Young explains how light waves can cancel
Light added to light can make a dark band. Thomas Young explained how two waves reinforce each other where their peaks line up and cancel where a peak meets a trough.
Quantum algorithms also rely on reinforcement and cancellation. What combines in a quantum circuit is an amplitude, a quantity used to calculate the chance of a particular result.
Still to solveYoung was describing ordinary light waves in his 1801 lecture. The paper appeared in 1802, about a century before the development of quantum mechanics.
In plain EnglishInterference The reinforcement or cancellation that happens when wave contributions combine.
Aligned waves reinforce. Opposite waves cancel. Quantum algorithms use a related pattern of reinforcement and cancellation to shape the chances of results.
Classical-wave analogy, not experimental data.Inside the idea Where does a dark fringe come from?
At one point on a screen, equal light waves arriving half a cycle apart have opposite electric fields. Their fields add to zero there. Elsewhere they can add together. Young’s example concerns light waves; a quantum circuit instead adds amplitudes for a particular measurement outcome.
OpenStax on wave interference ↗Sources & historical detail 1 source
The historical record: Young presents a wave account of light. Young reads his Bakerian lecture on light and colours to the Royal Society.
How to read this date: 12 November 1801 records the presentation date.
Scope & limitations: This is the lecture date, not the invention of quantum mechanics. The Philosophical Transactions paper followed in 1802.
- On the theory of light and colours: Bakerian Lecture (opens in a new tab)Royal Society Archives · archive
The next questionA wave can reinforce or cancel another wave. Much later, physicists would discover that nature needed more than this classical picture.