vacuum polarization

In a pot of boiling water, steam bubbles appear and disappear — a similar struggle takes place in two-dimensional materials. Here, electrons both create magnetism and try to extinguish it.

The universe sometimes resembles an old fabric: after rapid cooling, wrinkles could have remained — thin, almost invisible threads of monstrous density. They are called cosmic strings. Usually, at the center of such a string hides a singularity — a point where the laws of physics lose their meaning.

Many molecules, like gloves, come in left- and right-handed versions. Their energy difference, caused by the weak interaction, is minute, like a whisper in a noisy room. Physicists have figured out how to turn that whisper into a chorus. A mixture of precursor molecules in an ultracold gas yields mirror-image pairs.

Imagine a huge swimming pool. In one corner, a chemical reaction is underway that needs to be calculated with jeweler-like precision. But the surrounding water is not just decoration: its molecules jostle, attract, and influence the reaction. How do you account for this endless dance of particles without drowning in calculations?

Picture a crowded hall where each person is a molecule, and their private conversation is the motion of electrons within it. Normally, everyone talks to themselves, and the overall buzz is chaotic. But if a bright spotlight is turned on in the center, it begins to conduct the crowd: people synchronize their movements, even though the light merely reflects off the walls.

Quantum vacuum resembles a sea, constantly rippling with tiny splashes. An electron in an atom moves in this sea, and its path slightly changes due to the waves. Previously, such corrections were accurately calculated only for hydrogen-like ions with a single electron. But in highly charged ions with several electrons, the picture becomes more complex.

In an empty hall, sound bounces between walls, turning into a booming echo. An optical cavity is the same echo chamber, just for light.

According to the Standard Model, the vacuum is not emptiness but an ocean of virtual ghost particles. An ultra-strong electromagnetic field, like a storm, yanks electron-positron pairs into reality.

Two tiny dust grains hover at the crossing of laser beams. Each is held by its own 'tweezer'—a focused beam that keeps the particle from falling. Inside a mirrored cavity, light bounces between the walls, and its oscillations are coupled to the trembling of the grains.

In a dark room, an invisible lamp flashes. Its light is unlike anything familiar: it has no steady brightness, only rare but powerful bursts. This is bright squeezed vacuum — a state of light with no ordinary wave but strong quantum fluctuations. It is with such light that physicists bombarded xenon atoms.

In the crystal HfTe5, electrons behave almost like light: their mass is so small that they obey the laws of relativity. If you place such a crystal in a strong magnetic field, the electrons start to circle in tiny orbits. Their energy then changes not smoothly but in steps, like floors in a building.

A magnetar is a neutron star with a magnetic field hundreds of millions of times stronger than Earth's. If you brought an ordinary magnet near such a field, it would instantly lose its magnetism, and atoms would stretch into thin filaments.

A quantum dot the size of a virus, squeezed between mirrors, gives birth to two photons in a short flash of light. These photons fly out as a pair, and their polarizations, the directions of wave oscillation, are linked such that knowing one instantly tells you the other.

A laser beam holds a single ion in a vacuum, and that ion behaves like a ball trapped between two cups. The cups aren't pits in the ground but regions where the ion energetically prefers to be. In the classical world, a ball would roll into one cup and stay there.

The Wigner function is a kind of topographic map of probabilities: hills correspond to regions where a particle is most likely to be found, and valleys to where its appearance is practically ruled out.

Two water droplets tremble in sync — because they're connected by a straw. So it is with entangled particles: their unity may be held together by a microscopic wormhole.

In the quantum world, particles can walk through walls: this is quantum tunneling. If you place a detector right in the path of such a 'ghostly' passage, the moment of detection acts like a starting pistol: the particle gets a sharp kick and flies out of the barrier with excess energy, turning into a tiny engine.

In 1936, two physicists, Werner Heisenberg and Hans Euler, poring over the equations of quantum electrodynamics, found something strange. In a sufficiently strong magnetic field, vacuum should cease to be empty.

Light passing through a birefringent crystal changes its polarization depending on wavelength. This profile is like a mosaic assembled from rare flashes, where each shard hints at the shape of its neighbors.