Indistinguishability and transporters

I have a memory of  being in a bookstore and picking up a book with the title “The philosophy of Star Trek”.  I am not sure of how long ago this was or even what city it was in. However, I cannot seem to find any evidence of this book on the web.  There is a book entitled “Star Trek and Philosophy: The wrath of Kant“, but that is not the one I recall.  I bring this up because in this book that may or may not exist, I remember reading a chapter on the philosophy of transporters.  For those who have never watched the television show Star Trek, a transporter is a machine that can dematerialize something and rematerialize it somewhere else, presumably at the speed of light.  Supposedly, the writers of the original show invented the device so that they could move people to planet surfaces from the starship without having to use a shuttle craft, for which they did not have the budget to build the required sets.

What the author was wondering was whether or not the particles of a transported person were the same particles as the ones in the pre-transported person or were people reassembled with stock particles lying around in the new location.  The implication being that this would then illuminate the question of whether what constitutes “you” depends on your constituent particles or just the information on how to organize the particles.  I remember thinking that this is a perfect example of how physics can render questions of philosophy obsolete. What we know from quantum mechanics is that particles are indistinguishable. This means that it makes no sense to ask whether a particle in one location is the same as a particle at a different location or time.  A particle is only specified by its quantum properties like its mass, charge, and spin.   All electrons are identical.  All protons are identical and so forth.  Now they could be in different quantum states, so a more valid question is whether a transporter transports all the quantum information of a person or just the classical information, which is much smaller.  However, this question is really only relevant for the brain since we know we can transplant all the other organs from one person to another.   The neuroscience enterprise, Roger Penrose notwithstanding, implicitly operates on the principle that classical information is sufficient to characterize a brain.


10 thoughts on “Indistinguishability and transporters

  1. I agree that brains are likely sufficiently characterized by classical information. But do you know of any experiments that actually support this hypothesis?


  2. Well, we are virtually certain that any possible quantum effects between neurons in the brain would decohere in femtoseconds yet the brain is correlated on much longer time scales. That to me is sufficient evidence that the brain at the systems level is classical. Now, there have been arguments that there could be quantum coherence at the subcellular microtubular level but I see no experimental evidence for this.


  3. Neurotransmitter release is essentially a Poisson process. There are so many other fine reasons for why there couldn’t be any quantum coherence in the brain. However, one could playfully argue that the stochasticity of transmitter release *is* a quantum effect.


  4. So has anyone tried to make a neuron firing model with such coherent phase dynamics? Even in a DAG with appropriate multiple-slit topology, interference fringes would lead to quantized results if you put in some appropriate threshold.


  5. The physics of the brain is condensed matter (formerly solid state) physics. If you believe (reasonably) that all brain function is emergent from that physics — including the epiphenomenal, symbolic stuff represented by the words and ideas seen here on this page — then in order to understand that emergence and map the resulting mechanism you need a model, a comprehensive simulation of the fundamental physics. Or don’t you? And if not, why not?

    A comprehensive description of condensed matter physics isn’t an issue of coherent quantum mechanics per the arguably naïve approach of Penrose, Hameroff et alii but of Quantum Field Theory. And the principal QFT issue remains the fermion minus-sign problem (aka fermion sign problem, sign problem, many-body problem, n-body problem etc.). That is to say, the possibly insurmountable barrier to “understanding the brain” could be the observational confusion which occurs when fermions — including, of course, electrons in said brain — strongly interact (nothing to do with the “strong” force). Jan Zaanen, one of the leaders in the QFT-condensed matter field along with David Tong, calls the minus-sign problem “the nightmare of modern physics.” Computationally it appears to be NP-hard.


  6. Nick M: By your argument, any physical phenomenon must include all the physics from the bottom up. This implies that fluid dynamics simulations used to design aircraft couldn’t work or the Navier-Stokes equation for that matter couldn’t be useful. I for one am not interested in the physics of the brain per but the information processing ability of it. This almost certainly does not involve quantum information since any amount of quantum coherence will decohere almost instantly. Just like you don’t need to model transistors to understand computing, you don’t need to model fermion interactions to understand neural computing.


Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )


Connecting to %s