Quantum Physics quant-ph

A superconducting qubit, a tiny loop with zero resistance, crunches problems faster than you can blink. But cut the power, and everything it has calculated vanishes. Like a chef who cooks without writing down the recipe: as long as he's at the stove, he remembers every step, but an hour later — nothing. The authors of the study propose writing the result into diamond.

A woven basket holds its shape not because it has a rigid frame, but because each strand is interlaced with its neighbors. Pull one out, and the pattern unravels, leaving a heap of twigs. Quantum mechanics, according to a new paper, works the same way: its elementary objects do not exist independently, but only in interweaving with each other.

Hidden within the bulk of a diamond are tiny flaws — places where a carbon atom is replaced by nitrogen, with a vacancy gaping nearby. These defects, like beacons, can store and transmit quantum information. But around them rages a magnetic storm: the nuclei of atoms in the crystal jostle, creating interference.

A tiny diamond with defects, nitrogen atoms that replaced carbon, hides an unusual feature. Around each defect, an extra electron spins like a top that can be tilted by radio pulses. On its own, this top is too quiet to reach a superconducting qubit — an artificial atom operating at temperatures colder than outer space.

In 1982, physicist Richard Feynman proposed a simple idea: to understand a quantum system, you need to build another quantum system that behaves the same way. Thus was born the quantum simulator, a device that does not calculate equations but reproduces them in its own behavior.

In 1946, Felix Bloch predicted that even without an external magnetic field, a fluctuating magnetic moment exists in an ensemble of spins. It grows as the square root of the number of particles, and in small samples this noise can exceed thermal polarization.

In a dark room, a laser beam draws a bright spot on the wall. Light seems warm and uncontrollable, but for three decades physicists have used it as a conductor's baton, making atoms dance in unison.

A tuning fork sounds when you strike it. Its prongs vibrate, and you hear the sound until the vibration dies out. The quantum world has its own "tuning forks"—for example, a defect in diamond that responds to magnetic fields, and a carbon tube that can tremble at frequencies billions of times higher than the note A.

A stone falls into water, and ripples spread outward. In the quantum world, a magnetic impurity (that pebble) in a metal perturbs the surrounding electrons, and they form a special cloud around it. This is called the Kondo cloud. Like ripples on water in the dark, it long remained elusive.

A quantum computer is like an orchestra where every musician plays an invisible instrument. Instead of violins and trumpets, there are qubits — fragile particles that are easily knocked off beat by the slightest heat or noise.

Light strikes a metal plate, and electrons fly out. This is the photoelectric effect, and it works only if the light has enough energy to cross the threshold that holds electrons inside.

Inside a diamond, you sometimes find tiny flaws — a spot where a carbon atom is replaced by nitrogen, with a vacancy right next to it. Physicists call this an NV center (a nitrogen-vacancy defect). Such a defect acts like a magnetic needle that can store information in its spin.

A meteorologist stares at a pressure map, trying to figure out where the cyclone will go. They have a model, but it is flawed, and fresh measurements, but they are incomplete. Merging the two so that the forecast remains physically meaningful is harder than it seems: classical methods sometimes produce negative temperatures or impossible probabilities.

Quantum entanglement is like an invisible spring between particles — squeeze one, and the other twitches, no matter where it is. In the new work, physicists built a model of four spins (tiny magnetic arrows) in a chain, where the end spins are held by a local magnetic field.

In a chain of eight spins, a defect lurks — a tiny magnetic moment. The Kondo effect, known since the 1930s, makes electrons around it align into a collective screen. The material's resistance abnormally increases. But detecting such an impurity hidden deep in the structure is like finding a stone at the bottom of a dark pond.

In 2023, a group of researchers at Oak Ridge National Laboratory ran a simulation of a 61-qubit quantum circuit on the Theta supercomputer. Storing its state vector would have required 32 exabytes of memory, more than the total capacity of all hard drives on the planet. But thanks to data compression, they fit it into 768 terabytes.

A quantum battery is not a box of electrolyte but a handful of atoms or superconducting loops, with energy stored in excited states. It can be charged in fractions of a second using collective quantum effects.

Tuning a string: higher harmonics help hold the pitch without drowning out the fundamental note. In an optical microcavity, a tiny resonator made of two mirrors, light bounces between the reflective surfaces, and any jitter in the spacing knocks it off resonance.

A single quantum processor is like a solo musician. It can play a simple tune, but a symphony requires an orchestra. To solve problems that demand enormous computational power, processors must be networked.

A cloud of 41K87Rb molecules held in an optical trap expands like fog at dawn. Each molecule is a weakly bound pair of potassium and rubidium atoms, teetering on the brink of dissociation. Cooling such a cloud to near absolute zero without shattering the molecules has long been a challenge.

In the first moments after the Big Bang, space expanded at an incredible rate. A tiny quantum ripple, embedded in the uncertainty principle itself, pushed matter apart more strongly than any known force. This ripple is the generalized uncertainty principle, or GUP.

A quantum state under continuous measurement is not a frozen picture but a random dance. Each measurement outcome nudges the state one way or another, and to predict the future you have to track the entire trajectory.

A postal money order doesn't arrive instantly but after a set delay, and the amount credited to the recipient's account ends up larger than what the sender deposited in cash. That's roughly how the new protocol, dubbed temporal quantum energy teleportation (TQET), works. In ordinary quantum energy teleportation, two parties, Alice and Bob, share a common quantum state.

A quantum computer is an orchestra where every qubit must come in exactly on cue. But instead of a conductor with a baton, we have an arbitrary waveform generator (AWG) that delivers microwave signals lasting tens of nanoseconds.

Two actors on the same stage. One is a fermion, finicky and demanding, hard to make follow the rules of a quantum simulator. The other is a boson, easygoing and undemanding, ready to take any role. The director hopes the audience won't notice the substitution.

Imagine an orchestra where every musician plays an instrument that breaks at the slightest warmth. The conductor is the quantum processor, and the musicians are the qubits — fragile carriers of quantum information. To keep them in harmony, you need a whole team of tuners sitting in the next room, sending commands through a soundproof wall.

Every day, the power grid faces a puzzle: which power plants should be switched on to reliably meet demand without breaking the bank? For 15 generators and 24 hours, the number of possible schedules exceeds 2.3×$$10^{108}$$, more than the number of atoms in the visible universe. No classical supercomputer can sift through all of them, so dispatchers settle for a compromise.

A quantum computer is like an orchestra where strings and brass play in different languages. Superconducting processors operate with microwave photons in centimeter-scale circuits, while spin qubits, such as nitrogen-vacancy centers, store…

Niels Bohr insisted: you cannot simultaneously know which path a photon took and see interference. For a long time, this was considered a limitation of knowledge — we simply cannot obtain both types of information at once.

At the hilltop of classical physics, a particle is frozen in unstable equilibrium. The slightest nudge — and it rolls down with increasing speed. In the quantum universe, no nudge is needed: the uncertainty principle itself acts as an all-pervading wind, blowing the particle off the peak.

Among the fundamental symmetries of nature, mirror parity holds a special place. The Standard Model already knows one violation of it, in the weak interaction, but hypothetical long-range forces that don't conserve left and right could reveal a lot about dark matter.

A superconducting quantum processor is like a microscopic metropolis locked in a cryogenic fridge: streets of superconducting lines, blocks of qubits. Each resident demands silence and cold, but expanding the city inside a single cryostat is like stacking skyscrapers in a cramped courtyard — wires heat the environment, noise builds up, coherence threatens to collapse.

Quantum mechanics gave us a captivating image: a system’s state is not a frozen point but a wave of possibilities, dancing in an abstract space. Thanks to the work of Шрёдингера and Дирака, we represent it as vectors in Hilbert space.

A tiny tungsten tip with a radius of less than a hundred nanometers is the perfect stage for watching a quantum performance. Apply an electric field of a few volts per nanometer, and electrons start flying out of the metal: that’s field emission.

In the silent heart of creation, where particles converge and part, an act of pure harmony is born. Two Higgs bosons meet and for a fleeting moment form a single whole — and if one demands that their quantum entanglement always reaches its limit, like a tuning fork setting a perfect pitch, then the equations suddenly light up with a new symmetry.

Spontaneous emission, the very process that lights up lamps and stars, has long been considered a pesky noise in quantum physics. This cacophony of random photons ruthlessly destroys fragile quantum entanglement, like radio static drowning out a distant melody.

Detecting a single quantum emitter is like tuning a piano on a factory floor full of screaming machines: the pure tone drowns in noise. But the tuner doesn’t try to outshout the racket — he picks up a tuning fork and listens for beatings. That’s how even a barely audible echo becomes clear.

Strike a gong and the sound fades in layers: the low hum lingers longer, the high overtones vanish first, leaving silence behind. So too a qubit, living its quantum life, leaves not one but three echoes of its own past.

Picking up an ultraweak microwave signal is like trying to hear a whisper in a storm. Rydberg atoms, inflated to the size of bacteria, promise to become perfect antennas. But there's a fatal catch: during optical readout, up to 98% of messenger photons vanish without a trace in the detector.

In the eye of a migratory bird, a quantum drama quietly unfolds. The protein cryptochrome is its stage. Here, radical pairs are born: two molecules with unpaired electrons whose spins are entangled in a whimsical dance foreseen by John Stewart Bell.