Questions about recent paper on Entangled Histories

[quantumfunction]

I just read this paper and it was very interesting. The paper is called "Experimental Test of Quantum Histories" http://arxiv.org/abs/1601.02943

Here's some of an article about the paper.

Nobel laureate Frank Wilczek at MIT and colleague Jordan Cotler, now at Stanford University, provide evidence for what they call entangled histories in a paper posted online January 12 at arXiv.org. The researchers proposed and collaborated on an experiment that started and ended by measuring a particular property of a photon; in between, the experimenters subtly probed the photon without disturbing its delicate quantum state. The head-scratching result was that there was no way to create a single chronology that could describe how the photon changed. Instead, there must be multiple chronologies that are entangled, sharing a quantum connection usually reserved for groups of particles rather than chunks of time.

“There really is something very deep going on here about the nature of quantum mechanics and time,” Cotler says. “Our best description of the past is not a fixed chronology but multiple chronologies that are intertwined with each other.” The experiment may offer a new means of exploring and interpreting quantum weirdness.

Yet Cotler and Wilczek suspected that it wasn’t so simple. In a paper last year, they introduced the idea of entangled histories, cases in which a single chronology is insufficient to explain the observed changes in the properties of a particle. Just as the understanding of an entangled particle is impossible without considering its partner, the history of a particle could be incomplete without the existence of multiple entangled timelines.

Just as Cotler and Wilczek expected, the experimenters couldn’t formulate a chronology that was consistent with both the starting and ending measurements of each photon and the mirror-based evidence in between. The only way to reconcile all the observations, Cotler says, is to conclude that the photon went through multiple histories in parallel. When the researchers made the final measurement of the photon, those alternate timelines merged.

https://www.sciencenews.org/article/quantum-histories-get-all-tangled

I have been reading a lot lateley about these Temporal Correlations and some Scientist are saying they are the foundation of reality that give rise to spacetime.

The way I read it, is that there's correlation between events in time.

I wanted to make sure I had this right. Are they saying that events in time are correlated so these events don't take any causual or sequencial order?

To extrapilate this to a classical level, it would be like going to the store, Doctor and to a restaurant but all of these events occur essentially at the same time because there's no sequencial order of events. It ended this way.

Wilczek is far more optimistic. He calls the experiment “a rather direct realization” of a 60-year-old interpretation of quantum mechanics known as “many worlds,” in which measuring photons and other environmental interactions split reality into alternate timelines. Sometimes the different branches are consistent on their own and remain separate, Wilczek says. But in this case, the separate chronologies are intertwined and eventually come back together. “The deepest and most appealing aspect of this experiment,” he says, “is that it allows you in a mathematically precise way to nail what exactly many worlds is about.”

 

[jimgraber]

Is it better to have multiple chronologies all going forward, or a "single" chronology going forward and backward in time?

 

[DrChinese]

I wanted to make sure I had this right. Are they saying that events in time are correlated so these events don't take any causual or sequencial order?

You are correct. There are numerous quantum setups in which causal order is not classical. There is no single particular physical mechanism that can explain these setups. As a result, we have the interpretations. So your final conclusion will end up being interpretation dependent.

The relatively newer class of experiments in which there is some type of delayed choice (as an example) are very difficult to explain outside of quantum theory itself. These had been predicted by QM but had not been executed. In these, it appears "as if" the future affects the past. Of course, just as with the "older" non-local quantum effects, there is no possibility of signalling.

 

[quantumfunction]

You are correct. There are numerous quantum setups in which causal order is not classical. There is no single particular physical mechanism that can explain these setups. As a result, we have the interpretations. So your final conclusion will end up being interpretation dependent.

The relatively newer class of experiments in which there is some type of delayed choice (as an example) are very difficult to explain outside of quantum theory itself. These had been predicted by QM but had not been executed. In these, it appears "as if" the future affects the past. Of course, just as with the "older" non-local quantum effects, there is no possibility of signalling.

Thanks for the post and I found another recent article talking about this:

Quantum Links in Time and Space May Form the Universe’s Foundation

In 2012, http://www.smp.uq.edu.au/node/106/16 and Timothy Ralph, both physicists at the University of Queensland in Australia, laid out a procedure to encrypt data so that it can be decrypted only at a specific moment in the future. Their scheme exploits quantum entanglement, a phenomenon in which particles or points in a field, such as the electromagnetic field, shed their separate identities and assume a shared existence, their properties becoming correlated with one another’s. Normally physicists think of these correlations as spanning space, linking far-flung locations in a phenomenon that Albert Einstein famously described as “spooky action at a distance.” But a growing body of research is investigating how these correlations can span time as well. What happens now can be correlated with what happens later, in ways that elude a simple mechanistic explanation. In effect, you can have spooky action at a delay.

These correlations seriously mess with our intuitions about time and space. Not only can two events be correlated, linking the earlier one to the later one, but two events can become correlated such that it becomes impossible to say which is earlier and which is later. Each of these events is the cause of the other, as if each were the first to occur. (Even a single observer can encounter this causal ambiguity, so it’s distinct from the temporal reversals that can happen when two observers move at different velocities, as described in Einstein’s special theory of relativity.)

These temporal correlations are also challenging physicists’ assumptions about the nature of space-time. Whenever two events are correlated and it’s not a fluke, there are two explanations: One event causes the other, or some third factor causes both. A background assumption to this logic is that events occur in a given order, dictated by their locations in space and time. Since quantum correlations—certainly the spatial kind, possibly the temporal—are too strong to be explained using one of these two explanations, physicists are revisiting their assumptions. “We cannot really explain these correlations,” said Ämin Baumeler, a physicist at the University of Italian Switzerland in Lugano, Switzerland. “There’s no mechanism for how these correlations appear. So, they don’t really fit into our notion of space-time.”

Normally the rules of the game are set up so that Alice and Bob do this in a certain sequence. Suppose Alice is first. She can only guess at Bob’s outcome (which has yet to occur), but she can send her own result to Bob. Alice’s guess as to Bob’s flip will be right 50 percent of the time, but he will always get hers right. In the next round, Bob goes first, and the roles are reversed. Overall the success rate will be 75 percent. But if you don’t presume they do this in a certain sequence, and if they replace the sheet of paper with a quantum particle, they can succeed 85 percent of the time.

If you try to situate this experiment within space and time, you’ll be forced to conclude that it involves a limited degree of time travel, so that the person who goes second can communicate his or her result backward in time to the one who goes first. (The Time Patrol will be relieved that no logical paradoxes can arise: No event can become its own cause.)

http://www.wired.com/2016/01/quantum-links-in-time-and-space-may-form-the-universes-foundation/

I think this is very interesting and I have been reading up on these temporal correlations. They could be the foundation of everything. Events in spacetime might be entangled histories that only take on a sequencial order in spacetime. They talk about how you can encode information on these correlations that can only be read at a future time and it's like the information vanishes into the vacuum of these correlations until that specific time. It says:

Some physicists take this as evidence for a profoundly nonintuitive worldview, in which quantum correlations are more fundamental than space-time, and space-time itself is somehow built up from correlations among events, in what might be called quantum relationalism.

I think Scientist are scratching their heads because how do you explain these things in a physical context. It's the correlation of events in time with no causual or sequencial relationship. If you extrapilate this to spacetime, you would have all sorts of time travel and causual paradoxes. So the foundation of say me going to the store then going to the Doctor could be entangled histories on a quantum level that manifest as sequencial events on a classical level in spacetime. This would mean all events of the universe are correlated entangled histories that emerge as sequencial events in spacetime. Very good stuff and it would give new meaning to Einstein saying the distinction between the past, present and future is a persistent illusion.

The universe could essentially be some kind of computer. Some Scientist say a quantum computer. This because these events that are entangled histories consist of bits of information. This information seems to exist in these entangled states without space or time. When space emerges, you get a sequencial order of events in spacetime. So the universe could simply be calculating this information and the universe as we experience it is the result.

I also saw an interesting talk from John Preskill called "Is Spacetime a Quantum Error-Correcting Code?"

 

[quantumfunction]

Here's Physics Professor James Gates talking about finding error correcting codes in Superstring Equations.



Here's a paper called "Quantum Gates and Quantum Circuits of Stock Portfolio"

It's about a quantum code found in the stock market.

http://arxiv.org/abs/1507.02310

The astonishing thing is that, when simulating in topological quantum computation environment the time series of stock prices realize, in their braiding movement, elementary quantum gates. The quantum gates that prices of stocks in a portfolio are realized can be chained in quantum circuits.

It is absolutely fascinating to see how stocks of reputable companies like McDonalds or Walt Disney Company are literally realizing quantum gates in their New York Stock Exchange daily evolution.

Selecting a stock portfolio, from the shares of companies listed on Dow Jones Industrial Average market index, composed of McDonald's Corp. (MCD), The Walt Disney Company (DIS), American Express Company (AXP), and United Health Group Incorporated (UNH),an astonishing chain of quantum gates is recovered. Hadamard gate, Pauli gates and S-phase gate are all acting concerted in 1-qubit quantum circuit.

More complex quantum code structures arise considering increasing the number of stocks in the portfolio. 2-qubit quantum circuits are realized by adding Nike Inc. (NKE) and The Home Depot, Inc. (HD) to the initial portfolio of stocks.

Fragment of the Stock Market Quantum Algorithm realized by quantum computing simulation of a stock portfolio composed of: The Walt Disney Company (DIS), Nike Inc. (NKE), McDonald's Corp. (MCD), American Express Company (AXP), UnitedHealth Group Incorporated (UNH), The Home Depot, Inc. (HD)

Extended the process to the whole Dow Jones Industrial Average market index a mysterious quantum code of the stock market is revealed.

Here is the link to the quantum computational universe. This strange quantum code laying beneath the stock market transactions may be a small fragment of the universal code the entire Universe acts according with. This result may point out the shocking conclusion that New York Stock Exchange is perhaps a quantum computational virtual reality.

http://www.tgdaily.com/web/134656-is-there-a-hidden-quantum-code-that-rules-the-stock-market

So these temporal correlations or entanglement could the information that's being computed and our universe is the result. Spacetime is an error correcting code because the universe could constantly be computing itself and therefore updating itself. This should also mean errors occur because it's being copied so much and maybe we can detect those errors.

 

[Jilang]

What would Plank's constant represent in such a picture? Or c/h?

 

[quantumfunction]

What would Plank's constant represent in such a picture? Or c/h?

In this scenario, Planck's Constant would be the refresh rate. In other words, it limits how much information the universe could process at the speed of light. Gizmado had an interesting article on this based on Quantum Realism called "10 Reasons Our Universe Might Actually Be Virtual Reality."

Quantum Realism

: If the physical world is a virtual reality, it is the product of information processing. Information is defined as a choice from a finite set, so the processing changing it must also be finite, and indeed our world does refresh at a finite rate. A supercomputer processor refreshes 10 quadrillion times a second, and our universe refreshes a trillion, trillion times faster than that, but the principle is the same. As a screen image has pixels and a refresh rate, so our world has Planck Length and Planck Time.

In this scenario, the speed of light is the fastest speed because the network can't transmit anything faster than one pixel per cycle—i.e., Planck Length divided by Planck Time, or about 300,000 kilometers per second. The speed of light should really have been called http://brianwhitworth.com/qr/TheSpeedOfSpace.pdf.

http://gizmodo.com/5-reasons-our-universe-might-actually-be-a-virtual-real-1665353513

M.I.T. Professor Seth Lloyd calculated this and said the universe has done 10^120 logical operations on 10^90 bits.

Computational Capacity of the Universe
http://arxiv.org/abs/quant-ph/0110141

 

[ovi69]

In the same register
http://www.riseearth.com/2015/12/the-universe-is-quantum-algorithm.html

 

[quantumfunction]

In the same register
http://www.riseearth.com/2015/12/the-universe-is-quantum-algorithm.html

Thanks for the article.

I think there's growing evidence to support what M.I.T. Professor Seth Lloyd said years ago. He said the universe is a quantum computer. Maybe quantum mechanics isn't a physical theory but a computational theory and that's why there's a disconnect between classical physics and quantum mechanics.

When you talk about things like entangled histories and temporal correlations it shows at the fundamental level of reality there isn't any physical cause and effect or a sequencial order. So we may not be talking about anything physical but information and computation. If you look at this website for instance, you see cause and effect. If I hit Quantum Physics on the main page the effect is I'm sent to the Quantum Physics board. So if you look at the website you see cause and effect but it's just following the instructions of the code.

There was another recent study that showed there's no signaling between two entangled particles. This is just more evidence that what we call local realism is something that manifest on a classical level.

When you look at no signals between entangled particle pairs, this is something that could point to the universe as a quantum computer.

If you look at the spacetime as a computer screen and all of the matter in the universe as pixels on the screen, it's very easy to explain. I write code and let's say I write a program where red dots randomly move around the screen. If one of the red dots is clicked it turns blue or green. If two of the red dots touch each other then they're entangled. So now if I hit a red dot and it turns blue, the dot it's entangled with will turn green. If I click it and it turns green, the dot it's entangled with will turn blue.

There's no need to send a signal between the dots because there just following the instructions of the program. So it's about processing information. So if the universe is governed by quantum codes, you wouldn't expect to see any signal between entangled pairs because both particles are pixels on the spacetime screen.

 

[Justice Hunter]

If you look at the spacetime as a computer screen and all of the matter in the universe as pixels on the screen, it's very easy to explain. I write code and let's say I write a program where red dots randomly move around the screen. If one of the red dots is clicked it turns blue or green. If two of the red dots touch each other then they're entangled. So now if I hit a red dot and it turns blue, the dot it's entangled with will turn green. If I click it and it turns green, the dot it's entangled with will turn blue.

There's no need to send a signal between the dots because there just following the instructions of the program. So it's about processing information. So if the universe is governed by quantum codes, you wouldn't expect to see any signal between entangled pairs because both particles are pixels on the spacetime screen.

Never thought of it like that! That's really interesting.

 

[quantumfunction]

Never thought of it like that! That's really interesting.

Thanks and I write computer code and this explanation is just simple and elegant. There's growing support for this as well





So if spacetime is a non local computer screen, you just need the code to tell the pixels on the screen how to behave and what laws to follow.

 

[entropy1]

Wilczek is far more optimistic. He calls the experiment “a rather direct realization” of a 60-year-old interpretation of quantum mechanics known as “many worlds,” in which measuring photons and other environmental interactions split reality into alternate timelines. Sometimes the different branches are consistent on their own and remain separate, Wilczek says. But in this case, the separate chronologies are intertwined and eventually come back together. “The deepest and most appealing aspect of this experiment,” he says, “is that it allows you in a mathematically precise way to nail what exactly many worlds is about.

Can't believe this. This is exactly what I have been contemplating for a while now! I can't get my thoughts around it (but I try)! Thanks for the references!

NOTE: I like this one too (I call it: 'resonance'):

[..]but two events can become correlated such that it becomes impossible to say which is earlier and which is later. Each of these events is the cause of the other, as if each were the first to occur.
http://www.wired.com/2016/01/quantum-links-in-time-and-space-may-form-the-universes-foundation/

 

[Mentz114]

Thanks for the article.

I think there's growing evidence to support what M.I.T. Professor Seth Lloyd said years ago. He said the universe is a quantum computer. Maybe quantum mechanics isn't a physical theory but a computational theory and that's why there's a disconnect between classical physics and quantum mechanics.
[...]

There's no need to send a signal between the dots because there just following the instructions of the program. So it's about processing information. So if the universe is governed by quantum codes, you wouldn't expect to see any signal between entangled pairs because both particles are pixels on the spacetime screen.

Not only that but all possible outcomes can be encoded simultaneously with fewer degrees of freedom if there is a lot of entanglement.

You have not mentioned ( I think) the holographic principle. Here's a sort of introduction but there are dozens of publications on this kind of thing

https://www.tuwien.ac.at/en/news/news_detail/article/9447/

and

Susskind, Leonard (1995). "The World as a Hologram". Journal of Mathematical Physics 36 (11): 6377–6396. arXiv:hep-th/9409089

 

[entropy1]

Not only that but all possible outcomes can be encoded simultaneously with fewer degrees of freedom if there is a lot of entanglement.

Would that mean that if we consider the universe as a whole, we then observe a single and definite outcome (evolution), because the entanglement is maximal?

And a follow up question: in, for instance, the case of probabilistic QM (which is all of QM, probably), such as in the case of Alice and Bob measuring respective polarisations of entangled photons, would a measurement at t1 (one pair) and another at t2 (another pair) become entangled in the measurement setup in a whole different state of entanglement, and therefore depend on that state (of the measurement setup)?

I pose the question here, because the topic suits the perfect context for it.

 

[entropy1]

Might the Heisenberg uncertainty have something to do with the limited amount of knowledge we are allowed to have, thus allowing for (the interpretation of) multiple histories that (must) remain unknown?

Thanks.

 

[Zarqon]

I just came across this paper about entangled histories as well, and thought it better to continue in this thread rather than opening a new one.

It seems that Wilczek says this experiment favors the many world's interpretation, but without having gone through the paper in detail, I'm guessing it doesn't formally have this meaning? I would like to ask the notable proponents for other interpretations on this forum if they have thought about what is done in this paper and why it would favor MWI. Also, are there other, just as natural interpretations of these results in the other interpretations, like BM?