This essay tackles the notion of information as it’s used by physicists.
The science writer Philip Ball stresses the importance of what he and others call information. Ball allows the physicist Christopher Fuchs to express his own informationalist view when he writes:
“[Christopher Fuchs’] approach argues that quantum states themselves — the entangled state of two photons, say, or even just the spin state of a single photon — don’t exist as objective realities. Rather, ‘quantum states represent observers’ personal information, expectations and degrees of belief’, he says.”
According to this position, a photon isn’t in both spin up and spin down at one and the same time. Instead, we simply have the “information” that it can be either in spin-state up or spin-state down. In other words, until a measurement is made, we simply don’t know which state it’s in.
One may wonder, then, what point a realist notion of a spin state would serve — since (realist) physicists could never know if they were right about what they say. In other words, what’s the point of stating the following?-
Well, this photon is either in spin-state up or spin-state down, regardless of what we know — or our “information”.
Is it? How could this (or any) physicist know that?
Since we are discussing the state of a photon, let’s trace all this back to John Wheeler.
John Wheeler on Information
The American theoretical physicist John Archibald Wheeler (1911–2008) once wrote the following words:
“An example of the idea of it from bit: when a photon is absorbed, and thereby ‘measured’ — until its absorption, it had no true reality — an unsplittable bit of information is added to what we know about the world, and, at the same time, that bit of information determines the structure of one small part of the world. It creates the reality of the time and place of that photon’s interaction.”
Wheeler seemed to be arguing that a photon literally gains its “reality” when it’s “absorbed”. Thus, if a particular photon gained its reality only when (or after) it was absorbed, then it mustn’t have had any reality before that absorption…
So can we now conclude that there simply was no photon before the absorption!
Basically, then, Wheeler stressed that the absorption can be seen in informational terms. That is, when the photon was absorbed, then “an unsplittable bit of information is added to what we know about the world”. In other words, only when the photon was absorbed could “we” (i.e., experimental physicists) gain information about it. Before that, the photon had zero reality because such physicists had zero information about it.
In more general terms.
Wheeler believed that everything we discover (at least in science or, perhaps, only physics) is about bits of information. Indeed, Wheeler believed that an object (or what he called an “information-theoretic entity”) is derived from (our?) information. Technically, this is a transformation which Wheeler called “it from bit”.
Thus, we don’t have an “it” (i.e., a physical object) until we firstly have a “bit” (a unit of information).
What Is, and What We Know
Philip Ball also quotes the physicist and philosopher of physics Jeffrey Bub as essentially putting a similar point about information, and quotes him saying:
“[]‘[F]undamentally a theory about the representation and manipulation of information, not a theory about the mechanics of nonclassical waves or particles’ [].”
This means that there’s an important distinction to be made here between what is (i.e., regardless of minds, observations, tests, experiments, etc.), and the information we have about what is.
Fuchs (at least as presented by Ball) also makes it explicit that this stress on information is on a par with philosophical anti-realism when he argues that it isn’t an ontic position. (Neither Fuchs nor Ball ever mention the philosophical position of anti-realism.) It is, instead, an epistemic (i.e., a knowledge-based or information-based) position. In Ball’s words:
“Fuchs sees these insights as a necessary corrective to the way quantum information theory has tended to propagate the notion that information is something objective and real — which is to say, ontic. ‘It is amazing how many people talk about information as if it is simply some new kind of objective quantity in physics, like energy, but measured in bits instead of ergs’, he says. ‘You’ll often hear information spoken of as if it’s a new fluid that physics has only recently taken note of.’ In contrast, he argues, what else can information possibly be except an expression of what we think we know?”
This means that stuff (in a manner of speaking) gives off information, rather than stuff being information in and of itself. In other words, information as seen in the latter way almost seems like a misuse of the word “information”.
[See ‘Quantum Bayesianism’.]
Yet Fuchs’ position conflicts with what other philosophers and physicists see as information.
Such people believe (as Fuchs himself says) that information is in no way mind-dependent. It is “ontic”. [See note.] In other words, they believe that information is information regardless of persons, minds, observers/observations, tests, and experiments.
Note:
I’m not really sure about Philip Ball’s use of the word “ontic”, which I find difficult to decipher. That said, perhaps this position best squares with object-oriented ontology:
“Object-oriented ontology holds that objects are independent not only of other objects but also from the qualities they animate at any specific spatiotemporal location. Accordingly, objects cannot be exhausted by their relations with humans or other objects in theory or practice, meaning that the reality of objects is always ready-to-hand.”
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