Quantum Triplet: Three-Photon Entanglement Confirmed ⚡ экспресс
Generating entangled photons via spontaneous parametric down-conversion (SPDC) is a key resource in quantum optics. Previously, SPDC was limited to pairs, but strong nonlinearities in circuit quantum electrodynamics have enabled three-photon SPDC (3P-SPDC). This work experimentally confirms genuine three-particle non-Gaussian entanglement in the stationary output field of a 3P-SPDC source based on a superconducting parametric resonator coupled to a transmission line for the first time. Entanglement was probed using a witness constructed from three-mode correlation functions, and a maximal violation of the classical bound by 23 standard deviations was observed. The results show excellent agreement with the analytically predicted scaling of the witness. Additionally, the influence of the temporal mode function defining the photon mode on the measured witness value was studied.
Physicists have for the first time created a trio of photons entangled as a single whole, not just pairwise. To achieve this, a special chip was cooled to a temperature hundreds of times lower than that of deep space — any noise threatened to destroy the fragile link. Entanglement of three particles is like three billiard balls rolling in sync, even when placed in different corners of the table: a strike on one instantly changes the behavior of the others, and their shared trajectory seems to ignore the limits of the speed of light.
The mathematical test (an 'entanglement witness') showed a 23-fold excess over random synchrony — as if the balls always bounced off at exactly the same angle with micron precision. The resulting state also turned out to be 'non-Gaussian': its statistics are far from the usual gently sloping curves, as if the balls traced complex vortices, opening new tricks for quantum computing. The experiment confirmed the predictions of the Standard Model, the bedrock of particle physics.
🎯 The method for generating photon pairs, discovered back in the 1960s, has only recently made it possible to reliably create triples with controlled entanglement.
🎬 In the 'Three-Body Problem' trilogy, three celestial bodies move chaotically and unpredictably, while the three quantum photons in the experiment, on the contrary, demonstrate the highest degree of synchrony.