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Quaternary Ice Age divisions
The Quaternary Ice Age divisions are the glacial and interglacial subdivisions of the Pleistocene, classically the four Alpine ice ages Günz, Mindel, Riss, and Würm.
Quaternion
Quaternions, also called Hamiltonian quaternions, are four-dimensional numbers discovered by William Rowan Hamilton in Dublin in 1843, now the standard way to represent 3D rotations without gimbal lock.
Quaternion group
The quaternion group Q8 is the eight-element nonabelian group of unit quaternions, one of the two nonabelian groups of order 8, alongside the dihedral group D4.
Quaternions and spatial rotation
Quaternions and spatial rotation is the use of quaternions, four-dimensional numbers invented by William Rowan Hamilton in 1843, to represent rotations of objects in three-dimensional space.
QUBIC
QUBIC, the Q&U Bolometric Interferometer for Cosmology, is a ground-based experiment measuring CMB polarization to detect B-modes from inflationary gravitational waves, observing from about 4,900 meters in Salta, Argentina.
Qubit
A qubit, or quantum bit, is the basic unit of quantum information: a two-level quantum system that, unlike a classical bit, can exist in a superposition of states.
Qubit reset
Qubit reset is a quantum computing operation that returns a qubit to a known state, typically |0⟩, discarding prior superposition or entanglement, enabling qubit reuse and active error correction.
Qubitization and quantum signal processing
Qubitization and quantum signal processing are linked quantum computing techniques, developed by Guang Hao Low and Isaac Chuang, that evaluate functions of a Hamiltonian with optimal query complexity.
Qudit and continuous-variable entanglement
Qudit and continuous-variable entanglement extends quantum entanglement beyond two-level qubits. Qudits use d levels, continuous-variable systems use observables like light's quadratures, and both can carry more entanglement than qubits.
Qudit error correction
Qudit error correction protects quantum information stored in qudits, quantum systems with more than two levels, aiming to reduce the physical components needed for fault-tolerant quantum computing.
QuEChERS
QuEChERS, short for quick, easy, cheap, effective, rugged, and safe, is an analytical chemistry method extracting pesticide residues from food using acetonitrile and salt, followed by cleanup.
Quenched disorder
Quenched disorder is randomness in a physical system, such as random impurities or fields, that is frozen in place on observation time scales, contrasting with annealed disorder.
Quenching of the axial-vector coupling
Quenching of the axial-vector coupling is the empirical reduction of the weak coupling gA below its free value 1.27 needed to reproduce Gamow-Teller beta-decay rates in nuclei.
Quentin Williams
Quentin Williams is a Distinguished Professor of Earth and Planetary Sciences at UC Santa Cruz who studies the behavior of minerals, melts, and fluids at high pressure in planetary interiors.
Quest Carbon Capture and Storage
Quest Carbon Capture and Storage is a facility at Shell's Scotford Upgrader near Fort Saskatchewan, Alberta, capturing carbon dioxide from hydrogen production and storing it underground since 2015.
Quest Carbon Capture and Storage facility
The Quest Carbon Capture and Storage facility, operating since 2015 at Shell's Scotford upgrader near Edmonton, Alberta, captures CO2 from hydrogen production and stores it about 2 kilometers underground.
Questacon
Questacon, also known as the National Science and Technology Centre, is Australia's national hands-on science center in Canberra, opened as a Bicentennial project in 1988.
Questionnaire design
Questionnaire design is the social-science method of constructing written survey instruments that measure attitudes, behaviors, and characteristics, where wording, format, and question order affect measurement error.
Quetrupillan
Quetrupillan (Complejo Volcanico Quetrupillan) is a 2,360 m glacier-covered stratovolcano in Chile's Southern Volcanic Zone, between Villarrica and Lanin, with Holocene trachyte flank vents, last confirmed eruption 255 CE, in Villarrica National Park.
Quetta
Quetta (symbol Q) is the largest SI metric prefix, denoting 10^30, adopted by the CGPM in November 2022, largely for data science uses such as the quettabyte.
Queueing theory
Queueing theory, also known as teletraffic queuing theory, is the mathematical study of waiting lines, begun by Agner Krarup Erlang's 1909 work on telephone traffic in Copenhagen.
Quickest change detection
Quickest change detection (QCD) is the sequential statistical problem of detecting an abrupt change in a data stream's distribution as soon as possible, balancing detection delay against a false alarm budget.
Quicksand
Quicksand, also known as sinking sand, is sand saturated with water so that it flows like a liquid; people sink only to about the waist.
Quiescent black hole
A quiescent black hole, also called a dormant black hole, is a stellar-mass black hole that emits no detectable X-rays, found instead through its companion star's motion.
Quiescent H-mode
Quiescent H-mode (QH-mode) is a stationary, high-confinement tokamak plasma regime that achieves H-mode performance without damaging edge localized modes, first observed on the DIII-D tokamak in 1999.
QUIJOTE CMB experiment
QUIJOTE (Q-U-I JOint TEnerife) is a ground-based polarimeter at the Teide Observatory in Tenerife, Spain, measuring cosmic microwave background polarization at 10–42 GHz since 2012.
QuikSCAT
QuikSCAT (Quick Scatterometer) was a NASA satellite carrying the SeaWinds scatterometer, which measured ocean surface winds from its launch in 1999 until an antenna failure in 2009.
Quimsachata-Oroscocha
Quimsachata-Oroscocha is a pair of monogenetic volcanoes in the Cusco Region of southern Peru; Quimsachata erupted about 11,500 years ago and Oroscocha about 6,400 years ago.
Quinacrine
Quinacrine, also known as mepacrine and sold as Atabrine, is a yellow acridine-derivative drug that was the principal synthetic antimalarial of World War II and now treats giardiasis.
Quinapril
Quinapril, originally marketed as Accupril, is an ACE inhibitor prodrug converted in the body to its active form quinaprilat, used to treat high blood pressure and, as adjunctive therapy, heart failure.