Entangled Photons: A New Way to See the Invisible ⚡ экспресс
A new quantum spectroscopic method called BELS uses polarization-entangled photon pairs and two-photon interference. Instead of intensity, it measures coincidence correlations generated when entangled pairs pass through a sample. It turns out that classically indistinguishable optical elements can alter quantum states differently, allowing the separation of contributions from birefringence and magnetic rotation of the polarization plane (the Faraday effect) in a single experiment. This was confirmed experimentally on an anisotropic dielectric and a terbium gallium garnet crystal. BELS lays the foundation for ultra-sensitive spectroscopy of quantum materials.
Entangled photons are like two messengers walking in lockstep. Inside a material, their synchrony is broken. The way it breaks tells you what they met: a fork that scattered their routes, or a magnetic carousel that spun their step. That's how the BELS method works. It sends pairs through a sample and detects coincidences in the signals. One effect (birefringence) splits the beam like a fork; the other (Faraday rotation) twists the polarization like a magnetic carousel. Ordinary light can't tell them apart, but entangled light leaves an entropic trail—a unique pattern of correlations.
The method is based on the quantum mechanics of entanglement, for which Alain Aspect, John Clauser, and Anton Zeilinger won the Nobel Prize. BELS promises ultra-precise diagnostics for quantum devices: even a single defect in a nanochip will become noticeable. In the future, this will allow finding faults in quantum computers without direct intervention.
🎯 Entangled photons hold their connection record-breakingly long: their correlation has been confirmed via satellite over a distance of more than 1200 km.