An Introduction to Quantum Physics
Richard Webb in the New Scientist says, “Put simply, quantum physics is the physics that explains how everything works: the best description we have of the nature of the particles that make up matter and the forces with which they interact”.
Richard’s 12 paragraphs are the simplest explanation I know and the good news is, you do not have to understand or explain any of it, but it’s important to understand that you all rely on quantum physics (QP) everyday: electrons move in your computer chip, photons of light are turned to electrical current in your solar panel, and the sun keeps burning. All of these involve quantum physics.
There is no single theory about quantum physics. There are three quantum field theories and four fundamental forces by which matter interacts. The basic mathematical framework of QP dates back to the 1920s when Niels Bohr, Werner Heisenberg, Erwin Schrödinger et al explained the position or momentum of a single particle or a small group of them. However, to begin to understand how things work in the real world, quantum mechanics (the first theory) must be combined with other elements of physics – principally, Albert Einstein’s special theory of relativity, which explains what happens when things move very fast – to create what are known as quantum field theories. And guess what Einstein: was a real critic of QP.
QP predicts very strange things about how matter works that are completely at odds with how things seem to work in the real world. Quantum particles can behave like particles, located in a single place; or they can act like waves, distributed all over space or in several places at once. How they appear seems to depend on how we choose to measure them, and before we measure they seem to have no definite properties at all – leading us to a fundamental conundrum about the nature of basic reality.
Quantum particles also seem to be able to affect each other instantaneously even when they are far away from each other. This truly bamboozling phenomenon is known as entanglement, or, as Einstein said, “spooky action at a distance”. That’s the stuff you rely on when you think about a friend overseas and 10 mins later in comes an email from that friend. You will also discover you use it in PKP™.