The power of forgetting

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Thermodynamics places surprisingly few fundamental constraints on
information processing. In fact, most people would argue that it imposes
only one, known as Landauer's Principle: a process erasing one bit of
information must release an amount kT ln 2 of heat. It is this simple
observation that finally led to the exorcism of Maxwell's Demon from
statistical mechanics, more than a century after he first appeared.
Ignoring the lesson implicit in this early advance, however, quantum
information theorists have been surprisingly slow to embrace erasure as a
fundamental primitive. Over the past couple of years, however, it has
become clear that a detailed understanding of how difficult it is to erase
correlations leads to a nearly complete synthesis and simplification of
the known results of asymptotic quantum information theory. As it turns
out, surprisingly many of the tasks of interest, from distilling
high-quality entanglement to sending quantum data through a noisy medium
to many receivers, can be understood as variants of erasure. I'll sketch
the main ideas behind these discoveries and end with some speculations on
what lessons the new picture might have for understanding information loss in real physical systems.