World Quantum Day: Why is it celebrated on April 14?

In the age of AI, computing is taking over every aspect of human life in ways we hardly could have imagined a decade ago.

With the rapid progress of AI, World Quantum Day is more significant today than ever before.

The day is being celebrated to shed light on how quantum computing has evolved from theory into a paramount global priority.

On April 14, governments, universities and giant tech companies use this day to underscore the need for a new era of computing that has the potential to redefine everything.

Why April 14?

World Quantum Day was established in 2021, when scientists from over 65 countries came together to raise awareness.

The April 14 date was chosen based on the first digits of Planck’s constant (4.14).

For the unversed, Planck’s constant (symbol: *h*) is a small number that defines the smallest possible amount of energy that can be gained or lost by a wave, like light.

Before Planck, scientists assumed energy was continuous, like water flowing smoothly from a tap.

But Planck discovered that energy is actually grainy; it comes in tiny, invisible chunks called 'quanta" which is where the term 'quantum' originally comes from.

It defines quantum mechanics, the entire theory of atoms, electrons, light, and particles.

In a nutshell, Planck’s constant is nature’s rulebook saying energy isn’t continuous, it rather comes in small, indivisible steps.

And that’s why World Quantum Day is celebrated on April 14 (4.14), the first digits of its value in eV·s (4.1356677×10⁻¹⁵ eV·s).

It is the fundamental constant that rules quantum physics, defined as energy multiplied by time.

Google Doodle has also come forward to mark the occasion by launching the Doodle World Quantum Day 2026.