Reference Article: The Hindu
UPSC CSE Relevance:
GS Paper III: Science and Technology — Quantum technologies, superconductivity
The 2025 Nobel Prize in Physics has been awarded to John Clarke, Michel Devoret, and John Martinis for their experimental demonstration of quantum behaviour in macroscopic circuits, a breakthrough that confirmed quantum mechanics applies not only to subatomic particles but to visible, hand-scale electrical systems. This discovery — of macroscopic quantum tunnelling and energy quantisation in Josephson junctions — marked a defining leap in both fundamental physics and applied quantum engineering.
The Discovery: Quantum Phenomena Beyond the Microscopic
In the 1980s, the laureates at the University of California conducted experiments using Josephson junctions — circuits comprising two superconductors separated by an ultra-thin insulator. Classical physics predicted that an electric current could only cross this barrier if it possessed enough energy. However, at temperatures close to absolute zero, the team observed the current “tunnelling” through the barrier, a hallmark of quantum behaviour.
They further demonstrated that the superconducting system exhibited discrete energy levels, acting as a single quantum object, even though it contained trillions of electrons. To eliminate experimental noise, they meticulously shielded their apparatus from stray microwaves — ensuring that the results reflected genuine quantum coherence rather than external interference. These findings extended the reach of quantum mechanics from the atomic to the macroscopic world, confirming that collective properties such as the superconducting phase difference can behave as a single quantum variable.
Technological and Conceptual Impact
The implications of this work have been transformative. Josephson junctions today form the backbone of:
- Superconducting qubits, the building blocks of many quantum computers,
- Ultrasensitive magnetometers (SQUIDs) used in medical imaging and astrophysics,
- Quantum voltage standards, and
- Single-photon detectors crucial for secure communication and astronomical observation.
By proving that quantum laws govern macroscopic systems, the laureates effectively created the foundation for quantum engineering — a field that merges physics with advanced materials science and computation.
The current frontier of research now focuses on maintaining quantum coherence for practical use — improving material purity, cryogenic control, and hybrid architectures that combine superconducting, photonic, and spin-based systems. The challenge has shifted from proving macroscopic quantum effects to preserving and manipulating them.
Broader Significance and Lessons for India
This Nobel underscores the power of curiosity-driven inquiry. When Clarke, Devoret, and Martinis sought to test the limits of quantum mechanics, their goal was purely fundamental. Yet, their experiments catalysed the technologies now shaping quantum computing and sensing, areas where India’s National Quantum Mission (NQM) seeks to advance. The award is a reminder that long-term scientific investments rooted in basic research can yield transformative and strategic technologies decades later.
Conclusion
The 2025 Nobel Prize celebrates a landmark in humanity’s understanding of nature — showing that quantum mechanics governs not only the invisible world but also the devices we can build and hold. It bridges the divide between theoretical physics and engineering innovation, reinforcing that the path to technological leadership lies through sustained, curiosity-fuelled science.
Sample UPSC Mains Question (GS Paper III):
The 2025 Nobel Prize in Physics highlights how fundamental research in quantum mechanics has evolved into applied quantum engineering. Discuss the significance of this transition for India’s National Quantum Mission and its future technological sovereignty.
