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A Brief Introduction to Quantum Physics

“If quantum mechanics hasn’t profoundly shocked you, you haven’t understood it yet,” Niels Bohr once said—and quantum physics might be wacky, but it’s not incomprehensible, so prepare to be shocked. In the early 20^th century, scientists realised that the subatomic world can’t be explained by classical physics because microscopic things behave very differently to large things. Quantum theory was developed by scientists such as Bohr, Planck, Einstein, Heisenberg, and Schroedinger, based on observations of matter and radiation at a subatomic level. “Quantum” comes from the idea that the energy that particles emit isn’t a constant flow—instead, it comes in indivisible discrete units called “quanta”, which sometimes take the form of elementary particles (i.e., the quanta of electromagnetic radiation are photons). Elementary particles behave like both particles and waves, and their movement is random so they can actually exist in multiple states and places at the same time. According to the Uncertainty Principle, though, it’s physically impossible to simultaneous know both the position and momentum of a particle, because observation actually influences the particle—measuring the position changes the momentum, and vice versa. Particles can also become entangled through interaction, meaning that wherever they are in the universe, their movements will affect the other. This naturally raises the possibilities of teleportation, and quantum theory’s applications don’t stop there: the theory has successfully explained phenomena like radioactivity and antimatter, and is being used to develop cryptography, instantaneous communication, and lightning-fast computers.

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