Tuesday, April 6, 2010

Why Your Brain is not a Quantum Computer

Recently Ervin Laszlo has written a number of articles declaring that human brains are quantum computers. As a computer scientist who is also interested in psychology I found the topic to be very interesting. However, as I read the articles I became frustrated with the lack of detail and the way they seemed to put forth provocative ideas with no sound evidence or reasoning behind them. They were still useful to me, sometimes we can learn as much from a poorly thought out idea as a good one. Prior to reading the article I had no idea what a quantum computer was. Unfortunately, I didn’t gain much insight on that from the articles but I did do some research to better understand them. I would like to describe what I found here and describe why I strongly believe your brain is not a quantum computer.

The first important point is that everything I or anyone is about to say about quantum computers is all about the idea of a quantum computer. To date there are no quantum computers and there are many complex unsolved problems (indeed they may be unsolvable problems) that need to be addressed before such computers exist.

The most interesting thing I found on researching quantum computers is that in many ways they aren’t all that different from traditional computers. A traditional computer consists of memory and a Central Processing Unit (CPU) that manipulates the memory. The CPU does things like basic math and moving information from one place to another. The memory is represented as electrical impulses (bits) that can be either on or off, 0 or 1. The essential difference between a traditional computer and a quantum computer is that a quantum computer would take advantage of the very mysterious phenomenon of quantum entanglement. The significance of entanglement is that it offers a model where particles can be described as being in multiple states at the same time. An entangled bit (known as a qubit) can be in the state of on and off at the same time. Qubits allow highly parallel search of a problem space. Rather than investigating each solution one at a time, using a qubit you can test many different alternatives all at the same time.

While qubits and quantum computers offer exciting possibilities to solve certain very complex problems from a computer science standpoint they aren’t that revolutionary. In fact as I looked on the Internet I found some incorrect statements about how Qubits differ from traditional bits. JR Minkel at Scientific American stated in a video “even today’s fastest computers ultimately do things one at a time”. This is absolutely and patently false. Supercomputers in fact work precisely because they do many computations at the same time. In fact its even wrong when considering personal computers. If you have a desktop computer it most likely has at least two CPU’s. That’s one of the things that enables you to have multiple applications up and running at the same time. For supercomputers this is taken to the extreme, they have hundreds or more CPU’s that work in parallel. The difference is that those computers still work with traditional bits that can be either 0 OR 1. A quantum computer working with qubits that can represent both values at the same time would be able to be much more massively parallel than even our fastest supercomputers.

The thing about parallel computing is that it sounds wonderful in principle but its a bit more complicated in practice. Adding 100 CPUs does not at all guarantee that you will cut the time required to solve a problem by 100. There is effort to write a special program that can exploit the benefits of parallelism, essentially divide a big problem into a bunch of smaller problems, solve the smaller problems than combine those solutions into one big solution. Not all problems lend themselves to such a divide and conquer approach. In fact no computer scientist that I came across is talking about quantum computers as a significant step toward artificial intelligence or better understanding the human mind. The emphasis is on specific mathematical problems such as factoring integers which could be useful in code breaking.

So with that background on quantum computers we can address the question: “is there any evidence at all that our brain functions as a quantum computer?” The answer to that is an emphatic no. We do have a model for how a computer can mimic our brain. That model is neural networks, mathematical representations that simulate the biochemical neurons in our brains. That model has proven extremely powerful, to the point where we can use computer neural networks to replicate the pattern matching capabilities, the ability to recognize edges, shapes, even faces that our brains do. To date there is absolutely zero evidence that the neurons in our brain have any ability to communicate at the quantum level. In fact there is no evidence that any biological system has the capability to interact at the quantum level. This is not surprising, Entanglement is a phenomenon that is extremely difficult to measure in the laboratory. It requires setting up complex highly sensitive and sophisticated electronic devises such as beam splitters and the entangled states are very susceptible to being disentangled by such measurements. That is the whole point of quantum entanglement, that such states represent multiple possible probability functions before being measured but the probability waves collapse into one real value after they are measured. The idea that a biological capability to detect such entanglements could somehow evolve seems highly improbable.

I would like to close with a more general discussion of why I think its important to rigorously examine such claims as “your brain is a quantum computer”. As I and others with a scientific background commented on Dr. Laszlo’s articles we were often maligned as people with closed minds and no imagination. I think its important to distinguish between having an open mind and an uncritical mind. I believe that I’m very open to all sorts of possibilities. I do think that the potential philosophical implications of quantum physics and string theory for example may be mind blowing and are worth serious investigation. However, there is a difference between serious investigation and arbitrary speculation. Many authors on the Huffington Post these days love to attach the word quantum to whatever their pet theory is. Quantum consciousness, quantum alternative realities, quantum brains,... These authors take advantage of the fact that quantum theory is difficult to understand to give any pet theory the appearance of scientific validity. This is pseudo-science at its worst. It does nothing to educate people on the very interesting topics of quantum theory nor on their potentially very interesting philosophical implications.


  1. I think you missed two important points: Ervin Laszlo is a philosopher and a theorist. You might want to look these two words up in a dictionary. He does not claim to be a scientist.

  2. "In fact there is no evidence that any biological system has the capability to interact at the quantum level."

    Although I can find no absolutely credible link through a google search and the debate could be settled more easily if either of us spoke Russian and had a knack for tracking down relatively ancient research (1920s-30s)...

    Apparently the Russian scientist Alexander Chizhevsky, who proposed and thoroughly researched links between solar activity and biological response, found that bacteria in water responded to solar flares instantaneously, as opposed to the 8.3 minutes it should take for the photon bombardment to elicit a response. This would seem to indicate some sort of nonlocal connection.

    At any rate, as difficult as it is to prove scientifically with our limited understanding of the universe, I find it much more difficult philosophically to accept that the action of something is unrelated to the actions of somethings that constitute its parts. Namely that macroscopic objects would not be, at some very subtle level, participating in quantum mechanical phenomena that we can only experimentally observe at a subatomic level.

    I understand the skepticism, especially when quantum mechanics can be latched to any pseudo-religious theory as to the workings of the universe. However, I tend to think that this may be a sign that what science is discovering experimentally is what mystical experience has discovered intuitively for thousands of years. The language used to describe it back then was imprecise and fanciful, but what could you have possibly said to explain the interconnectedness of the universe at a more fundamental level than our everyday perception?

    Unfortunately, the cultural chrysalis that was used to distort these more fundamental truths attributed a large degree of dogma to what they understood as God. Reading any religious mystic (say... Theresa of Avila and St. John of the Cross for Christianity, Ibn Al-Arabi and Ahmad ibn-Ajiba for Sufism/Islam) text, however, you find their insight into reality is doused in critical thought and extending love into any crevice it can fit into.

  3. A while ago, PsychicLady commented on my post about Ervin Laszlo’s articles claiming that our brain is a quantum computer. I apologize for the late reply.

    PsychicLady said...
    I think you missed two important points: Ervin Laszlo is a philosopher and a theorist. You might want to look these two words up in a dictionary. He does not claim to be a scientist.

    I’m sorry PsychicLady but I don’t see how that is relevant. Oh to begin with I should say that I didn’t need to look those words up. I know what a philosopher is. I’ve met several of them and read many more. At one point I even thought that I might want a career as a philosopher but I decided I couldn’t take all the pressure.
    I don’t see what that really has to do with what Dr. Laszlo says though much less how it relates to my criticism. When someone makes claims about quantum physics or quantum computers it doesn’t matter what they call themselves. The bottom line is that what they say is either true or false. Of course we can’t always tell for sure whether something is true or false. Sometimes (and I must confess that I think this is often the case for people like Dr. Laszlo) what they say is so muddled that we can’t even be sure what they are actually saying. I tried to keep my critique of Dr. Laszlo’s article confined to the few statements that I could make sense of and hence could validate against what I know about computer science.