By: Kevin Wang
Quantum physics is a science that focuses on the details of really small things such as atoms, electrons, and light. In classical physics, particles act as particles, and waves act as waves, but in quantum physics, particles start to exhibit wave-like properties, and waves start to exhibit particle-like properties. Quantum physics may seem almost magical, but according to Caltech, “quantum science closes gaps in our knowledge of physics to give us a more complete picture of our everyday lives.”
According to Quantum Physics for Dummies by Steven Holzner, one of the main ideas in quantum physics is quantization, or “measuring quantities in discrete, not continuous, units.” The discovery of energy in discrete quantities dates back to the 19th century and 20th century with the black-body radiation problem. In the problem, a hole is heated and begins to emit light, and scientists would measure out the spectrum of light coming from the hole. The puzzling part of this problem was that classical physics predictions didn’t match the observed spectrum of light coming from the hole when heated. It was Max Planck, a German theoretical physicist, who finally solved the problem. According to Medium, “He proposed that energy was emitted or absorbed in discrete units.”
Encouraged by Planck’s success, Albert Einstein, a famous German mathematician and physicist, proposed that light – previously only considered to be a wave – can also have particle-like properties as a photon. In 1923, French physicist Louis de Broglie added to Einstein’s proposal and suggested that particles could also have both particle and wave-like properties. Researchers tested this hypothesis by creating a double-slit rig. In the experiment, the researchers would send a beam of electrons through the rig. Author Steven Holzner relayed that the results of the experiment showed that instead of the intensities of the electrons just adding when both the slits are open, they created an interference pattern similar to how waves would add together.
A famous concept in quantum physics is superposition, where objects can have multiple states at once. Australian-Irish physicist Erwin Schrödinger’s thought experiment, “Schrödinger’s cat,” explained this principle using a hypothetical scenario. In the scenario, a cat is placed in a box with an unstable atom, a poison, a hammer, and a Geiger counter – a device that measures radiation levels. If the Geiger counter detects radiation from the atom, the hammer will smash the poison, and the cat will die.
Quantum mechanics states that, until the box is opened and observed, the radioactive atom is both decayed and not decayed, so the cat is also both dead and alive at the same time. Once observed, the superposition collapses into one state, decayed or not decayed and dead or alive. Schrödinger created this thought experiment to challenge the idea that quantum effects only apply on atomic scales, not that things can be in two places at once.
Discoveries in quantum physics have been useful in our basic understanding of many things, such as materials, chemistry, and astronomy. These discoveries were useful in innovation, leading to the rise and improvement of quantum computers, lasers, and transistors. Quantum science may even reveal whether everything in the universe is all connected.