All articles starting with Q
2,252 articles
Quantum error correction
Quantum error correction, also known as quantum code, protects quantum information by encoding logical qubits across many physical qubits so errors can be fixed without destroying data.
Quantum error correction with GKP bosonic qubits
Quantum error correction with GKP bosonic qubits encodes a logical qubit in one oscillator's grid states, per the 2001 Gottesman–Kitaev–Preskill code, correcting small displacement errors.
Quantum error detection
Quantum error detection is a cheaper alternative to full quantum error correction that flags errors without fixing them, discarding failed runs; it works only where post-selection is available.
Quantum error mitigation
Quantum error mitigation (QEM) is a set of methods that reduce noise in quantum computers by classically post-processing noisy measurements, used on near-term NISQ devices lacking error correction resources.
Quantum ESPRESSO
Quantum ESPRESSO, whose core package is PWscf, is an open-source suite of codes for electronic-structure calculations and materials modeling, based on density-functional theory, plane waves, and pseudopotentials.
Quantum extremal surface
A quantum extremal surface is a codimension-two surface in a gravitational spacetime at which the generalized entropy is stationary, introduced by Netta Engelhardt and Aron C. Wall in 2014.
Quantum federated learning
Quantum federated learning is a distributed machine learning method, proposed in 2021, in which clients train quantum models locally and a server aggregates parameter updates into a global model.
Quantum feedback
Quantum feedback is the control of a quantum system using a measurement record or engineered coherent feedback, with measurement back-action included, enabling qubit stabilization and error correction.
Quantum field theory
Quantum field theory (QFT) is the framework describing particles as excitations of fields defined at every point of spacetime, and the basis of the Standard Model of particle physics.
Quantum field theory in curved spacetime
Quantum field theory in curved spacetime (QFTCS) studies quantum fields on a fixed classical curved geometry, explaining Hawking radiation and the Unruh effect in black holes and the early universe.
Quantum finite automaton
A quantum finite automaton, also called a quantum finite state machine, is a theoretical computation model whose state is a quantum superposition, introduced in 1997.
Quantum Fisher information
Quantum Fisher information (QFI) is a quantity in quantum estimation theory that measures how much information a quantum state carries about an unknown parameter, such as a phase or magnetic field.
Quantum Fisher information as an entanglement witness
Quantum Fisher information as an entanglement witness is a diagnostic in which the quantum Fisher information, a quantity from quantum metrology, certifies multipartite entanglement in quantum many-body systems.
Quantum Flagship
The Quantum Flagship, launched by the EU in 2018 after the 2016 Quantum Manifesto, is a €1 billion, 10-year initiative funding quantum computing, communication, simulation, and sensing research.
Quantum fluctuation
A quantum fluctuation, also called a vacuum fluctuation, is the random variation in a physical quantity that arises from quantum mechanics even in a system's lowest-energy state.
Quantum foam
Quantum foam, also called spacetime foam, is the hypothesized picture of spacetime at very small scales, where quantum fluctuations make geometry vary wildly like a froth of bubbles.
Quantum formal languages and grammars
Quantum formal languages are sets of strings described by quantum devices with amplitude-weighted rules; quantum context-free languages strictly extend classical context-free languages, and bounded-error one-way quantum automata recognize only some regular languages.
Quantum foundations
Quantum foundations is the research field asking what quantum theory says about reality, centered on the measurement problem and including hidden variables, collapse theories, and many-worlds.
Quantum Fourier transform
The quantum Fourier transform (QFT) is a quantum algorithm applying the discrete Fourier transform to a quantum state's amplitudes, used in Shor's algorithm and phase estimation.
Quantum frequency conversion
Quantum frequency conversion shifts single photons from one optical frequency to another while preserving their quantum state, letting quantum memories interface with low-loss telecom fiber networks.
Quantum friction
Quantum friction, also called Casimir friction or vacuum friction, is a predicted contactless drag force between bodies in relative motion, mediated by quantum electromagnetic vacuum fluctuations.
Quantum gas microscope
A quantum gas microscope is an apparatus that images ultracold atoms in an optical lattice with single-atom, single-site resolution, first built at Harvard University and reported in 2009.
Quantum gate teleportation
Quantum gate teleportation is a quantum computing technique that applies a gate by teleporting data through an entangled resource state, proposed by Gottesman and Chuang in 1999.
Quantum generative adversarial network
A quantum generative adversarial network (QGAN, also QuGAN) is a generative adversarial network with quantum components, introduced by Seth Lloyd and Christian Weedbrook in 2018.
Quantum genetic algorithm
A quantum genetic algorithm is an evolutionary optimization method that encodes candidate solutions as quantum-inspired probabilistic bits, updated by rotation gates, and runs on ordinary classical computers.
Quantum geometry in loop quantum gravity
Quantum geometry in loop quantum gravity is the body of results showing that area and volume operators have discrete spectra, so Planck-scale space is built from quanta.
Quantum graph
A quantum graph is a graph whose edges are one-dimensional intervals carrying a self-adjoint differential operator, combining graph theory with spectral theory to model waves in mesoscale systems.
Quantum gravimeter
A quantum gravimeter is an instrument measuring absolute gravitational acceleration through interferometry on freely falling, laser-cooled atoms, combining absolute measurement, continuous operation, and zero drift; first demonstrated at Stanford in 1991.
Quantum gravimetry
Quantum gravimetry is the measurement of gravity using atom-interferometric gravimeters, where laser-cooled falling atoms act as the test mass, first demonstrated by Kasevich and Chu in 1991.
Quantum gravity
Quantum gravity, also known as quantum gravitation, is the sought-for theory unifying quantum mechanics and general relativity, with string theory and loop quantum gravity its leading approaches.