Quantum mechanics: the evolution of its applications
Raoul Kemp
Introduction
Quantum mechanics is a unique branch of physics that seemingly defies the established laws of physics to explain certain phenomena. An example of these ideas is entanglement, which means two particles which are ‘ entangled ’ can communicate instantly no matter the distance between them; another is the idea that two particles can exist in the same space at the same time. Due to these ideas being very abstract and complex, it leads some to think that quantum mechanics is just a set of theories that have little use in the real world, but this could not be more untrue. The development of quantum mechanics has opened up many applications in many industries to solve problems which classical physics cannot, and without its developments the modern world would look unrecognizable. Although it has already been crucial in many revolutionary inventions, it is still in its infant stage and its potential is vast: we have only seen the beginnings of what it can do for science and technology.
History
The term quantum mechani cs was first used in Born’s 1924 paper ‘ Zur Quantenmechanik ’ but pinpointing the exact start of it is quite difficult, as ideas clearly belong to quantum mechanics had been circulating for a while. The beginnings of quantum theory were in 1900 with Max Pla nck’s work on black body radiation, where he proposed the idea that energy is quantized. This was further backed up in 1905 with Einstein’s work on the photoelectric effect , which also demonstrated that light was made of photons carrying discrete packets of energy called quanta. This was furthered when in 1913 Niels Bohr proposed a new model of the atom where electrons move between discrete energy levels by absorbing or emitting quanta of energy. By this point, there was no idea of quantum mechanics as a whole but this changed drastically in the 1920s, particularly with the work of Heisenberg and Schrödinger. Louis de Broglie developed the idea of wave-particle duality, which combined the accepted view that light was a wave and electrons were particles with new ideas of light being particles and electrons being waves into one by saying they can exhibit properties of both. This was further worked on by Schrödinger when he developed the Schrödinger equation which became a key tool to describe the quantum behaviour of particles, a basis of quantum mechanics. Heisenberg was also crucial in this time. His uncertainty principle states that there is a fundamental limit to how precisely one can simultaneously measure certain pairs of properties, such as a particle's position and momentum; he thereby opened up the probabilistic nature of quantum mechanics. These groundbreaking works are what truly created ‘ Quantum Mechanics ’ and invited physicists to work on theories of their own, through the 1930s and 1940s. It is at this point that quantum mechanics moved from pure theory to becoming applicable to the real world, providing a basis for many important inventions.
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