"Anyone who is not shocked by quantum theory has not understood it." said Niels Bohr.
"If you think that you understand quantum mechanics, you don't understand quantum mechanics." said Richard Feynman.
"Quantum physics makes me so happy ... it's like looking at the universe naked." said Sheldon Cooper.
Of course, the first two quotes are from real Nobel Prize winning physicists and the third is from a character in the TV sitcom "The Big Bang Theory" but each makes the point that there is something special - and difficult - about quantum mechanics.
Many science undergraduate students discover this very early in their careers. Indeed, it is even discussed in high school physics and chemistry classes.
Quantum mechanics is weird.
To illustrate, consider the macroscopic world that we all occupy. If you are watching a baseball game, and you see the pitcher pitch the ball, you can track the flight of the ball from the pitcher's hand all the way to the catcher's mitt (or the hitter's bat).
With a 95 mile-per-hour fastball, it might be hard to see the ball as anything other than a blur but with a high speed camera, you could slow the action down and track each and every moment that the ball is in flight.
More importantly, you could use the information from any given point - the velocity and position of the baseball - to determine exactly where the ball would be at any point in its flight either forward or backwards.
This is the deterministic universe that most of us live in. In the world of the very large, where objects are composed of countless atoms and molecules, we expect behaviour to be continuous and to some extent predictable. We certainly expect that we can deterministically demonstrate the ballistic flight of the baseball from pitcher to catcher.
However, if we were to try and play a game of baseball in world of atoms, with an electron as the ball, then things get very different. The flight of the electron is not deterministic but probabilistic. Where the electron is at any point is a matter of probabilities.
More to the point, if we know its exact position, its velocity becomes uncertain and the more precisely we know its position, the more uncertain becomes its velocity.
The consequences is that if we were atom size and pitching an electron, it might leave the pitcher's hand and suddenly appear in the catcher's mitt without ever traversing the space in between.
Imagine a real baseball pitcher pulling off that trick!
Of course, most students respond "maybe we couldn't track it but it must have travelled the space in between or how did the electron get from A to B?"
But in the world of quantum mechanics - in the world of atoms and molecules - things can traverse intervening space without ever being in between. That is why quantum mechanics leaves so many people baffled.
Even better is that the electron can travel through regions of space where it is not allowed to be. It can tunnel through energy barriers that are too high to climb. And this is not just a property of electrons as atoms can do this, too.
Needless to say, the world of quantum mechanics is nothing like the macroscopic world around us and, yes, it is a bit like looking at the universe naked with all of its secrets revealed.
This year's Nobel Prize in Physics was awarded to Serge Haroche and David J. Wineland for their independent research into experimental methods that enable the measurement and manipulation of quantum systems.
Dr. Wineland devised a method to trap ions - charged atoms - with static and oscillating electric fields and then, using laser pulses, lower their energy state to their lowest level or ground state. Single atoms in a vacuum at their lowest energy state behave as quantum particles.
Using this apparatus, he demonstrated the super-position of quantum states by partial excitation of an atom. By giving the atom only enough energy to get halfway to its first excited state, he was able to observe the collapse of the wave function as the atom probabilistically shifted into either its first excited state or returned to the ground state.
Dr. Haroche devised a trap for photons using superconducting mirrors which allowed his group to experiment on single photons and observe their quantum interactions with matter. In this case, they used a constructed molecule called a "Rydberg atom" to measure the photon without destroying it.
What is the practical upside of their work? They have been able to make even more precise clocks than the present atomic clocks used by our GPS systems. With these new clocks, your GPS system has a higher probability of telling you exactly where you are.
Of course, the real benefit is that their experiments broaden and deepen our understanding of quantum mechanics. Understanding fundamental physics leads to a better understanding of the universe.
