Thursday, October 27, 2011

Quantum Discomfort

Quantum physics has always been this mystical thing to me.  Throughout my years of academic studies in engineering, the word quantum may have been uttered by a professor, but it was never explored in any kind of depth.  Engineers are practical, and while quantum physics is fascinating, it is of little practical importance to most engineers at present.

A physics professor might say, "Classical physics is not theoretically sound, as it is only an approximation, and may only be accurately applied to things that do not move too fast and are not too small."  An engineering professor might then respond, "Most things are reasonably large and move reasonable slowly... In any case, any error less than 5% is good enough for me."

For nearly all engineers, the entire field of study may be ignored, and is.  For theoretical physicists on the other hand, it appears that there is not much outside quantum physics to ponder anymore.

In reality, for an object of reasonable size, the amount of error introduced by simply ignoring quantum aspects is negligible.  Still, this field of study is so fundamentally different from all of the science that came before it, that it is always categorized separately; that is, there is quantum physics, which centers around wave functions and probabilities, and then there is classical physics, which is everything else.

Quantum physics as a field of study was established in the mid-1920s with physicists such as Max Planck, Albert Einstein, Neils Bohr, and Werner Heisenberg.  The fundamental principle of quantum physics was discovered by Heisenberg, who showed that one could not be 100% certain of both the momentum and position of a given particle.  The law is known as the 'uncertainty principle', not to be confused with the 'what the heck is going on principle' commonly exemplified by certain physics students.  

I remember the moment when I realized that I liked physics.  I was sitting in my grade 11 physics class learning about projectile motion.  When the teacher explained that you could determine where and when a ball thrown from a specific location with a specific velocity would land, I was hooked.  Predicting the future with certainty - what an empowering notion.

Had I learned that a given circumstance has a wide variety of possible outcomes, as quantum physics shows, the allure of physics would have been greatly diminished for me.  Another downside about quantum physics, is that its concepts are hard to wrap one's head around.  My distaste for quantum physics probably stems from the fact that it is less connected to our every day life experience than are other aspects of science.  Also, I was never formally introduced to it in an academic setting, and so perhaps I associate my quantum discomfort with a  lack of familiarity - I may warm up to this branch of science in time, like a father might a son-in-law.

If you are like me, and find quantum physics to be somewhat unsettling, do not feel bad, as we are both in good company.  Einstein famously rejected quantum physics, stating that "God does not play dice".  It was a powerful and memorable line, but was refuted by an even better response from the quantum community: "Stop telling God what to do!"

In the end, it is somewhat ironic that Einstein did not support quantum physics, as he is indeed one of its founding fathers.  Einstein received the Nobel Prize for physics for his development of the photoelectric effect theory (1905), which showed that light behaves as a particle - this notion got the quantum ball rolling.

The term quantum was coined by Max Planck from the root word "quanta".  It describes a finite, minimum currency for energy.  It is like the dollar currency system, which does not allow physical exchanges of money by fractions of a penny.  You can have no money, or you can have one penny, but you cannot possess any amount in between.  Similarly, a particle of light (photon) can have no energy, or it can have E = hf (where h is Planck's constant and f is the frequency of the light), but it cannot have hf/2 of energy, for example. [note: this article was written before the pennies were out of circulation... The new quantum for cash is the nickle]

It is a truly fascinating disconnect between most physicists and engineers: the first group believes that quantum physics is the only truth, and the second group shrugs their collective shoulders.  Most engineers work on a macroscopic scale.  Unless you are an engineer specializing in semi-conductors (and there are more than a few), the effects of quantum physics on your work are likely to be insignificant for now.

That being said, the scientist within me has his curiosity piqued by one particular area of quantum research: quantum computers.  In this semester alone, a few physics students have independently brought the subject to my attention without being prompted to do so.

Quantum computing was introduced by Richard Feynman in the early 1980s.  The concept is a computer that takes advantage of certain quantum mechanics phenomena.  The end goal is not so surprising: a CPU that can operate much faster than any of the traditional transistor-based variety can.  I am always simultaneously fascinated but also concerned at the prospect of "smart" computers, as the very notion is indicative of a technological singularity.  We humans will know our time is short once robots start building smarter robots than themselves.

It turns out that I am not only uncomfortable with quantum phenomena, but also fearful of the technologies that they may lead to.  Maybe I will just go on avoiding quantum physics, and attribute my disregard to the uncertainty principle.


- J said...

Great article! I love your point of view.

Moussa FU said...

The fundamental concepts of physics are put in contrast with the 1 of quantum physics In an unique way here. Furthermore I didn't know we could a tribute the virtues of artificial intelligence to quantum phenomenas. Very interesting point of you and I would indeed comply with the feeling of keeping my distance withquantum physics if I were to undertake whatever task required.