This year's Nobel Prize in Physics was awarded to John Clarke, Michel Devoret, and John Martinis for their groundbreaking work on 'passing through walls'—a concept straight out of Harry Potter's Platform 9¾.

The Magic of Quantum Tunneling

The core of their work is the quantum tunneling effect—a particle's ability to pass through an energy barrier it shouldn't be able to cross. In classical physics, a ball lacking the energy to roll over a hill will simply roll back. The quantum world, however, operates differently.

A particle is also a wave. This wave function doesn't abruptly stop at a barrier; it can penetrate it.
Waves can penetrate barriers. The wave decays exponentially inside the barrier, but if it isn't infinitely thick, a 'tail' of the wave can emerge on the other side.
Probability is key. Where there's a wave function, there's a non-zero probability of finding the particle, allowing it to effectively 'tunnel' through.

When you throw a ball at a wall, you expect it to bounce back. You'd be shocked if it suddenly appeared on the other side. This is precisely the kind of phenomenon that gives quantum physics its reputation for being strange and counterintuitive. ©Johan Jarnestad/The Royal Swedish Academy of Sciences

When you throw a ball at a wall, you expect it to bounce back. You'd be shocked if it suddenly appeared on the other side. This is precisely the kind of phenomenon that gives quantum physics its reputation for being strange and counterintuitive. ©Johan Jarnestad/The Royal Swedish Academy of Sciences

A Leap from Particles to Systems

The laureates proved this isn't just a trick for single particles. They demonstrated it works for entire mesoscopic systems—the realm between the micro and macro worlds. In their experiment, all the electrons in a superconducting circuit paired up to form 'Cooper pairs,' which then acted in unison as a single, giant 'super-particle.' This super-particle was then made to tunnel through a system.

Creating and Controlling an 'Artificial Atom'

Their second major achievement was observing and controlling discrete energy levels within these systems, much like the energy levels of an electron in an atom. The laureates built an 'artificial atom' from a superconducting circuit containing a special component called a Josephson junction.

In a normal conductor, electrons collide with the material. When a material becomes a superconductor, electrons form 'Cooper pairs' and create a current with zero resistance. These pairs behave as a single entity, described by a collective wave function that was central to the laureates' experiment. ©Johan Jarnestad/The Royal Swedish Academy of Sciences

In a normal conductor, electrons collide with the material. When a material becomes a superconductor, electrons form 'Cooper pairs' and create a current with zero resistance. These pairs behave as a single entity, described by a collective wave function that was central to the laureates' experiment. ©Johan Jarnestad/The Royal Swedish Academy of Sciences

To manipulate this 'atom,' they exposed it to microwaves. The system only absorbed energy at specific frequencies corresponding to the gap between its energy levels, causing it to jump to an excited state. This confirmed its quantum nature—a classical object would just heat up, but this system only accepted energy in discrete packets (quanta). In this excited state, the probability of tunneling increased significantly.

The biggest takeaway? Quantum magic doesn't just disappear with size. If you can properly organize particles and shield them from noise, they retain their extraordinary quantum nature.
The Essence of the Discovery

Paving the Way for Quantum Computing

This breakthrough enables the creation of a new kind of 'quantum transistor' that switches between quantum states instead of electrical currents. This is a direct path toward building stable qubits, the fundamental units of quantum computers. Qubits can exist in multiple states at once (like Schrödinger's cat), promising an exponential leap in computational power.

While this research doesn't unify quantum and classical physics, it erases the hard line between them. It demonstrates that the distinction isn't about size, but about isolation from environmental 'noise.' By achieving this isolation, even large systems can be coaxed into behaving by the strange and powerful laws of the quantum world.

#nobel #news