Comments about the News and Views article in Nature: A Holographic wormhole in a quantum computer

Following is a discussion about this article in Nature Vol 612 1 December 2022, by Adam R. Brown & Leonard Susskind.
To study the full text select this link: In the last paragraph I explain my own opinion.



The holographic principle is a guide in our quest to understand how to combine the two most celebrated theories of modern physics — quantum mechanics and general relativity.
According to this principle, theories that include both quantum mechanics and gravity can be exactly equivalent to other theories that involve quantum mechanics but not gravity.
See also: Reflection 1 - Proper Science
It is not possible that a theory which includes both quantum mechanics and gravity can be exactly equivalent as a theory that involves only quantum mechanics. It should be understood that a theory is a (predicted) description of the behaviour or evolution of a certain process.
Such an alternative description is known as a dual, and has fewer dimensions than its gravitational counterpart — much like how a hologram projected on a 2D surface displays a 3D image.
The problem in this sentence is a clear definition a dimension, specific in the context of: fewer dimensions.
Any physical process or object has always 3 dimensions. A photo (the image of a 3D object) or projection on a screen has 2 dimensions.
On page 51, Jafferis et al report using a quantum computer to generate a state that mimics a hologram whose dual is an entity known as a wormhole, and then evolving this state to simulate a message traversing the wormhole.
This sentence requires a clear definition of the concepts: quantum computer, hologram and wormhole.
A Quantum Computer consists of Qubits and Quantum Logic. A hologram and a wormhole are physical objects. They cannot be simulated on a QC. See also: Reflection 1 - Proper Science
Every black hole has both an interior region, from which nothing can escape, and an exterior region, from where escape is still possible.
The interior region consists of compressed baryonic matter. The exterior region consists of space.
My understanding is that radiation can be ejected from the interior into the exterior region but not outside the exterior region.
Radiation, originating from outside the exterior region, can travel through the exterior region (the outside of) and escape.
The two regions are demarcated by a surface called the event horizon. What Einstein and Rosen noticed is that, in a mathematical idealization of a black hole, there is actually not one exterior region, but two, and they are connected through a kind of wormhole now known as an Einstein-Rosen bridge.
This type of reasoning is logical wrong and does not belong to what is called Proper Science.
In order to study and understand the evolution of any process you should start with a physical description of what is involved and secondly with a mathematical description.
From a physical point of view the event horizon is not a border but much more a region. This region should function like a membrane.
But this is no ordinary bridge. On the one hand, in the version studied by Einstein and Rosen (and unlike that considered by Jafferis and colleagues), it is impossible to travel through the wormhole from one exterior region to the other - the wormhole cannot be traversed. On the other hand, if someone jumps into the interior region of the black hole from one exterior region, it is possible for them to meet someone jumping in from the other exterior region, but their time together would be brief, because by jumping in they'd be doomed to certain death. The bridge cannot be crossed, but people from opposite ends can briefly meet in the middle
The concept that the border functions like a membrane supports this idea.
There are two distinct situations. However, in real, around the black there exists no membrane, nor are there wormholes
The trio's paper examined quantum mechanics (without gravity), and identified the phenomenon now known as quantum entanglement, which Einstein described as "spooky action at a distance".
The evolution of processes that incorporate quantum entanglement is completely normal and does not involve any "spooky action at a distance".
This pattern of correlations is a signature of quantum mechanics, because it cannot be reproduced by any classical process that doesn't involve faster-than-light communication.
This correlation is established at the moment when the two photons are created, as part of the original reaction. There is no faster than light communication involved. To be more to the point: When the polarization of one photon is measured the polarization of the other photon is not affected and vice versa.
However, quantum entanglement cannot itself be used to send messages faster than light, and so although entanglement might indeed seem spooky, we now understand that it's not really action at a distance.
There is correlation, but this correlation is not physical.
At the time, these two ideas — wormholes and entanglement — were considered to be entirely separate. But since then, the relationship between them has become increasingly central to our understanding of quantum gravity.
The question is: which physical process does one try to explain. Has it something to do which the internal structure of the elementary particles? I doubt that. The most important point is that black holes are invisible for humans, but they emit gravitational radiation, which can be detected.
As such the meaning of quantum gravity is not clear.
The two exterior regions of the black hole are connected by a huge amount of quantum entanglement, and the inability to travel from one exterior region to another is understood to be 'holographically dual' to the inability to use entanglement to send messages faster than light speed.

Figure 1 - An emergent wormhole in a quantum computer.

Quantum systems can display a non-classical pattern of correlations, even when the parts are separated by long distances, because of a property known as quantum entanglement.
All correlations between particles or radiation is caused by normal (classical) reactions.
For an actual experiment to generate 2 'entangled' photons read this document:
The holographic principle tells us that some non-gravitational quantum states have an alternative description in terms of higher-dimensional gravitational states.
You need a more convincing argument than "tell us".
Jafferis et al.1 generated a certain highly entangled quantum state between the two halves of a quantum computer, chosen so that its holographic dual is an entity known as an ‘emergent wormhole’ stretched between two exterior regions. They then simulated a message traversing this wormhole.
There is nothing wrong with this simulation. The question is what does this simulation in a QC tells us about the physical situation around a BH.
Later, the connection between wormholes and entanglement was taken a step further, with a thought experiment that considered what would happen if the two exterior regions could be made to interact
It is impossible to use a thought experiment to consider what happens in the reality. Specific if different humans predict different scenarios it is only possible by a real experiment to decide which one is right.
The message simply passes through the wormhole.
Physical processes don't operate by sending messages.
A modified version of this thought experiment was later proposed — one that could actually be performed as an experiment on a quantum computer
of course it is possible to propose an experiment and perform that experiment on a quantum computer. The problem is, what does this experiment tells us related to what happens in the real the physical world.
The first step is to generate a particular entangled state between the two halves of a quantum computer, chosen to be the holographic dual of two exterior regions connected by an emergent wormhole.
Does this processes resembles what happens in the neighbourhood of the event horizon?
We should stress that, in this simulation, the ‘gravity’ experienced by the message traversing the wormhole is the emergent gravity in the holographic description, and is therefore entirely unrelated to the gravitational forces that moor the quantum computer to Earth.
Okay but tricky.
This means, for example, that there is no risk of the quantum computer being swallowed by the black hole.
The reason is because I expect that only certain physical aspects are simulated on the QC and what ever you do on a QC can not mimic a real Black Hole.
At the same time in the real world, Black Holes can swallow wormholes, which makes this discussion tricky.
The holographic duality is sharpest in systems that contain a huge number of degrees of freedom, but state-of-the-art quantum computers have such high error rates that they can simulate only a modest number of qubits.
What this sentence means is that a quantum computer with nine qubits is already unreliable.
With nine qubits in total, Jafferis and colleagues' quantum system is so small that the holographic wormhole is of low resolution.
Furthermore, because nine qubits can be easily simulated on a classical computer, the results of this experiment cannot teach us anything that could not be learnt from a classical computation, and will not teach us anything new about quantum gravity.
Such a simulation does not use the concept of superposition, with made any link to the physical world doubtful.
The past decade has seen an explosion of ideas connecting black holes with quantum computing - a dialogue that holds great potential for stimulating ideas in both fields.
General speaking there exist no relation between the processes that take place in a black hole or a star has any relation between the processes that take place inside a quantum computer, consisting of Qubits.

Reflection 1 - Proper Science

Proper Science requires that all concepts used should be clearly defined. That means also the concepts Quantum Mechanics and Gravity.
Using this definition both concepts are distinct from each other.

This document uses the concepts: Holographic principle, A dual, dimension, Quantum computer, wormhole, holographic wormhole, E-R bridge, qubit, quantum entanglement, a message (physical), emergent gravity.
Each of then should be clearly defined, which is not easy.

Reflection 2 - Event Horizon.

The horizon is the horizontal dividing line between what we see from the sky above us and the ground on which we stay. It is a visible demarcation line and not a physical line because if you look carefull when you observe a ship moving away, it showly disappears below this horizon.
The event Horizon is a sphere around the sun in physical space.
The event Horizon defines the region where physical events that happen at the surface of the Black Hole are visible. Outside this sphere they are not visible. Events that happen at the event horizon are both visible inside the event horizon or within the sphere that defines the event horizon and outside the event horizon. What is also possible, because the subject is radiation, that radiation comes from the outside, goes a short distance through the inside and again leaves the BH via the event horizon.

The same type of processes are also possible around stars but than the object is not always radiation but also small objects.
For example in the case of sun flares 'material' is emitted and will return. Comets can collide or pass around.

What ever the process, but in order to explain or understand, concepts like superposition, entanglement or wormholes are not required.
Why should there be wormholes around a BH? How are they created? What are wormholes in the first place?
For some, my free interpretation, they function like elevators which move objects, instantaneous, from one universe to an other universe. IMO these type of machines most probably don't exist.

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Created: 20 December 2022

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