Hardware for cellular automata
Introduction
The most suitable hardware currently available for implementing cellular
automata in is probably a type of electronic circuit called a
"cellularstyle" FPGA (Field Programmable Gate Array).
Some future technologies will undoubtedly have an impact on the type of
physical substrate most suitable for implementing universal cellular
automata in:
 Nanotechnology
 Nanotechnology will almost certainly result in a break from
transmitting and storing information using electricity. Instead,
mechanical methods will be used to store and manipulate information on
the atomic or molecular levels.
 Biological computation
 Biological computation may be seen as essentially a simplified method
of approaching nanotechnology. Rather than engineer novel structures
from scratch, biological computational approaches hope to make use of
modified existing organisms, their products, or their components to
provide high tech, nanotechnological machinery for computation. There
have already been some minor successes from this field  notably ones
using nucleic acids as information storage devices.
 Crystal computation
 Crystal computation is one of
the hopes for offerring a shortcut to nanotechnological computation in
cellular automata. Crystalline structures tesselate in ways which
reflect the structure of various types of cellular automata, may be
relatively simply constructed (indeed they exhibit strong tendencies
towards selfassembly), and have the potential to be a virtually
ideal medium for hardware implementation of cellular automata.
 Quantum computation
 When it becoms possible, and if it becomes
practical, quantum computation may offer the possibility of massively
parallelising certain types of operation, in effect by executing them
simultaneously in parallel universes.
There are currently some uncertainties associated with to what degree it
will be possible to insulate the computational systems from interactions
with the system observing it  any such interactions have the capacity to
destroy the details of the computation.
It has been argued that gravitational processes will cause this type
of interaction  regardless of any efforts by experimenters to prevent
them. Although gravitation does not prevent interference effects between
photons from occurring, quantum computations will necessarily be larger
in size and require a number of interactions to occur in serial before
they can be used for nontrivial purposes.
It seems likely that there will be upper limits, both on the
size of quantum circuitry and the and time available for performing
computations in before the system decoheres. Exactly where these
limits lie in practice is not yet known.
Quantum computation offers perhaps the most in the way of possible
benefits, but may be the most distant, and technologically challanging of
the techniques listed here.
