Physics Nobel 2025 For Showing Quantum Effects Existing in Macroscopic Electric Circuit

The Nobel Prize in Physics for 2025 has been declared. The Royal Swedish Academy of Sciences has decided to confer the award to  John Clarke, Michel H. Devoret and John M. Martinis for their works in discovering macroscopic quantum mechanical tunnelling and energy quantisation in an electric circuit. Their pathbreaking experiments on a chip revealed quantum physics in action.

The Major Question in Quantum Physics

A major question in physics is, what is the maximum size of a system that can demonstrate quantum mechanical effects? The 2025 physics laureates revealed that an electrical circuit that is big enough to be held in the hand can show quantum effects. They demonstrated both quantum mechanical tunnelling and quantised energy levels in the electrical circuit. 

In Quantum mechanics, tunneling is the process that allows a particle to move straight through a barrier. As soon as large numbers of particles are involved, quantum mechanical effects usually become insignificant.

The laureates’ experiments demonstrated that quantum mechanical properties can be made concrete on a macroscopic scale.

History of Their Experiment

The three laureates, John Clarke, Michel H. Devoret and John M. Martinis conducted a series of experiments with an electronic circuit built of superconductors, back in 1984 and 1985.

Superconductors are components that can conduct a current with no electrical resistance. "In the circuit, the superconducting components were separated by a thin layer of non-conductive material, a setup known as a Josephson junction. By refining and measuring all the various properties of their circuit, they were able to control and explore the phenomena that arose when they passed a current through it. Together, the charged particles moving through the superconductor comprised a system that behaved as if they were a single particle that filled the entire circuit,"--reads the Nobel website. 

"This macroscopic particle-like system is initially in a state in which current flows without any voltage. The system is trapped in this state, as if behind a barrier that it cannot cross. In the experiment, the system shows its quantum character by managing to escape the zero-voltage state through tunnelling. The system’s changed state is detected through the appearance of a voltage"--it explains. 

The laureates could also demonstrate that the system's behaviour is in accordance with the principles of quantum mechanics. 

The transistors in computer microchips are one example of the established quantum technology that surrounds us. This year’s Nobel Prize in Physics has provided opportunities for developing the next generation of quantum technology, including quantum cryptography, quantum computers, and quantum sensors.