Can entangled qubits be used to probe black holes? (Update)

Can entangled qubits be used to probe black holes?
Schematic of the black hole information paradox. Alice drops a qubit into a black hole and asks whether Bob can reconstruct the qubit using only the outgoing Hawking radiation. Credit: Norman Yao, UC Berkeley

Physicists have used a seven-qubit quantum computer to simulate the scrambling of information inside a black hole, heralding a future in which entangled quantum bits might be used to probe the mysterious interiors of these bizarre objects.

Scrambling is what happens when matter disappears inside a black hole. The information attached to that matter—the identities of all its constituents, down to the energy and momentum of its most elementary particles—is chaotically mixed with all the other matter and information inside, seemingly making it impossible to retrieve.

This leads to a so-called "black hole information paradox," since quantum mechanics says that information is never lost, even when that information disappears inside a black hole.

So, while some physicists claim that information falling through the event horizon of a black hole is lost forever, others argue that this information can be reconstructed, but only after waiting an inordinate amount of time—until the black hole has shrunk to nearly half its original size. Black holes shrink because they emit Hawking radiation, which is caused by quantum mechanical fluctuations at the very edge of the black hole and is named after the late physicist Stephen Hawking.

Unfortunately, a black hole the mass of our sun would take about 1067 years to evaporate—far, far longer than the age of the universe.

However, there is a loophole—or rather, a wormhole—out of this black hole. It may be possible to retrieve this infalling information significantly faster by measuring subtle entanglements between the black hole and the Hawking radiation it emits.

Two bits of information—like the quantum bits, or qubits, in a quantum computer—are entangled when they are so closely linked that the quantum state of one automatically determines the state of the other, no matter how far apart they are. Physicists sometimes refer to this as "spooky action at a distance," and measurements of entangled qubits can lead to the "teleportation" of quantum information from one qubit to another.

"One can recover the information dropped into the black hole by doing a massive quantum calculation on these outgoing Hawking photons," said Norman Yao, a UC Berkeley assistant professor of physics. "This is expected to be really, really hard, but if quantum mechanics is to be believed, it should, in principle, be possible. That's exactly what we are doing here, but for a tiny three-qubit `black hole' inside a seven-qubit quantum computer."

By dropping an entangled qubit into a black hole and querying the emerging Hawking radiation, you could theoretically determine the state of a qubit inside the black hole, providing a window into the abyss.

Yao and his colleagues at the University of Maryland and the Perimeter Institute for Theoretical Physics in Waterloo, Ontario, Canada, will report their results in a paper appearing in the March 6 issue of the journal Nature.

Ion experiment aces quantum scrambling test
Scientists have implemented a test for quantum scrambling, which is a chaotic shuffling of the information stored among a collection of quantum particles. Quantum scrambling is one suggestion for how information can fall into a black hole and come out as random-looking radiation. Perhaps, the argument goes, it is not random at all, and black holes are just excellent scramblers. Credit: E. Edwards/Joint Quantum Institute

Teleportation

Yao, who is interested in understanding the nature of quantum chaos, learned from friend and colleague Beni Yoshida, a theorist at the Perimeter Institute, that recovering quantum information falling into a black hole is possible if the information is scrambled rapidly inside the black hole. The more thoroughly it is mixed throughout the black hole, the more reliably the information can be retrieved via teleportation. Based on this insight, Yoshida and Yao proposed last year an experiment to provably demonstrate scrambling on a quantum computer.

"With our protocol, if you measure a teleportation fidelity that is high enough, then you can guarantee that scrambling happened within the quantum circuit," Yao said. "So, then we called up my buddy, Chris Monroe."

Monroe, a physicist at the University of Maryland in College Park who heads one of the world's leading trapped-ion quantum information groups, decided to give it a try. His group implemented the protocol proposed by Yoshida and Yao and effectively measured an out-of-time-ordered correlation function.

Called OTOCs, these peculiar correlation functions are created by comparing two quantum states that differ in the timing of when certain kicks or perturbations are applied. The key is being able to evolve a quantum state both forward and backward in time to understand the effect of that second kick on the first kick.

Monroe's group created a scrambling quantum circuit on three qubits within a seven-qubit trapped-ion quantum computer and characterized the resulting decay of the OTOC. While the decay of the OTOC is typically taken as a strong indication that scrambling has occurred, to prove that they had to show that the OTOC didn't simply decay because of decoherence—that is, that it wasn't just poorly shielded from the noise of the outside world, which also causes quantum states to fall apart.

Yao and Yoshida proved that the greater the accuracy with which they could retrieve the entangled or teleported information, the more stringently they could put a lower limit on the amount of scrambling that had occurred in the OTOC.

Monroe and his colleagues measured a teleportation fidelity of approximately 80 percent, meaning that perhaps half of the quantum state was scrambled and the other half decayed by decoherence. Nevertheless, this was enough to demonstrate that genuine scrambling had indeed occurred in this three-qubit quantum circuit.

"One possible application for our protocol is related to the benchmarking of quantum computers, where one might be able to use this technique to diagnose more complicated forms of noise and decoherence in quantum processors," Yao said.

Yao is also working with a UC Berkeley group led by Irfan Siddiqi to demonstrate scrambling in a different quantum system, superconducting qutrits: quantum bits that have three, rather than two, states. Siddiqi, a UC Berkeley professor of physics, also leads the effort at Lawrence Berkeley National Laboratory to build an advanced quantum computing test bed.

"At its core, this is a qubit or qutrit experiment, but the fact that we can relate it to cosmology is because we believe the dynamics of quantum information is the same," he said. "The U.S. is launching a billion-dollar quantum initiative, and understanding the dynamics of quantum information connects many areas of research within this initiative: quantum circuits and computing, high energy physics, black hole dynamics, condensed matter physics and atomic, molecular and optical physics. The language of quantum information has become pervasive for our understanding of all these different systems."

Aside from Yao, Yoshida and Monroe, other co-authors are UC Berkeley graduate student T. Schuster and K. A. Landsman, C. Figgatt and N. M. Linke of Maryland's Joint Quantum Institute. The work was supported by the Department of Energy and the National Science Foundation.


Explore further

Researchers demonstrate teleportation using on-demand photons from quantum dots

More information: Verified quantum information scrambling, Nature (2019). DOI: 10.1038/s41586-019-0952-6 , https://www.nature.com/articles/s41586-019-0952-6
Journal information: Nature

Citation: Can entangled qubits be used to probe black holes? (Update) (2019, March 6) retrieved 23 October 2019 from https://phys.org/news/2019-03-ion-aces-quantum-scrambling.html
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Mar 06, 2019
What happens when an antimatter black hole collides with a matter black hole of equal weight? Does it explode? Does it just disappear?

Mar 06, 2019
Since energy can't get out of a black hole, nothing would be visible outside the event horizon. Antimatter-matter interactions make energy. And energy is conserved.

Antimatter doesn't make matter's energy content, you know E=mc² and stuff, disappear. And vice versa. Unless you believe in negative energy. Which is silly because we have measured the energy from matter-antimatter interactions and there's none missing, indicating the mass-energy of both matter and antimatter is positive.

Supposing two equal-mass black holes, one matter and one antimatter, merged, what you would have is called a "kugelblitz;" a black hole made of energy. But there would be no practical difference outside the event horizon.

Good question, BTW. You don't usually get 5 stars from me but for this one you did.

Mar 06, 2019
Now back to the article, from a practical standpoint of actually investigating black holes this is meaningless. Even a stellar-mass black hole would emit so much Hawking radiation that no quantum correlation could be reliably detected.

However, from the quantum computing point of view, this is very useful and not only as a test for the correct operation of a quantum processor error checking algorithm; it's an algorithm to add to the stack in and of itself. Should give some clues on quantum gravity theory too.

Mar 06, 2019
Oh? Now, you want my opinion?

I would assume, the only message we will receive from within the Event Horizon of a Stygian Oubliette, will be:

"Bano Occupado!"

Mar 06, 2019
Da Schneib, thank you for reminding me of Hawking radiation. I could have used that in my tirade on BH/SOs.

I asked why, in this Stochastic bedevilment of a Universe,
wasn't there some sort of "glow" along the outer edge of an Event Horizon?
That sheer random chance should have ejected, repelled or refused incoming matter & energy.
Even if already being disassembled.

Mar 06, 2019
A hole has to be really little to give much Hawking radiation. Once they're the mass of a star, they take enormous amounts of time to evaporate, like a 1 followed by 67 zeroes years.

Mar 06, 2019
By dropping an entangled qubit into a black hole and querying the emerging Hawking radiation, you could theoretically determine the state of a qubit inside the black hole, providing a window into the abyss.

Yeah, well...but aren't you only gathering information on what you drop in? You're not really probing what is already in there if I understand this correctly.

Mar 06, 2019
From the article:
"At its core, this is a qubit or qutrit experiment, but the fact that we can relate it to cosmology is because we believe the dynamics of quantum information is the same," he said.
The 'connection' drawn with possible BH-info testing/retrieval using these entangled Qubits is silly because in the real world they would not be able to discern the 'whisper' of the supposedly outward-tunnelling info/radiation from the 'hurricane' of the quantum-uncertainty and quantum 'virtual-pair-production/annihilation' going on at/through such extremely tumultuous 'boundary domains'. This 'long bow' drawn as possible BH-testing method is patently calculated to 'suck in' gullible grant-givers in the cosmology field, as well as those in the quantum-computing field. These kinds of obviously misleading/dishonest claims/connections for their 'work' is what makes the 'profession' look/sound like 'hustlers' rather than objective honest scientists. Pity.

Mar 06, 2019
well RC, after parsing through your comment?

I find it a dubious assertion on your part that you have any competency to decide who is competent in the scientific fields of which you are so dismissive.

What are your credentials to support your denunciation of the involved researcher's work, their analysis of collected data & their conclusions?
Or your allegation of criminal cobspiracy of the members of the peer-review system that approved the their empirical evidence?

Who would stand to defend your research work?
& What are their credentials?

Mar 06, 2019
"1067 years" must be a typo. It probably should be 10 to the 67.

Mar 06, 2019
@rrwillsj.
I find it a dubious assertion on your part that you have any competency to decide who is competent in the scientific fields of which you are so dismissive.

What are your credentials to support your denunciation of the involved researcher's work, their analysis of collected data & their conclusions?......
Its in the article, in their own words, mate. It's a quantum-computing project, NOT a BH-study project. :)

The unwarranted, disingenuous 'use for BH-info testing etc' SUGGESTION is made solely by THEM, based on patently UN-tenable and UN-realistic scientific/technical 'arguments'.

If you can't see the obvious when it's spelled out for you by an objective 'messenger' (ie, me in this case), @rrwillsj, then you have no chance of being objective/relevant enough in this matter; hence your opinion is as 'iffy' as your attempt to couch it in terms of 'criminal conspiracy' on their part (your straw man). Chasing 'grants' is an imperative for most 'physicists'. :)

Mar 06, 2019
"..that recovering quantum information falling into a black hole is possible if the information is scrambled rapidly inside the black hole. The more thoroughly it is mixed throughout the black hole, the more reliably the information can be retrieved via teleportation."

@RealityCheck
LOL This is such deceptive nonsense. Information, just like Matter/Energy is never lost. However, when information is so thoroughly mixed, as they are saying, it can never be retrieved again UNLESS that information had been known already beforehand. If it was known prior to the Event, then it would be easy to retrieve it from a computer if it was already on record. If not on record, the information is lost. If an attempt is made to retrieve that information, it would take possibly billions or more of attempts, and even then, the information might not be in the proper sequence to be properly understood.

Mar 06, 2019
RC, You insist your interpretation of this article as a confession to criminal conduct by the research team?
& then you complain when I judge your comments by the same rules you used to denounce the researcher's work?

The only evidence of culpability on the part of tha accused?
Your personal opinion that you do not approve of their methods, evidence or conclusions.

Did you present any specific evidence of their guilt? No.
Did you present any proof of their criminal intent? No.

Would you be willing to stand trial accused of crimes based on such flimsy conjecture?

You are flummoxed too tears, that I or anyone else would use your own despicably mean-spirited attempt to discredited these scientists reputations with a vile campaign of baseless accusations.

Because? They did not report the results of their experiments, you wanted to hear!!

Mar 06, 2019
well of course RC, the sillyegghead is supportive of your drivel. Parasites of a fetter, stick together, in the nearest pile of steaming crap.

Any moment now. I expect the rest of your coven of looneytoons to start bleating on your behalf.

The idiotocracy you all embrace, is a deplorable sign of America's degeneracy into anti-science fascism
The flock of you haven't the moral character of a mud puddle.

Mar 06, 2019
@rrwillsj
The idiotocracy you all embrace, is a deplorable sign of America's degeneracy into anti-science fascism
rc is not american - he's from oz

that idiot even posted his own name, address and more on his pseudoscience site
http://earthlingclub.com/

don't blame america for the idiocy that is rc
just report the idiot to ACORN like everyone else - he's already known to them
https://www.afp.gov.au

Mar 07, 2019
"1067 years" must be a typo. It probably should be 10 to the 67.

Pretty common formatting error on phys.org.
(They don't author these articles, but aggregate them from elsewhere. Sometimes the formatting doesn't survive the copying process)

Mar 07, 2019
but, but, but Captain...
who would I have then? to vent my spleen upon with wordy abandon?

Mar 07, 2019
" a future in which entangled quantum bits might be used to probe the mysterious interiors of these bizarre objects."

Maybe it's just me but I don't think these mysterious objects contain any info at least in these interiors. As I read Hawking's ideas particles check their info at the event horizon in what he calls hair. Only their internal energy enters the BH. This figures because of what they call spaghettification. The internal energy is essentially squeezed out of the particle before it enters the horizon. BHs essentially contain no matter in their interiors, only their internal energy left over after falling into the singularity and being ejected through wormholes to the dark matter halo around the galaxy.

Mar 07, 2019
What happens when an antimatter black hole collides with a matter black hole of equal weight? Does it explode? Does it just disappear?
The anti-matter galaxy hair gets mixed in with the normal matter hair and the internal energy of both BHs. Not aware of any antimatter BHs around unless there is a parallel universe out there somewhere which interacts with our universe after sucking up all their matter and antimatter and having nothing left to do but interact with each other. Leading to a new big bang perhaps (or probably IMO).

Mar 07, 2019
BHs essentially contain no matter in their interiors, only their internal energy left over after falling into the singularity and being ejected through wormholes to the dark matter halo around the galaxy.
So note dark matter is pure energy stripped of its info. Sure would be hard to detect except through it's gravitational effects. You mean energy density has an affect on gravity? Better believe it.

Mar 08, 2019
@rrwillsj
@Captain Stumpy.

Haven't you two anything better to do than troll/bot-vote a poster who is being confirmed correct all along by recent mainstream discovery/reviews? The latest eg?...re the vast amounts of recycled material which has been going into deep space, just as I have been pointing out for you, and which material reforms into new 'primordial looking' stars/clusters galaxies which until now have been INCORRECTLY interpreted as being "BB-primordial" features, but which in fact are being produced all the time via recycled materials going into deep space, as per admission by mainstream in the following linked work:

https://phys.org/...ies.html

You two need to re-do your info base as to who is correct on the science before you again embarrass yourselves before the whole forum. Please learn to discern correct from incorrect; and then stop being incorrect bot-voting/trolling nincompoops on the internet. Try. Thanks.

Mar 09, 2019
@RC
'virtual-pair-production/annihilation' going on at/through such extremely tumultuous 'boundary domains'.
Don't think you'll find any of this going on inside a BH. Certainly not the singularity. The lack of such production is the source of the BH gravity, I would say, rather than its mass. Quantized matter certainly does reduce the intensity of this activity in the region around the matter but the BH goes all the way and eliminates it even further..

Mar 09, 2019
@Seeker2.
'virtual-pair-production/annihilation' going on at/through such extremely tumultuous 'boundary domains'
Don't think you'll find any of this going on inside a BH. Certainly not the singularity. The lack of such production is the source of the BH gravity, I would say, rather than its mass. Quantized matter certainly does reduce the intensity of this activity in the region around the matter but the BH goes all the way and eliminates it even further..
I suspect you misunderstood the thrust of my comment there, mate. I alluded to NO 'singularity' NOR 'BH interior'. Please re-read it and note the context/region my comment relates to:
...at/through such extremely tumultuous 'boundary domains'.
I was referring to the quantum tumult at/through Event Horizon of BH, which would 'swamp' any alleged "information" from their "entangled qubits" which might be contained in the Hawking Radiation they are counting on for their method to work as they hope. Ok? :)

Mar 14, 2019
@RC
...at/through such extremely tumultuous 'boundary domains'.
I was referring to the quantum tumult at/through Event Horizon of BH, which would 'swamp' any alleged "information" from their "entangled qubits" which might be contained in the Hawking Radiation they are counting on for their method to work as they hope. Ok? :)
Note 1: Some say it will take forever for BHs to evaporate through Hawking radiation so info may be conserved but it would take forever to recover it. I can understand that but I never could understand Hawking radiation because what happens to matter at the event horizon could just as well happen to antimatter assuming both act similarly in a gravitational field. Still as long as the BH temperature is above absolute zero I think it should evaporate and the info could be retrieved from the evaporating radiation.

Mar 14, 2019
Note 2: However as I understand Hawking the info is checked at the event horizon in the form of black hole hairs. I can understand this because matter would be progressively spaghettified as it approaches the event horizon. I would say what falls into the singularity is the remaining compressed spacetime of energy mc^2 - which blows out the singularity through wormholes. Faster than the speed of light, by the way, somewhat supported by the discussion at
https://www.answe...ck_hole,

Mar 14, 2019
Note 3: Nothing "tumultuous" going on inside the event horizon, at least involving matter whose info is checked at the event horizon. This substance, having no internal energy and therefore no temperature, would not be subject to evaporation. Strangely, this info could be recovered in the collision of 2 or more BHs where the surrounding spacetime replaces the energy previously sucked out of these BH hairs.

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