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Threshold for Life: 

Threshold for Life MIT Media Laboratory Prof. Isaac Chuang

Objective: 

Objective Claim: Life can be constructed from faulty components

An Amazing Theorem: 

An Amazing Theorem von Neumann (1956) Quantum version: Preskill, Shor, Aharonov, Ben-Or, Gottesman, Chuang*,… * D. Gottesman and I. Chuang, Nature, vol. 402, p. 390, 1999

Fault-Tolerant Circuits: 

Fault-Tolerant Circuits

Fault-Tolerant Circuits: 

Fault-Tolerant Circuits

The Fault-Tolerance Threshold: 

The Fault-Tolerance Threshold A circuit containing N (error-free) gates can be simulated with probability of error andlt; e, using cdN faulty gates, which fail with probability p, if pandlt;pth. Proof: Assume 3-input gates. N=1 easy.

Efficient Fault Tolerance: 

Efficient Fault Tolerance A circuit containing N (error-free) gates can be simulated with prob. of error andlt; e, using O(N log N) faulty gates, which fail with prob. p, if pandlt;pth. Status: pth ¼ 1/6 (Hajek andamp; Weller ’91)

Fault-Tolerant Life: 

Fault-Tolerant Life Nature does not seem to use such constructions How can life be made fault-tolerant?

What is Life?: 

What is Life? Desirable characteristics: Self repair Self reproduction Growth Evolution Schrodinger von Neumann (1966) Theory of Self-Reproducing Automata: elementary machine capable of reproduction and universal computation

Von Neumann’s Automaton: 

Von Neumann’s Automaton Model based on 29 state Cellular Automaton (simulation from H-H Chou) Langton’s 8-state replicator (not universal) Universal Turing machine Universal constructor

Visions of Fault-Tolerant Life: 

Visions of Fault-Tolerant Life Two interesting questions: What is the fault-tolerance threshold for Life? Rad-hard biology Immortal Biosystems …Reproduction?