theory

quantum mechanics

The fundamental theory of physics describing nature at the smallest scales, involving wave-particle duality and quantization.
8 related articles

Description

Quantum mechanics is the fundamental theory of physics that describes nature at atomic and subatomic scales. It replaces the deterministic, continuous world of classical physics with a probabilistic, discrete one: energy comes in quantized packets, particles exhibit wave-particle duality, and measurement itself affects the system. It explains everything from the stability of atoms to the behavior of semiconductors, and it underpins modern chemistry and electronics.

History

Quantum mechanics was developed in the 1920s by a cohort including Max Planck, Albert Einstein, Niels Bohr, Werner Heisenberg, Erwin Schrödinger, and Paul Dirac, building on Planck's 1900 quantum hypothesis.

How it works

The theory is built on a few core principles. First, a quantum system is described by a wavefunction, which encodes the probabilities of finding the system in various states. Second, observable quantities like energy or momentum are quantized—they can only take certain discrete values. Third, the act of measurement 'collapses' the wavefunction to a definite outcome, a process that remains deeply mysterious. Mathematically, the Schrödinger equation governs how wavefunctions evolve in time, and the Heisenberg uncertainty principle sets fundamental limits on simultaneous measurements.

In practice

It is the basis for all modern electronics—transistors, lasers, LEDs, MRI scanners—and for emerging technologies like quantum computing and quantum cryptography.

Fun fact

The famous 'double-slit' experiment, where single electrons create interference patterns, demonstrates that particles behave as waves until observed—a result that still has no classical explanation.

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Related articles · 10

cs.SC2026-09-082 minarXiv:2609.08536
The Ecology of Physical Laws: A Map of Coexisting Mechanisms
In a rubber band stretched in the lab, three different elasticity mechanisms operate simultaneously. At small strains, Hooke's law prevails; at intermediate strains, entropic chain elasticity; at large strains, strain-induced crystallization.
Quantum Physics2026-05-191 minarXiv:2605.19706express
Quantum Droplets: Precision Unattainable
The quantum world is usually drawn with points, but real instruments only see blurry spots. Heisenberg and von Neumann long suspected: precision is unattainable.
Statistical Mech2026-05-101 minarXiv:2605.16368express
Lightning and Quantum Avalanches: One Signature
A lightning strike splits the sky in a fraction of a second, leaving a branched trail. At the same moment, in a tiny superconducting crystal cooled to near absolute zero, an avalanche of magnetic field rushes through — thin fingers of magnetization piercing the material.
Quantum Physics2026-04-302 minarXiv:2605.00205express
Quantum and the Cell: Three Roads at the Crossroads
Three craftsmen work in the same workshop. The first tries to figure out whether tiny hourglasses are built into nature's own machinery. The second attaches a laser pointer to a microscope to see details invisible to the naked eye. The third, conversely, takes living threads and carefully weaves them into fragile quantum circuits.
Quantum Physics2026-04-062 minarXiv:2604.05038express
How to Catch Chaos in the Quantum World
A spoon drops into a cup of hot coffee, and ripples spread across the surface. They show how quickly the disturbance moves away from the point of impact. In the quantum world, physicists look for similar 'ripples on water'—how information spreads along a chain of atoms.
Quantum Physics2026-01-301 minarXiv:2601.22697express
Billiards and Quanta: One Equation for All
The world of physics works like a music box: there's a speed knob. Turn it slowly, and the melody is strict — balls roll along trajectories (classical mechanics). Speed it up — the notes blend into a chord: a particle is in many places at once, all probabilities (quantum regime). The secret of switching is in the parameter κ.
Quantum Gases2026-01-081 minarXiv:2601.04662express
How a Pair of Particles Bounces Off a Wall
Two particles cling to each other like climbers on the same rope and fly toward a wall. When they hit, will they bounce off together, or will the rope snap? What does it depend on? Physicists considered the simplest case: everything happens on a single line, the particles attract only when they occupy the same point, and the wall is perfectly rigid.
Quantum Physics2025-12-201 minarXiv:2512.18400express
The Quantum Coin: Bohr & von Neumann's Solution
A quantum particle, an inhabitant of the elementary particle world, resembles a coin spinning in the air: neither heads nor tails, but a blend of possibilities. Yet when it lands on the table, the outcome becomes definite. What serves as the table in a measurement?
Quantum Physics2025-12-011 minarXiv:2512.01982express
Seven Truths That Can't Coexist in the Quantum World
We are used to thinking that events have causes, objects exist independently, and signals cannot outpace the speed of light. Quantum mechanics, which describes the Standard Model of particles, challenges all these assumptions at once — as if a recipe couldn't use all seven ingredients.
A Lattice with No Inside or Outside: Quantum Mechanics as a Description of Entanglement
A woven basket holds its shape not because it has a rigid frame, but because each strand is interlaced with its neighbors. Pull one out, and the pattern unravels, leaving a heap of twigs. Quantum mechanics, according to a new paper, works the same way: its elementary objects do not exist independently, but only in interweaving with each other.