Quantum Mechanics Articles

Quantum mechanics is a mathematical framework for understanding physical phenomena that fail to be described sufficiently by classical physics: the work of Newton, Maxwell, and others. You might ask, ‘Why can’t we use classical methods at that point?’ We’re unable to sufficiently probe atoms and subatomic particles with classical instruments at that scale. The simplest instruments that we can use at that scale, like probing with an electron or photon, are either too energetic or don’t have the right properties to measure what we want to measure.

This doesn’t just mean that WE are unable to measure it, but that, and this is what makes QM weird, physics doesn’t allow us to learn any more about it. So instead of being able to watch particles zooming and blipping and popping about like we are able to watch a ball on a playground, we have to use statistical methods to determine where some particles might be and where it might be going. This is the very broad description of how QM works.


beginner guide to baryons

A Beginner Physics Guide to Baryon Particles

Introduction At the beginning of the 20th century, it was thought that all matter consisted of only three particles: the electron, the neutron, and the…
quantum entanglement

Answering Mermin’s Challenge with the Relativity Principle

Note: This Insight was previously titled, "Answering Mermin's Challenge with Wilczek's Challenge." While that version of this Insight did not involve any…
Quantum Mechanical Commutator

The Classical Limit of Quantum Mechanical Commutator

The Classical Limit of Commutator (without fancy mathematics) Quantum mechanics occupies a very unusual place among physical theories: It contains classical…
What is the double split

What is the Double Slit? A 5 Minute Introduction

Definition/Summary The double-slit is a simple configuration used to demonstrate interference effects in waves.Equations At distances that are…
rules of quantum mechanics

The 7 Basic Rules of Quantum Mechanics

For reference purposes and to help focus discussions on Physics Forums in interpretation questions on the real issues, there is a need for fixing the common…
Quantum Particles

Clarifying Common Issues with Indistinguishable Particles

Commonly there is a lot of imprecision in talking about ''indistinguishable'' (or ''identical'') particles, even in serious work. This Insight article…
quantum qubit

Exploring a Classical View of the Qubit

This Insight article is part of my paper Foundations of quantum physics III. Measurement, featuring the thermal interpretation of quantum physics. See…
quantum mechanics is incomplete

9 Reasons Quantum Mechanics is Incomplete

I argue that all interpretations of quantum mechanics (QM) are incomplete, each for its own reason. I also point out that for some interpretations (those…
against quantum interpretations

Against “interpretation”

I am against "interpretations" of Quantum Mechanics (QM) in a sense in which John Bell [1] was against measurement in QM and Travis Norsen [2] is against…
Quantum Eraser

The Quantum Mystery of Wigner’s Friend

In this Insight I will introduce the quantum mystery called ``Wigner's friend'' using Healey's version [1] of Frauchiger and Renner's (FR's) version [2]…
Super Quantum

The Unreasonable Effectiveness of the Popescu-Rohrlich Correlations

In this Insight, I will show how the Popescu-Rohrlich (superquantum) correlations provide an unreasonable advantage in a particular "quantum guessing game''…
why quantum

Why the Quantum | A Response to Wheeler’s 1986 Paper

Wheeler's opening statement in his 1986 paper, ``How Come the Quantum?'' holds as true today as it did then [1] The necessity of the quantum in the construction…
information definition

How to Better Define Information in Physics

When I ask questions about the conservation of information I frequently get the reply, “It depends on what you mean by information.”   So, I researched…

Addressing the “Classical Physics Is Wrong” Fallacy

One of the common questions or comments we get on PF is the claim that classical physics or classical mechanics (i.e. Newton's laws, etc.) is wrong because…

The Fundamental Difference in Interpretations of Quantum Mechanics

A topic that continually comes up in discussions of quantum mechanics is the existence of many different interpretations. Not only are there different…

Introduction to Perturbative Quantum Field Theory

This is the beginning of a series that gives an introduction to perturbative quantum field theory (pQFT) on Lorentzian spacetime backgrounds in its…

How I Stopped Worrying and Learned to Love Orthodox Quantum Mechanics

Many people here know that I am a "Bohmian", i.e. an adherent of a very non-orthodox interpretation of quantum mechanics (QM). Indeed, in the past, I have…

Learn Entanglement Entropy in Quantum Mechanics

Quantum Mechanics(QM) is one of the greatest intellectual achievements in human history. Not only because it describes the world at the microscopic level…

Explore The Vacuum Fluctuation Myth in Quantum Theory

This Insight Article is a sequel of the Insight Articles ”The Physics of Virtual Particles” and “Misconceptions about Virtual Particles“ which…

Why Is Quantum Mechanics So Difficult?

Strangely enough, QM's formalism isn't any more difficult than other areas of physics. The mathematics of the "standard" QM isn't any worse than, let's…

Learn the Top Misconceptions about Virtual Particles

This Insight Article is a sequel to the Insight Article ''The Physics of Virtual Particles'', which contains an exposition of definitions that are physically…

How the EPR Paradox Fits Between Entanglement and Nonlocality

If we violate a Bell inequality, we know we have quantum entanglement, and it used to be thought that these two notions were one and the same.At least,…

Tools to Enrich our Quantum Mechanics Interpretations Discourse

IntroductionMany times, we encounter ourselves tangled into some Quantum Mechanics (QM) interpretations debates. Unfortunately, the standard…

Examples of Prequantum Field Theories IV: Wess-Zumino-Witten-type Theories

  At the end of this page, we will have come full circle back to the first article in the series 20 years ago -- The M-Theory Conjecture.We…

Struggles With The Continuum: Quantum Mechanics of Charged Particles

 Last time we saw that nobody yet knows if Newtonian gravity, applied to point particles, truly succeeds in predicting the future. To be precise:…

Learn a Misconception of the Heisenberg Uncertainty Principle

One of the common misconceptions about the Heisenberg Uncertainty Principle (HUP) is that it is the fault of our measurement accuracy.A description…

Why You Can’t Quantum Tunnel Through a Wall

We periodically get questions on PF about people wanting to know if a tennis ball, a ping pong ball, a person, a cow, etc. can tunnel through a wall, or…

Retrocausality: How Fundamental is the Arrow of Time?

In this Insight, I'll discuss a recent experiment ([1]  [2] [3]) by some Australian physicists that has brought a thought experiment into the real world…

Weak Values Part 2: The Quantum Cheshire Cat Experiment

In a previous Insight, Weak Values Part 1: "Asking Photons Where They Have Been," I showed different methods for computing the relative intensities in…
2D Animation

How to Visualize the 2-D Particle in a Box

Introduction The particle in a box is a staple of entry-level Quantum Mechanics classes because it provides a meaningful contrast between classical and…