Testing quantum collapse theory with the XENONnT dark matter detector

Scientists are repurposing the XENONnT dark matter detector to test quantum collapse theories, marking the first large-scale experimental probe of objective collapse models proposed in the 1980s. The experiment targets spontaneous wavefunction collapse by searching for tiny energy deposits—predicted by theories like Continuous Spontaneous Localization (CSL)—that would disrupt quantum superpositions without external measurement. Data collection began in 2025, leveraging the detector’s ultra-sensitive liquid xenon chamber, originally designed to hunt dark matter, to instead hunt for collapse-induced signals at unprecedented precision. If detected, these signals could resolve the long-standing "measurement problem" by proving superpositions collapse objectively, not just upon observation, challenging standard quantum mechanics interpretations. Results, expected by late 2026, may either validate collapse theories or set strict new limits on their parameters, advancing foundational quantum physics research.