Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Why quantum computing is hard - and quantum cryptography is not provably
  secure   Despite high hopes for quantum computation in the 1990s, progress in the past
decade has been slow; we still cannot perform computation with more than about
three qubits and are no closer to solving problems of real interest than a
decade ago. Separately, recent experiments in fluid mechanics have demonstrated
the emergence of a full range of quantum phenomena from completely classical
motion. We present two specific hypotheses. First, Kuramoto theory may give a
basis for geometrical thinking about entanglement. Second, we consider a recent
soliton model of the electron, in which the quantum-mechanical wave function is
a phase modulation of a carrier wave. Both models are consistent with one
another and with observation. Both models suggest how entanglement and
decoherence may be related to device geometry. Both models predict that it will
be difficult to maintain phase coherence of more than three qubits in the
plane, or four qubits in a three-dimensional structure. The soliton model also
shows that the experimental work which appeared to demonstrate a violation of
Bell's inequalities might not actually do so; regardless of whether it is a
correct description of the world, it exposes a flaw in the logic of the Bell
tests. Thus the case for the security of EPR-based quantum cryptography has
just not been made. We propose experiments in quantum computation to test this.
Finally, we examine two possible interpretations of such soliton models: one is
consistent with the transactional interpretation of quantum mechanics, while
the other is an entirely classical model in which we do not have to abandon the
idea of a single world where action is local and causal.

29
The categories of this paper are: funct-an
28
The categories of this paper are: alg-geom
21
The categories of this paper are: adap-org
20
The categories of this paper are: acc-phys
4
The categories of this paper are: cond-mat
24
The categories of this paper are: dg-ga
10
The categories of this paper are: q-bio
17
The categories of this paper are: q-fin
11
The categories of this paper are: hep-lat
36
The categories of this paper are: cmp-lg
32
The categories of this paper are: atom-ph
6
The categories of this paper are: astro-ph
37
The categories of this paper are: supr-con
25
The categories of this paper are: patt-sol
30
The categories of this paper are: q-alg
8
The categories of this paper are: hep-ex