The Quantum Evolution: Quantum Mechanics Developed Just Like Quantum Mechanics Works

How 7 Revolutionary Studies Changed Physics Forever

Quantum confinement effect: controlled dance of electrons at microscopic level

The 10 Best Quantum Mechanics Books

We are celebrating 100 years since the beginning of quantum mechanics. The development of quantum mechanics was as unpredictable, uncertain, and weird as quantum mechanics itself. Instead of a smooth, logical progression, it developed in discrete, unexpected quantum jumps. So, let’s take a journey through seven groundbreaking research papers that defined quantum mechanics.

In 1900, Max Planck was trying to solve a problem: Why do hot objects glow with specific colors? None of the theories from classical mechanics could explain it. Desperate for a solution, Planck made a radical assumption – quantization of energy. He published a research paper on the law of energy distribution in the spectrum and stated that energy doesn’t come in a continuum but in tiny packets called ‘quanta,’ laying the foundation of quantum mechanics.

1. Planck, M. (1901). “On the Law of Distribution of Energy in the Normal Spectrum.” Annalen der Physik, 4(3), 553–563.

The next quantum jump in the development of quantum mechanics came in 1905 when Albert Einstein tried to explain the photoelectric effect (how light ejects electrons from a metal surface). He proposed that light is made of particles called photons. Considering light as a collection of particles rather than waves could explain the photoelectric effect. The first wave-particle duality concept surfaced here.

2. Einstein, A. (1905). “Über einen die Erzeugung und Verwandlung des Lichtes betreffenden heuristischen Gesichtspunkt.” Annalen der Physik, 17, 132–148.

In 1913, Niels Bohr solved a mystery: Why don’t electrons crash into the nucleus? He introduced a model on the Constitution of Atoms and Molecules. His model states that electrons orbit in fixed energy levels around the nucleus. These energy levels are quantized, and electrons jump from one energy level to another while absorbing or emitting photons. This model explains atomic spectra. Though the model was not fully correct and was later modified, it was revolutionary in concept.

3. Bohr, N. (1913). “On the Constitution of Atoms and Molecules, Part I.” Philosophical Magazine, 26(151), 1–25.

In 1924, de Broglie proposed that electrons and all matter behave like both particles and waves. He introduced the concept of matter waves and a formula to determine the wavelength of any matter, including us. The wavelength associated with us is very small and insignificant at macroscopic level.

4. de Broglie, L. (1924). “Recherches sur la théorie des quanta.” Annales de Physique, 10(3), 22–128.

The first complete quantum mechanics theory was developed by Heisenberg, Born, and Jordan in 1925. They introduced it in the form of matrix mechanics, where quantum states and observable quantities were described using matrices. They stated that quantum states are matrices rather than classical numbers. Though matrix mechanics made no physical sense at the time, it explained all experimental observations remarkably well.

5. Heisenberg, W., Born, M., & Jordan, P. (1925). “Zur Quantenmechanik II.” Zeitschrift für Physik, 35(8-9), 557–615.

Inspired by de Broglie’s matter wave concept, in 1926, Erwin Schrödinger proposed an alternative to matrix mechanics, called wave mechanics. He considered electrons as waves and described them using a wave function, though he could not explain the physical meaning of the wave function. He formulated an equation of motion, known as Schrödinger’s equation of motion, which is analogous to Newton’s equation of motion.

6. Schrödinger, E. (1926). “Quantisierung als Eigenwertproblem.” Annalen der Physik, 79(4), 361–376.

In 1926, Max Born provided an interpretation of the wave function. He stated that the wave function itself does not have a direct physical meaning, but its square modulus represents a probability density, which gives the likelihood of finding a particle at a given position. Born demonstrated that quantum mechanics is inherently probabilistic, which was shocking at the time. Even Einstein famously objected to this interpretation, stating, “God does not play dice.” However, experiments ultimately proved Born right.

7. Born, M. (1926). “Zur Quantenmechanik der Stoßvorgänge.” Zeitschrift für Physik, 37(12), 863–867.

Today, quantum mechanics underpins everything. It’s not just rewriting physics; it’s rewriting reality itself.

Interested in the complete history of Quantum Mechanics?

“Quantum: Einstein, Bohr, and the Great Debate” – Manjit Kumar

“The Quantum Story” – Jim Baggott