From: Joscha Bach Sent: Sunday, August 14, 2016 11:03 AM To: Jeffrey Epstein Cc: Joi Ito; Nowak, Martin Subject: Re: Jeffrey, there are several sides to this: 1. Computers that are technically different from our current digital =omputer architectures, but can do the same things, because they can =athematically be proven to be equivalent, and we can build a digital =quivalent. Examples are computers with ternary logic, neural networks, =actor graphs etc. 2. Probabilistic computers: instead of deterministic state transitions, =hey change state with a certain probability. We can get them to =pproximate determinism with arbitrary precision by stacking the =robabilistic gates. Many cognitive scientists and AI researchers =elieve that brains are in that category. (We can also reproduce their =ehavior on a digital computer by adding random noise.) 3. Computers that are technically different from our current digital =omputers, but are still mathematically equivalent, yet it may not be =ractical to build a digital equivalent, because it would be too large =r too slow. Examples are DNA computers, chaotic computers etc. Digital =hysicists (Steven Wolfram, Ed Fredkin) believe that even the universe =s in this category. Chris Eliasmith thinks the brain is in this =ategory (we need to build electronic simulations of spiking neurons). 4. Quantum computers: they still cannot do anything but manipulate =nformation, but they can (hopefully one day) do a few things =fficiently, like factoring large numbers, so they are in principle more =owerful than conventional computers. Seth Lloyd thinks the universe is =n this category, and Penrose thinks the brain is in this category. 5. Hypercomputers with true continuum dynamics. Such computers can solve =he 3 body problem with infinite precision in finite time etc. (Most of) =raditional physics believed that the universe must be continuous, and =ven contemporary physics usually has continuous time etc. Such =ompute