information spread

Quantum communication is like sending a secret letter that tears apart at any attempt to peek. So far, such a letter can only be sent along one road, and that's slow. Scientists have figured out how to send 16 couriers along 16 parallel roads, different frequencies of light, and verified that the letters arrive intact.

When a heavy atomic nucleus splits into two fragments, an invisible quantum thread remains between them. This thread is entanglement: the state of one fragment is instantly linked to the state of the other, as if they were still a single whole. For the first time, physicists have precisely calculated how long and strong such a thread can be, tracing the fission process step by step.

A camera looks at two distant sparks. They're so close together that they merge into a single fuzzy blob. It seems impossible to tell them apart — the classic limit of optical microscopy has been reached. But quantum mechanics hints that the light field still holds a secret about where each spark sits.

The quantum vacuum is not empty: it is permeated by entanglement linking distant regions. But when physicists tried to compute this entanglement, it turned out to be infinite. The culprit: particles with very low energy that can smear out over arbitrarily large volumes. They are like waves with no shores to contain them.

A disease outbreak is like a wildfire: the fire runs through dry grass, and its speed depends on wind and humidity. But an infection has its own 'wind'—how often people infect each other. When this rate changes along with the fraction of already infected, the epidemic wave can behave differently.

A quantum computer relies on two forces: entanglement (particles behaving as a single whole) and "magic"—a measure of how far a state is from familiar classical physics. But how these two resources relate as a many-particle system evolves in time has remained a puzzle. The authors approached the problem through time.

The old question of Maxwell’s demon, can an intelligent being circumvent the second law of thermodynamics and pump heat from cold to hot, gains new resonance in the quantum world.

A light beam approaches a black hole not head-on, but at a glancing angle. If the angle is just right, the light neither falls in nor escapes: it starts looping around, like a figure skater circling the rim of a funnel. This narrow track is the photon ring. It acts like a lens, repeatedly reflecting the image of everything that falls into the hole.

An acoustic black hole is a fluid flow faster than sound, so sound waves can't escape. The boundary, the surface where the flow speed reaches the speed of sound, spawns pairs of phonons: sound quanta, one flying away, the other plunging inward.

Neutrinos are nearly elusive particles that permeate everything around us. In a dense cloud, such as during a star explosion, they begin to collectively change their type, or 'flavor.' This process is like a crowd of people synchronously changing the color of their clothes, but not all at once — rather in waves.

A quantum particle can be in two states at once, like a coin spinning, both heads and tails. Near a black hole, the event horizon, where spacetime curvature bends space and time to the extreme, acts as a one-way gate.

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?

Spread a handful of coins on the table. Each coin is a possible outcome: heads, tails, or something else. If we know how chaotic this set is (its entropy), which combinations of probabilities will we encounter more often? It turns out the answer depends on how much chaos we allow.

On the surface of a tiny sphere live two invisible fields, like two kinds of ripples on a soap bubble. These fields don't just oscillate on their own: they constantly influence each other, like musicians playing in unison. In a new study, physicists derived exact equations that describe how this ripple changes over time, heats up, and descends into chaos.

Three people sit in three corners of a room. Each receives a sealed envelope from an invisible courier, but the couriers do not coordinate and have never met. The people open the envelopes and see a note with one word: "yes" or "no." They choose nothing themselves: they just read.

A black hole doesn't just swallow everything around it: it also slowly evaporates, like a chunk of ice in the sun. As the hole shrinks, the quantum fields around it start behaving unusually. In a new study, physicists traced how entanglement, a special kinship between particles that persists even when they are far apart, changes.

Two mailboxes at opposite ends of a city. Drop a letter in one, and an identical one instantly appears in the other. That's roughly how quantum entanglement works: two particles behave as a single unit, even when separated by a great distance. But until recently, this connection could only be maintained within a single room or across a lab bench.

Quantum entanglement is like an invisible web that connects particles even when they are far apart. In large systems (say, a piece of material) this web can either quickly weave through all the atoms or tangle into a knot and stay put. The first case is called quantum chaos, the second localization.

A spoon drops into a cup of hot coffee, and ripples spread across the surface. They show how quickly the disturbance moves away from the point of impact. In the quantum world, physicists look for similar 'ripples on water'—how information spreads along a chain of atoms.

When two atomic nuclei collide, the outcome depends on their energy and the angle at which the fragments fly apart. Typically, such calculations demand enormous computing power, and accuracy hits a wall due to approximations.

A broken guitar string doesn't just go silent. It still vibrates for a while, and by the character of that vibration, a luthier can tell what kind of string it was — thick or thin, tightly wound or loose. In much the same way, physicists listen to the "vibration" of quantum systems when they want to understand their structure.

Physicists have discovered exact laws by which quantum entanglement mixes in chaotic systems. In a model with rhythmic jolts — like a baker kneading dough — they studied the growth of entropy of entanglement, a measure of quantum disorder.

Hot tea normally takes longer to cool than warm tea, but water sometimes breaks this rule: back in the 1960s, schoolboy Erasto Mpemba noticed that hot ice cream freezes faster than cold. This paradox has moved into the quantum world: a collection of particles can settle down faster if it was initially more excited.

Imagine two particles that behave as if they share a telepathic link: measuring one instantly determines the state of the other — at any distance.

Liquid helium at ultra-low temperatures enters a state of superfluidity: it flows without friction, like a perfect lubricant.

A quantum walk is like a drunk person who turns randomly at every intersection. Except instead of streets, there are graph nodes, and instead of steps, there are quantum transitions. Scientists have discovered that such a walk has a hidden measure — Krylov complexity.

A light pulse can be sliced into short time bins, like a train into carriages. If two photons are born together and their carriages are tightly linked, the arrival of one in a specific bin guarantees that the other arrives in the paired bin, this connection is called time-bin entanglement.

The atomic nucleus is not just a bag of protons and neutrons. It is a quantum system where particles are bound by invisible threads of entanglement. When two protons or neutrons interact, their states become intertwined so that describing one without the other is impossible.

Hot water sometimes freezes faster than cold — this is the Mpemba effect. In the quantum world, it’s even more astonishing: a system bubbling with disorder (with high entropy) can settle incredibly faster than one that is almost calm. The solution lies in islands of silence within any system — regions untouched by the destructive noise of the environment.

Hundreds of cooks in a kitchen — total chaos. Usually disorder grows. In quantum physics, the measure of such disorder is called entropy John von Neumann. For a many-particle system, entropy typically increases with their number. But scientists have found an exception. The secret lies in a strict rule: two cooks cannot enter the same aisle at the same time.

Regular quantum communication is like a postal service that sends letters strictly one at a time. If the route is long, you have to wait an indecently long time for a reply. Physicists sped up the process by dispatching ten 'postal trucks' — light pulses — into a single optical fiber, but in different time windows.

In September 2024, the concert hall in Linz had more than just an orchestra on stage. Next to the musicians, a setup was generating pairs of entangled photons: a laser with a wavelength of 405 nm passed through a nonlinear crystal and split into two photons at 810 nm, which flew off to two measurement stations, Alice and Bob.

In 1989, John Wheeler proposed a bold idea: "it from bit," meaning everything that exists arises from information. For a long time, this remained a beautiful metaphor, but now physicists have found a concrete mechanism that turns bits into particles.

When light passes through biological tissue or frosted glass, it scatters and loses the image. Researchers at the Paris Institute of Nanosciences have shown that a scattering medium can be tuned to transmit images encoded in the correlations of entangled photons while remaining opaque to classical light.

In 1867, James Clerk Maxwell imagined a demon that sorts gas molecules and thereby violates the second law of thermodynamics. The demon needs to know the speeds of the particles. In the quantum world, a similar task arises: keep entanglement from growing like an avalanche, but you cannot observe the entire system.

In an empty concert hall, two musicians play a single part. First the violin, then the cello, or the other way around. It has always been this way: every note has its place in time, its own "earlier" and "later." But what if an orchestra could play both versions at once, in a quantum superposition of two orders?

Five superconducting qubits on a chip: the stage for a performance of quantum chaos. Four qubits form the system, and the fifth acts as the environment, introducing dissipation. After a short evolution, the environment is discarded, leaving the system with an open quantum map, an operator that transforms the system's state.

Inside a cryostat cooled to tens of millikelvins live superconducting qubits. There aren't many of them: tens, at most hundreds. Crosstalk and thermal noise prevent packing more. But cracking RSA-2048 requires anywhere from ten thousand to ten million physical qubits.

Two particles begin their dance in complete independence. Neither knows of the other's existence. But under the invisible music of deformed spacetime, their motions gradually synchronize: entanglement is born in the system—that very quantum connection Einstein called 'spooky action at a distance.' In the ordinary world, energies add up simply: take the energy of…

A wave rolls onto the sand, leaving a pattern of foam and shells. A moment later it recedes, but the traces are no longer the same: the sand is smoothed, the shells are flipped over. Something similar happens in the quantum world when a system moves from a nonequilibrium state toward equilibrium.