Introduction to the Quantum Realm

Abstract

Q uantum mechanics describes nature at very small scales – at the atomic and subatomic levels, but quantum effects have been observed in large molecules as well. The idea that our everyday world is made from small particles, which we call atoms, dates to the ancient Greeks. Today we think of atoms as small spherical objects that are ten-billionths of a meter in diameter. This measurement (10 × 10−10 m) is so common that it has a special name – the Angstrom – and a special symbol, Å. Objects that are angstrom-sized behave very differently than objects the size of everyday objects like tennis balls and automobiles. Because humans grow up looking at and manipulating everyday objects, most people do not have any intuition about how angstrom-sized objects behave until they have been educated in modern physics. While Democritus of Abdera came up with the idea of atoms more than 2500 years ago and our understanding of chemistry has evolved over many centuries, our understanding of quantum mechanics was developed mostly over the past 125 years. Information theory concerns how information is stored, communicated and quantified. Although humans have been storing and communicating information for thousands of years, our mathematical understanding of what information actually is dates to a paper by Claude Shannon from 1948, “A Mathematical Theory of Communication.”1 Among other things, the paper introduced the term “bit,”