is the process by which something comes into thermal equilibrium with its surroundings.

Their the results have been published on January 31, 2020, in the prestigious magazine Physical examination letters.

We’re all familiar with thermalization – just think about how your coffee reaches room temperature over time. Quantum entanglement, on the other hand, is another story.

Yet the work done by Marlon Brenes, Ph.D. Candidate and Professor John Goold of Trinity, in collaboration with Silvia Pappalardi and Professor Alessandro Silva of SISSA in Italy, shows how the two are inextricably linked.

Explaining the significance of the discovery, Professor Goold, head of Trinity’s QuSys group, explains:

“Quantum entanglement is a counterintuitive feature of quantum mechanics, which allows particles that have interacted with each other at some point to become correlated in ways that are not classically possible. Measurements of one particle affects the measurement results of the other, even if they are light years apart. Einstein called this effect “frightening action at a distance”.

“It turns out that tangle is not just scary but actually ubiquitous and in fact, what’s even more amazing is that we live in a time when technology is starting to exploit this feature to accomplish feats that were thought impossible just a few years ago. These quantum technologies are being developed rapidly in the private sector with companies such as Google and IBM leading the way.”

But what does all this have to do with cold brew coffee?

Professor Goold clarifies:

“When you brew a cup of coffee and leave it for a while, it cools down until it reaches the temperature of its surroundings. This is thermalization. In physics we say the process is irreversible – as we know our coffee once hot will not magically cool and warm The way irreversibility and thermal behavior emerge in physical systems is something that fascinates me as a scientist because it applies to scales as small as atoms, to cups of coffee, and even to the evolution of the universe itself.In physics, statistical mechanics is the theory that aims to understand this process from a microscopic point of view For quantum systems, the emergence of thermalization is notoriously tricky and is at the center of this current research.

So what does all this have to do with tangle and what do your results say?

Professor Goold says:

“In statistical mechanics, there are different ways, called sets, of describing how a system thermalizes, all of which are considered equivalent when you have a large system (roughly on scales of 10^23 atoms). However, this what we show in our work is that not only is entanglement present in the process, but its structure is very different depending on how you choose to describe your system, so it gives us a way to test fundamental questions in statistical mechanics The idea is general and can be applied to a range of systems as small as a few atoms and as large as black holes.

Marlon Brenes, Ph.D. candidate at Trinity and first author of the paper, used supercomputers to simulate quantum systems to test the idea.

Brenes, a digital specialist, said:

“The numerical simulations that I carried out for this project are at the limit of what can currently be done at the level of high performance computing. To run the code, I used the national facility, ICHEC, and the new Kay machine. So, in addition to being a nice foundational result, the work has really helped us push the boundaries of this kind of computing approach and establish that our codes and the national architecture are working at the cutting edge.

Reference: “Multipartite Entanglement Structure in the Eigenstate Thermalization Hypothesis” by Marlon Brenes, Silvia Pappalardi, John Goold and Alessandro Silva, January 31, 2020, Physical examination letters.
DOI: 10.1103/PhysRevLett.124.040605

Professor Goold’s research is supported by an SFI-Royal Society University Research Fellowship and a European Council Starting Grant.

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