Quantum jumps were observed (as predicted) in the lab long ago; see ''Are there quantum jumps?'' from my Theoretical Physics FAQ.Quantum Jumps are predicted using microwave monitoring. Weird.
But there are no relations to Schrödinger's cat.
This is serious work about tracking and controlling the continuous measurement of single quantum systems. One of the coauthors is Carmichael, a well-known expert in quantum optics and author of two volumes on Statistical methods in quantum optics.Minev et al. said:we experimentally demonstrate that the jump from the ground state to an excited state of a superconducting artificial three-level atom can be tracked as it follows a predictable ‘flight’, by monitoring the population of an auxiliary energy level coupled to the ground state. The experimental results demonstrate that the evolution of each completed jump is continuous, coherent and deterministic. We exploit these features, using real-time monitoring and feedback, to catch and reverse quantum jumps mid-flight—thus deterministically preventing their completion. Our findings, which agree with theoretical predictions essentially without adjustable parameters, support the modern quantum trajectory theory
Minev et al. said:despite the long-term unpredictability of the jumps from |G〉 to |D〉, they are preceded by an identical no-click record from run to run. Whereas the jump starts at a random time and can be prematurely interrupted by a click, the deterministic nature of the uninterrupted flight comes as a surprise given the quantum fluctuations in the heterodyne record Irec during the jump—an island of predictability in a sea of uncertainty. [...]
From the experimental results of Fig. 2a one can infer, consistent with Bohr’s initial intuition and the original ion experiments, that quantum jumps are random and discrete. Yet the results of Fig. 3 support a contrary view, consistent with that of Schrödinger: the evolution of the jump is coherent and continuous. The difference in timescales in the two figures allows the coexistence of these seemingly opposed point of views and the reconciliation of the discreteness of countable events, such as jumps, with the continuity of the deterministic Schrödinger’s equation. [...]
although all 6.8 × 106 recorded jumps (Fig. 3) are entirely independent of one another and stochastic in their initiation and termination, the tomographic measurements as a function of Δtcatch explicitly show that all jump evolutions follow an essentially identical, predetermined path in Hilbert space—not a randomly chosen one—and, in this sense, they are deterministic. These results are further corroborated by the reversal experiments shown in Fig. 4, which exploit the continuous, coherent, and deterministic nature of the jump evolution
The claim there is the usual unjustified amplification of science made sensational for the public.I'm always highly skeptical of sensational-sounding claims on phys.org.
As far as I can see, this is not much more than an experimental demonstration of the known fact that decoherence lasts a finite time.
Probably not. The system in the experiments reported is very special, and a single system, while a radioactive solid consists of a huge number of radiactive atoms, of which a random one will decay, and then another random one.If this is the case, is the the triggering of the decay of a individual atom in a radioactive solid also predictable?
https://www.nature.com/articles/s41586-019-1287-zHere we answer this question affirmatively: we experimentally demonstrate that the jump from the ground state to an excited state of a superconducting artificial three-level atom can be tracked as it follows a predictable ‘flight’, by monitoring the population of an auxiliary energy level coupled to the ground state. The experimental results demonstrate that the evolution of each completed jump is continuous, coherent and deterministic.
Please give a reliable source. Or did you mean that he said the following?There is an anecdote that Erwin Schrödinger threatened to quit physics, if people keep talking about "quantum jumps".
''If I had known we were going to go on having all this damned quantum-jumping, I would never have got involved in the subject.''Erwin Schrödinger said:Wenn es bei dieser verdammten Quantenspringerei bleiben soll, so bedaure ich, mich mit der Quantentheorie überhaupt befaßt zu haben.
''If I had known we were going to go on having all this damned quantum-jumping, I would never have got involved in the subject.'' (not completely faithful) translation from here, with reference to the original)
Or Lubos Motl in his critique; he is not the ultimate arbiter of science.Lubos Motl criticizes harshly the language which the authors of the Nature paper use. A "quantum leap" and a "trajectory" are not terms of the standard quantum mechanics.
Nature should be more careful in their editorial policy.
Yes, but in typical experimental quantum foundations papers in Nature, the purpose of changing the terminology is not a progress in understanding quantum foundations. The purpose is to rise hypes, which helps to publish in Nature, which helps to get funds for producing next papers of a similar kind, ...Terms in physics evolve and are adapted to whatever they are needed for. Otherwise we would have never progress in physics.
They don't change terminology for the purpose of getting publicity. They use long established terminology in their field that just happens to be rejected and miscredited by Lubos Motl.Yes, but in typical experimental quantum foundations papers in Nature, the purpose of changing the terminology is not a progress in understanding quantum foundations. The purpose is to rise hypes, which helps to publish in Nature, which helps to get funds for producing next papers of a similar kind
Many Nobel prizes were given for experimental work demonstrating existing features of Nature that were either predicted or later explained by standard quantum theory.Progress in understanding quantum foundations can be achieved in two ways: either by further developments of the theory, or by experiments the results of which differ from predictions of standard quantum theory. The present work achieved neither of those two.
Demonstrating the existence of a feature is one thing, understanding its existence is another. Typically the former comes from experiments and the latter from theories.Many Nobel prizes were given for experimental work demonstrating existing features of Nature that were either predicted or later explained by standard quantum theory.
The paper under discussion is about such a demonstration (though not of Nobel prize quality), and an explanation of it in terms of existing theory. Thus it is progress.Demonstrating the existence of a feature is one thing, understanding its existence is another. Typically the former comes from experiments and the latter from theories.
Read the original Nature paper rather than discussions of popular versions of it!https://motls.blogspot.com/2019/06/experimenters-and-especially.html
Lubos Motl criticizes harshly the language which the authors of the Nature paper use. A "quantum leap" and a "trajectory" are not terms of the standard quantum mechanics.
So I must have missed it, how does the paper explain it in terms of existing theory?The paper under discussion is about such a demonstration (though not of Nobel prize quality), and an explanation of it in terms of existing theory. Thus it is progress.
Read my post #20, the appendix of the paper, and references [5-9] on ''modern quantum trajectory theory''. Nowhere is any theory beyond that assumed.So I must have missed it, how does the paper explain it in terms of existing theory?
This criticism (should it be one) is very strange.Indeed, the association with quantum foundations has convinced many observers that quantum trajectory theory is different from standard quantum mechanics, and therefore to be regarded with deep suspicion [...] these same types of equations arise quite naturally in describing quantum systems interacting with environments (open systems) which are subjected to monitoring by measuring devices. In these systems, the stochastic equations arise as effective evolution equations, and are in no sense anything other than standard quantum mechanics
https://en.wikipedia.org/wiki/Quantum_jump_methodThe quantum jump method is an approach which is much like the master-equation treatment except that it operates on the wave function rather than using a density matrixapproach. The main component of the method is evolving the system's wave function in time with a pseudo-Hamiltonian; where at each time step, a quantum jump (discontinuous change) may take place with some probability. The calculated system state as a function of time is known as a quantum trajectory, and the desired density matrix as a function of time may be calculated by averaging over many simulated trajectories.
No. Scientific papers should ignore popular science, not give it credit for using poor terms.The authors should stress that this has nothing to do with quantum leaps of popular science.
They don't change terminology for the purpose of getting publicity. They use long established terminology in their field that just happens to be rejected and miscredited by Lubos Motl.
I don't think the paper I analyzed there is comparable in the quality of terminology to the one under discussion here. I'd appreciate if you would either moderate your severe accusations, or justify them in detail in the discussion thread associated with that Insight article.you took a similar approach some time ago in your insights article (https://www.physicsforums.com/insights/vacuum-fluctuations-experimental-practice/) which is an unjustified mixture of quoting stuff out of context, misapplying terminology that is used differently in different subfields and rejecting and miscrediting its usage in other fields.
This is an important experimental point.Having reread the present Nature article several times now, I think it is indeed worthy of being published in Nature. However, I consider the experimental ability to control a quantum system as the really important point here. In some sense, this is similar to Haroche's seminal work on cavity QED (https://www.nature.com/articles/nature05589, https://www.nature.com/articles/nature10376).
I don't think the paper I analyzed there is comparable in the quality of terminology to the one under discussion here. I'd appreciate if you would either moderate your severe accusations, or justify them detail in the discussion thread associated with that Insight article.
This is an important experimental point.
The interest for foundations is that monitoring and controlling the state of an individual quantum system can now be done to a point where earlier, more idealized instantaneous quantum jumps can be resolved in time, adding insight to the nature of these ''jumps''.
Since this is about the measurement of a single quantum system, I'd be interested how the minimal (statistical) interpretation makes sense of the correspondence between state and measurement results in this particular case.As you bring this "quantum jumping" up again, just have a look at this (all standard QT, no discontinous jumps) (including the theory part which is in the supplements):
https://www.nature.com/articles/s41586-019-1287-z
But on a single system. They can approximately tell from their measurements when this single system is in which energy eigenstate.Well, where is there a problem. They measure pretty many "quantum-jump events" in their given setup.
So, where is the problem with the standard minimal statistical interpretation? I've only glanced over the theoretical evaluation part (in the addons to the paper), but I don't see anything which is not in accordance with the standard interpretation, and this analysis explains the data.But on a single system. They can approximately tell from their measurements when this single system is in which energy eigenstate.
But how is your condition realized in this experiment??Whether you do the repeated measurements on one and the same single electron or on always other new electrons, doesn't play a role at all. The only thing you have to do is to prepare it always in the same state and then do the same measurements under the same conditions.