The story of Quantum Mechanics

The story of Quantum Mechanics

Quantum mechanics (QM) stands as one of the most successful theories of the 20th and 21st centuries, profoundly influencing our perspective on the world and revolutionizing our understanding of reality.
Moreover, it is responsible for driving our rapid technological advancement.
There have been many arguments against QM in the past, even by Einstein, but all their claims were falsified. To date, no new findings have emerged that contradict the theory of quantum mechanics or falsify any of its predictions (Dechamps et al., 2021).

The foundation of quantum theory was laid at the beginning of the 20th century through the insights of Max Planck, for which he was awarded the Nobel Prize in Physics in 1918. He discovered that radiation is emitted not continuously but in the form of small energy packets—quantum of actions. This implies that energy levels change not linearly, but always in discrete amounts (each by the Planck constant h), commonly known as quantum leaps.

To each change in nature corresponds an integer number of quanta of action. Action variables may only change by integer values of h, requiring all other physical quantities to change by discrete steps, “quantum jumps”.
(Capellmann, 2021, p. 1)

This revelation was groundbreaking for science, impacting all branches of natural sciences. In 1932, Werner Heisenberg was awarded the Nobel Prize in Physics for “the creation of quantum mechanics.” He is credited, along with Erwin Schrödinger, with the development of the Copenhagen interpretation, although it incorporates many other influences, such as those of Niels Bohr.(Faye, 2019; Heisenberg & Bohr, 1963).

Quantum mechanics fundamentally differs from classical mechanics; it follows its own set of laws. For instance, due to the Heisenberg uncertainty principle, it is not possible to perform an exact measurement in a quantum system, upon which a prediction about the system’s future behavior could be based—because two complementary properties of a particle (e.g., position and momentum) cannot be simultaneously precisely determined. Measurement of one property affects the measurement object and alters it, resulting in an uncertainty regarding the complementary property. This is termed “invasive measurement.” For example, attempting to determine the position of an electron by bombarding it with a photon alters the electron’s velocity (momentum) due to the collision of the two particles. Thus, only one property can be determined at a time (Busch et al., 2007).

Furthermore, entangled states exist in the realm of quantum mechanics, allowing for superpositions—i.e., a duality of two opposing entities that contradict each other. Quantum superposition is one such state that seems to defy the known laws of physics: Quantum entities exhibit both particle and wave properties.
The famous thought experiment by Schrödinger (1935) was devised to visually illustrate the empirical findings of the double-slit experiment: a cat that is simultaneously dead and alive. (Heisenberg & Bohr, 1963; Schrödinger, 1935; Susskind & Friedman, 2020)

Particle or wave?

Whether a quantum appears as a particle or a wave is not determined before the measurement.

Before the moment of measurement, the state of superposition exists - the quantum system is both wave and particle simultaneously, yet neither. This means that only the measurement instrument (MI) determines the state of the measurement object (MO), and before that, the measurement object does not have a defined state. This realization implies that the two can no longer be treated as separate systems after the measurement instrument influences the measurement object - they are not independent of each other. In quantum mechanics, the measurement instrument and the measurement object are considered entangled (Heisenberg, 1989; Schrödinger, 1935).

”Quantum measurements are moments of creation.” (Fuchs, 2010, p. 14). Thus, quantum mechanics provides an alternative scientific approach to describe our (physical) reality (Rosenblum & Kuttner, 2011).

Sources

• Born, M., & Jordan, P. (1930). Elementare Quantenmechanik. Springer Verlag.

• Busch, P., Heinonen, T., & Lahti, P. (2007). Heisenberg’s uncertainty principle. Physics Reports, 452(6), 155–176.

• Capellmann, H. (2021). Space-Time in Quantum Theory. Foundations of Physics, 51(2), 44. https://doi.org/10.1007/s10701-021-00441-0

• Dechamps, M. C., Maier, M. A., Pflitsch, M., & Duggan, M. (2021). Observer Dependent Biases of Quantum Randomness: Effect Stability and Replicability. Journal of Anomalous Experience and Cognition, 1(1–2). https://doi.org/10.31156/jaex.23205

• Faye, J. (2019). Copenhagen Interpretation of Quantum Mechanics. In E. N. Zalta (Hrsg.), The Stanford Encyclopedia of Philosophy (Winter 2019). Metaphysics Research Lab, Stanford University. https://plato.stanford.edu/archives/win2019/entries/qm-copenhagen/

• Filk, T. (2019). Optische Experimente zur Quantentheorie. In T. Filk (Hrsg.), Quantenmechanik (nicht nur) für Lehramtsstudierende (S. 295–308). Springer Berlin Heidelberg. https://doi.org/10.1007/978-3-662-59736-1_15

• Fließbach, T. (2018). Quantenmechanik: Lehrbuch zur Theoretischen Physik III. Springer-Verlag.

• Heisenberg, W. (1989). Physics & philosophy. Penguin.

• Planck, M. (1914). The theory of heat radiation. Blakiston.

• Rosenblum, B., & Kuttner, F. (2011). Quantum enigma: Physics encounters consciousness (2nd ed). Oxford University Press.

• Schrödinger, E. (1935). Die gegenwärtige Situation in der Quantenmechanik. Die Naturwissenschaften, 23(48), 807–812. https://doi.org/10.1007/BF01491891

• Susskind, L., & Friedman, A. (2020). Quantenmechanik: Das theoretische Minimum: Alles, was Sie brauchen, um Physik zu treiben. Springer.

• Wigner, E. P. (1963). The problem of measurement. American Journal of Physics, 31(1), 6–15.