attosecond laser

Tuning a string to the right note: the laser pulse is adjusted so that harmonics play in unison at kiloelectronvolt frequencies. Visible light oscillates at hundreds of trillions of times per second.

A blacksmith pumps the bellows, and a slow stream of air turns into a sharp jet that can ignite a flame. Physicists treat light much the same way: they take a long laser pulse and squeeze it into a short, powerful flash.

When a laser beam hits a gas, it tears electrons from atoms and accelerates them to nearly the speed of light. As these electrons fly through the plasma, they emit X-rays, like a glowing trail from a fast particle. In the new work, physicists made a single laser pulse create not one but two such trails in succession.

A shooter aims at a target, pulls the trigger, and hears two shots: one loud, one quiet. That's how the new setup works, except instead of bullets, there's an electron bunch, and instead of shots, there are two flashes of light. One flash is X-ray, the other is terahertz. They fly to the same point with perfect timing.

Two electrons that leave a metal needle tip almost simultaneously start to repel each other, like two people trying to squeeze through a narrow door at the same time. The closer they are, the more they get in each other's way.

A superconducting qubit is like a finicky musical instrument: until you tune it, you won't get a clean note. But even after tuning, the pitch drifts. The culprits are tiny defects in the material that physicists call two-level systems. They're like invisible cracks that appear and disappear, throwing off the processor's rhythm.

In the silent ocean of the Galaxy, mature civilizations have likely long chosen an unexpected strategy: instead of loud beacons, they scatter quiet fireflies — autonomous interstellar laser beacons, drifting in the void and dropping microsecond flashes. These 'seeds of contact' are not tied to their home stars and do not drown in their glow.

Light waves are never perfectly smooth — they are constantly jittered by quantum ripples. These almost invisible nudges were studied by Nobel laureate Roy Glauber, who laid the foundations of quantum optics. Now physicists have learned to freeze these ripples.

3I/ATLAS burst into the Solar System like an uninvited guest, a gift of fate for hunters of extraterrestrial intelligence. This comet-like wanderer from the depths of the Galaxy flew close enough to be heard in all its details — unlike distant exoplanets.

A charged particle streaks through a silicon sensor, leaving behind a trail of free electrons. The time it takes for this charge to be collected at the electrode depends on how deep in the crystal it was born. A particle entering head-on carves identical paths through neighboring pixels: their signals arrive almost simultaneously.

Neutron stars are the ultra-dense remnants of stars, where matter is compressed to the limit described by Subrahmanyan Chandrasekhar. Magnetars are a type of neutron star with a magnetic field a quadrillion times stronger than Earth's.

In a benzene molecule, electrons buzz around the nuclei like a swarm of bees around a hive. But this swarm doesn't just hum: it pulses: every 856 attoseconds, the electron cloud completes a full oscillation cycle. The hive itself, the carbon nuclei, rocks more slowly, with a period of 36 femtoseconds.

Usually, isotopes are separated by exploiting the difference in nuclear weight. That difference is tiny, like sorting grains of sand that differ by one hundredth of a millimeter. The new method ignores weight and instead looks at the nucleus's rotation: its spin. The laser hits the molecules twice with a short pause in between.

A laser hits a target of thin wires, and within tens of femtoseconds (billionths of a billionth of a second) knocks out a stream of protons. These protons fly into a converter made of lithium and deuterium, where neutrons are born.

An ordinary camera flash lasts thousandths of a second. An attosecond pulse is a trillion times shorter — in the time it takes, light travels a distance smaller than the size of an atom. Such flashes act as an ultra-high-speed shutter: they freeze the motion of electrons, letting us see them jump between orbitals or take part in a chemical reaction.

An ordinary camera flash lingers for hundredths of a second, but for atoms, that's an eternity. Inside molecules, electrons jump in attoseconds: billionths of a billionth of a second. To capture that, you need a light pulse shorter than the event itself. Physicists take an electron beam in a linear accelerator and compress it so that individual bunches become thinner than a hair — in time.

Light can carry information faster than any electronics. But usually, between a computer and a laser sits a digital-to-analog converter — a device that turns zeros and ones into electrical signals. It's the bottleneck. The new transmitter does away with this middleman.

An electron in an atom is like a tennis player waiting for a serve. The light flash is the ball, moving at a speed the eye can't follow. The new device catches the moment the racket meets the ball with a precision previously unimagined. The setup uses two laser beams: one strikes the atom, the other acts as a stopwatch.

A laser flash lasting 50 femtoseconds is like a shot that lasts one billionth of a second. In that time, light travels only 15 micrometers — less than the thickness of a human hair. But if you send such a flash through an amplifier, it starts to stretch like a rubber band and loses its sharpness.

When light knocks an electron out of an atom, it flies off like a ball thrown into a crowd. Scientists have long wanted to know the exact moment each electron leaves the atom, but direct measurement disturbed the very process. Now physicists have proposed a method that uses a second light pulse to 'photograph' the moment of the electron's birth.

Light is not just a beam but a wave with an electric field that changes at a speed unimaginable to ordinary clocks. Until now, this field could only be measured at a single point, like taking temperature with a single thermometer. Now researchers have created a method that shows the entire field at once, like a thermal imager showing a heat map.

A chef tastes the soup after every pinch of salt and instantly decides what to add next. That's roughly how the new setup for growing thin crystalline films works — except instead of taste, it uses an image from an electron microscope, and instead of a chef, a computer program.

A laser pulse racing through plasma is like a runner carving a path through a crowd. It shoves electrons aside, leaving behind a rarefied channel, just as the crowd parts for a sprinter. In this channel, the crest of the light wave moves slightly faster than light in a vacuum, and it is this speed that determines how efficiently the pulse transfers energy to particles.

Ultraviolet light with a wavelength of about 300 nanometers is invisible to the eye, but it can destroy the DNA of microbes, make certain substances glow, and carry information. Until now, lasers in this range were bulky, expensive, or short-lived.

A short laser pulse strikes the air, and a tiny lightning bolt flashes at the point of impact. It lives longer than you'd think: the bright glow is visible for half a millisecond, and a faint one for nearly twenty milliseconds.

An ordinary camera flash lasts a thousandth of a second. The new setup at the ELI ALPS laboratory in Hungary produces flashes a billion times shorter. Each flash consists of a few hundred oscillations of the light wave, packed into a time interval in which light travels a distance smaller than the thickness of a human hair.

Ordinary light always jitters a bit: its brightness and color fluctuate, like the air in a balloon after a tap. In 'squeezed' light, these fluctuations are redistributed — as if you squeeze the balloon from one side, making it thinner here and thicker there, but the total volume stays the same.

A firefly blinks for one ten-billionth of a second somewhere above the Siberian taiga. Seeing such a thing is impossible, but the TAIGA-HiSCORE array, spread across a valley in the Tunkinsky district of Buryatia, tried to catch exactly such flashes — not from insects, but from the depths of space.