Positronium and Quantum Hide-and-Seek: How to 'Push' a Photon to Uncover the Mystery ⚡ экспресс
An electron and a positron can form a metastable bound state—positronium—which annihilates with the emission of photons. For para-positronium (singlet state, spin 0), it is theoretically predicted that the two annihilation photons are in a maximally entangled Bell state. It is shown that polarization-dependent Compton scattering provides a method for experimentally verifying this entanglement. The theoretical approach is based on the formalism of two-photon density matrices and combines concepts from relativistic quantum electrodynamics and quantum information theory. The results confirm the fundamental quantum-informational nature of particle decay and may be used to test the foundations of quantum mechanics.
An electron and its antiparticle — the positron, predicted by Дираком, — upon meeting, momentarily form позитроний: a tiny pair circling each other, like in an atom but without a nucleus. Almost instantly it decays, emitting two photons that turn out to be mysteriously linked. This connection, квантовая запутанность, resembles a pair of magic coins: no matter how far apart they fly, if one shows 'heads,' the other always shows 'tails.' Джон Белл proved that such behavior is not a trick but a fundamental property of the microworld.
To test this, physicists came up with the following: they 'push' one photon against an electron (a phenomenon known as комптоновское рассеяние). By seeing how the photon bounces, one can tell which side our coin landed on. And as soon as we know that, the second photon instantly becomes definite, even if it has already traveled to the other end of the galaxy. This experiment will pave the way to creating perfectly secure communication channels and quantum computers.
🎯 Positronium is the lightest exotic 'atomic' system: it is 920 times lighter than hydrogen and decays in 0.1 nanoseconds.