Nature Computes

Use Nature to compute: store, transmit, and operate on data; that is, find mechanisms in Nature that can be used/exploited for computation: data storage, data transmission, and data manipulation.
Our attempt to prove that Nature is universal.
History:
- History of Computer Science
- Timeline of Computing
Compare our investigations and discoveries of how we can use Nature for computing to similar investigations and discoveries in artificial (life) environments, like The Game of Life.
Partly automatic mechanisms:
- Stone tablets (administration), papyrus, paper
- Abacus
- Planetarium/astrolabe, clock/calendar
- Keyed locks
- Book printing, typewriter, cryptomachines
- Centrifugal governor, camshaft
- Slide rule
- Mechanical calculator (Leonardo da Vinci, Blaise Pascal, Leibniz, Babbage)
- Loom controlled by punched cards (Jacquard)
Analog versus digital; encoding, translation, reduction
Relay and solenoid (electrons and mechanical switches)
Electronic signals (telegraph, telephone, telex)
Vacuum tube/radio valve (used to switch/amplify electronic signals)
Electromagnetic (EM) signals (morse code, radio, tv, video)
Memory: Acoustic liquid mercury delay line; magnetic cores (rings), magnetic rotating disks, capacitors/CMOS transistors
One bit per molecule
Transistor (fully electronic switch)
- Seven-atom transistor (24 May 2010)
- Single-atom transistor (27 Feb 2012)
Integrated Circuit, microprocessor, VLSI
Laser, optical fiber (data transmission)
Optical storage (CD, DVD)
Optical computing (photon based)
Molecular computing, DNA computing
- Biology, cell replication based on transcribing and copying DNA
- The human brain, and its (symbolic) computational powers
- Creative blocks -- The very laws of physics imply that artificial intelligence must be possible. What's holding us up? by David Deutsch
- Leonard Adleman's experiment, see e.g., Jeez, These Things Could Compute! (A Primer on DNA Computers)
- Adleman's experiment cannot be "understood" from (bio)chemical principles only.
- Biology studies biochemical information processing; living organisms are hard to "understand" without employing notions from informatics (information, program text, program execution).
  Animations of unseeable biology
- Also see the Challenge of writing a self-reproducing program
- DNA self-assembly
- DNA for long-term storage
- DNA computer plays tic-tac-toe [article]
- DNA art: Sierpinski triangle in DNA, DNA origami
Transistor-Less Magnonic Logic Circuits
Quantum cryptography (secure data transmission)
Quantum computer
- Quantum mechanics, also see
  - Lecture on Quantum Mechanics by Richard Fitzpatrick, especially the introductory part about polarized light (photons)
  - The Principles of Quantum Mechanics by Paul Dirac (especially Part I)
  - The Feynman Lectures on Physics, especially Volume 3, and the Feynman Lectures on Computation.
  - Quantum Lab
  - Quantum Computing Since Democritus, a lecture series (also a book now)
  - Google's Quantum Computing Playground
  - Leonard Susskind and Art Friedman. Quantum Mechanics: The Theoretical Minimum - What you need to know to start doing physics, Basic Books, 2015.
  - John H. Conway and Simon B. Kochen. Free Will Theorem
- Superposition offers the possibility to encode "more" information in the state of a "simple building block" (qubit, e.g. a photon, electron, or Calcium ion) than just one bit, viz. a linear combination (with complex coefficients, whose absolute squares sum to one) of the classical states; however, this information has an inherently probabilistic nature (the absolute square is the probability of observing a particular classical state).
- Entanglement offers the possibility to combine the states of multiple particles into one "exponential" state vector (a non-local property): for N particles, the state vector has 2^N coefficients, one for each combination of classical states.
  It is possible to change this entangled state in a single computational step, effectively multiplying the state vector by a unitary 2^N x 2^N matrix (to accomplish the same with a classical computer, would need a number of steps that is exponential in N). A quantum gate can perform such an operation; it is always reversible (in contrast to classical digital logic gates).
- (Decoherence is the (undesirable) effect where a superposition state "collapses".)
- (Tunnelling)
- Quantum computers, a review in Nature where the authors "describe the latest developments for each of the leading approaches and explain the major challenges for the future".
- Shor's Quantum Factorization Algorithm, explained to the man in the street: Shor, I'll do it
Memristor
4 Strange New Ways to Compute
Samuel K. Moore, IEEE Spectrum, 29-Nov-2017.
Digital Physics
- God Is the Machine: "In the beginning there was 0. And then there was 1. A mind-bending meditation on the transcendent power of digital computation."
- "It from bit", a theory by Archibald Wheeler
- Rebooting the Cosmos: Is the Universe the Ultimate Computer?
- Stephen Wolfram. A New Kind of Science (NKS). Wolfram Media, 2002.
  To improve our ability to "exploit" Nature, we want to know how she "works". Nature shows very complex behavior. The more we investigate, the more complex she seems to be. Therefore, our models of Nature have also become very complex, and this only seems "natural". However, the underlying "Laws" of Nature could be very simple, and still give rise to complex macroscopic behavior.
- Gerard 't Hooft. The Cellular Automaton Interpretation of Quantum Mechanics, arXiv.org, 2014-2015.