Tuesday, 7 February 2017

Is the information of physics 'about' anything?

The New Scientist has been talking about reality again, and concludes:
"But to Susskind [Leonard Susskind of Stanford University] at least, the idea that reality might be rooted in 0s and 1s is poetically beautiful. Perhaps, he says, we will one day be able to sum up the universe in a simple epigram: “ah, everything is information”".

Note, though:
"[T]he sort of quantum information that might underlie space-time must be a little different [from Shannon information]. The information in a stream of words is about something. By contrast, the quantum information from which space emerges in Carroll’s [Sean Carroll of the California Institute of Technology] work is just there. “The quantum state is not of or about anything,” says Carroll. 
One of the ongoing issues in information research is whether a unified theory of information (UTI) is possible. I've recently been thinking of it in terms of a unified narrative of information: an agreed way of talking about information, and trying to come up with the things we can say about whatever it is we are calling information. One of those things seemed to be that it is always about something. (Though we have to be careful about what it means to 'be about' something. I think my trapeziums help.)  So, here's a question: could it be that the physicists are wrong? Could it be that even their information is about something? Could it be that in order to understand 'reality' you need a type of information that is about something? Could it be that they are missing something?

Anyway, here's a fuller quote from the New Scientist article.
It is all very well to suggest that space and time are made of quantum entanglement and possibly quantum complexity – but what are they made of? Here is where we edge closer to finding the true bedrock of reality. Because both approaches suggest the same tantalising answer: information.

The mathematician and engineer Claude Shannon gave us a neat way to define information in 1948. He showed that the amount of information in something like a stream of bits or letters is related to its entropy, a measure of disorder. The greater the entropy, the greater the information. For example, a stream of three-bit numbers that are always 000 contains less information than a stream in which the numbers can also be 001, 101 or 111.

So in what sense is information at the root of things? Well, entanglement is information: the greater the entanglement between two systems, the more information they share. But there’s a caveat. The information Shannon defined certainly seems to exist and has real effects. Experiments just last year showed a nanomachine could use information to chill metal. But the sort of quantum information that might underlie space-time must be a little different. The information in a stream of words is about something. By contrast, the quantum information from which space emerges in Carroll’s work is just there. “The quantum state is not of or about anything,” says Carroll. “It is simply our best mathematical description of the universe.”

It actually makes sense that quantum information would be the foundation everything is built on, says Carroll. If you start with quantum mechanics and don’t presume anything else exists, then “basically all you have to play with is quantum information”. That would make information a basic constituent of the universe. “You can find people who think that information is all there is,” says Carroll.

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