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July 10, 2005
A field guide to teleportation options
Teleportation is a staple of science fiction novels, but not all teleportation is created equal. This post attempts to provide a field guide. The entries below are roughly in order of my estimate of how attractive they are as methods of travel. Note, this unavoidably contains spoilers for a few SF books (though in most of them teleportation is just background). You have been warned.
Wormholes, tesseracts, etc.
This is the standard science-fiction teleport. We somehow connect
space-time at point A to space-time at point B and then just walk
through. This is pretty much the optimal form of travel: fast
travel with no sticky philosophical problems about identity (though
if you get there faster than the speed of light, you have to
worry about causality violation and all its philosophical problems).
Examples: Hyperion, Pandora's Star, A Wrinkle In Time.
Quantum teleportation
When you read about teleportation in the popular press, the
articles are typically about some sort of
quantum entanglement. You arrange for system A and system B to be in an
entangled quantum state, allowing you to move system B into the
same state as system A (while destroying the state at A).
This has actually been demonstrated in the lab with a pair of
particles, which is only about 25 or so orders of magnitude removed
from the size of a human being.
The obvious downside of quantum teleportation is that the local copy of your body is destroyed. Now, from a quantum physics perspective, this isn't really a problem: once teleportation is complete, the new system is in exactly the same quantum state as the original system, so they're interchangeable. However, many people don't find this satisfactory, since the original you is, after all, gone.
Examples: Spin State.
Scan and transmit
A more "conventional" approach is to use some sort of high resolution
scanning to capture an exact image of your body. You then transmit it
from point A to point B where a copy is assembled. The philosophical
problems here are much more severe than with quantum teleportation,
because there are two copies. You can certainly treat the system
as a duplicator, in which case you're not really travelling, and worse
yet, scattering copies all over the world. Alternately, you can
destroy the first copy, but this starts to feel much more like a
death machine than a teleporter.
What makes the destroy-the-original variant particularly problematic is the possibility that there are temporarily two copies of you and then you destroy one of them. They have the opportunity to diverge in the time between the duplication and the destruction, at which point you're killing a distinct person. In this respect, any teleportation process which inherently destroys the original is superior since there is no possibility for divergence. How you feel about this goes to the heart of your opinions about identity. This obviously gives people pause. Parfit's Reasons and Persons has a particularly good analysis of this case.
A related variant is an inherently destructive scan (with the idea that a really deep san is destructive) + transmit. This has similar philosophical issues to quantum teleportation. The difference is primarily one of mechanism, though you would expect that a quantum copy would be more accurate.
Examples: Think Like A Dinosaur, Just Peace in Vinge's Threats and Other Promises.
Mental transmission
Finally, consider the possibility of transporting just your personality.
At the other end, it gets implanted in some host body. Once again,
we have both the destructive scanning option and the duplication option.
To make matters worse, we have the uploading into a computer option.
As before, things are a lot easier if the scanning process is inherently
destructive, since we don't have any chance of there being multiple
copies.
Examples: Altered Carbon, Mindswap, Warpath. Also, see Greg Egan's Axiomatic and Diaspora for treatments of uploading, copying, and mental identity.
Posted by ekr at July 10, 2005 10:16 PM | Filed under:
Comments
The made-for-engineers, 2004 indie sci-fi movie "Primer" invents a neat variant, although it's technically a time-travel machine, not a teleportation device. (Space travel, time travel, same difference, right?)
You start the device at time T, get into the device at time T+X, spend X hours cocooned in the device (with time flowing backwards during this period) and emerge from it at time T. Between times T and T+X, there are two copies of you going around, but if you don't screw up causality, the first copy enters the device at T+X and disappears.
Posted by: PG at July 11, 2005 11:45 AM
The bigger problem with "quantum teleportation" as a means of transporting people is that it only works for quantum information--that is, information that is in the form of (indeterminate) quantum states, rather than, say, classical bits. In all likelihood, the vast majority of the information that makes up a person is not in the form of quantum information at all, and getting it into that form poses the same problem as getting it into any other trasmissible form--electromagnetic signals, for instance.
To a large extent, the term, "quantum teleportation" is a triumph of marketing. To scientists, it's a clever trick that allows otherwise inaccessible quantum state to be transmitted from one place to another, while retaining its quantum nature. To the public, it looks like it has something to do with using the magic of quantum mechanics to teleport people from one place to the other. Both groups are impressed, and since they don't talk to each other much, they're both happy in their differing understandings of the phenomenon--only one of which is even close to correct.
Posted by: Dan Simon at July 17, 2005 6:57 AM