Quantum Light Swimmer Breaks Newton's Third Law — SkimNews
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- Yi Hu at Nankai University and colleagues demonstrated that a passive swimmer made of quantum light can move upstream against a river of quantum light, breaking Newton's third law of motion.
- The team created the quantum light fluid by shooting lasers into a special crystal exposed to electric voltage, causing photons to interact; the swimmer was a separate shaped beam forming a single solitary wave.
- The swimmer felt attraction from the river while the river felt repulsion from the swimmer — a 'non-reciprocal' interaction that produced a net upstream force on the swimmer, according to Hu.
- Mathias Albert at Côte d'Azur University noted prior upstream motion in quantum light fluids relied on creating tiny vortices behind the swimmer and harnessing their recoil, making the new mechanism fundamentally different.
- Unlike those earlier systems, the experiment focused on a passive object that does not consume energy yet still benefits from non-reciprocal interactions, potentially enabling a new class of active matter in quantum systems.
- Albert said future applications could include controlling chunks of light in preferred directions within quantum communication and quantum information processing devices, where quantum light is already prevalent.
- The study was published in Physical Review A (DOI: 10.1103/lwyj-7m5f); Hu said the team now plans more complex experiments with finer swimmer control and multiple swimmers.
Why it matters: By demonstrating that a passive quantum-light swimmer can move upstream without consuming energy — propelled only by non-reciprocal forces — the Nankai team introduces a new mechanism for controlling photons in quantum systems. For quantum communications and information-processing labs, this offers a way to steer light in preferred directions without the vortex-recoil tricks previous quantum-fluid experiments depended on.
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