Reversible Computation Avraham Guttman Topics in Biological Physics
Reversible Computation Avraham Guttman Topics in Biological Physics Prof. Elisha Moses, Dr. Roy Bar-Ziv R. Landauer, IBM J. Res. Dev. 3, 183 (1961) Bennett, C. H. , IBM J. Res. Dev. 17, 525 (1973) R. Landauer, Physica Scripta. Vol. 35, 88 -95, 1987 Feynman, Lectures on Computation, 1999
Reversible Computation - Outline • Thermodynamic Reversibility • Physics of Logic Reversibility 0 • m. RNA Transcription 1 0 1 T 0 1
Memory Tape 0 1 0 0
Single Bit Operation 0 1
Carnot Engine http: //galileoandeinstein. physics. virginia. edu/more_stuff/flashlets/carnot. htm
Carnot Cycle Thermodynamically Reversible
AND - Irreversible gate Loss of Information
Physically Loss of Information 0 1 T Loss of free energy
von Neumann – Landauer Limit In each irreversible bit operation:
Information Erasure Irreversible Process Loss of energy Infinite tape: No need for erasure For N erased bits: Nonphysical
Physical Reversible Copy Copier Model X
Bennetts’ Three-Tape Reversible Computation 1. Algorithm steps while saving 2. Copying the output 3. Retracing the algorithm steps Standard History Copy 0 1 1 0 R 1 -1 R 2 -1 R 3 -1 1 0 1 0 1 R 02 R 03 0 0 0 0 1 0 0 1 0 0 1 R 3 R 2 R 1 0 1
m. RNA Transcription from DNA to protein
=G , C, A , U m. RNA Transcription RNA (N bases) +X-S-P-P-P RNA (N+1 bases) +P-Pi (Triphosphate) (Pyrophosphate) Transistor:
Reversible Computation - Outline • Thermodynamic Reversibility • Physics of Logic Reversibility 0 • m. RNA Transcription 1 0 1 Thank You T 0 1
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