Tunneling: Passing Through Walls
A quantum particle can cross a barrier it does not have the energy to climb, because its wave does not stop dead at the wall. The wave fades inside the barrier, and if the barrier is thin some of it leaks out the far side. Tunneling powers the Sun, the scanning tunneling microscope, and the Josephson junctions inside superconducting qubits.
Why does tunneling matter for quantum computers?
Many of today's quantum computers use superconducting chips. Each qubit is built around a tiny part called a Josephson junction. It only works because of tunneling. The 2025 Nobel Prize in Physics was awarded for showing that a whole electric circuit can tunnel. So tunneling is not a side story. It sits inside the hardware.
- What would a ball do at the bottom of a hill?
- Can light tunnel too?
- Worked example: why thickness matters so much
- Where does tunneling show up in the real world?
- How did a whole circuit tunnel?
- Run it: a particle sloshing between two wellsINTERACTIVE
- Try this: wait for a full hopINTERACTIVE
- Try this: a thicker hillINTERACTIVE
- Where can you learn more about the hardware?
You’ve read the opening of chapter 10. Pro unlocks the other 9 sections — plus every chapter of every course, with circuits you can run right on the page. That’s $11.99 a month, about the price of a coffee, or $99.99 a year (save 30%). The first chapter of every course, and the whole math course, stay free.