2025 Nobel Prize in Physics Explained: Macroscopic Quantum Tunnelling in Josephson Junctions and Quantum Circuits

Short Summary

Explore the 2025 Nobel Prize in Physics and the physics behind macroscopic quantum tunnelling in superconducting circuits. The video explains how a Josephson junction, formed by superconductors and an insulator, supports delocalized quantum states across a circuit with billions of electrons, linking this to qubits in quantum computing. It also covers experimental tools like scanning tunneling microscopy (STM) and the cooling methods that reach near absolute zero, while touching on the prize’s historical context and broader impact on physics education and research. The discussion demonstrates how energy quantization in these circuits mirrors atomic levels and how tunnelling probabilities depend on barrier height and particle energy, all within a rich lab and classroom setting.

Overview

The video dives into the 2025 Nobel Prize in Physics, discussing the discovery of macroscopic quantum tunnelling and energy quantization in electrical circuits. It highlights how a Josephson junction, a sandwich of a superconductor, an insulator, and another superconductor, enables collective quantum states in a macroscopic system. This is presented as a bridge between fundamental quantum phenomena and practical quantum computing hardware.

Nobel Context and People

The discussion notes the prize being awarded for work conducted decades earlier, around 1985, and reflects on the legacy these researchers built. It also touches on the historical gender context of the field and how future prizes may reflect greater diversity in physics.

Key Concepts: From Atoms to Circuits

The narrative contrasts classical and quantum behavior, explaining how electrons pair up into Cooper pairs in superconductors, forming a single macroscopic quantum state. The role of energy gaps, superconducting gaps, and the Josephson current is explored, illustrating how quantum states can be delocalized across large-scale systems and why tunnelling through barriers is possible in such setups.

Implications for Quantum Computing

The bottom-up hardware perspective is emphasized, describing qubits as quantum bits and showing how superconducting circuits and Josephson junctions underpin some quantum computing architectures. The discussion covers why certain tasks may benefit from quantum speedups and how this hardware enables simulations of complex physical systems, weather modelling, and other advanced physics research.

Lab Realities and Tools

Practical lab examples include scanning tunnelling microscopy, cryogenic environments with liquid helium, and ultra-sharp tips used to probe quantum phenomena at the nanoscale. The dialogue ties these tools to the Nobel Prize themes, linking theory with measurable quantities such as tunnelling currents and energy gaps.

Closing Reflections

The video closes with reflections on the significance of Nobel prizes for science communication and education, and how the revealed physics continues to shape our understanding of the quantum world and the development of quantum technologies.