Editorial 1: ​​​Radical tunnel

Context

The Physics Nobel underscores the worth of curiosity-driven inquiry over immediate practical utility.

Introduction

The 2025 Nobel Prize in Physics celebrates a milestone in quantum mechanics, honouring John Clarke, Michel Devoret, and John Martinis for proving that quantum laws extend beyond the microscopic world. Their discovery of macroscopic quantum tunnelling and energy quantisation in visible circuits not only redefined the boundaries of physics but also laid the groundwork for modern quantum technologies.

Pioneering Discovery

• In the 1980s, John Clarke, Michel Devoret, and John Martinis demonstrated that the laws of quantum mechanics extend beyond subatomic particles to macroscopic electrical circuits.
• Their experiments revealed macroscopic quantum tunnelling and energy quantisation in circuits visible to the naked eye.
• For this breakthrough, they received the 2025 Nobel Prize in Physics, marking a rare return of pure quantum mechanics to the Nobel spotlight.

Experimental Breakthrough

• Conducted at the University of California, their work used a circuit made of two superconductors separated by an ultrathin insulating barrier—a Josephson junction.
• In classical physics, current would remain trapped unless sufficient energy crossed the barrier; but near absolute zero, it ‘tunnelled’ through—a uniquely quantum phenomenon.
• The circuit behaved like a single giant particle with discrete energy levels, confirming that collective superconducting properties act as a single quantum variable.
• To rule out interference, the team meticulously shielded the setup from microwave noise, ensuring the authenticity of their results.

Applications and Legacy

• Josephson junctions today form the core of superconducting qubits used in modern quantum computers.
• Their principles underpin quantum voltage standards, ultrasensitive magnetometers, and single-photon detectors vital to astronomy and biomedical imaging.
• The discovery proved that quantum laws apply to systems “large enough to hold in hand”, establishing the field of applied quantum engineering.

Continuing Challenge and Broader Message

• The current focus lies in preserving quantum states by improving materials, filtering, cryogenic control, and hybrid architectures combining superconducting, mechanical, photonic, or spin systems.
• The 2025 Nobel also symbolizes the value of curiosity-driven inquiry, pursued without concern for immediate utility.
• What began as an abstract test of quantum limits has become the foundation of next-generation technologies, inspiring scientists and engineers worldwide — including in India’s quantum-technology missions.

Conclusion

By extending quantum mechanics into the macroscopic realm, the 2025 laureates blurred the line between theoretical physics and applied engineering. Their work proves that curiosity-driven research can reshape the technological landscape. From Josephson junctions to quantum computers, their discovery bridges imagination and innovation—affirming that the quest to understand nature’s limits remains humanity’s most powerful driver of progress.