The physical interpretation of the concept of information is very usual
among physicists and communication engineers (Landauer 1996). According
to this view, information is a physical item whose essential property
consists in its capacity to be generated in one place and to be
transmitted to another place. It can also be stored, accumulated and
transformed from one form to another, like other physical quantities. In
some cases, information is conceived as a physical magnitude with the
same ontological status as energy (Stonier 1990): like energy,
information needs a signal acting as its physical carrier, and can only
be transferred through interactions.
In spite of its wide diffusion, this interpretation began to be
challenged by the advent of “quantum” information. In fact, entanglement-assisted
communication shows that, although mere correlation is not sufficient
for communication, asking for a physical signal acting as a carrier of
information from source to destination is a too strong requirement. The
traditional physical view leads to hardly acceptable conclusions. An
option is to accept artificial solutions as those of information flowing
backwards in time (Penrose 1998, Josza 1998) or of quantum information
hidden in classical bits (Deutsch and Hayden 2000). The other option is
to accept that entanglement-assisted communication does not involve
transmission of information at all. This situation faces the physical
interpretation with a serious problem: does it mean that we must discard
the physical interpretation?
We want to argue that, even in the case of entanglement-assisted
communication, there is no need to discard the physical interpretation
of information. For this purpose it is necessary to furnish the physical
interpretation with some further ideas. In fact, we need to retain the
idea of information as a physical magnitude without falling into a mere
epistemic view of information, but without requiring a physical carrier
for its transmission. What is needed, therefore, is to support the idea
that what happens at the source of information causes what happens at
the destination, but with a concept of causality that does not rely on
physical interactions or space-time connections. We think that a
manipulability account of causation works perfectly in this sense.
Intuitively, any transmission of information produces a relationship
between source and destination, and from the manipulability approach
this relationship is causal because it is potentially exploitable for
purposes of manipulation and control (Woodward 2003, 2013, Pearl 2009).
The link between transmission of information and manipulability lies in
the fact that there is transmission of information whenever we can
change the informational content of the destination (effect) by
manipulating the source (cause). Although still relying on physical
actions, in this characterization of information transference nothing
alludes to interactions or carrier signals.
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Landauer, R. (1996). “The Physical Nature of Information.” Physics
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Pearl, J. (2009). Causality. New York: Cambridge University Press.
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Stonier, T. (1990). Information and the Internal Structure of the
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The Stanford Encyclopedia of Philosophy (Spring 2011 Edition), URL = <http://plato.stanford.edu/archives/win2013/entries/causation-mani/>.