Schrödinger's Cat, Superposition, and its Applications
- Seoyeon Lee
- Jun 6
- 3 min read
Image credit: iStock
Erwin Schrödinger and his Thought Experiment
Erwin Schrödinger was born in Austria in 1887 between Rudolf Schrödinger, a botanist, and Georgine Schrödinger, whose father was a chemistry professor. He was awarded the Nobel Prize due to his development of fundamental results in quantum theory, specifically for postulating the Schrödinger equation and creating the term, quantum entanglement. Furthermore, he also contributed to other aspects of science such as physics: statistical mechanics and thermodynamics, color theory, general relativity, cosmology, physics of dielectric, electrodynamics, and more.
However, in addition to all these phenomenal contributions to science, Erwin Schrödinger is most famous for his thought experiment in the field of quantum physics, the Schrödinger’s cat. The idea behind this thought experiment is that there is a cat inside a box along with a bomb that has a 50% chance of killing the cat. If one were to be asked, what would be the state of the cat inside the box, they would usually respond, either alive or dead. However, Schrödinger’s response was different in that before the box is opened, the cat is in a superposition state in which it is 50% dead and 50% alive.
Superposition State
A superposition state refers to the ability of a quantum system to be in multiple states at the same time until it is measured. In the case of Schrödinger’s cat, the cat is in a dual state, alive or dead, before it is measured, and it is only measured after Schrödinger opens the box to check the actual state of the cat. Superposition is the consequence of the dual particle and wave nature of everything.
In order for an object to have a wavelength, it must extend over some region of space, meaning that it occupies many positions at the same time. The wavelength of an object limited to a small region of space cannot be perfectly defined. Therefore, it exists in many different wavelengths at the same time. Wavelength is inversely proportional to momentum as shown by the Broglie equation p(momentum) = h (Planck’s constant) / λ (wavelength), meaning that objects with a large mass, which has a larger momentum, (p = mass * velocity), have shorter wavelengths and this wavelength is so small that it cannot be detected. As a result, since Schrödinger’s cat has such a large mass, wave behavior cannot be seen in the cat, and usually, in many everyday objects.
Conversely, in a tiny particle such as an electron, a dramatic dual nature can be seen. If electrons are shot one at a time at a set of narrow slits cut in a barrier, each electron on the far side is detected at a single place at a specific instant, like a particle.
However, if this experiment is repeated many times, a pattern that is characteristic of wave behavior can be observed with some regions having many electrons separated by regions where there are none at all.
However, when one of the slits is blocked, the electrons only accumulate at one region of the slit. This shows that the pattern observed is a result of each electron going through both slits at the same time and that a single electron is not choosing to go right or left, but left and right simultaneously.
Application of Superpositions
Understanding this concept of superposition on the basis of electrons allows the understanding of modern technologies such as computers. An electron near the nucleus of an atom exists in a spread-out, wave-like orbit. If two atoms are brought closer together, then electrons are shared between them, forming a covalent bond. In this case, the electron is not just on one atom but is orbiting two atoms simultaneously, and it can be said that the electron is attached to both atoms.
If more atoms are added on, the electrons are spread out more and are shared between vast numbers of atoms at the same time over a large region of space.
This gigantic superposition of states determines the ways electrons move through the material, whether it’s a superconductor, an insulator, or a semiconductor. For example, understanding how electrons are shared among atoms allows the precise control of the properties of semiconductor materials such as silicon. Combining different semiconductors in the right way allows the creation of transistors on a tiny scale, millions on a single computer chip. Those chips and their spread-out electrons power the computer that people use to do all sorts of activities.
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