42,772 articles
Quantum superdiffusion
Quantum superdiffusion is anomalous quantum transport where spin or charge spreads faster than ordinary diffusion but slower than ballistic motion, seen most clearly in Heisenberg spin chains.
Quantum superposition
Quantum superposition, also known as superposition of states or quantum linear superposition, is the principle that a physical system can exist in a combination of two states, producing interference.
Quantum support vector machine
A quantum support vector machine (QSVM) is a quantum-computing version of the support vector machine, a supervised learning model, with part of training or prediction run on a quantum processor.
Quantum supremacy
Quantum supremacy, also called quantum advantage, is when a quantum computer performs a task no classical computer can in feasible time, a term coined in 2012.
Quantum switch
The quantum switch is a quantum process in which two operations act in a superposition of their two possible orders, with no definite causal order between them.
Quantum teleportation
Quantum teleportation is a protocol that transfers an unknown quantum state to a distant receiver using shared entanglement and two classical bits, proposed in 1993 and first demonstrated in 1997.
Quantum theory of atoms in molecules
The quantum theory of atoms in molecules (QTAIM) is a quantum chemistry method, developed by Richard Bader, that analyzes electron density to characterize bonding, atomic properties, and molecular structure.
Quantum thermodynamics
Quantum thermodynamics extends thermodynamics to systems small enough that fluctuations, coherence, and correlations matter, redefining work and heat and asking whether quantum effects improve heat engines.
Quantum thermometry
Quantum thermometry is the measurement of temperature using quantum probes like mesoscopic circuits and diamond NV centers, together with the theory of the precision limits such thermometers can reach.
Quantum trace
The quantum trace is a categorical generalization of the trace of a linear map, defined in ribbon categories and used to build knot invariants from braid representations.
Quantum trajectory theory
Quantum trajectory theory describes how a continuously measured open quantum system follows a random state path, whose average recovers the Lindblad master equation; introduced in the early 1990s.
Quantum transducer
A quantum transducer is a device that converts quantum signals between microwave and optical photons while preserving their quantum state, enabling superconducting quantum computers to be networked over optical fiber.
Quantum tunnelling
Quantum tunnelling, also called barrier penetration, is the quantum-mechanical phenomenon in which a particle passes through an energy barrier that classical mechanics forbids, explained by the wavefunction's exponential decay.
Quantum tunnelling regime of plasmonics
The quantum tunnelling regime of plasmonics covers metal nanogaps below about one nanometre, where electrons tunnel between the metals and replace red-shifting gap plasmons with blue-shifting charge-transfer plasmons.
Quantum turbulence
Quantum turbulence, also known as superfluid turbulence, is the turbulent motion of quantum fluids such as superfluid helium, where rotation is carried by quantized vortex lines.
Quantum Turing machine
The quantum Turing machine, also called the universal quantum computer, is a mathematical model of computation generalizing the classical Turing machine, formalized by David Deutsch in 1985.
Quantum twisting microscope
The quantum twisting microscope (QTM) is a scanning probe instrument that resolves electrons in momentum space by scanning the twist angle of an atomically thin tip, demonstrated at the Weizmann Institute in 2023.
Quantum utility
Quantum utility is a quantum computing term, popularized by IBM in 2023, for reliable quantum computation at a scale beyond brute-force classical simulation, weaker than quantum advantage.
Quantum vacuum state
The quantum vacuum state, also called the zero-point field, is the ground state of a quantum field: it holds no particles, yet its fluctuations produce measurable effects like the Casimir force.
Quantum valley Hall effect in silicene
The quantum valley Hall effect in silicene is a predicted transport phenomenon in which electrons of opposite valley index flow to opposite edges of a buckled, one-atom-thick silicon sheet.
Quantum volume
Quantum volume (QV) is a single-number benchmark for quantum computers, introduced by IBM in a 2019 paper. It is the largest square random circuit a machine can run reliably.
Quantum vortex
A quantum vortex, also called a quantized vortex, is a line defect in a superfluid whose circulation is quantized; rotating superfluids form lattices of them.
Quantum walk with single photons
A quantum walk with single photons is an experiment in which a single photon performs a discrete-time quantum walk, its polarization acting as the quantum coin.
Quantum well
A quantum well is a semiconductor layer a few nanometers thick between wider-bandgap barriers, confining electrons to two dimensions with quantized energy levels, used in quantum well lasers.
Quantum well laser
A quantum well laser is a semiconductor diode laser with an active layer only a few nanometers thick, giving lower threshold current and narrower emission.
Quantum wire
A quantum wire is a narrow semiconductor conductor, typically under 100 nm wide, where electrons are confined in two directions and move freely only along its length.
Quantum Yang–Baxter equation
The quantum Yang–Baxter equation is a cubic operator equation, R₁₂R₁₃R₂₃ = R₂₃R₁₃R₁₂, introduced by C. N. Yang and R. J. Baxter in 1967 and central to quantum integrable systems.
Quantum yield
Quantum yield (Φ) is a measure of the efficiency of a photochemical or photophysical process, the number of molecules changed or photons emitted per photon absorbed, and can exceed 1 in chain reactions.
Quantum Zeno effect
The quantum Zeno effect is the inhibition of transitions between quantum states by frequent measurement, first demonstrated theoretically in 1977 by Misra and Sudarshan; its converse, the anti-Zeno effect, accelerates decay.
Quantum-confined Stark effect
The quantum-confined Stark effect (QCSE) is the shift and weakening of exciton absorption in a quantum well under an applied electric field, named in 1984.