Recent breakthroughs show that quantum systems can exhibit reversibility in ways previously thought impossible, challenging our understanding of time's arrow and irreversibility.

In 2025, researchers at the University of Surrey demonstrated that two arrows of time can emerge simultaneously in quantum systems. "While our common experience tells us that time only moves one way, we are just unaware that the opposite direction would have been equally possible," explains Dr. Andrea Rocco, lead author of the study[^1].

The key insight comes from examining open quantum systems - those that interact with their environment. While classical physics suggests processes like spilled milk spreading across a table must be irreversible, quantum mechanics operates differently. Even after applying standard simplifying assumptions, the equations describing quantum systems behave the same way whether moving forward or backward in time[^1].

This theoretical work gained experimental validation in July 2025 through a breakthrough "entanglement battery" that allows physicists to manipulate quantum entanglement reversibly[^2]. Just as a regular battery stores energy, this quantum device can store and release entanglement while preserving the total amount, enabling previously impossible reversible transformations of quantum states.

However, this reversibility has strict limits. According to physicist Thomas Guff, it only works when specific mathematical conditions are met - particularly that a "memory kernel" remains symmetrical in time[^3]. The reversal also becomes impossible if an observer retains information about measurement outcomes, as this resets the initial conditions within that observer's branch of the universe[^4].

[^1]: Cosmos Magazine - Theoretical physicists show that quantum systems have opposing arrows of time

[^2]: Science Daily - Breakthrough battery lets physicists reverse entanglement

[^3]: EurekAlert - Physicists uncover evidence of two arrows of time emerging from the quantum realm

[^4]: Physics Stack Exchange - Where does the irreversibility came from if all the fundamental interaction are reversible?

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[–] 3 points 1 year ago

Why does "quantum" have to be bright like it's some kind of Cherenkov effect?

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  • 16 comments in c/science@lemmy.world view that post
    [–] 72 points 1 year ago (7 children)

    I'm not gonna even click, that headline is some incredibly bad pop sci

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  • [–] [S] 11 points 1 year ago* (3 children)

    I know it's an awful headline. I'd still be interested in what people think of the content, because there's something legit in there it seems, but this article (which is published on a number of websites and may be a fairly unedited press release) doesn't explain much. The headline writers seem to see the word "battery" and run with that, even though it's misleading.

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  • [–] 24 points 1 year ago (1 child)

    I went ahead and read the article. I know a bit about quantum computing. Here’s my summary of it:

    Entanglement is a useful resource for quantum networking, enabling things like quantum-secure communication and distributed quantum computing.

    TLDR The paper describes algorithms to more efficiently create a form of entanglement that’s useful from the error-prone “dirty” entanglement you get from entanglement-generating hardware.

    When you make entanglement, it often doesn’t come out perfect, and you need a technique to “distill” “good” entangled states out of a collection of “dirty” entangled states.

    The typical “rules” for this involve two parties that create dirty shared entanglement (shared entanglement means a pair of entangled qubits, but each party has one of the qubits). They can then do whatever they like with their qubits individually and can communicate (over classical channels e.g. the internet) but they can’t do anything “quantum” between the two of them.

    This paper analyzes the case where there is a 3rd party that follows these same rules but has been previously set up as an “entanglement battery”, which means preparing it in a special state from which entanglement can be “borrowed” or “returned” to the battery using only local operations and classical communication.

    In particular it’s looking for “reversible” (meaning no loss in total entanglement over the process) “entanglement manipulation” (changing the entanglement from one form into another, presumably more useful form). It goes into a lot of analysis as to what the limits on this process are, and makes analogies to how engines work in thermodynamics.

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  • [–] 2 points 1 year ago

    So, this magazine isn't one of the ones that has a hard prohibition on rephrasing headlines, from what I can tell.

    You could simply edit the title to better reflect the actual content of the article.

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  • [–] 15 points 1 year ago (1 child)

    Wake me up when they can rip through spacetime and find me an alternate reality where I’m not so tired.

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  • [+] 10 points 1 year ago* (1 child)
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    [–] 4 points 1 year ago
    [–] 3 points 1 year ago (1 child)

    Big battery will never let this see the light

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