How well can information be stored from the beginning to the end of time?

January 13, 2015 by Lisa Zyga, Phys.org feature

(Phys.org)—Information can never be stored perfectly. Whether on a CD, a hard disk drive, or a piece of papyrus, technological imperfections create noise that limits the preservation of information over time. But even if you had a perfect storage medium with zero imperfections, there would still be fundamental limits placed on information storage due to the laws of physics that govern the evolution of the universe ever since the Big Bang. But what exactly these fundamental limits are is still unclear.

In a new paper published in the New Journal of Physics, Stefano Mancini and Roberto Pierini at the University of Camerino and INFN in Italy, along with Mark M. Wilde at Louisiana State University, have investigated these to preserving on a literally cosmic scale.

Specifically, they wanted to know how well a given amount of information can be preserved from the beginning to the end of time, with limitations only from physical laws and not technological imperfections in the specific .

"The motivation that has led us to consider this goal, though it may appear unrealistic, was the discovery of ultimate limitations in information processing," Mancini told Phys.org. "Above all, we want to try to understand if and how spacetime dynamics affects ."

To do this, they modelled information transmission over a "channel" that is essentially spacetime itself, described by the Robertson-Walker metric. Their model combines the theories of general relativity and by considering the quantum state of matter (specifically, spin-1/2 particles) as the universe expands. In this model, the evolution of the universe creates noise which, in the context of quantum communication, acts like an amplitude damping channel.

Mark M. Wilde from Lousiana State University talks about information preservation from the beginning to the end of time in this video abstract. The paper was published in the New Journal of Physics. Credit: New Journal of Physics

The physicists' main result is that, the faster the universe expands, the less well the information can be preserved. To deal with this "problem" of the expanding universe on information preservation, the researchers investigated strategies for preserving as much information as possible over billions of years of expansion. Doing this involved using a communication-theoretic paradigm in which information is encoded at the beginning of the universe's evolution and decoded at the end of its evolution. This model allowed the scientists to develop a strategy for preserving both classical and quantum information, which use different storage techniques and so require a trade-off.

So to answer the original question of how much information can be stored from the beginning to the end of time, the results suggest "not very much."

Plot of the transmissivity, η, of the channel where information travels, shown as function of the momentum, k, of the matter field where information is encoded. Credit: Mancini, et al. CC-BY-3.0

"I would say that, for most cases (except when particles are at rest or moving very fast), the impact of spacetime dynamics would be large, so little information can be preserved," Mancini said. "However, a quantitative answer could be provided by using a more accurate evolution model of the universe. This is left as work for the future."

There are a number of other interesting future directions that this work could take. For instance, implementing correction measures at various times during the evolution of the universe could reduce the degradation of the stored information. More speculatively, future research might focus on entanglement-assisted communication in Einstein-Rosen bridges—better known as wormholes—and even entanglement between different eras in the universe. This research could have implications for understanding dark energy and the evolution of the overall.

Explore further: Gravity may have saved the universe after the Big Bang, say researchers

More information: Stefano Mancini, et al. "Preserving information from the beginning to the end of time in a Robertson-Walker spacetime." New Journal of Physics. DOI: 10.1088/1367-2630/16/12/123049

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7 comments

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russell_russell
not rated yet Jan 13, 2015
Confusion might arise between preservation and principles of conservation.
Probably from poor wording the article uses. A reasonable objection.
tadchem
not rated yet Jan 13, 2015
Consider entropy. Information is contained in a system that has less than the maximum possible entropy. The 'end of time' for a system may be defined as the state of maximum entropy for that system.
Ergo, arrival at the 'end of time' for a system necessitates the loss of all information within the system.
Uncle Ira
2.6 / 5 (5) Jan 13, 2015
Very interesting. I hope L. Susskind will comment explicitly, having declared his First Principle of Physics.


Well I will tell one thing that is true Skippy. I read a book by the Susskin-Skippy not very long ago and it was a tough one for ol Ira-Skippy. In it he declared a lot more than just the number one principle of the physics, it was more like one after the another one after another one.

Which one was his first one? Was it the one that said time only moves one way so all the information is conserved? Whatever that is supposed to means,,,,, that's part of the stuffs I couldn't understand so good. Everybody says he is the really smart physics-Skippy so it's probably my fault what he was saying got me confused.

I read the book about the minimum stuffs to know about physics. Is that the one you read too?
russell_russell
not rated yet Jan 13, 2015
Further reading;
http://arxiv.org/abs/1305.6341

My defense:
'Current' is eighteen months ago for me.
Uncle Ira
not rated yet Jan 13, 2015
I read the book about the minimum stuffs to know about physics. Is that the one you read too?
Susskind has written four, I believe, popularized books, and authored/co-authored 125 papers publicly available at arXiv. Understood, understood entirely, or not, I have read at them all and sat through about 300 hours of video lecture. I bait mouse-traps with Skippy.


I only read the one book about the minimum stuffs you need for physics. Like I said, it was way over my head, so I figured if that was the minimum, I sure was not ready for the extra stuff. If you can understand that one and the extra physics you need that he wrote, , my hat's off to you Skippy. I am not sure about the mouse traps parts, what does that mean? Down here we bait mouse traps with peanut butter.
Uncle Ira
not rated yet Jan 13, 2015
P.S. for you Doug-Skippy. Sometimes I am slow on the uptake, I get him now. Skippy, peanut butter, we on the same page with that one, eh Cher? You got me looking foolish there, but they won't let me take it back after three minutes so I'm stuck looking foolish me.
antialias_physorg
not rated yet Jan 14, 2015
The physicists' main result is that, the faster the universe expands, the less well the information can be preserved.

Information (or SNR) based on the speed of expansion. Interesting.
It sort of makes sense when you consider that faster expansion means a higher rate of stuff dropping over each other's information horizon.
So the sum over all local possible information exchanges drops at a rate dependent on the rate of expansion.
There may be an equivalence, here, that is worth investigating (a sort of 'information pressure')

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