How does one combine the basis of Quantum Physics that the information cannot be destroyed with the GR statement that black holes destroy the info?
Philadelphia, PA
Dear Duxbury,
Interesting question. I wonder what our theoretical physicists may have to say.
As I recall Hawking's last papers, his answer was basically that there are "really" no black holes, since they all are supposed to eventually evaporate? One might attempt to evaluate that sort of answer. But what of the dim prospects of determining the heterogeneity of what goes in on the basis of the homogeneous exit radiation?
Another approach would be to examine the concept of "information" involved. What is involved is a quantum version of (backward and forward) physical determinism which must in some fashion discount the 2nd law of thermodynamics. That may lead into debates on the quantum measurement problem including recent approaches based on decoherence.
A third sort of answer proposes the "holographic principle." In effect, all the information about what falls into a black hole is thought to be preserved at the event horizon.
H.G. Callaway
Dear Natalia S Duxbury :
The famous resolution to the so called Black Hole's Loss Information Paradox gives the basis of your question, i.e. the resolution is the answer to it.
The solution to this "long term struggled paradox" was developed by Gerard t'Hooft and Leonard Susskind, and it lies in two basic principles, the first was the basis for the second.
In the 90s Susskind came up with his "Principle of Simultaneity", applied to Black Holes.
The philosophy behind Susskind's Principle of Simultaneity is the same as the one Niels Bohr was trying to express (with not much of success) when he created it for the first time for its Interpretation on QM (Susskind got lucky Bohr never really expressed himself 100% clear on this).
In particular, the Principle of Simultaneity applied to Black Holes seeks to reconcile the description of the "Free Fall" experience, that a free falling observer who is at the point of crossing the Event Horizon, "the Point of No Return" with the description that a far free observer, above the Event Horizon, would be seeing, on a second observer falling to the BH, crossing the Event Horizon.
("Einstein Strong Equivalence Principle" tells us that an observer in Free Fall, accelerated inside a Gravitational Field, cannont distinguish this scenario from the scenario where Gravity would be the driven force, i.e. with Gravity and without gravity but uniform acceleration).
Thus the solution to the Paradox was the Principle of Simultaneity.
Later on, this was the basis to the aswer the second Paradox : the "Information Loss Paradox". And then, the great Leonard Susskind came up with his Holgraphic Principle.
There is a good amount of story behind this Paradox. But in the end, everything lies in Entropy (the Entropy of a BH), and Information (Quantum Information).
Bekenstein and Hawking discovered that Black Holes have Entropy, and not just like that, but an enormous amount of Entropy. They discovered that the Entropy of a BH is proportional to the Area of its Event Horizon, and not to its Volumen.
So, Susskind , t'Hooft and others (Joe Polchinski, John Preskill, etc.) understood that the meaning of Entropy of a Black Hole (and this is not particular for Black Holes, we think this nature of Quantum Information is deeply linked to the nature of Space) (...cont) that the Entropy is the amount of "hidden" Information... Hidden where? Well, spreaded over the surface of the Event Horizon, loosely speaking.
Hence, in a figurative sense if you like, we can say that the Information (Quantum Information) falling into a BH, end stored, or "stuck" over an infinitely thin layer above the Event Horizon... is spread out, plastered .
So, the ultimate soution to the conservation's (or Loss) of Quantum Information Paradox into a BH is the Hawking's Radiation mechanism:
The Information is not lost, is of course, Conserved. But QM had to enter into the game.
The Hawking mechanism is not to difficult to understand, since its nature is equivalent to the nature of the Black Body Radiation that a hot body, (like the interior of an oven) emits. The solution to this problem (which later was known as the "Ultraviolet Catastrophe"), found by Max Plack in the 1900s, explained why, no matter what Temperature, while above 0 K, all bodies have to be radiating and emi
any body with a Temperature above 0 K has to be radiating an Emission Power Spectrum with a finite amount of Energy.
Hawking discovered that Black Holes are't bodies at 0 K. Therefore, they must radiate in the EM spectrum, i. e. they are Hot (and by QM, the Hawking Radiation also can carry other more energetic partícles like relativistic Neutrinos, but in a tiny fraction). He discovered that this Radiation Spectrum corresponds almost exactly to the emission spectrum of a perfect Black Body.
However, the key is that this Radiation (which in most part, is composed of very low Energy Photons) comes form the Event Horizon, and not from the inside of the BH (is very weird, but is Quatum Mechanics).
Thus, the ultimate solution, which the fact that this is so, can be proven by the Holographic Principle, and using another more powerfull and novel tool: the Juan Maldacena's "AdS/CFT Correspondence"... Is that the Information comes back in the entangled Photons in the Hawking Radiation. But this is a very messy state of Entanglement. The word, used in a loosely manner, within the comunity is the word "scrambled", to refer to the state of the Qubits which return to the Universe with the Hawking's Radiation. The information felt before into the BH, doesn't get lost, get stored, and when the Black Hole evaporates (due to Hawking Radiation) this information comes back in the Photons of the Hawking Radiation. But in a useless manner, or better to say, in an state which is impossible (or highly difficult in practice) to reconstruct.
The Photons of the Hawking Radiation can be entangled with very distant regions of Space, form the Black Hole (I know, very weird too indeed).
At this point is where new descriptions of Quantum Gravity and the nature of Space must enter into the game.
Best Regards !
Why is the basis of Quantum Physics that the information cannot be destroyed? I suppose that you mean that the basic quantum evolution is unitary, but there is obviously non-unitary evolution as well. Otherwise entropy would never increase. This is certainly a more general question than what refers to black holes: information is destroyed whenever entropy increases.
Dear Jose Gaite :
The fundamental reason due to we know that Quantum Information cannot be neither destroyed, nor created, is because there is this such fundamental principle in QM; The Principle of Quantum Information Conservation.
This fundamental principle, along with other fundamental principles like the No-Clonning Theorem in Quantum Information, prohibits by all means, that Quantum Information to be created (copied, or just "grow" a long a particular quantum process) nor destroyed (or in parlant lingo: Lost).
(caviat here: "Quantum Information", so these principles does n't say anything about Clássical Information)
These are two fundamental principles of Quatum Mechanics and Quantum Information Theory. They are grounded like axioms, in emergent areas like Quantum Information, Quantum Computing, Quantum Metrology, and Quantum Criptography.
And you can test these theorems (mathematically, of course). You can put them to test, in particular scenarios, in the above sub-fields I just mentioned, and throw everything you have at them, trying to break them. But you won't find a way to get around them.
Regards !
I do not think information or entophy will be conserved for all physics. They are only conserved within certain range. Energy, either linear or squared, is the physics inside and outside black holes. For example, the collision of two astronomically high energy protons creates almost infinite number of elementary particles, so how entropy or information can be preserved? Those infinite particles form celestial bodies and eventually some blackholes, then information or entropy start to shrink.
Dear Hong Du :
Entropy is certainly Not conserved . Entropy can be generated.
Then two black holes collide head on and destroy each other into elementary particles, physics starts outside black holes again. So information show up again. The preserved quantity is energy. Therefore in black holes, the energy is preserved in their own physics principles. Information is the energy and the related physics principles inside black holes that the energy obey. The physics we know doesn’t work inside black holes. The principle for black holes is there, but is not known to human.
Hong Du, thank you.
Did you meant your 1st word as “When”?
What institutional are you from?
Dear Franklin Uriel Parás Hernández,
I agree that the unitary evolution is a fundamental principle of QM, which you may translate as "Quantum Information cannot be neither destroyed nor created". But this principle refers to pure quantum states, that is to say, to the basic states of QM, and not to mixed states. I suppose that you are also saying this in your caveat, since you distinguish quantum information from classical information: I interpret that quantum information refers to pure states, which undergo unitary evolution, while classical information refers to mixed states, which undergo non-unitary evolution (in my view, the classical limit of QM involves a rather different question).
If the evolution of the universe were unitary, there would be no increase of entropy anywhere. Unfortunately, as far as we observers are concerned, the universe is in a mixed state and we have to endure the increase of entropy. Clausius introduced the concept of entropy in 1865 and stated:
"The energy of the universe is constant. The entropy of the universe tends to a maximum."
In my opinion, this statement still stands, and it is more general than anything related to what happens in black holes.
Best regards.
Dear Hong Du :
Quantum Information cannot be destroyed, cannot be copied, and cannot grow in any particular Quantum Mechanical process. This is to say that QI has to be conserved in any Quantum Mechanical process. This is a fundamental principle of QM.
The branches of Quantum Information and Quantum Computing (among others) are based on this principle.
There is a real application of Quantum Information which is called "Quantum Teleportation" . This branch uses the "Quantum Teleportation Protocol" in QI to "teleport" Quantum States of different Qubits. I write " " marks infront and behind the term "teleport" to point out that this is not the Teleportation process we see in Star Trek.
Quantum Teleportation is very real. And we (by we, I mean mankind) already have teleported Quantum States from entangled Photons several times, through large distances.
The record of this is the teleportation process of the state of an entangled photon (in 2012, or 2013) when a Chinese collaboration sent (or teleported) a Quantum State with two entangled Photons, from a Chinese Laboratory here in Earth, to a chinese Satellite 12 000 km above the surface.
So, the fact that Quantum Information always has to be conserved is a fundamental principle, which is embedded in the laws of Physics and in the laws of QM. Is not a phenomenological law, or an aproximate law, like Newton's laws, nor an statistical law like the Second Law of Thermodynamics.
This is a Principle, like a mathematical axiom, which avoids you from creating, or destroying, a number of Qubits. In other words, the total number of Qubits is always conserved.
John A. Wheeler, famously coined the phrase : "It ... from Bit" .
He was just approximate with this, he missed the " It .. from Qubit"
So, returning to Black Holes.
I think you believe that the material (jets) "coming" from Black Holes is Matter or Energy which come from the inside of the Black Hole, so the Black Hole ends "creating" Information, or "creating" Entropy
But these jets, doesn't come from the inside of the BH. They come form the material surrounding the Event's Horizon region of a BH, but always from above of the point of No Return.
This is the article in Wikipedia of the "Information Loss Paradox" of BH.
https://en.wikipedia.org/wiki/Black_hole_information_paradox#:~:text=The%20black%20hole%20information%20paradox,devolve%20into%20the%20same%20state.
I'm not saying Wikipedia is the best source to understand the foundations in these topics. But I have read the page a couple of times, and I believe, if you get to read it, I believe you will end agreeing that Information (quantum Information) cannot be lost in a Black Hole.
Otherwise, I can recommend you the semi-techincal book of Susskind : "The Black Hole War".
In his book, Susskind presents the strong arguments for: 1) The wrong idea Stephen Hawking was addressed in the decade of the 70s; i.e. exactly this idea: That Information is lost inside a Black Hole, whic is not true. And Susskind takes you by the hand from the principles of Quantum Mechanics and Special Relativity to his Principle of Simultaneity (which is what he firstly introduced as "Black Hole Complementarity", and later became the "Holographic Principle") to show you why is this so: Why the original statement of Hawking's solution to the "Information Loss Paradox" cannot be true. He explains in a very clear and conveincin form, why Stephen Hawking was wrong (Sthepen Hawking was the leader of group which subscribed to the idea (or the view) that Quantum Information is lost forever when matter, light, etc. falls into a BH).
And, 2) His book tell you the whole story, between arguments and counterarguments (is a complete story). Is a story of a Paradox which lasted more than three decades to be solved. It tells you how t'Hooft and Susskind started to work and to really address the problem in a deep way, throwing all the kitche set to it. And how they arrived to the Holographic Principle: "The information is not lost, is "stored" somehow, in the Surface of the Event Horizon of the BH".
The book was written around the year 2008 I believe. So it end presenting in a very general form the ideas and concepts of Juan Maldacena, about his Maldacena's Conjecture, or better known as the "AdS/CFT Correspondence". And why Maldacena's ideas will be able to clarify further the field and the solution to the Information Loss Paradox, and why these ideas give somekind of "hope" for a ground of testing, about all these weird ideas in Black Hole Physics.
Maldacena's AdS/CFT Correspondence is becoming a tool. A tool that may be (just maybe, in a near future, and just if we are luckily) useful to make testable predictions about the theory.
Best Regards too sir !
Franklin Uriel Parás Hernández,
Thank you for your detailed reply.
Dear Hong Du :
Yes indeed my friend, I agree with you. hopefully humankind will continue to be interested in these questions.
Kind Regards !
Dear Franklin Uriel Parás Hernández, Hong Du, and all,
Indeed, some of these topics are open: they are connected with the theory of quantum gravity, yet to be constructed (string theory and holography, with the AdS/CFT correspondence, or loop quantum gravity are only attempts).
However, I think that the "black hole information paradox" is surrounded by too much hype. The reason is, of course, the attraction of Hawking's public figure and his wager. There was much theatre in Hawking's conceding that black hole evaporation in fact preserves information.
The paradox arises because the initial matter configuration is assumed to be constructed as a pure quantum state. As I have already remarked, this is unphysical. The article in Wikipedia about the "black hole information paradox" cites Penrose saying that the loss of unitarity in quantum systems is not a problem and that quantum systems do not evolve unitarily as soon as gravitation comes into play. This is most patent in theories of cosmological inflation.
Of course, the definitive answer to Natalia S Duxbury's question will come with the final theory of quantum gravity. We can keep looking forward to it :-)
Best wishes to the seekers of final theories!
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