Sunday, June 28, 2009

I'm quite optimistic about the future, but I seem to be posting anti-predictions instead of predictions. Perhaps I'll post positive predictions someday, but today I have some more negative ones:

  1. Quantum Computers. Yes, I know that there's a now quantum computer chip but I'm pretty pessimistic anyway. Quantum computers let you explore 2N states with N quantum bits; it would take 2N regular bits to do the same. However, I think the difficulty of maintaining the entangled quantum state will be proportional to 2N — that is, adding one quantum bit entangled with all the existing ones will double the difficulty of preventing decoherence. To explore a large search space, it will be far easier to build more very simple conventional processor than to build one very complex quantum processor.

  2. DNA Computers. Making DNA compute for us seems like a cool idea. We can grow this stuff in vats and have hugely parallel computers. The problems here are that (a) you have to get the problem transmitted to all the DNA in the vat, (b) there's no guarantee of finding the answer, and (c) DNA just isn't a great medium for the kinds of controlled programs we want to write. Here too I think it will be far easier to build a simple massively parallel computer from electronic parts than to build a DNA computer. DNA does have the advantage of easy replication, but conventional computers will also benefit from self-assembly.

  3. Practical Teleportation. There have been experiments showing that teleportation is possible. The basic approach is to entangle two particles at the quantum level, and then destroy the original, leaving you with the “teleported” one. It's pretty cool. But it suffers the same problem as quantum computers: there's a huge amount of complexity involved in teleporting real objects (unlike movie teleportation, I don't think it matters too much whether they're biological or not), and I'm rather pessimistic about being able to entangle a large number of particles simultaneously.

  4. Faster than Light Travel. Physicists seem to think that faster than light travel is possible using wormholes. The idea is that you bend space and time in such a way that where you are and where you want to be are “close” together in another dimension, and then you leap across. I think this is possible in theory. But bending the universe is going to take far too much energy and cause too much collateral damage for this to work in practice. Instead, we'll have to hope for existing wormholes, and there won't be any that are useful.

So there you go. Another fit of negativity from me. I really should start collecting positive thoughts about the future.

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xaminmo wrote at Sunday, June 28, 2009 at 10:19:00 PM PDT

1) I think the quantum computing will be somewhere in the middle.. Basically, parallel multi-qubit processors. I see them being useful for pattern recognition and encryption, but not for "traditional" processing.

2) DNA computing is useful only for such a tiny fraction of workloads. If you have a hugely parallel workload that would take weeks to run, then DNA computing is worthwile. You'll spend a day "programming" it (sequencing the components), a day "processing" (combining and replicating), and a day getting the output "selecting the "correct" answers out of the soup.

3) I think teleportation with entangled particles is a pipe dream. A few bits per particle, and you still have to ship the particles? It would only be possible if you could reentangle remotely.

I think it's more likely that replication style teleportation would be possible. With great amounts of energy, it's possible to create matter from energy. So, you transmit a pattern (we're what, about 15PB of data?) and parallelize the data into a fabricator. Once you've assembled the replacement, and verified that it's indeed correct, you would disassemble the source. For a person, this would mean that you copy them, then kill the original.

This would take a ridiculous amount of energy. To store and utilize that energy compactly enough, you'd have to be dealing with matter/antimatter reactions. Antimater manufacture and containment also takes ridiculous amounts of energy. This would be best relegated to a solar or nuclear platform in space.

4) Wormholes, I think, would not be stable. If they were stable and naturally occurring, either we would suffer their consequences already, or they avoid matter, or they would somehow not be readily usable by us.

Even so, I think bending space is less likely than punching a programmed hole through a dimension in which our two desired points in our spacetime were already proximal. We might be able to create tunnels through which we could pass data, but probably not whole, solid objects, without the use of something powerful such as black holes. Any that we could keep, control, or maintain would be too small (microsecond life span with an event horizon big enough for an electron? How much space could you warp with this? Maybe an array of them could be used?)

Amit wrote at Monday, June 29, 2009 at 2:37:00 PM PDT

Thanks for the comments xaminmo! I think quantum computers will be useful but conventional computers will be useful for so many more problems that they'll get faster even quicker than quantum computers. General purpose seems to win over special purpose in most areas because of network effects. For example GPUs are being more and more general purpose and can take more problems that would've been solved by FPGAs.

Replication style teleportation requires us to measure and reproduce the state of all the particles. Unfortunately quantum mechanics limits our ability to measure everything. This is why the entanglement approach is interesting — it manages teleportation without having to measure everything.