March 9, 2012 weblog
Physicist suggests Einstein could have beaten Bohr in famous thought experiment
(PhysOrg.com) -- Way back in the 1930’s, Albert Einstein and Niels Bohr were sparring over ideas related to whether the new field of quantum mechanics was correct. In one thought experiment that Einstein said showed that quantum mechanics was inconsistent, he said the Heisenberg principal could be shown to be inconsistent by imagining a box of photons that could be measured both time-wise and energy-wise at the same time. Bohr knocked down Einstein’s arguments and in the process elevated his stature among their peers. Now, however, Hrvoje Nikoli at the Rudjer Boskovic Institute in Croatia says that Einstein could have won that argument had he used the argument he gave Bohr just five years later in trying to explain how entanglement made quantum mechanics inconsistent. Nikoli has published his reasoning on the preprint server arXiv.
In the first thought experiment presented by Einstein, he proposed that if the lid were opened on a box full of photons allowing just one to escape, it could be measured time-wise by simply measuring how long the box was open. He then said it could be simultaneously measured energy-wise by measuring the change in the total amount of energy in the box. This he said disproved the Heisenberg principle which meant quantum mechanics was inconsistent. After some thought, Bohr replied that if Einstein’s own theory of relativity were brought into the experiment, the apparent inconsistency could be explained away by noting that the measurement took place in a gravitational field, thus, the measurement of the time that the lid was open on the box would depend on it’s position. Einstein was unable to counter Bohr’s argument and lost that round.
Five years later, the two were at it again. This time Einstein said that there was no way quantum mechanics could include both entanglement and the belief that nothing could travel faster than the speed of light. If causing a change to one particle instantly caused a change in the other, how could it do so without violating such a basic principle? He called the whole thing “spooky action at a distance.” Bohr was unable to come up with a reasonable argument in response. And neither has anyone else for that matter, though John Bell made it more palatable in 1964 by declaring entanglement a wholly new kind of phenomenon, which he dubbed "nonlocal."
This is where Nikoli comes in. He says that had Einstein put forth his arguments regarding entanglement five years earlier during their debate about the Heisenberg principle, he could have won by suggesting that the photon escaping from the box was entangled with the box itself, thus quashing any possible response from Bohr. But alas, that was not to be, Einstein didn’t think of that and thus, Bohr went on to win that first round, one of just a few such occurrences in Einstein’s illustrious career.
Explore further
In 1930 Einstein argued against consistency of the time-energy uncertainty relation by discussing a thought experiment involving a measurement of mass of the box which emitted a photon. Bohr seemingly triumphed over Einstein by arguing that the Einstein's own general theory of relativity saves the consistency of quantum mechanics. We revisit this thought experiment from a modern point of view and find that neither Einstein nor Bohr was right. Instead, this thought experiment should be thought of as an early example of a system demonstrating nonlocal "EPR" quantum correlations, five years before the famous Einstein-Podolsky-Rosen paper.
via Arxiv Blog
© 2011 PhysOrg.com
User comments
perrycomo,
very interesting comment. care to elaborate on how we conceptualize the singularity as the base of the universe? Thx
Remember, we supply these concepts and apply them to realty, expecting consistentcy. But reality as it is in itself (unconceptualized), has no need for such intellectual ordering faculaties. These concepts have evolved in us to operate and order experience on the macroscopic scale. We Kant expect to subject reality to conditions for the understanding and maintain consistentcy at all scales.
Except position. So they're still in a unique state.
We can't exactly measure position and momentum. This is Heisenberg's uncertainty principle, right?
What is the link with time and energy? How are they related to "disallow" exact measurement of them simultaneously? Why is time even in this conversation since it is part of the "fabric"?
Knowing exactly when a photon left a box is supposed to limit how exactly we can measure that photon's energy? Why?
Anybody have any thoughts on this? I can understand the introduction of nonlocality, but I find it unnecessary since a measured time of escape and measurement of total energy in the box seem not to conflict in my opinion. The energy is what it is, measuring the box doesn't "set" the photon's energy, not measuring it doesn't leave it grey as with spin, et al. Then again, maybe it just does and that is my problem. Help?
To answer your question, since energy of a photon or any particle, is related to its (waveform) frequency, the shorter in time one examines it, the less waveform one has available to determine it's energy,... i.e. a time so short that you only see part of a frequency cycle.
There is no tangible "fabric". Time is merely a relation between to events. IOW, time is not a discoverable entity, it is only applied as a relation of things.
Very helpful. that makes more sense to me than the duration of the opening I was struggling with. I think Einstein also has an issue with whether the photons are even in the box due to uncertainty as well. This whole thing stinks of a classical experiment used to prove or disprove QM, which doesn't work.
The certainty of confinement goes out the window at the quantum level.
So, if a universe has only one object, time does not exist. Does length, width and height exist? If a universe has two objects displaced by a static distance, I would surmise time still does not exist. However if the distance between them changes, then I surmise time has started to "exist". Does the existence of two objects affect the dimensions of length, width and height.
Quanta moves though, quantum uncertainty is about quantum jumps. Can an electron from over here suddenly go missing here and appear over there.
If there were a perfect box that didn't allow any leaks of electrons, could the electrons leave the box?
The quantum world says that it is impossible to know whether an electron is bound only by one region of space because the quantum field fluctuates. It so happens that generally the fluctuation is extremely local, you can't prove that the single electron doesn't reside in all locations simultaneously either. Reality is a weird combination of chaotic events. Particles of the body are fireballs. Electromagnetic charges. Water is made of fire.
In the quantum world: Hydrogen is a little fireball. Oxygen is a little fireball. They combine into an H2O molecule.
In the classical world (relativistic): those particles of fire are wet water.
http://www.vacuum...id=19=en
Time and space exists only when one ask such questions of two objects. They are relations between things, not things in themselves. They are real aspects of phenomenal reality, yes, if "phenomenal reality" is understood as reality perceived by mind, otherwise it is meaningless to surmise that time exists "out there" independent of its use (by mind), in ordering experience.
In qm, this conceptual structure that we submit reality to, cannot be applied with rational consistently, so such intuitions are exposed as a-priori artifacts of the mind, and not fundamental to reality itself. QM is non-intuitive.
The problem is that there is and assumption that 'we' have to ask the question. Actually, the quantum world asks these 'questions' continuously, so of course they exist, whether we choose to recognize them or not.
At the heart of quantum dynamics is a limitation of the energies that may be exchanged between particles, the shorter the wavelength the higher the energy, and hence the uncertainty-shoot plastic beads at a house made of tissue to determine its shape, and you rip the tissue apart by the time you use sufficient energy to see the smallest features.
Might the Heisenberg Uncertainty Principle be only an artifact of limitations in our measurement techniques, rather than a fundamental law in quantum mechanics?
What would happen to the Uncertainty Principle if we were to fortuitously develop the means to observe a particle that did not perturb the particle?
Nothing in the electromagnetic spectrum, obviously, can yield such an observation method. So the question is very academic. And yet, are we certain there can never be such an observation method? As we dig deeper into the fabric of space-time and discover the secrets of virtual particles and gravity, is it truly impossible that we might discover a means to observe particles without perturbing them?
Does even the *possibility* (however remote) of discovering such observation techniques open a theoretical can of worms?
The principle is a result of the information gathered. If you do not interact with a particle (i.e. perturb it) the you do not get information. The uncertaninty principle is independent of whichever way you measure (there are ways of squeezing one entity at the expense of having the other more uncertain. But there's no free cake , here)
If QM doesn't meet our intuition, our intuition is wrong or QM is incomplete. My intuition says that spooky action at a distance is not possible and that our ideas about measurement are wrong. Of course we can't measure something without affecting it if the measurement is intrusive (active sonar as opposed to passive sonar for example) and it probably has to be intrusive in the case of particles. If we ever find a way to make passive measurements then the I think our ideas will be radically be changed.
@Urgelt & Moebius,
When Heisenberg explained uncertainty by invoking the intuitive example of trying to observe the position and momentum simultaneously of a particle without disturbing it, he was giving only an intuitive and qualitative description. It is more profound than this. It's not merely about what we can know as a matter of practicality, it's what is meaningful to say about a particle,... its a limit on the definition of concepts.
Where did you get your intuitions (of space, time, causality)? They evolved in a biological blob (mind) as a means of ordering experience for consciousness on the macroscopic scale of things. Why should one expect reality at the qm level to conform to these notions? Reality, as it exists apart from being conceptualized by mind, has no use for these concepts,.. so it is no wonder that we have discovered the seam in reality between the phenomenal world and the noumenal world,.. by which I mean the non-intuitive nature of the qm realm.
Early arguments about quantum mechanics tried to describe whether the Universe was real or unreal, local or non-local. Real or un-real is a philosophical dispute we can never answer. Local or nonlocal has been determined by experiment: the Universe is non-local, for some set of actions. If there are only four forces, then our candidates are decided: gravity, em, strong, weak. Which of these participates in nonlocal actio
Early arguments about quantum mechanics tried to describe whether the Universe was real or unreal, local or non-local. Real or un-real is a philosophical dispute we can never answer. Local or nonlocal has been determined by experiment: the Universe is non-local, for some set of actions. If there are only four forces, then our candidates are decided: gravity, em, strong, weak. Which participates in nonlocal action?
Rather than "real or unreal", I would suggest that two different perspectives were in play, 'scientific realism', Einstein and Schrodinger, and 'scientific positivism', Bohr and Heisenberg. IMO, positivism has won out resoundingly.
Also, it's not one of the four forces Causing non-locality,... it's that a entangled system can only be consistently described as one entity.
When you go to sleep tonight you will exist in two places at the same time , so you don't need entanglement . good night .
The principal principle, principally concerns itself with principals, not principles, whereas the principal principal principally determines principles. Amazing how they can't get that right, like "their" instead of "there" and "they're," used quite interchangeably, and "the phenomena IS" instead of the singular "phenomenon is" and plural "phenomena are." It seems academe is getting progrssively illiterate, grunt, grunt...
The principal principle, principally concerns itself with principals, not principles, whereas the principal principal principally determines principles. Amazing how they can't get that right, like "their" instead of "there" and "they're," used quite interchangeably, and "the phenomena IS" instead of the singular "phenomenon is" and plural "phenomena are." It seems academe is getting progrssively illiterate, grunt, grunt...
Now, if these postulates would be fully consistent in the sense of formal rigor, then we could substitute one postulate with another one and we could get a single universal postulate. But our theory would change into tautology again (you can draw infinite many arrows trough single point).
From the above follows, your postulates must always remain inconsistent at least a bit, or your theory will not remain predicative anymore. It means, you cannot have fully consistent and useful theory at the same moment - the validity scope of every theory will remain limited, if it shouldn't serve as a tautological circular reasoning.
This is essentially, what the geometric representation of Goedel's theorems means in implicate geometry of AWT.
Nonlocality is nothing more than a spacetime jump. A wormhole is one way of visualizing this process. Another way of visualizing this process is simply a glitch in Universal programming. The particle is misplaced into another region.
Evidence for nonlocality can be found through experimentation. 1. Casimir effect. 2. Virtual particles - Photon production from vibrational energy (phonons).
Entangle two particles. Take 1 far away. Change the direction of spin for 1 particle and the spin of the other changes. The particles act as if they still comprise the same chunk of matter (molecule in this case) even though they've been physically separated.
Entangled particles act as if they are together even with space between them.
Almost but not quite: Entangle two particles. Take 1 far away. Measure the direction of spin for each particle within a time much less than their separation. When the spin of the first is measured, that of the other becomes defined. The value measured for the first is random (and which is first is frame dependent since they are spacelike separated). Obviously it can't work if you already know the spin of one because by definition it must already have been measured, and since the first result is always random you can't use the effect to convey information.
Take two pieces of paper. Go into a dark room and scribble on one. Photocopy the first onto the second paper without looking at it. Still without looking seal both in envelopes.
Before we open an envelope what may be on the paper is random. Once we open one we know what the second one looks like.
In what ways can we tell that spin is unmeasured/random rather than just unknown? Once we measure it the spin is "fixed" (the whole, observation determines reality schtick). But how do we know it isn't really fixed all along and not "random"?
I don't know your eye color so it may be brown, or blue, or green, etc. That doesn't mean your eye color is random until I see you. It just means I don't know it.
@Turrit: No good. You can't change the state of one by changing the other. Only "determine" it through observation/measurement. Fleet said this, but I thought it worth repeating.
How does a particle with "determined" spin act differently than a particle with "random/unmeasured" spin? When you measure one of the two entangled particles there is no difference observed in its pair. You have only discovered the result of a measurement on the second if you chose to make it.
I can't figure out how my analogy is any different.
Your analogy is not representative of qm entanglement, it is still a classical experiment. You need to use a Bell theorem compatible analogy.
Each observer measures spin at independently chosen angles, and maintains a log of results to be compared. There is a probability for measuring each combination of angles and results.
For an entangled pair, there is no way to account for the statistical correlation through any type of a classical analogy.
In your example the statistics work out fine , and there is no "problem". See wiki "Bell theorem".
The two tangled particular quanta when separated pulsate in phase, they spin in phase.
The test of entanglement is to change the state of one of the pair at a distance. If one reacts to the change in the other (whatever, shake one up and down, if the other reacts to the shaking that's an entangled state of the quanta).
For instance (Up quark): quark antiquark pair pulled from neutral field. Opposite charge and spin. Changing the spin of one changes the other. What happens when they are separated?
Virtual up quark anti-up quark pair made real. Flipping 1 polarly causes the other to flip. The pair has common polarity with inversed spin and charge. They are entangled spacialy, their spin, their charge, their polar field. Particle antiparticle pair after realization. While tangled they share all these characteristics that mutually sum up. All characteristics are opposite other than polarity (which is the result of wave directionality the pair deviated from).
Changing the polarity of the antiup quark causes the change in the polarity in the up quark.
With entangled particles this takes place nonlocally.
The quark antiquark pair is a momentary deviation of quantum field fluctuation before annihilation. Should sufficient energy be employed annihilation would be averted. An entangled state between the 2 would still require a change in the state of the other even with physical separation.
Early arguments about quantum mechanics tried to describe whether the Universe was real or unreal, local or non-local. Real or un-real is a philosophical dispute we can never answer. Local or nonlocal has been determined by experiment: the Universe is non-local, for some set of actions. If there are only four forces, then our candidates are decided: gravity, em, strong, weak. Which participates in nonlocal action?
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