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In previous articles, we have learnt about various concepts related to quantum mechanics, such as wave-particle duality (where light has both properties of waves and particles) and quantum entanglement (where particles in an entangled state will always share the same quantum state regardless of distance). However, where did all of this come from? When did this first start? And how is quantum mechanics being used today? In this article, we will explore the history behind quantum mechanics and its applications to the real world.
History of Quantum Mechanics
An image of the many scientists involved in the debate that is quantum physics (as cited in Veisdal, 2021)
It can be said that the history of quantum mechanics started when Max Planck solved a problem that was proposed by Gustav Kirchoff. In 1859, Gustav Kirchoff proposed that “the energy emitted by a blackbody is dependent on the temperature and frequency of the emitted energy” (Brahambhatt, 2021). A “blackbody” refers to an object that is completely black, so the object absorbs all energy that falls onto it and reflects back no light. Even though it reflects back no light, the blackbody will still emit energy due to the temperature of the object. This gave rise to the problem: to find the equation that relates energy, temperature and frequency of the emitted energy together.
In 1900, Heinrich Ruebens worked to measure the energy of blackbody radiation, and visited physicist Max Planck to explain his results (Brahambhatt, 2021). This caused Planck to figure out an equation, but came to a realisation that the relationship he came up with implied that only combinations of colours were emitted. This confused Planck as the people at this time believed that light behaves as waves, so the values of colour emitted should be a continuous spectrum instead of individual combinations of colours. However, classical methods to calculate this proved to be unsuccessful (Squires, 2021). This led to Planck making a bold assumption: the radiation energy is emitted not continuously as previously believed, but rather in discrete, individual packets called quanta. This went against the common knowledge at the time as this suggested that light can also be a particle.
This would be the groundwork for quantum mechanics as different physicists would try to prove his hypothesis. For instance, in 1905, Einstein extended Planck’s hypothesis to explain the photoelectric effect (Squires, 2025). Bohr would go on to apply Planck’s hypothesis to Ernest Rutherford’s model of the atom and make claims of how electrons only orbit at certain distances, and how electrons can “jump” between these orbits, giving off energy at certain wavelengths of light and thus be observed as spectral lines (Brahambhatt, 2021).
From there, the field evolved as more physicists continued their research in the field. With emerging evidence of light having the characteristics of both waves and particles, Louis-Victor de Broglie suggested that “material particles can behave as waves and that their wavelength λ is related to the linear momentum p of the particle” (Squires, 2025). Werner Heisenberg also came up with what is known as the Heisenberg’s uncertainty principle to show that “the more precisely an electron’s position is known, the less precisely its speed can be known, and vice versa” (Brahambhatt, 2021).
Applications
As time progresses, quantum mechanics is being used in many different areas. Some examples include:
Quantum computers
An image of a quantum computer (Summers, 2018)
Computers that run on current known laws of physics are known as classical computers. However, their computation abilities can be extremely lacking. Especially if there are extremely complex problems to be solved, these classical computers that we know today would take a rather long time frame. This is where quantum computers can come into play. Using the concepts in quantum mechanics, the creation of “qubits” have taken shape. With the concept of superposition, these “qubits” are able to be in more than one state (such as being both ‘1’ and ‘0’ at the same time), unlike their classical counterparts that can only be in ‘1’s or ‘0’s. This allows qubits to be able to handle more complex calculations, leading to “powerful algorithms for complex problem-solving” (Hannan, 2023)
Lasers
As light can be seen as a particle, lasers “work by stimulating atoms to emit light of a particular wavelength” (GeeksforGeeks, 2024), which causes a particular colour of laser to appear. Hence, the laser beams work on theories such as the photoelectric effect mentioned in quantum mechanics to function (Brahambhatt, 2021).
If you are interested in learning more about how lasers work, read this article (Woodford, 2024) to find out more!
Conclusion
In conclusion, quantum mechanics came from the need to better understand the particulate property of light that is sometimes observed despite being established as waves. From there, the field branched out to question what was initially believed in classical physics. This led to numerous inventions and technologies such as quantum computers that make use of quantum mechanics. Without the discoveries made by the numerous scientists, the realm of quantum mechanics may have never been found.
Works cited
Brahambhatt, R. (2021). Quantum Theory: A Scientific Revolution that Changed Physics Forever. [online] interestingengineering.com. Available at: https://interestingengineering.com/science/quantum-theory-a-scientific-revolution-that-changed-physics-forever. [Accessed 4 Mar. 2025]
GeeksforGeeks. (2024). Real Life Applications of Quantum Mechanics. [online] Available at: https://www.geeksforgeeks.org/real-life-applications-of-quantum-mechanics/. [Accessed on 1 Mar. 2025]
Hannan, H. (2023). A Wonderful History of Quantum Mechanics [online] Quantum Positioned. Available at: https://quantumpositioned.com/the-history-of-quantum-mechanics/#:~:text=Originating%20in%20the%20early%2020th%20century%2C%20quantum%20mechanics,the%20stage%20for%20further%20advancements%20in%20quantum%20theory. [Accessed on 19 Feb. 2025]
Squires, G.L. (2025). quantum mechanics. [online] Encyclopedia Britannica. Available at: https://www.britannica.com/science/quantum-mechanics-physics [Accessed on 5 Mar. 2025]
Summers, N. (2018). This is what a 50-qubit quantum computer looks like. [online] Engadget. Available at: https://www.engadget.com/2018-01-09-this-is-what-a-50-qubit-quantum-computer-looks-like.html. [Accessed on 5 Mar. 2025]
Veisdal, J. (2021). The Golden Age of Quantum Physics (1927). [online] Privatdozent.co. Available at: https://www.privatdozent.co/p/the-golden-age-of-quantum-physics-ff7. [Accessed on 5 Mar. 2025]
Woodford, C. (2024). How do lasers work? | Who invented the laser? [online] Explain that Stuff. Available at: https://www.explainthatstuff.com/lasers.html. [Accessed on 5 Mar. 2025]
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