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Mathematical device or physical fact? The elusive nature of the quantum wavefunction may be pinned down at last.
At the heart of the weirdness for which the field of quantum mechanics is famous is the wavefunction, a powerful but mysterious entity that is used to determine the probabilities that quantum particles will have certain properties. Now, a preprint posted online on 14 November1 reopens the question of what the wavefunction represents — with an answer that could rock quantum theory to its core. Whereas many physicists have generally interpreted the wavefunction as a statistical tool that reflects our ignorance of the particles being measured, the authors of the latest paper argue that, instead, it is physically real.
“I don't like to sound hyperbolic, but I think the word 'seismic' is likely to apply to this paper,” says Antony Valentini, a theoretical physicist specializing in quantum foundations at Clemson University in South Carolina.
Valentini believes that this result may be the most important general theorem relating to the foundations of quantum mechanics since Bell’s theorem, the 1964 result in which Northern Irish physicist John Stewart Bell proved that if quantum mechanics describes real entities, it has to include mysterious “action at a distance”.
Action at a distance occurs when pairs of quantum particles interact in such a way that they become entangled. But the new paper, by a trio of physicists led by Matthew Pusey at Imperial College London, presents a theorem showing that if a quantum wavefunction were purely a statistical tool, then even quantum states that are unconnected across space and time would be able to communicate with each other. As that seems very unlikely to be true, the researchers conclude that the wavefunction must be physically real after all.
David Wallace, a philosopher of physics at the University of Oxford, UK, says that the theorem is the most important result in the foundations of quantum mechanics that he has seen in his 15-year professional career. “This strips away obscurity and shows you can’t have an interpretation of a quantum state as probabilistic,” he says.
Historical debate
The debate over how to understand the wavefunction goes back to the 1920s. In the ‘Copenhagen interpretation’ pioneered by Danish physicist Niels Bohr, the wavefunction was considered a computational tool: it gave correct results when used to calculate the probability of particles having various properties, but physicists were encouraged not to look for a deeper explanation of what the wavefunction is.
Albert Einstein also favoured a statistical interpretation of the wavefunction, although he thought that there had to be some other as-yet-unknown underlying reality. But others, such as Austrian physicist Erwin Schrödinger, considered the wavefunction, at least initially, to be a real physical object.
The Copenhagen interpretation later fell out of popularity, but the idea that the wavefunction reflects what we can know about the world, rather than physical reality, has come back into vogue in the past 15 years with the rise of quantum information theory, Valentini says.
Rudolph and his colleagues may put a stop to that trend. Their theorem effectively says that individual quantum systems must “know” exactly what state they have been prepared in, or the results of measurements on them would lead to results at odds with quantum mechanics. They declined to comment while their preprint is undergoing the journal-submission process, but say in their paper that their finding is similar to the notion that an individual coin being flipped in a biased way — for example, so that it comes up 'heads' six out of ten times — has the intrinsic, physical property of being biased, in contrast to the idea that the bias is simply a statistical property of many coin-flip outcomes.
Quantum information
Robert Spekkens, a physicist at the Perimeter Institute for Theoretical Physics in Waterloo, Canada, who has favoured a statistical interpretation of the wavefunction, says that Pusey's theorem is correct and a “fantastic” result, but that he disagrees about what conclusion should be drawn from it. He favours an interpretation in which all quantum states, including non-entangled ones, are related after all.
Spekkens adds that he does expect the theorem to have broader consequences for physics, as have Bell’s and other fundamental theorems. No one foresaw in 1964 that Bell’s theorem would sow the seeds for quantum information theory and quantum cryptography — both of which rely on phenomena that aren’t possible in classical physics. Spekkens thinks this theorem may ultimately have a similar impact. “It’s very important and beautiful in its simplicity,” he says.
- Journal name:
- Nature
- DOI:
- doi:10.1038/nature.2011.9392
Really sad that individuals are at a stage where they do not cite other peoples work related to the same conclusion.
This theorem seems to be correct and has far reaching consequences for almost all statistical interpretational models of quantum mechanics but with one exception. This exception is the interpretation pioneered by the Egyptian Mohamed El Naschie, called E-infinity theory, based on the assumption of a Cantorian transfinite fractal space-time at the core of quantum mechanics. The explanation of why this theorem does not apply to this interpretation, and possibly only to this interpretation at present, lies in Ultimate L logic of the American mathematician Hugh Woodin. Simply stated, the mathematical logic of E-infinity theory is that of Ultimate L while the mathematical logic used by Pusey et al in the proof of their present fantastic theorem is ordinary mathematical logic. This makes their proof incomplete in terms of Ultimate L, thus does not apply to the E-infinity interpretation of Mohamed El Naschie which belongs to the Ultimate L universe. To see how this happens to be true, one needs to understand in details the basics of Ultimate L logic and that of E-infinity to get to be convinced that the latter logic definitely belongs to the earlier.
I personally think that the above observation, if true, should be considered as another proof of the correctness of El Naschie's ideas, where the more favored statistical interpretation will survive.
Assuming that the outcome of a measurement is determined by the measurement apparatus and the physical properties of the quantum system alone, then the authors CLAIM that you can arrange for a measurement where the apparatus returns results inconsistent with the predictions of quantum mechanics, resulting in a paradox. They then conclude the paradox constitutes proof of the quantum state (or wavefunction) corresponding to and underlying objective physical reality. Detroit psychics
"Then even quantum states that are unconnected across space and time would be able to communicate with each other. As that seems very unlikely to be true" and what if it's true? What then? :D
lenjerie intima online
I did no have a chance to red the paper, but it seems that the proof uses a reductio ad absurdum argument?
Realism can be seen only from the anti-real space/energy. Quantum numbers do not reflect properties due interference of particles/strings/waves. Quantum states do touch on general directionality of states of a wave function, however NOT reality. Einstein never realized the intricate nature of nano and sub nano space-time, because neither energy nor quantum space has been defined in complex matter states. We can only measure the effect (difractability) of a cause (interference). Particles are not particles, strings are not strings and waves are not waves. Statistical mechanics in electron delocalization works to a limited space/energy. It does fail to establish the connectivity between entanglement and dissipation in expanded energy/spaces and the so 'mysterious' action at a distance. Space is matter/antimatter occupying time determined by interference of particles/strings/waves. How that happens ? I am in a deep doubt that current math tools can formulate it clearly due uncertainty in numbers themselves. Heisenberg did break off philosophy of Einstein. I guarantee you interference intensity will change as air quality (carbon molecule density) changes. We need neither position nor momentum. All we need is to define at least two entangled states of interference that can be amplified in space/energy, thus compute discontinuous quasi states of a continues interference. Carbon rules. limited states = unlimited observables.
I read the preprint a few days ago . My conculsion Everett was right and realism rules.
webdeluxe
Leonardo RUBINO:
I think the universe is quantized as it's oscillating (Big Bang-Crunch-Bang) and it's got an oscillation frequency and all frequencies in the universe must be a multiple of it (when trying to understand the nature, search into simplicity):
http://www.fisicamente.net/FISICA_2/quantizzazione_universo.pdf
http://www.fisicamente.net/FISICA_2/UNIFICAZIONE_GRAVITA_ELETTROMAGNETISMO.pdf
http://www.mednat.org/new_scienza/strani_legami_numerici_universo.pdf
Ciao.
Leonardo RUBINO.
leonrubino@yahoo.it
What do you think about this earlier paper by Dolev and Elitzur which argues that the behavior of the wavefunction is fundamentally non-sequential instead of sequential:
http://arxiv.org/abs/quant-ph/0102109
Thanks.
@Matteo Staffaroni you've pretty much nailed it ! The authors' misunderstanding of the quantum theory of measurement is obvious. I don't know how the paper got positive comment from Nature, but I doubt we will be seeing it in a refereed journal any time soon.
@ matteo staffaroni & joseph palazzo
where is the error precisely?
Radoslav time cannot compress with matter (mass) as time is a numerical sequence of material change.
In the universe time exists exclusively as a mathematical quantity – numerical sequence that we measure with clocks. This is the core of Einsteins' idea of timeless universe.
Universe does not run in time, on the contrary time run in the universe as a numerical sequence of its changes.
yours amrit
Their paper has been refuted:
http://www.physicsforums.com/showpost.php?p=3627144&postcount=95
http://www.physicsforums.com/showpost.php?p=3628836&postcount=123
@matteo Staffaroni
You are correct. The authors have made a crucial error in taking their vectors to be orthogonal when they are not, and have drawn the wrong conclusion.
Dear Camp L Obacter:
Who is this Wallace you speak of?
Dear Delua Lunatone:
A bit condescending aren't you? How do we know WHO you are?
Uncertainty principle can be precisely defined by a given function. Calculated value of Planck constant can be obtained from it, this must be the function's minimum value. I have done the work:
http://outlawphysics.bravehost.com/
Cheers!
The fundamental physical reality is that particles are not particles, waves are not waves and strings are not strings all the time. Simply, transformation of fundamentals appear not only in functional groups atomic rearrangement as measured by chemical physics. All it matters is the interference of particles/strings/waves that sets up time. Statistical wave function of a quantum state of a particle appears as an outcome of freedom although limited states equal unlimited observables (matrices). That is to say uncertainty principle ( for existing only observables) = wave function (Schrodinger) states. Limited Entangled States emerge into unlimited Observational Reality. This works in biological set clocks for time and should for any other physical system. However, time cannot be coupled to space because space is open and undefined. Thus, time compresses with matter in order to expand computation on energy coupled to space. That is the reverse of looking at light spectra considering matter compressibility principle that break down uncertainty principle of particle location. Simply no need for momentum and position of a quantum system. There is only need of how entangled states relate to each other as a function of time- interference of particles, strings and waves. If there were N systems of observables , then via compressibility principle one would be possible to formulate N-x systems, where x is rid off uncertain previously observed systems. thus by reducing observed systems, quantum states should increase in order to catch up entangled states.
Action on distance is a result of energy density of quantum vacuum.
see more on home page of our institute
www.spacelife.si
article: Mass and gravity have origin in energy density of quantum vacuum.
yours amrit
Schrodinger Equation represents electrical or magnetic field transmitting through charged particles. The famous equation can be directly derived by Newton's second law and Maxwell's equations. I have worked it out in 2008. Here is the link:
http://outlawphysics.bravehost.com/
If you need a sample,please leave your e-mail. Thanks!
Is it possible that finally the partisans of scientism currently imposing exclusive use of the term, 'counter-intuitive', solely apt in particular contexts, although clearly not in relation to paradoxes, will be forced to accept that there can be no skirting around description of paradoxical phenomena as plainly 'counter-rational' by very definition?
Quantum nonlocality is consistent with Einstein locality in the sense that the nonlocality of quantum mechanics does not allow any faster-than-light communication or superluminal energy transport. It is an example of what Gell-Mann meant when he said, â€৊nything that can happen will happen.” Quantum mechanics pushes this to the extreme, and, as Gell-Mann emphasizes in The Quark and the Jaguar, quantum mechanics (like evolution) is a fact, not a theory.
	There is no real contradiction between classical and quantum physics. Classical physics gives very reasonable and logical laws which either allow or disallow a variety of phenomena. Quantum mechanics goes farther by allowing phenomena that classical physics neither allows nor disallows, but quantum mechanics does not allow anything which is classically forbidden. It boils down to semantics. Instead of saying that quantum entanglement allows action at a distance, it should be said that entanglement creates an illusion of action at a distance, in processes where there is no real action, in the sense that there is no superluminal communication or energy transport. The cleverest EPRB experiments demonstrate quantum sleight of hand, not spooky action at a distance. When people speak loosely of such things, confusion results. Einstein’s objection to spooky action at a distance was an objection to such loose talk, not an objection to quantum mechanics.
	For detailed analysis of the entanglement phenomenon, see the article â€ৎntanglement Untangled” in Physics Essays volume 19, pages 299-301 (June 2006).
I am willing to bet money that neither the opponents or proponents in this comment section have any idea what this means. Because you would have to be quantum physicists. The chance of even one of you knowing enough about this to speak in either direction is immensely small.
Just sayin'.
Some very highly respected experts in quantum mechanics say this is important research and potentially a game-changer.
Time will tell.
Avidly have I read Wallace's work in pursuit of expanding my physics ken; no other books in my library are as treasured as his "Brief Collisions with Hideous Particles" and "Consider the Neutrino". It's truer now than ever to say that he was ahead of his time.
It's usually a good idea to actually read the preprint before taking to the comments section and endorsing the work of someone else .
If you're too lazy to read the preprint, I have summarized its essence for you:
The authors begin by making two claims,
1) If a quantum state reflects an underlying objective physical reality, then a list of values of physical properties (i.e., commuting observables) should be sufficient to uniquely determine a quantum state.
2) If a quantum state does not reflect an underlying objective physical reality but is merely a mathematical tool for obtaining probabilities concerning the outcome of an experiment, then a list of values of physical properties cannot uniquely determine the quantum state. There may be several distinct states statistically compatible with a given list of values of physical properties.
The authors then want to determine whether (1) or (2) is the correct by considering a thought experiment. Suppose you prepare two different quantum states, both of which are compatible with a given list of values of physical properties. Assuming that the outcome of a measurement is determined by the measurement apparatus and the physical properties of the quantum system alone, then the authors CLAIM that you can arrange for a measurement where the apparatus returns results inconsistent with the predictions of quantum mechanics, resulting in a paradox. They then conclude the paradox constitutes proof of the quantum state (or wavefunction) corresponding to and underlying objective physical reality.
The problem here is that the results of the thought experiment are, in fact, in accordance with the laws of quantum mechanics. The authors are apparently a bit rusty with the concept of orthogonality in the context of quantum state vectors and basis functions, and consequently they have misinterpreted the outcome of their imagined experiment. Were they to be familiar with such concepts they would have realized that there is no paradox. Just read the paper and actually go over the math. I don't know what more to say. It's embarrassingly obvious...
Nearly 35 years ago a discrete fractal paradigm applicable to all scales of nature, referred to as Discrete Scale Relativity when the discrete self-similarity is exact, asserted that Schrodinger's wavefunction is a physical plasma of subquantum scale particles that are exactly self-similar to the familiar subatomic particles, but smaller by a factor of 10e17 and less massive by a factor of 10e56.
The exact physical properties of the subquantum particles comprising atomic scale wavfunctions can be calculated via the discrete scale invariant scaling equations of Discrete Scale Relativity.
RLO
What is really surprising about the preprint?
If I understood it correctly it can be summarized as:
1) if you know the Wave-Function you know all physical properties
2) if you know ALL physical properties you also know the WF
3) the measurement process (collapse of wave-function) is a real physical process which selects one of the possible outcome
Again, what is surprising about it?
In an alternative model of the elementary particles, the particles consist of looping EM waves. In such a model the wavefunction would certainly be physically real.
The model is described on: the neoclassical atom
In an alternative model of the elementary particles, the particles consist of looping EM waves. In such a model the wavefunction would certainly be physically real.
The model is described on: the neoclassical atom
Hallelujah.
It has been a long time coming.
Away with the Platonic smoke and mirrors, and back to physical reality.
RLO
http://www3.amherst.edu/~rloldershaw
Fractal Cosmology
I read the preprint a few days ago . My conculsion Everett was right and realism rules.
In my book "Quantum-Classical Correspondence: Dynamical Quantization and the Classical Limit" (Springer, 2004) one can read by way of conclusion: "According to dynamical quantization, quantum physics can be formulated without appealing in any way to a dualistic framework of matter (wave vs. particle). Consequently, the trajectory concept exists as an intrinsic or ontological attribute for both quantum and classical particles. An electron around an atomic nucleus, for example, actually follows a certain quantum trajectory, since the density matrix does possess the same ontlogical status as the classical Wigner function. This characteristic is not destroyed by our quantization procedure." (A. O. Bolivar)
Further, on page 149 I assert the following: "The Schrödinger function plays a secondary role in the theoretical framework of quantum physics. In general, open systems are not described in terms of it. the description in terms of the von Neumann function is fundamental due to its logical priority and its physical generality". (A. O. Bolivar)
How in God's good name can the wavefront not be real if it is influencing where the particle is? If the chances of finding the particle at a given location are as described by a wave function, this is enough to make it phyically real in my opinion.
As for Bohr's view that the wavefront is collapsed by observation: That to me has always been laughable. The wavefront is collapsed by an interaction with another object, with the chances of such an interaction occuring being governed by said wave function. and the wave function of the other object. If the particle moves on past our experiment, the issue is only that we did not observe it, and not the its wave function cannot be collapsed later.