quantum sensing

Quantum systems made of many particles are the basis of future computers and secure networks. But the more particles there are, the harder it is to understand how they are arranged: the number of possible states grows like an avalanche. The usual approach, measuring everything, takes an incredibly long time.

A superconducting quantum interferometer is a device that senses magnetic fields billions of times weaker than the needle of an ordinary compass. Inside it, there is a narrow bridge where superconductivity briefly breaks.

A handful of coins drops onto a table — heads and tails land wherever they please. The same goes for an instantaneous snapshot of a quantum chain: in some places a particle is present, in others it is not. But behind the disorder lurks a precise angle. In this work, a chain of particles closed into a ring was considered. It was divided into four arcs: two were measured, two were left untouched.

An electron beam is a stream of tiny particles carrying an electric charge. When such a beam hits a material, it doesn't just heat it or knock out atoms: it also gives the surface a slight push, like a jet of water pushing against your palm.

A short flash of light is like a musical phrase: you can distinguish individual notes if you listen very carefully. But in the quantum world, these 'notes'—temporal modes — are squeezed down to picoseconds, and ordinary optics can barely tell them apart.

Imagine a huge puzzle where each piece is a quantum particle. To complete the picture, you don't just fit the pieces together: you need to entangle them in a special way. Usually, this is done by carefully applying operations one after another, like assembling the puzzle strictly by the instructions, row by row.

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.

Radiation therapy is a precision strike on a tumor, but every shot must be calibrated to within a millimeter and a fraction of a second. The problem is that existing dosimeters are either bulky, or they distort the beam themselves, or they require pauses for readout.

Imagine an orchestra where every musician is a tiny magnetic sensor inside a diamond. To play cleanly, they need silence: no extra vibrations, no background noise. But when creating such orchestras, thin diamond films with nitrogen defects, dissonance bursts into the material. An international team of physicists studied how this disorder arises.

In a dark room, a whisper is barely audible. To make out the words, you need to get close, or set up many sensitive microphones. That's roughly the reasoning behind the new work: the authors place quantum "ears" right inside a resonator, where a high-frequency gravitational wave turns into an electromagnetic echo.

An empty resonator isn't truly empty. Even in an absolute vacuum, where not a single photon exists, quantum fluctuations persist. They resemble ripples on water in a dead calm: the surface appears smooth, but molecules keep jittering. Physicists have learned to turn this jitter into real waves.

Gravity in our world is curved spacetime. That's how Einstein's general theory of relativity describes it. But what happens to gravity at the level of atoms and particles, where quantum mechanics rules? This question has remained unanswered for nearly a century.

A delicate watermark on wet paper, and a fogged-up glass before your eyes. That's roughly what reading quantum states of light looks like: fragile photon patterns get distorted by losses, and detectors catch only a small fraction of the signal.

A tiny magnetized sphere floats in a vacuum, held by invisible fields. It starts to spin around the axis of the magnetic field, just like a top that's been given a gentle nudge. That's precession. But when the sphere becomes really small, quantum laws come into play.

A bee-sized quadcopter autonomously charts its route indoors, like a space probe through an asteroid field. Its camera works as a photometry instrument, capturing reflected light, while the processor decides where to turn at the speed of light.

The quantum many-body world is a jazz ensemble, where each electron improvises, continuously listening to all the others, and the overall wave function is born from this tense dialogue.

A spotlight blazes straight into your eyes, and a few steps away a tiny firefly flickers. That's roughly what it's like hunting for an Earth-like planet around a neighboring star: the planet is a hundred million to ten billion times fainter than its star, and in the sky they almost merge into a single point.

A quantum computer is like an orchestra without a conductor: each qubit is a musician, and the slightest slip throws off the entire symphony. To keep the music from turning into cacophony, quantum error-correcting codes were invented.

A living cell constantly emits faint magnetic signals, as if whispering. Scientists eavesdrop on this whisper with two microscopic 'microphones'—magnetic field sensors.

A cook spends years honing the skill of reducing a recipe to three or four essentials and recreating the dish from them. If the ingredients are familiar, the expected meal lands on the plate. A foreign ingredient disrupts compression, and you get something unrecognizable. The Quantum Compressor does the same with medical scans.

When a building collapses, steel rebar turns into a chaotic magnetic compass. Entropy, a measure of disorder, increases, but it's this very disorder that points to voids where people might be.

Dark matter leaves no trace in ordinary detectors: it passes through them like wind through gauze. To spot it, you need instruments that can feel a mosquito's punch in a storm. Quantum sensors with a threshold of a fraction of an electronvolt (a thousand times less than the energy of visible light) are just that.

Two pendulums hang from the same crossbar. A push, and they start swinging, gradually falling into and out of sync. In a topological qubit, Majorana particles, special excitations that can store quantum information, play the role of these pendulums.

Toss a handful of phosphorus into silicon, and at a certain impurity concentration the material suddenly starts conducting electricity. This is a metal-insulator phase transition, and it happens abruptly. But what exactly changes in the electron wave functions when an insulator becomes a metal?

A tiny defect in a boron nitride crystal behaves like a microscopic indicator bulb. Shine light on it, and it glows, with the shade shifting with temperature: the warmer it gets, the redder the glow.

Gravitational-wave observatories are like a keen ear listening for distant rumbles of cosmic catastrophes. To catch the faint whisper of merging black holes, detectors of gravitational waves use specially prepared light — known as squeezed vacuum.

A thrown stone follows a smooth arc: its path is easy to predict. But if the stone skips across water, the trajectory becomes jagged and far more interesting. Quantum particles behave much the same way when their state is not a calm wave with fixed energy but a turbulent mix of several waves at once.

A boiling kettle with the lid on doesn’t show the bubbling, but the sound and vibration betray the intensity of the water boiling.

A quantum cat is a special state of light, the idea of which was proposed by Erwin Schrödinger in his famous thought experiment.

Any measuring device is spoiled by quantum noise — the chaotic jitters of elementary particles. To tame it, physicists used a trick on calcium fluoride molecules, much like squeezing a balloon: press in one spot, and it bulges in another.

You're pouring water into a glass, but you want exactly one million drops — not approximately, but exactly. An ordinary faucet pours a stream where the number of drops always varies. In the quantum world, photons have the same problem: a laser emits light where the number of particles fluctuates like a crowd in a square.

Imagine a library where instead of books, you have every conceivable combination of a few dozen quantum particles. The number of combinations grows like a snowball: add one particle, and the volume doubles. For fifty particles, there are more shelves than atoms in the visible universe.

The familiar metronomes placed on a movable platform eventually start to swing in sync. In the quantum world, this trick long eluded scientists. But now physicists have synchronized even the most exotic state — a Fock state, where the number of light particles is precisely defined, like in a counter.

A levitating dust grain in an optical trap is an ideal pendulum for measuring gravity. It hangs in vacuum, never touching the walls, and its motion depends only on external forces. The new work proposes an improved sensor: a mechanical 'squeezed' qubit based on a nonlinear oscillator.

Physicists have proposed an experiment: a laser beam acts as a quantum detector and splits into two beam-ears. Each ear is directed through a tiny cloud of ultracold atoms — in this state, atoms merge into a single wave.

In 1948, engineer Claude Shannon laid the foundations of information theory. The Nyquist–Shannon theorem gave the first answer: to avoid losing a signal, you need at least twice as many measurements as the fastest feature in the signal. In 2006, the method of compressed sensing relaxed this requirement.

Ordinary batteries lose charge like tea cools down. A quantum battery works differently: its heart is a tiny cavity with darting photons. If you illuminate it with special photon pairs, energy flows into a chain of qubit cells instantaneously — much like a swing gets a boost from strong pushes.

Dark matter has eluded direct observation so far, even though its gravity holds galaxies together. One hypothesis: it’s made of axions — ultra-light particles predicted by theory.

Four tiny puddles, and in them ripple droplets of a superfluid. These droplets are atoms cooled to near absolute zero and paired up like little magnets. When the whole setup rotates, the fluid flows between the puddles. Simply counting how many droplets end up in each reveals the angle and angular velocity.

An ordinary battery in a phone stores energy in chemical bonds — slowly, with heat and wear. A quantum capacitor works differently: it charges not with matter but with rhythm. A swing that is pushed in time with its motion accumulates energy in the motion itself, without friction.