Some tech revolutions enter with drama and explosion, others wiggle unnoticed in our daily experience. One of the quietest revolutions of our century has been the entry of quantum mechanics into our everyday technology. Quantum effects used to be confined to the laboratories of physics and microscopic experiments. But modern technology increasingly relies on quantum mechanics for its fundamental processes, and quantum effects will only increase in importance in the coming decades.
As such, it is time to explain quantum mechanics – or, at least, its basics.
My goal in this seven-part series (!) Is to present the strange beautiful effects of quantum mechanics and explain how they got into our everyday world. Each release will feature a guided hike into the quantum jungle of quantum mechanics where we’ll enjoy a new – and often surprising – effect. Once back at the visitor center, we’ll talk about how this effect is used in technology and where to look for it.
Embarking on a series of quantum mechanics articles could be intimidating. Few things give rise to more fear than a simple Introduction to Physics. But as for the boldness and the courage, I’ll make some promises before we start:
- No math. While the language of quantum mechanics is written using fairly advanced mathematics, I don’t think one has to read Japanese before you can appreciate Japanese art. Our journey will focus on the beauty of the quantum world.
- No philosophy. There has been a fascination with the “meaning” of quantum mechanics, but we’ll leave that discussion until we’re over at the pub. Here we will focus on what we see.
- Everything we encounter will be verified empirically. While some of the results may be surprising, there will be no guesswork for us.
If you choose to follow me through this series of articles, we will see quantum phenomena on galactic scales, watch particles mix and mix, and see how these effects give rise to our current technology and the developments that are about to emerge from the lab.
So put on your brainstorming shoe, grab your binoculars, and follow me as we set out to explore the quantum world.
What is quantum mechanics?
My mom once asked me, “What is quantum mechanics?” This question has kept me confused for a while now. The best answer by far is that quantum mechanics is the study of how small particles move and interact. But this is an incomplete answer, because quantum effects could be important on galactic scales as well. It is doubly unsatisfactory because many effects such as superconductivity result from the mixing and mixing of multiple molecules.
In many ways, the role of quantum mechanics can be understood by analogies with Newtonian gravity and Einstein’s general relativity. They both describe gravity, but general relativity is the most correct – it describes how the universe works in every situation we have been able to test. But 99.99% of the time, Newtonian gravity and general relativity give the same answer, and Newtonian gravity is a lot Easier to use. So unless we approach a black hole, or make accurate measurements of time with an optical clock, Newtonian gravity is good enough.
Likewise, classical and quantum mechanics describe both motions and interactions. Quantum mechanics is more correct, but classical mechanics is good enough for the most part.
What I find wonderful is that “good enough” is increasingly not. Much of the technology developed in this century began to draw on quantum mechanics – classical mechanics is no longer accurate enough to understand how these inventions work.
Let’s start the day’s rally with a deceptively simple question, “How do particles move?”
Quantum Mechanics Kitchen
Some of the experiments we’ll see will require specialized equipment, but let’s start with an experiment you can do at home. Like a cooking show, I’ll explain how to do it, but encourage you to go ahead and experiment for yourself. (Share your photos in the discussion below. Additional points for setting up the experience in your booth / workplace / other creative space.)
To study how particles move, we need a good particle shooter to make lots of particles for us to play with. It turns out that the laser pointer, in addition to entertaining the cat, is a Great Particle source. They make copious amounts of photons, all of them moving in roughly the same direction and with roughly the same energy (as indicated by their color).
If we look at the light from a laser pointer, it exits the end of the laser pointer and moves in a straight line until it hits an obstacle and is scattered (or collides with a mirror and returns) at this point, it is tempting to guess that we know how the particles move: they come out of the end of the laser like little balls and move In a straight line until you collide with something. But as good observers, let’s be sure.
Let’s challenge particles with an obstacle course by cutting thin slits in aluminum foil with razor blades. In aluminum foil I made a few different pieces. The first is a single slit a few millimeters long. The second time, I stacked two razor blades together and used them to cut two parallel slits a few tenths of a millimeter apart.
In a dark room, I set my laser pointer to shoot across the room and crash into an empty wall. As expected, I see a spot (provided the cat is not around). Next, I put the single slit in the aluminum foil into the laser path and look at the pattern on the wall. When we send light through the single slit, we see that the ray is greatly expanded in direction vertical To the slit – not along the slit.
interesting. But let’s press.
Now let’s place convergent slits in the laser beam. The light is scattered again, but now there is a striped pattern.
Congratulations! It just discovered a quantum mechanical effect! (Animated emoji whoo hoo) This is the classic double slit experience. The bar pattern is called interference, and is a hallmark of quantum mechanics. We’ll see a lot of lines like this one.
Now you may have seen interference like this before, because water and sound waves show this kind of plotting.
In the image above, each ball creates waves that move in a circle. But a wave has a peak and a bottom. In some places, the peak of the wave from one of the balls always coincides with the trough of the other (and vice versa). In these areas, waves always fade and the water is calm. In other locations, wave crests from both balls always come together and combine to form a very long wave. In these locations, basins are also added to be very deep.
So does the fact that we see lines when the laser pointer passes through two slits mean that the particles are waves? To answer this question, we need to look more closely.