[hamdani yusuf (OP)]

https://www.quantamagazine.org/quantum-leaps-long-assumed-to-be-instantaneous-take-time-20190605/
Quantum Leaps, Long Assumed to Be Instantaneous, Take Time

An experiment caught a quantum system in the middle of a jump — something the originators of quantum mechanics assumed was impossible.

When quantum mechanics was first developed a century ago as a theory for understanding the atomic-scale world, one of its key concepts was so radical, bold and counter-intuitive that it passed into popular language: the “quantum leap.” Purists might object that the common habit of applying this term to a big change misses the point that jumps between two quantum states are typically tiny, which is precisely why they weren’t noticed sooner. But the real point is that they’re sudden. So sudden, in fact, that many of the pioneers of quantum mechanics assumed they were instantaneous.

A new experiment shows that they aren’t. By making a kind of high-speed movie of a quantum leap, the work reveals that the process is as gradual as the melting of a snowman in the sun. “If we can measure a quantum jump fast and efficiently enough,” said Michel Devoret of Yale University, “it is actually a continuous process.” The study, which was led by Zlatko Minev, a graduate student in Devoret’s lab, was published on Monday in Nature. Already, colleagues are excited. “This is really a fantastic experiment,” said the physicist William Oliver of the Massachusetts Institute of Technology, who wasn’t involved in the work. “Really amazing.”

But there’s more. With their high-speed monitoring system, the researchers could spot when a quantum jump was about to appear, “catch” it halfway through, and reverse it, sending the system back to the state in which it started. In this way, what seemed to the quantum pioneers to be unavoidable randomness in the physical world is now shown to be amenable to control. We can take charge of the quantum.

[evan_au]

I imagine that during the transition, the quantum system is in a superposition of two quantum states.

One of them wins out, in the end...

[yor_on]

Yep, that's what the article states. A superposition that unfold in time, that you even can reverse. And it is apparently related to a quantum trajectory theory  https://www.quantamagazine.org/how-quantum-trajectory-theory-lets-physicists-understand-whats-going-on-during-wave-function-collapse-20190703/
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As for the question I think this is pretty interesting. "  One thing is clear: It’s not like a classical trajectory, meaning a path taken in space. It’s more like the path taken through the abstract space of possible states the system might have, which is called Hilbert space. In traditional quantum theory, that path is described by the wave function of the Schrödinger equation. But crucially, QTT can also address how measurements affect that path, which the Schrödinger equation can’t do. In effect, the theory uses careful and complete observations of the way the system has behaved so far to predict what it will do in the future. "

There is one thing with it though. You need perfect control over all possible events / possibilities to use it. so the real difference with older descriptions are just the way it seem to take time, which then implies a continuous process instead of something that just switch 'instantly'. Because you're not allowed to observe the process, as that finalize it 'instantly', force it into a defined state. It's indirect measuring that tells them that it should be continuous, not direct observations.

And that is weird, isn't it? What kind of evolution 'jumps' to finalization just by you taking a direct observation of it? This type of indirect measuring (it has another name but I can't remember it for the moment) is in vouge, used to 'prove' a lot of things but they are still somewhat more or less questionable to me.

[hamdani yusuf (OP)]

I wasn't convinced by instant jump since it would imply infinite force.

[yor_on]

I don't know, But I find it very strange that a direct observation would 'finalize' it instantly while a indirect observation place this transformation, change of state, as a evolution under time. Why would you looking at it finalize it? That's the 'direct jump' you don't like. If they are correct it seems to me that it shouldn't matter how you study it.
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there is this discussion of what a probing means, as when you probe something you also disturb the state for it. But let's assume something in where it emits light. You don't do anything more than watch it with a high speed camera (detector) of some sort. There are no active measurements taken, you don't probe at all, you're perfectly passive. If it changes from a evolution to a final state instantly by you starting that observation, isn't that a proof of something more than just a time evolution?

you can't use a reflecting light for it, or maybe you can? That you need to know all parameters influencing this system to describe that time evolution doesn't state that it is in perfect isolation, does it? If all quantum processes needed to be in perfect isolation to exist there would be none.

In the end it doesn't matter, why would me probing force a 'instant transformation'? How can the process change from being 'indeterminate' to finalized timelessly by it, if it otherwise is described as a evolution taking time. Because a probe will define it instantly.

to get a better handle on it. As far as I know your probe will show you a already finalized state. There will be no moment of uncertainty to that observation. It's 'timeless'.

[alancalverd]

I imagine that during the transition, the quantum system is in a superposition of two quantum states.

Whatever happened to "forbidden transitions"? IIRC there is an infinity of them between any two quantum states, which may allow us to model a temporal path.