"Black Holes, Worm Holes and the secrets of Quantum Spacetime" in Scientific American of November 2016

This document contains comments about the article Black Holes, Worm Holes and the secrets of Quantum Spacetime by Juan Maldecena In Scientific American of November 2016
The weird quantum phenomenon of entanglement could produce shortcuts between distant black holes

Introduction

Theoretical physics is full of mind-boggling ideas, but two of the weirdest are quantum entanglement and wormholes.

There should be nothing weird about these physical concept if you can clearly define what it means, supported by actual experiments or observations.
In the same context there is nothing weird about a BH, we can not directly observe, but which we can infer because we can observe stars which rotate about the BH inside our Galaxy.

It also suggests that entangled objects - despite having long been viewed as having no physical connection to one another - may in fact be connected in ways that are far less fantastical than we thought.

The whole issue is what such a connection physical means.

In fact, entanglement was a property of quantum mechanics that greatly bothered the German physicist, who called it "spooky action" at a distance.

In fact if you would have performed two almost identical real experiments with two slightly different outcomes: One showing no correlation and the other one showing a correlation than I expect his first remark would have been: Interesting result. Exactly what causes this difference?
The strange thing is that the experiment described in the box: "Entanglement Meets Wormholes" IMO impossible can demonstrate entanglement.

Black Holes and WormHoles

Black holes are regions of curved spacetime that differ drastically from the relative nondistorted space we are used to.

The readers of this article I advice to read: Historical Overview #5

The distintive feature of a black hole is that we can separate its geometry into two regions: the exterior, where space is curved but objects and messages can still escape and the interior lying between the point of no return.

IMO from a distinctive physical point of view there are three regions:

• A region that is outside the black hole and from which light can escape.
• A region that is outside the black hole and from which no light can escape.
• A region that is inside the black hole.

The boundaries between the three is not sharp.

General relativity tells us that the horizon is just an imaginary surface: an astronaut crossing it would not feel anything special at that location.

We are discussing here physics. What happens which a spaceship close to a blackhole depents about the speed of the spaceship and the approaching angle. The spaceship can be torn apart. This definitly will be happen when the spaceship is inside the blackhole.

(In fact, the interior is actual in the future compared with the exterior, so the traveller cannot escape because he or she cannot travel to the past)

What happens near or inside a blackhole has nothing to do with the future nor the past.

The wormhole in Schwarzschild's solution differs from black holes that form naturally in the cosmos in that it contains no matter - merley curved spacetime.

And what does that physical mean? I think nobody knows.

Nevertheless, it is an interesting solution and physicists have wondered about its physical interpretation.

And the most common answer is?

Alternativily we can say that the bridge collapses before we can cross it.

This seems like trying to find the bowl of gold which lies where the rainbow touches the ground.

The lovers decide to jump into the interior of their respective black holes.

Immediate when they do that they both will be killed, independent if there is a wormhole or not.

Quantum Entanglement

Before searching your pocket, you do not know whether you have the left or right glove.

That is a reasonable assumption.

Once You see that you have the right-hand glove, though, you will immediatly know that the one at home is the lefty.

But ofcourse this has nothing to do with (quantum) entanglement.

But entanglement involves a different kind of correlation, one that exists between quantities governed by quantum mechanics, which are subject to Heisenberg's uncertainty principle.

Heisenberg's uncertainty principle is not a law of nature and can not be used to describe other physical phenomena. Heisenberg's uncertainty principle is a law which describes our human limitations.
See also Comments about Uncertainty principle in Wikipedia

This principle says that there are pairs of physical variables that are impossible to know accurately at the same time.

That is correct. There are physical variables that cannot be measured simultaneous by us humans, but that does not say anything about the physical processes involved.

EPR wondered what would happen if we decided to measure either the positions or the velocities of the indivudual particles in a pair separated by a wide distance.

Generally speaking the distance has no influence, the outcome will be the same.

We prepare them in such a way that their center of mass has a well-defined position, which we call xcm equal to xR (the position of R) plus xj (the position of J).

A rather difficult experiment. In the next sentence we read:

We can require the center of mass equal zero - in other words, we can say that the two particles are always equidistant from the origin.

To make such a claim you have to measure the arrival times of the two particles at equal distances. And this 1000 times.
For the velocities, to make similar claims, you have to do the same; perform each experiment 1000 times. To make the particles relative vrel equal to v0 is extremely complex.

We are here specifying a position and a velocity accurately but not for the same single object so we do not violate Heisenberg's uncertainty principle.

The first part is impossible. See Reflection 1 - Romeo and Juliet

At first glance this situation appears to allow an instantaneous transmission of information: Juliet can measure the position and then Romeo would see a defite position for his particle, thus inferring that Juliet measured the position.
Romeo would not be able to realize however, that his particle has a definite position without knowing the actual value of the position that Juliet measured. So in fact, correlations caused by quantum entanglement cannot be used to send signals faster than the speed of light.

I think there exists a much stronger rule: Quantum entanglement cannot be used in any communicaton scheme except if you can control the particles at the source.

Although it has been experimentally confirmed, entanglement may still seem just an esoteric property of quantum systems.

The concept of entanglement has nothing spooky. There is nothing spooky that when you start from a central source which emits two particles simultaneous that always one particle has the value A+ and the other one A-. The combinations A+A+ and A-A- are not measured.

Equivalence

How might our two different, bizarre phenomena - worm holes and entanglement - be related?

Worm holes is a bizarre phenomena, Entanglement, describing the behavior of certain particles, is not.

The fact that black holes radiate implies that they have a temperature - a notion with important ramifications.

A much better name for a black hole is a black star.

We also believe, at least from the outside, black holes should behave as quantum systems; that is they should be subject to all the laws of quantum mechanics.

Such as: etc? etc?
Black stars behave like black stars. They are very compact, very dense.

Because black holes look like ordinary quantum systems from the outside, nothing prevents us from considering an entangled pair of them.

You can not compare two black holes with a pair of gloves.
I know nowhere this is mentioned in the article, but in some sense the author does that
You also cannot compare with two polarized photons which are entangled.

Now imagine an entangled pair of black holes in which each quantum state in the first black hole is correlated with the corresponding quantum state of the second.

This is more a thought experiment.....
Identical twin are highly correlated, but are they also entangled?. IMO no.
The reader is adviced to read the text before the following quote himself.

In other words, quantum entanglement creates a geometric connection between the two black holes.

Quantum entanglement does not make connections between objects. Physical processes can make connections between rotating stars, but the two objects involved are not entangled. See for example: Cataclysmic variables and X-ray binaries

From EPR's point of view, the observations near the horizons of each black hole are correlated because the black holes are in a state of quantum entanglement.

In this sentence quantum entanglement is supposed to be a fact of live. In reality you have to demonstrate that there is entanglement in the first place.

They then need to build very complex quantum computers that will manipulate their respective quantum particles and combine them in a controlled way to create a pair of entangled black holes.

IMO this is all hocus pocus.

A Universal principle?

Although we identified the connection between worm holes and entangled states using black holes, it is tempting to speculate that the link is more general - that whenever we have entanglement we have a kind of geometric connection.

The word speculate is correct.

This expectation should hold true even in the simplest case, in which we have only two entangled particles.

Sorry, in the case of two entangled particles there exists no physical connection between the two. Sorry.

In such situations, however, the spatial connection could involve tiny quantum structures that would not follow our usual notion of geometry.

Sorry, again, I doubt this.

It is as if entanglement can be viewed as a thread connecting two systems.

THis is not the case. See also Reflection 2 - Quantum entanglement

When the amount of entanglement becomes larger, we have lots of threads and these threads could weave together to form the fabric of spacetime.

Entanglement has nothing to do with space nor time.

For now, this picture is still wild speculation etc.

That is all what it is: speculation.
The sad thing is that I do not think that all people agree with this.

Reflection 1 - Romeo and Juliet

In the chapter Quantum Entanglement Romeo and Juliet are used to perform similar experiements a certain distance apart. They are used to measure the position and velocity of the particle.
To measure the position you need a detector and a watch. In the article is written: the two particles are always equidistant from the origin. My first guess is that than also their speeds should be the same (in absolute sense). A logical implication should be that the mass should be the same.
To measure the speed directly of a particle is much more complicated. Generally speaking you need the position twice.

The biggest problem IMO to what extend has the operator at the source control over the particles? IMO nothing. IMO he or she can not control when the particles are emitted. Neither can they control what the speed is.

IMO this whole paragraph is rather shaky.

Reflection 2 - Quantum entanglement

The concept of quantum entanglement has nothing spooky.
The simplest experiments which demonstrate quantum entanglement often start which a source which contains a radio active element which emits two particles (photons, electrons) in two opposite directions. In order to demonstrate that the two particles are correlated (entangled) you measure the same parameter in each particle. The two particles are correlated when always when you measure A+ in one particle you will measure A- in the other particle. That means the combinations A+A- and A-A+ are observed. The combination A+A+ and A-A- is (almost) never observed.

The explanation of the behavior is in the reaction in the source i.e. in the radio active decay.
There exists no physical connection between the two particles.

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