New painful hype on «spooky nonlocalities»
Luboš Motl, October 22, 2015
Quantum mechanics was first discovered by Heisenberg in 1925. As we can see with the hindsight today, it was the first time when even the basic logic of a physical theory was so intellectually demanding that even most of the people otherwise considered intelligent just weren’t smart enough to «get it».
Albert Einstein, after he made all the important contributions of his career, became a celebrity on top of a brand new movement – a movement constantly producing totally wrong «objections» against quantum mechanics. While between 1935 and his death in 1955, Einstein was rightfully considered a hasbeen who had simply lost the contact with the state-of-the-art research in fundamental physics, the influence of the anti-quantum movement actually grew since the 1960s.
A vast majority of popular books on the subject of quantum mechanics literally live in an alternate reality. They try to present quantum mechanics as a suspect sitting on the bench – while some alternative theory proposed by Einstein or Bell or Bohm or Everett or Ghirardi or… plays the role of the judge. The only problem is that there exists no viable alternative theory. Quantum mechanics has been the only framework for a successful description of new experiments for more than 90 years and nothing at all has changed about the basics since that time.
Big bogus stories about the «revolutions» in the foundations of quantum mechanics emerge every month. The latest one was sparked by an August 2015 Dutch-Spanish-British preprint by Hensen et al.
which produced some stories in the Summer. However, days ago, the paper has been published in Nature which sparked yet another wave of the hype.
The most influential news outlet that has written a ludicrous story about this experiment yesterday was the New York Times:
Sorry, Einstein. Quantum Study Suggests ‘Spooky Action’ Is Real.
Sorry, John Markoff, but your story is nothing else than a pile of trash.
The two and a half loopholes
First, let me say a few words about the experiment. It is nothing else than a repetition of Aspect’s experiment that verified the violation of Bell’s inequality in Nature – and the detailed predictions of quantum mechanics. There are only two special improvements in this version of the experiment that are sold as closing
- the locality loophole
- the detection loophole
The locality loophole refers to the suggestion that the two measurement events could communicate with each other in order to fake the correlations. To close this would-be loophole, the spacetime points where the measurements occur are spacelike-separated – the actual places are very distant, 1.3 kilometers.
This detail is being hyped like mad but there is nothing new about the big separation. From this 1998 paper by Zeilinger’s group, these experimenters and a few others have been playing with big distances between the two measurement points. The two entangled degrees of freedom were made to span the Canary Islands in 2007; the distance was 144 kilometers.
There is absolutely nothing new about the separation of 1.3 kilometers and the very suggestion that the entanglement should suddenly disappear or cease to work is just plain idiotic. Even a millimeter is a «de facto infinite» length scale relatively to the length scales of fundamental (particle) physics. So if the entanglement works at the millimeter scale, it pretty much certainly has to work at the Hubble scale of billions of light years, too.
The second would-be loophole they claim to close, the detection loophole, is connected with the low success rate of detections. When such experiments are done with ordinary photons, only a small fraction of photon pairs is detected and those reveal the correlation. You could suggest a conspiracy theory that whenever the correlations in the measurements would be too bad, some dark force beneath Nature guarantees that nothing is detected at all. So these people have increased the «success rate», basically by using massive objects, electrons (and their spins), and (solid) diamond.
They also make sure that all the «switches» in their system operate as quickly as possible – and as late as possible – and all the predictable or pseudorandom generators are replaced by physically random ones. That’s nice but someone could claim that the «random numbers» in their experiment aren’t random, either. To believe that they’re «genuinely random», we have to believe quantum mechanics, anyway.
At any rate, the loopholes have nothing to do with any reasonable alternative cause of the correlations found in similar EPR experiments. And they have nothing to do with the reasons why quantum mechanics is hard for the people, too. Some teenagers may have played with diamonds but the contribution of this experiment to our understanding of quantum physics is clearly zero. The claims about the «closed loopholes» are just cheap dishonest verbal tricks to make their experiment look substantially new even though it is not.
The real problem here is that there exists no viable alternative theoretical explanation of similar experiments that would differ from quantum mechanics and that would exploit these loopholes. Indeed, the assumption that Nature doesn’t exploit the loopholes – the conspiracies from the conspiracy theories – depends on our belief in a theoretical picture. Quantum mechanics unambiguously implies that these loopholes are rubbish. Indeed, we have to depend on a theoretical framework. But that’s no specific disadvantage of quantum mechanics. Whenever we explain anything about Nature using any theory, we always have to rely on some theoretical assumptions. It would be true even if you «replaced» quantum mechanics by a hypothetical different theory.
My broader point is that when an experimenter is looking for some new effect, there should exist at least some vaguely rational reason to expect that such a new effect could suddenly emerge. When there is no such a possible reason, and this is an example, it is simply stupid to perform the experiment at all. People are not paying millions of dollars for experiments to find out whether the exact amount of 31415926.535 liters of water will spontaneously change into wine. You know, it will not! In the same way, it’s clear that these conceptually not new experiments won’t find any statistically significant deviation from the predictions of quantum mechanics.
Totally wrong interpretations
So it’s clear what the result of the experiment is actually going to be. The only freedom you have is to offer your own interpretation of what is observed and what quantum mechanics correctly predicted. And all the interpretations you can read in the New York Times etc. are complete rubbish. The rubbish starts with the title, of course:
Sorry, Einstein. Quantum Study Suggests ‘Spooky Action’ Is Real.
No, there is no «spooky action». The two measurements are correlated because of the contact of the two particles in the past, because of events in the intersection of the two particles’ past light cones, because of the «origin» that both particles share. The correlations do not arise from any action or any influence at the moment of the measurement. What is observed is correlation (between A and B) but correlation doesn’t imply a causation (A’s influence on B or B’s influence on A). Instead, the correlation is explained by the initial state of both particles, C, that has influenced the results of measurements of A as well as B.
Einstein chose the term «spooky action» in order to suggest that quantum mechanics predicts something illegitimate – and the action at a distance would certainly be illegitimate because it would conflict with relativity. However, Einstein’s argument was just wrong. Quantum mechanics doesn’t need any action to guarantee the correlations that follow from entanglement. It doesn’t transfer any transformation superluminally. Never. Ever. Quantum mechanics doesn’t necessitate any contradiction with relativity and quantum field theories are 100% exactly compatible both with special relativity and with the postulates of quantum mechanics.
In a landmark study, scientists at Delft University of Technology in the Netherlands reported that they had conducted an experiment…
It is not a landmark study. It is just another unnecessary repetition of the Aspect experiment, an experiment that was unnecessary already the first time when it was done.
…that they say proved one of the most fundamental claims of quantum theory — that objects separated by great distance can instantaneously affect each other’s behavior.
But objects separated by a distance don’t instantaneously affect each other’s behavior – which is prohibited by relativity – and this experiment doesn’t show any «spooky» effect of this kind. It only shows correlations that are predicted by quantum mechanics using entangled initial states.
The existence of quantum entanglement is perhaps a fundamental claim of quantum mechanics but it’s such a trivial one that everything would be impossible if we tried to invalidate it. Almost all states in the Hilbert space (of a composite physical system) are entangled! The non-entangled states are the states of the form of a tensor product \(\ket{\psi_1}\otimes \ket{\psi_2}\) and such states are a measure zero subset of the full Hilbert space.
Also, whenever a physical system is composed of at least two subsystems A,B whose mutual interaction is nonzero, it’s guaranteed that the energy eigenstates – and the ground state in particular (the energy eigenstate with the lowest energy eigenvalue) – are entangled states:
\[ H_{AB} \ket{\psi_0} = E_{AB,0}\ket{\psi_{AB,0}}\quad\Rightarrow\quad\\
\Rightarrow\quad \ket{\psi_{AB,0}}\neq \ket{\psi_{A,0}} \otimes \ket{\psi_{B,0}} \] It’s just impossible for non-entangled states to be energy eigenstates. So the entanglement is a norm, not some «special mysterious effect» you have to seek by contrived experiments for 90 years. Every composite object around us has to be described by an entangled state in quantum mechanics. The electrons in any atom with \(Z\geq 2\), starting with helium, are inevitably entangled with each other. They are not independent. They can’t be independent. Even in the simple hydrogen molecule \(H_2\), the spins of the two protons are entangled with one another. You either deal with the orthohydrogen or the parahydrogen. They have different energies. The photon emitted from the transition between the two levels has the wavelength of 21 centimeters. We see it everywhere. If there are at least two interacting pieces in any system, the ground state is unavoidably entangled.
The finding is another blow to one of the bedrock principles of standard physics known as “locality,” which states that an object is directly influenced only by its immediate surroundings.
It is not. Locality is as valid as it has always been – and we’ve known that locality is 100% valid in the Minkowski space since 1905 when Einstein discovered special relativity. While criticizing quantum mechanics, Einstein claimed that quantum mechanics needed to contradict locality and therefore relativity. But this claim by Einstein has always been wrong. It is wrong now, too. The 125425th repetition of the same unnecessary experiment can’t change an epsilon about the fact.
The Delft study, published Wednesday in the journal Nature, lends further credence to an idea that Einstein famously rejected. He said quantum theory necessitated “spooky action at a distance,” and he refused to accept the notion that the universe could behave in such a strange and apparently random fashion.
But what was wrong about Einstein’s claims wasn’t the claim that Nature was perfectly local – Nature is local. What was wrong was his assumption that the properties of physical objects may be finally described by the classical logic, as «objective properties» that everyone may in principle agree on. It is not true. One needs a qualitatively different logic, the logic of quantum mechanics, which only allows to make statements about physical objects from the viewpoint of an observer and the observer’s observations.
In particular, Einstein derided the idea that separate particles could be “entangled” so completely that measuring one particle would instantaneously influence the other, regardless of the distance separating them.
And he was right: the measurement of one particle does not influence the other particle. But the two particles’ properties may be found to be correlated even without such an instantaneous influence, and that’s what quantum mechanics implies.
Einstein was deeply unhappy with the uncertainty introduced by quantum theory and described its implications as akin to God’s playing dice.
This is a different aspect of his (and others’) discomfort about quantum mechanics. Quantum mechanics generically predicts observations to be uncertain – and only calculates the probabilistic distributions for outcomes. But it also predicts many measurements to be far more certain or constrained than any classical theory could. The «greater than Bell’s bound» correlations predicted by quantum mechanics are actually an example of that. In the EPR setup, quantum mechanics allows you to predict the «relative polarizations» of the two spins with certainty even though any classical theory would make even the «relative polarizations» uncertain.
But since the 1970s, a series of precise experiments by physicists are increasingly erasing doubt — alternative explanations that are referred to as loopholes — that two previously entangled particles, even if separated by the width of the universe, could instantly interact.
These experiments haven’t been erasing doubts that competent theorists constructing viable theories could have had. There were no such doubts. Unfortunately, these experiments haven’t been erasing the doubts of the laymen who still have problems with quantum mechanics. Clearly, despite the decades of such experiments, all of which have 100% confirmed the predictions of quantum mechanics (while no viable competing theory has been constructed), the laymen are still disbelieving quantum mechanics, using the words such as «spooky» and «weird» for this foundation of the modern science.
All these experiments are clearly useless from both of these conceivable points of view.
The new experiment, conducted by a group led by Ronald Hanson, a physicist at the Dutch university’s Kavli Institute of Nanoscience, and joined by scientists from Spain and England, is the strongest evidence yet to support the most fundamental claims of the theory of quantum mechanics about the existence of an odd world formed by a fabric of subatomic particles, where matter does not take form until it is observed and time runs backward as well as forward.
This is pure hype. The innovativeness of this experiment is basically zero. It teaches us zero about quantum mechanics that we didn’t know before. The self-promoting unimportant experimenters may confuse «importance», «depth», or «originality» with the «distance» or the «hardness» of their diamond. But they’re different things. There is virtually no importance, depth, or originality in their experiment. And the miraculous comments around their experiments, such as the claim that «time runs backward as well as forward», are as unjustified by their – or another – experiment as they have always been. They are pure dishonest lies.
The rest of the NYT article says a few basic things about the experiment, some skeptical words unrelated to the essence of this story – the essence is the uselessness of this whole enterprise. It tones down the adjective for quantum mechanics – instead of «spooky», it is just «exotic» now – and speculates about things like the quantum Internet.
I find this kind of anti-quantum hype to be absolutely outrageous. Sadly, almost all the experimental people in that discipline are involved in that. Take the spacelike separation EPR experiment by Zeilinger’s group from 1998. It was totally analogous to the new paper by Hensen et al. They were also claiming to close some «loopholes» except that they would never care that no coherent theory that could use such loopholes existed (or could have existed). Look at one of the final paragraphs of the 1998 paper:
Further improvements, e.g. having a human observers choose the analyzer directions would again necessitate major improvements of technology as was the case in order to finally, after more than 15 years, go significantly beyond the beautiful 1982 experiment of Aspect et al [4]. Expecting that any improved experiment will also agree with quantum theory, a shift of our classical philosophical positions seems necessary. Among the possible implications are nonlocality or complete determinism or the abandonment of counterfactual conclusions. Whether or not this will finally answer the eternal question: “Is the moon there, when nobody looks?” [18], is certainly up to the reader’s personal judgement.
You see that the hype about the «progress» was the same even though it is clear that the actual progress has always been zero. Zeilinger’s group hyped the spacelike separation as if it were a game-changer. Now, 17 years later, another group hypes the very same spacelike separation again. They’re the first ones to «close this loophole», they basically say. Oh, really?
Note that Zeilinger et al. were sensible enough to admit that most likely, «any improved experiment will also agree with quantum theory». But what do these outcomes universally confirming quantum mechanics mean for the people’s thinking? We hear that «a shift of our classical philosophical positions seems necessary». That’s great but the people interested in physics whose brain wasn’t dysfunctional made this shift from the classical thinking to the quantum thinking in 1925, 90 years ago, not now or in 1998.
But the following sentence is really shocking and reveals that your optimistic expectation «at least they admit that the shift to QM is necessary now» was totally wrong:
Among the possible implications are nonlocality or complete determinism or the abandonment of counterfactual conclusions.
Holy cow. What about embracing the implications that are actually implied by the correct theory, quantum mechanics? Quantum mechanics doesn’t envision any nonlocality as a mechanism behind these experiments. It replaces the classical determinism with the quantum determinism – only the probabilities are predictable but the particular outcomes are not. And quantum mechanics allows one to make conclusions about everything, including the past – but they may only be derived from actual observations and will depend on the choice of the observed quantity by the observer.
If you had some basic common sense and honesty, your conclusion would be to switch to abandon the classical way of thinking and switch to the quantum way of thinking. You would stop talking about «spooky» and «weird» and «nonlocal» things that may be implied by a classical model but it contradicts the insights that modern physics has actually made about the essence of the laws of Nature.
But I guess that it’s more convenient for this corrupt community to keep on playing with diamonds in totally stupid ways and write nonsensical hype about these games in the newspapers.
