A special day.
14 April: A whole day dedicated to quantum physicsImagine there’s a World Day for something you can’t see, can’t touch and can barely imagine – and yet it’s one of the most important foundations of our modern world. That’s exactly what World Quantum Day is, celebrated every year on 14 April.
The date is no coincidence. In 1900, the physicist Max Planck introduced a number that would change science forever: Planck's constant, written as a lower-case h. Its value is approximately 4.1357 × 10⁻¹⁵ electronvolt seconds (eV·s). This tiny constant describes how energy behaves at the smallest scales and marked the beginning of quantum physics.
In honour of this number, April 14 (4/14 in the American date format, reflecting the first digits of h) was chosen as World Quantum Day—an international initiative launched in 2021 and first celebrated globally in 2022 to bring quantum science closer to society.
At phaeno, we’re using this day to put our quantum section firmly in the spotlight, showcase new exhibits and invite curious visitors of all ages to marvel at what’s on offer. Come along!
The basics: explained simply.
What exactly is a quantum – and why is it so special?The word ‘quantum’ comes from Latin and simply means ‘quantity’. In physics, it refers to the smallest possible unit of something. Energy, for example, does not occur in arbitrarily small portions – it comes in fixed packets, or ‘quanta’. And it is precisely in this world of tiny packets that rules apply which contradict our everyday understanding. Here are the key points:
Three fundamental principles of the quantum world
- Superposition: A quantum particle can exist in several states at the same time – only when we measure it does it ‘decide’ on one. A qubit (quantum bit) is therefore not simply 0 or 1, but both at the same time.
- Entanglement: Quantumentanglement describes the state in which particles remain correlated across any distance: the measurement of one particle instantly determines the state of the other.
- Quantum tunnelling effect: Particles can penetrate barriers that they could never overcome in classical terms – as if they were simply walking through a wall.
“Anyone who is not shocked by quantum mechanics has not understood it.” – Niels Bohr, Nobel Laureate in Physics
These strange properties are not merely theoretical. They form the basis for technologies that are currently transforming our world.
Why quantum technology will be groundbreaking
Classical computers operate with bits – 0 or 1. A quantum computer uses qubits, which, thanks to superposition, can exist in many states simultaneously. This makes it exponentially more powerful for certain tasks – no classical computer in the world could keep up with it.
The implications are enormous: in medicine, quantum computers could simulate new active ingredients that were previously too complex for any data centre on Earth. In communications, quantum encryption enables tap-proof transmissions – physically guaranteed, not just mathematically. In navigation and sensor technology, quantum sensors measure magnetic fields and gravity with a precision that could eventually replace GPS.
In short: quantum technology is not the next improvement – it is a paradigm shift.
Making quantum physics accessible.
At phaeno, you can do more than just read about quantum physics – you can touch it, play with it, measure it and be amazed by it. Here are the exhibits in our quantum section:Science meets outreach.
Why cooperation is keyphaeno sees itself as a bridge between the university and society. We bring the latest research into the science museum – presented in an accessible, tangible and interactive way. This is made possible by a network of dedicated scientists, educationalists and institutions:
- Braunschweig University of Technology – As part of the ‘HolodeckQ’ and DiQuaMus projects, researchers from the Institute for Science Education, in collaboration with phaeno, have developed interactive exhibits that not only explain quantum phenomena but also bring them to life. PhD students from the university also personally lead the workshops for upper secondary school pupils.
- University of Leipzig – Felix Bloch Institute for Solid State Physics – Researchers at the institute developed the diamond magnet sensor from scratch – as a genuine research exhibit that visitors can operate themselves. No model, no dummy: real quantum research, hands-on.
- Physikalisch-Technische Bundesanstalt (PTB) Braunschweig – As the national metrology authority, the PTB brings precision expertise to phaeno: the mechanical particle trap and other exhibits were developed in close collaboration with PTB researchers.
- Quantum Valley Lower Saxony (QVLS) – As part of this regional innovation network comprising science, research institutions and businesses, phaeno is actively involved in the strategy for the development and dissemination of quantum technologies in the region.
- German Physical Society (DPG) – The world’s largest national physics society developed the Quantum History Wall, which can be seen at phaeno.
- Federal Ministry of Research, Technology and Space (BMFTR) – Public funding makes it possible to develop innovative science programmes such as the quantum section and ensure they remain accessible in the long term.
Science communication at phaeno means: always close to the heart of science – the universities. Our aim is to bring research into the museum, broken down for our visitors. To spark curiosity. To nurture the next generation. To inspire wonder. That is our contribution to the scientific literacy of tomorrow.
To conclude: a thought experiment.
Schrödinger's cat – explained simply🐱📦 The cat that is both alive and dead – at the same time
Imagine a cat in a closed box. Inside the box is also a radioactive atom that has a 50% chance of decaying within an hour. If it decays, it triggers a mechanism that opens a vial of poison – the cat dies. If it does not decay, the cat lives.
So far, so simple. But this is where quantum physics comes into play: as long as we do not open the box and look inside, the atom is in a superposition – it has both decayed and not decayed at the same time. And so, from a purely quantum mechanical perspective, the cat is also in a superposition: both alive and dead at the same time. Only when we look, when we measure, does the superposition collapse into one of the two states.
Schrödinger devised this thought experiment in 1935 – not as proof that cats can really be both alive and dead at the same time, but as a critical provocation: to show how absurd it would be if quantum mechanics were simply applied to the everyday world. The question of when and why a superposition collapses continues to occupy physicists to this day.
And it is precisely this principle that lies behind Quantum Tic-Tac-Toe at phaeno on World Quantum Day. Here you can win, lose, or sometimes both sides can win – at the same time. Sounds impossible? That is exactly what quantum physics is all about.
Want to know more?
Come to phaeno and experience quantum physics first-hand. Play Quantum Tic-Tac-Toe. Measure a magnetic field using a diamond. Make a cat both alive and dead at the same time.