Researchers measured 1-μs microwave pulses at 8.4 GHz with an estimated full-width-at-half-maximum energy resolution of 0.83 ± 0.04 zeptojoules, finer than the directly demonstrated 0.95 ± 0.02 zJ threshold.
The metallic superconductor-normal-conductor-superconductor sensor used matched filtering on single-shot traces, boosting signal-to-noise by about 30% and enabling resolution of pulses carrying roughly 150 photons at 8.4 GHz.
At the chosen operating point, the device posted a 49 zW/√Hz noise-equivalent power and a 260-μs thermal time constant; a noise-based estimate had predicted about 1.03 zJ resolution, close to the measured result.
The current dynamic range is only a few zeptojoules because the resonance shifts and saturates at higher pulse energies, but the team said extra probe tones or a frequency comb could extend it.
The result marks a step toward real-time, energy-resolving detection of single microwave photons in the 10-GHz range, with possible gains from quantum-limited amplifiers and lower-heat-capacity absorbers such as graphene.
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Breaking the Zeptojoule Barrier: Aalto Team Achieves 0.83 zJ Quantum Sensor Sensitivity
Overview
On May 12, 2026, researchers at Aalto University, led by Professor Mikko Möttönen, set a new world record in quantum sensor sensitivity by measuring an incredibly small energy pulse of just 0.83 zeptojoules. This achievement, published in Nature Electronics, was made possible by a novel calorimeter device developed by the team. Their breakthrough not only surpasses previous technologies but also opens new possibilities for understanding and manipulating quantum systems. This leap in sensitivity marks a significant step forward for quantum technology, paving the way for advances in quantum computing and fundamental physics.