FQXi has an ESSAY CONTEST It From Bit or Bit From It:
http://www.fqxi.org/community/essay/winners/2013.1
Here I would like to argue that it from qubit, not bit. (See 我们生活在一个量子计算机里 We live inside a qubit world )
Wheeler's "it from bit" represents a deep desire to unify matter and information. In fact, it happend before at a small scale. We introduced electric field to informationally (or pictorially) describe Coulomb law. But later, electric field became real matter with energy and momentum, and even a particle associated with it.
However, in our world, "it" are very complicated. (1) Most "it" are fermions, while "bit" are bosonic. Can fermionic "it" come from bosonic "bit"? (2) Most "it" also carry spin-1/2. Can spin-1/2 arises from "bit"? (3) All "it" interact via a spectial kind of interaction -- gauge interaction. Can "bit" produce gauge interaction? Can "bit" produce waves that satisfy Maxwell equation? Can "bit" produce photon?
More generally, there are Eight wonders in our universe (ie "it" has eight wonders)::
(1) Identical particles.
(2) Gauge interactions.
(3) Spin-1/2.
(4) Fermi statistics.
(5) Chiral fermions.
(6) Small mass of fermions. (Much less than Planck mass)
(7) Lorentz invariance.
(8) Gravity.
It turns out that we can only produce the first of eight wonders from bits (with local interactions).
However, if we start with qubits, we can obtain Fermi statistics, spin-1/2, Maxwell equation, Yang-Mills equation, and the corresponding gauge interations. So far, we can unify seven out of eight wonders (1 -- 7) by qubits (see arXiv:1305.1045 ), and we are trying to add the gravity (see http://arxiv.org/abs/0907.1203 ).
So It from qubit, not bit. Bit is too classical to produce Gauge interactions, Fermi statistics, and Chiral fermions. Those phenomena (or properties) come from quantum many-body entanglement, which exists only for qubits.
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