Was Einstein Right? EPR Paradox Resolved with Quantum Computing | Paradoxes Ep. 07

The EPR paradox is commonly said to demonstrate an unobservable "spooky-action-at-a-distance" between entangled particles, suggesting that the universe is fundamentally non-local.

In this video, Oxford PhD researcher Maria Violaris resolves the EPR paradox without any instantaneous action-at-a-distance between entangled particles. Maria explains how to implement the thought experiment yourself on a quantum computer with Qiskit, tracking the local flow of information throughout the thought experiment and seeing how it is consistent with Bell's theorem and Bell-non-locality. Resolving the EPR paradox reveals how quantum systems can carry locally inaccessible information, that is robust to decoherence (without using Bell's hidden variables).

Relevant papers to find out more:

Watch the other videos in the Quantum Paradoxes series:

________

#qiskit #ibmquantum #learnquantum

[JoseMoreno-ko]

No, you are presenting a strawman argument: the appropriate way to show how quantum mechanics is "non-local" is the way Mermin did it in "Quantum mysteries revisited", that is, assuming that 3 quanta (or qubits) have pre-arranged information from the start in a GHZ state somehow, and that later space-like separated measurements are performed, in different ways, whose outcomes cannot reproduce those predicted by quantum mechanics. Sure, there are loophole's to Einstein's original thought experiment as well as a typical two quanta (qubits) Bell-type experiments (including Aspect's experiment), which is why Mermin presented a "Revised" version of a paper he had previously presented.

[MrandMrsStuckey]

In order to have a consensus solution to the mystery of entanglement, one has to explain the violation of Bell's inequality by correlated, spacelike separated measurement outcomes without violating locality, statistical independence, intersubjective agreement, or the uniqueness of experimental outcomes. To understand your proposed solution to this mystery, let's map your circuit diagram into spacetime. Alice's probabilities depend on her setting theta alone (local to her), same for Bob's with phi (local to him). It's only when the outcomes are collected for comparison (local for both Alice and Bob's results) that we see the mysterious correlations as a function of theta minus phi. Each of these three steps is indeed local and requires no hidden variables, but that does nothing to solve the mystery, it's simply a statement of the facts responsible for the mystery. Indeed, what Bell's theorem tells you about the violation of Bell's inequality by correlated, spacelike separated measurement outcomes is that any attempt to explain the correlations constructively, i.e., via causal mechanisms, will necessarily violate locality, statistical independence, intersubjective agreement, and/or the uniqueness of experimental outcomes. See Maudlin's book "Quantum Non-Locality and Relativity" for an exhaustive review of such attempts. So, in 1996 Rovelli suggested we try to explain the correlations in principle fashion a al special relativity. There Einstein abandoned his "constructive efforts" to explain length contraction and time dilation and proposed the relativity principle to justify the empirically discovered fact called the light postulate. In response to Rovelli, quantum information theorists have rendered quantum mechanics a principle theory based on the empirically discovered fact called Information Invariance & Continuity. And, as we show in our book "Einstein's Entanglement: Bell Inequalities, Relativity, and the Qubit" (due out in June 2024 with Oxford UP), Information Invariance & Continuity can also be justified by the relativity principle. So, quantum information theorists have indeed solved the mystery of entanglement, i.e., they've explained it without violating locality, statistical independence, intersubjective agreement, or the uniqueness of experimental outcomes, by abandoning "constructive efforts" just like Einstein did with special relativity. Pretty ironic, since it was Einstein who introduced the mystery in 1935 🙂

[SorinBolos]

Great video. I was especially surprised by the affirmation "Theta cannot be accessed by measurements on Alice's qubit alone, even if we had infinite copies of Alice's qubit". I tried it out with a simulation and now I understand a lot better: With an unentangled qubit changing theta will change the counts in the measurements result (counts[0] vs counts[1]). In entangled qubits changing theta will change the counts of *corelated* results (counts[00+11] vs counts[10+01]).
Great stuff. Thanks for this video

[diegoalejandrosanchezherre]

I don't know, this fully local interpretation don't convince me, it's naively simplistic...

[diemilio]

wow, great video! I recently learned about how using the Heisenberg picture and q-numbers shows that QM can be seen as being local. Was even planning to cover this on a video in the near future 😅

I came about this idea in an explanation from Chiara Marletto, where she shows that this view can even describe the Aharonov-Bohm effect as being local. Very interesting subject.

[xbrlinfinity]

Reading the papers in chronological order, I have just finished Deutsch and Hayden. What a wonderful paper!

Locally inaccessible information causes behaviour similar to the behaviour possible from hidden variables.

I also see from eq 28, that it is only expected, not certain, that a pair of entangled qubits will return the same outcome when measured the same way (I wondered about that). This in itself rules out superluminal causality, which would have zero variance.

It's possible I misinterpret what it means for the expected value to be 1. If 1 means certainty, what does it mean for the expected value to be certain?

[Edit: I did misinterpret; re-reading my book, I see the the expected value of an observable is the expected value of an eigenvalue, -1 or 1, with an expected value of zero meaning -1 or 1 is equally likely. But Deutsch and Hayden find the expected value not of observables, but of their associated projectors whose eigenvalues are 0 and 1. In any event, using the formula from my book for the variance (expected value of squared eigenvalues minus square of expected eigenvalue) I see the variance for the expected value in eq 28 would be zero when theta equals phi, so it is certain that a pair of entangled qubits will return the same outcome when measured the same way. I am twice quilty; first of writing when I don't know what I am writing about and second of writing an edit that may be too long].

[성이름-ezp]

Thank you for this video. May I ask a question? I have trouble understanding entanglement. If two particles are entangled and one particle's state is determined, then the other particle's state will be determined instantaneously. However, isn't simultaneity relative? Who observes two particles' states being determined instantaneously?

[firstnamelastname]

Amazing to see all popular classical material presented in QCs. Contrary to most previous episode quantum circuits, this time you draw but you do not run. Not on your github notebook either. Is there no need to run these quantum circuits this time? I am a bit but not deeply familiar with quantum.

[Ankit_sw]

How to build actual own quantum computer?? Let me know you

[anirbanganguly]

Very interesting and well presented. However, some things were unfortunately not very clear to me. I think the explanation of the Heisenberg formalism was followed up very discretely by the information flow quantum circuit diagram. Perhaps, the connection between the two wasnt properly explained or maybe I didnt get it. Another more fundamental grievance would be the discussion about the necessity of locality for quantum gravity. The theories of relativity (special and general) imply causality, not locality if we go by the definition of locality in quantum foundations (which compared to the physically intuitive causality, is a more mathematical thing, arising from the tensor product structure of the Hilbert space.) And causality was never violated by quantum mechanics in any interpretation. Not by the EPR paradox, not by quantum teleportation. There was always the need for light speed classical communication in order for information to be actually transferred. So, I am not sure I understand why locality (not causality) is so important for QG? I would tend to think, the problem with QG is more about non-renormalizability and that stuff.

[terrencemcginnis]

Of topic a little bit: It is one of the biggest open questions absorbing gravity into the mix, etc., but to me the biggest question facing physics is to explain how consciousness impinges on and directly interacts with matter. All that we perceive as the outer material world might turn out to be a projection of our collective unconscious. We may be locked into a vivid dream that is actually constructed out of our personal and collective consensus reality. Enlightened people may consider it all to be a lucid dream. I have had many lucid dreams where the material world felt as real as my waking world in terms of being a solid and tangible place. I'd go around knocking on wood, pinching my hand, examining my fingerprints, etc., all while being aware that I was actually in bed supposedly asleep. I was fully awake inside these dreams. The mind is fully capable of creating a solid material world completely out of itself from memory and knowledge of how it works. You do however get to bend the rules and can fly like Superman and float through walls, etc. since it's a personal projection. When you wake up into the "real" you get locked into the consensus reality and the superpowers are gone. We may share unconsciously a universal mind that is shaping our material world according to our changing consensus reality. We may find out that we are inside of our collective mind, the dreamer and part of the dream. The knower, and the known. When Buddha was asked if he was a god, he said, he was human, but awake. To him it's all illusion, all temporary, all self experiencing self at different stages of self recognition, from asleep at the wheel, to fully awake. I think that the study of quantum field mechanics may end up discovering mind of the universe, and agreeing with all the highest teachings of the great wisdom traditions.