Guang-Can Guo

For the quantum internet, we need to learn how to hold light — much like mail is sorted at intermediate nodes. The technology is based on a thin crystal plate doped with europium ions, a rare-earth element that, incidentally, is responsible for the red glow of smartphone screens.

Open systems exchange energy with their surroundings, like a guitar string fading into the air. Scientists built such a system out of light, twisting the beams into corkscrews and forming an artificial lattice — a maze where losses can be controlled at every step. Light in this maze always moves at the maximum possible speed, but its energy can fade or grow.

The quantum network works like a series of turnstiles that open only for a pair of perfectly synchronized photons. The central node tells them which turnstile to go to, but cannot forge the synchronization. 200 users can communicate with each other over distances up to 200 km — about the size of a large city.

Creating light with an exact number of photons is like stamping exactly 100,000 flawless coins. Until now, physicists could only control dozens of particles. The 'optical lathe' technology breaks this barrier: virtual lenses, like milling cutters, eliminate 'blurriness' and ensure each bunch contains exactly the specified number of photons. Counting becomes perfect.

Quantum light is not just a stream of particles but an intricate pattern woven from space and time. A single photon can be stretched, squeezed, smeared across different directions.

In a silicon carbide crystal, which looks like a transparent stone, there are hidden defects — places where atoms are out of line. One such defect acts as a quantum node: an electron inside it spins and processes information, while the nucleus of a neighboring atom quietly stores it.

Two simultaneous interpreters sit in the same booth. The first translates from English into Russian but swallows half the words. The second goes from Russian into French, and also loses half. If you put them together, you'd expect a mess: the losses would add up, and only a quarter of the meaning would reach the listener. But what if they start correcting each other?

An orchestra of billions of cesium atoms struck a single note, and it sounded for 17 hours without fading. That’s no exaggeration: Chinese physicists created a continuous time crystal with a record-breaking lifespan. A time crystal is a system that breaks time symmetry, spontaneously pulsating in an unchanging rhythm.

A single photon is like a perfectly smooth brick from which quantum technologies can be built. But to build a house, you need thousands of identical bricks. Rubidium atoms are natural emitters: each atom emits photons of exactly one wavelength, like a tuning fork that always produces a single note.

Light passing by a tiny structure changes direction. If the structure is smaller than the wavelength of the light, it acts like a lens and focuses the light into a spot smaller than the wave itself.