Space Tangled Up in Spacetime in Scientific American of January 2017

This document contains comments about the article Space Tangled Up in Spacetime by Clara Moskowitz In Scientific American of January 2017.
The collaborative project It from Qubit is investigating whether space and time sprang from the quantum entanglement of tiny bits of information.

"Summary"

The article starts with the following sentence:

Space, the conventional thinking goes, is not made up of anything at all.

The "conventional thinking" is that with space we mean: the space between the objects we observe and is empty. In reality this is not true. This so called empty space is not empty but filled with photons, gravitons or Higg's particles, to name a few.

Scientists have begun to question this convention, however. Space - or rather, in the language of GR, spacetime - may actually be composed of tiny chunks of information.

When you enter the realm of "tiny chunks of information" things are becoming non-physical.
Why not stick to the words space and time. When you use words like spacetime you must also explain what spacetime means. Does spacetime exists or is it more a mathematical construct? If it exists how do you measure it? If it is a mathematical construct than you can only calculate it. In that sense speed is a mathematical construct.

This notion, if correct, would not just explain spacetime.

Such a notion does not explain spacetime, nor space and time, but replaces it by a new one: What are these "tiny chunks of information"

The excitement of such a possibility has lately engrossed hundreds of physicists who meet every three months or so under the auspices of a project dubbed It from Qubit

It is interesting to study what type of progress they make. About something they all agree about.

Introduction

The animating idea behind "It from Qubit" (IfQ) is the notion that the universe is built up from some underlying code and that by cracking this code physicists will have finally found a way to understand the quantum nature of large-scale events in the cosmos.

Understanding the cosmos implies understanding the physical processes that take place. Understanding the evolution of the universe means understanding the always changing chemical processes in time that take place and how they interfere which each other.
All these changes are not controlled by some code, "entangled" in the processes itself.

Because the project involves both the science of quantum computers and the study of spacetime and general relativity, it brings together two groups of researchers who do not usually collaborate - quantum information scientists on one hand and high-energy physicists and string theorists on the other.

I hope that there is no Babylonian confusion in the meetings.

Entangling Spacetime

The new view holds that spacetime, rather than being fundamental, might "emerge" via the interactions of qubits.

A discussion if space, time or spacetime are fundamental is rather fruitless. It is important to define space as something physical, not empty, containing matter. Within that context qubits play no role.

What exactly are these bits made of and what kind of information do they contain? Scientists do not know.

This sentence already describes a bleak picture.
The sentence also assumes that qubits are real. The question is if that is true. IMO they more belong to the realm of "make belief"

Yet intriguingly, that does not seem to bother them.

Also this describes a bleak picture.

"What matters are the relationships" between the bits more than the bits themselves, says IfQ collaborator ...

This seems more like a strange academic thought exercise than a true physical pursuit. A little further on we read:

The key to this organization may be the strange phenomenon known as quantum entanglement - a weird kind of correlation that exist between particles wherein actions performed on one particle can affect the other even when a great distance separates them.

There is nothing weird in quantum entanglement. Quantum entanglement means that two particles created simultaneous at a common reaction are correlated. This correlation is established when both particles are measured. There is no communication involved between the particles when they are measured and the idea that an action on one particle influences the other is a misconception.

"Lately one absolutely fascinating proposal is that the fabric of spacetime is knitted together by quantum entanglement of whatever the underlying 'atoms' of spacetime are," says ... "That's amazing if true."

Again this seems like a world of make belief. The word like "whatever" bothers me.

The reasoning behind the idea comes from etc, showing a connection between entanglement and the geometry of spacetime.

And what is connection? Unfortunate the article does not discuss this "important" issue.
Next we read:

Building on that work, physicists etc found that if two black holes became entangled they would create a wormhole - a shortcut in spacetime predicted by GR

Apparently there is a difference between two BH's that merge and two entangled BH's that merge.
A wormhole is like a whirlpool in space in which a snake (specific its head) can be drawn in today and be ejected in a different era ("yesterday"), still having the capability to eat his own tail.

To understand how entanglement might give rise to spacetime, physicists first must better understand how entanglement works.

You first must clearly define what entanglement is and how it can be measured (established). Next you can try to better understand it.

The phenomena has seemed "spooky" in the words of Albert Einstein, ever since he and collaborators predicted it in 1935, because it involves an instantaneous connection between particles at great distances that seems to defy the limitation that nothing can travel faster than the speed of light.

See also Reflection 1 - Entanglement I doubt if Albert Einstein predicted entanglement. He IMO did have doubts that the explanation of any correlation between two particles requires an instantaneous physical connection. IMO he is correct.

Lately scientists have been studying several different kinds of entanglement.

When you want to study entanglement the first step is to establish that the particles studied are entangled.

Conventional entanglement involves linking a single characteristic (such as a particle's spin) in multiple particles of the same type spread out in space.

Why such a difficult sentence (at the end)? Why not ending this sentence with a period after: multiple particles?

One could, for instance, entangle particles of a certain kind at one location with particles of a different kind at the same location an entanglement that does not involve space.

I think we should first start with explaining and demonstrating what does it means to have two particles (of the same type) entangled at the same location.

Once the dynamics of entanglement are clearer, scientists hope to comprehend how spacetime emerges, just as the microscopic movements of molecules in the air give rise to the complex patterns of thermodynamics and weather.

The first question to answer is what spacetime and entanglement have in common. IMO nothing. Maybe an even more important question is what is spacetime. What is the difference between space and spacetime. The problem is that empty space does not exist. Space in some sense is a human concepts and defines an area outside the physical objects we observe as empty, but that is not empty.
At the end of this paragraph we read:

This is one of the most fascinating things about "It from Qubit" because we don't understand the fundamental quantum dynamics from which spacetime emerges.

This is sentence is 100% correct and I think this will be the situation for a long time to come.

Cosmic Holograms

The "It from Qubit" scientists are banking on an idea known as the holographic principle to help them.

Now it becomes interesting (and dangerous).

This principle suggests that some physical theories are equivalent to simpler theories that work in a lower dimensional Universe.

Lower dimensional 2D universes do not exist. 2D objects also do not exist. The surface of the earth is not a 2D object.

In the same way that a 2D postcard with a hologram of a unicorn on it can contain all the information necessary to describe and portray the 3D shape of the unicorn.

A hologram is not a 2D object. It is an almost flat 3D object, just thick enough to store additional information about the shape of an object.

Because finding a working theory of quantum gravity is so hard, this thinking goes, physicists could aim to discover an equivalent, easier-to-work-with theory that operates in a universe with fewer dimensions than ours.

and which does not exist.
The problem which such a theory is that you can never be sure that the theory is wrong, because their are always more trails to investigate.

One of the most successful embodiments of the holographic principle is a discovery known as de Ads/CFT correspondence, which shows one can completely describe a black hole by describing what happens on its surface

How do you prove that "one can completely describe a BH" etc?

In other words, the physics of the inside - the 3D bulk corresponds perfectly to the physics of the outside - the 2D boundary.

It will be interesting to compare what we know of the outside of the sun with the inside of the sun. See also: https://en.wikipedia.org/wiki/Sun#Structure
What makes this physics complex is the fact that a BH contains a singularity. See also: https://en.wikipedia.org/wiki/Gravitational_singularity

"Theories with gravity are very difficult to get quantum descriptions of whereas theories that don't have gravity are much easier to describe completely" Balasubramanian says.

In this case: to describe what? Be more specific. A theory is a (mathematical) description of a physical phenomena. For example the movements of the planets around the sun.

For about 20 years scientists have found that the AdS/CFT correspondence works - a 2D theory can describe a 3D situation, a setup known as a duality - but they do not fully understand why.

Unfortunate the article does not give an example of such a duality, which leaves the reader guessing.
When you read the following text, almost everything is quicksand.

Quantum information theory may be able to help because a concept from the field called quantum error-correcting codes could also be at work in the Ads/CFT correspondence.

No one has ever built a reasonable working quantum computer. Part of the reason is that QC's are phrone to errors. As such to get them working you need quantum error correction logic. This is a necessity.
A PC also contains error correcting logic, but that is more to detect an error, not so much to correct it.
To assume that error-correcting are also at work in the physical universe seems outlandish.

Quantum computers, rather than encoding information in single bits, use highly entangled states of multiple bits.

A PC works both with single bits and multiple bits or words (of 8 bits)

It seems that the arrangement scientists use to entangle multiple bits together into error-proof networks could also be responsible for encoding the information from the interior of the Black Hole onto its surface through entanglement.

Nobody currently knows if there is any physical process active inside a Blackhole that can be classified as entanglement. As such anything written here is pure speculation.

"It's very intriguing that you find quantum error-correcting codes inside black holes" says Dorit Aharonov.

It is even more interesting how these codes are created when black holes form out of a normal star
The idea of a code is not completely strange because humans have also DNA and RNA, but of course that is completely different....

The correspondence itself works only in a "toy model" of the universe that is somewhat simplified from the fully realized cosmos we inhabit.

So it is much more a thought experiment? And what about the code? Is that also a thought experiment?

"AdS/CFT has a kind of gravity, but it's not the theory of gravity in an expanding universe like the one we live in" Swingle says.

Than what is the purpose?
Immediate next we read:

"It describes a universe as if it was in a bottle - if you shine a light beam, it bounces off the walls of space. That does not happen in our expanding universe"

This more or less seems like a dream, with thoughts.

The Payoff

Standford theorist Eva Silverstein who is not part of the collaboration, concurs: "It is clearly worthwhile to develop and apply quantum information to these problems."

IMO it does not make sense to apply QI to understand physics. It is the other way around. It is a challenge to understand a QBit and to build a Quantum Computer, but both have nothing to do with physics in general.

Bringing the techniques and ideas of string theory and general relativity to bear on questions of quantum information can for instance help to better define the different types of entanglement both for understanding spacetime and for constructing quantum computers.

String theory, general relativity and Quantum Information are highly mathematical concepts.
If you want to understand entanglement you have to start with experiments. Some of these experiments are used to build QBits. The final step is to build a Quantum Computer. Of course in order to optimise each of these issues, using some form of mathematics will be helpful.

Any physical theory can be thought of as a computer, its input and output akin to the theory's initial state and a later state that can be measured - and some computers are more powerful than others.

To consider Newton's Law as a computer is a misnomer.

Once researchers have deduced a quantum gravity theory, they could ask what is the theory's computational power.

I don't understand this question. A more practical question what are the benefits of this QG theory?

"If the power is too large, if our quantum gravity model would be able to compute things that we don't believe can be computed " in our world , that would at least raise a question mark on the theory" Aharonov says.

IMO this whole sentence raises a question mark. What means too large?

"I became a grad student in 1984, when the so-called first string theory revolution took place" says Hirosi Ooguri

And what has the string theory brought us?

Reflection 1 - Entanglement

It is a very tricky exercise to try to use the concept of entanglement to explain astro-physical problems. Entanglement only has something to do with the state of pairs of particles (photons) who have a common origin. That is more or less all.
To try to define the concept: "Entangling Spacetime" IMO is outlandish.

Reflection 2 - General

One question to answer is what have QuBits to do with the state of the physical world, in casu the total universe.
A different question is what has information theory to do with the state of the physical world, in casu the total universe
IMO not much.
The evolution of the universe can be described, accordingly to the Big Bang theory as a sequence of chemical processes. The most important parameter is the average temperature of the universe which shows that the evolution is a cooling process. This is equivalent as an expanding universe. In fact these two parameters are the code that control the evolution of the entire universe.

A whole different issue is what "exactly" is gravity. We call it a force, but that does not explain much. Humans can observe the physical reality by means of our eyes. Our eyes have the capability to detect light, more specific photons. This capability is the result of millions years of a slowly changes. These changes to adapt to the environment we call evolution. At the same time when our eyes evolved also our brains evolved, which give us the capability to discover that the space surrounding us is not empty but filled which photons, which are the basic ingredients to see and observe.
For gravity such a similar picture exists. The capability that objects can respond to each other is caused by gravitons. We humans do not have this capability. As such the laws of nature that describe the movement of objects are not dependent about photons (the speed of light) but about gravitons (the speed of gravity).

Both photons and gravitons belong to particle physics i.e. quantum mechanics. General Relativity and Newton's Law are descriptions of the movement of objects. To try to unify both IMO does not make much sense.

Laws are descriptions of physical processes. As such no physical law can directly incorporate imaginary numbers because "imaginary parameters" do not exist. Objects exist. If you want improve the laws of nature than one of the first steps should be to describe some meta-law which defines the rules of "the laws of nature". This meta-law should also make a difference between what science is and what is speculation. IMO a lot what is written in the article "space Tangled Up in Spacetime" are suppositions or is purespeculation.

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