Higher-Energy X-Rays Could Enable a New Form of Quantum Sensing

Insider Brief

• Researchers used entangled electrons in helium atoms to produce higher-energy X-rays beyond the limit predicted by standard theory, potentially opening a new approach to quantum sensing.
• Two correlated electrons returned to the same ion simultaneously and released their combined energy as a single X-ray photon, an effect observed for the first time.
• The method could help detect paired-electron correlations in gases and materials, with possible applications in quantum computing and advanced nanomaterials.
• Artist’s rendering of an ultraviolet laser pulse (dark blue waves in foreground) acting on a helium atom (center). Two electrons are pulled away and driven back (pale blue spiral waves trace their return). When they recombine, they emit light at extreme ultraviolet frequencies (violet waves) and X-rays (white). (Tenio Pompmintchev lab / UC San Diego)

PRESS RELEASE — When certain atoms are irradiated with laser light, they can produce laser pulses with extremely high frequencies in the X-ray range. Until now, the theoretical model of this effect predicted an upper limit to the energy, known as the energy cutoff. Past this point, hardly any X-rays are produced.

New research from the University of California San Diego, TU Wien (Austria) and the University of Salamanca (Spain) succeeds in overcoming this cutoff. Using helium atoms, the researchers reached a much higher energy range than standard theory predicts, because the atom’s two electrons can release their energy together as a single X-ray photon.