All articles starting with Q

Quantum logic

Quantum logic is the non-distributive propositional structure of quantum mechanics, proposed by Birkhoff and von Neumann in 1936, where propositions are closed subspaces of a Hilbert space.

Quantum logic clock

A quantum logic clock is an optical atomic clock whose reference is a single aluminum ion, read out through a co-trapped partner ion; NIST's version holds accuracy records.

Quantum logic gate

A quantum logic gate, or quantum gate, is a reversible unitary operation applied to one or more qubits, unlike irreversible classical gates such as AND.

Quantum logic spectroscopy

Quantum logic spectroscopy uses a co-trapped helper ion to cool, prepare, and read out atomic or molecular ions that cannot be directly laser-cooled or detected.

Quantum logic spectroscopy of molecular ions

Quantum logic spectroscopy of molecular ions is a technique that probes a single trapped molecular ion through a co-trapped atomic "logic" ion, proposed at NIST around 2001.

Quantum low-density parity-check code

A quantum low-density parity-check (qLDPC) code is a quantum stabilizer code with sparse checks, allowing fault-tolerant computing with fewer physical qubits than the surface code.

Quantum machine learning, also called quantum artificial intelligence, studies whether quantum computers can run machine learning faster than classical computers, and learning applied to quantum data.

Quantum Machines

Quantum Machines is an Israeli quantum computing company founded in 2018 by Itamar Sivan, Yonatan Cohen, and Nissim Ofek, building control hardware and software for quantum processors.

Quantum magnetometry

Quantum magnetometry measures magnetic fields with sensors that depend on quantum phenomena, chiefly atomic-vapor magnetometers, SQUIDs, and diamond NV centers, reaching sensitivities classical sensors cannot.

Quantum magnonics

Quantum magnonics is a research field dedicated to controlling and reading out magnons, quanta of collective spin excitations in magnetic materials, aiming to advance quantum information science and sensing.

Quantum many-body scarring

Quantum many-body scarring is a form of weak ergodicity breaking in which non-thermal eigenstates embedded in a thermalizing spectrum produce long-lived revivals, discovered in 51-atom Rydberg simulators in 2017.

Quantum many-body scarring in Rydberg atom arrays

Quantum many-body scarring in Rydberg atom arrays is the presence of non-ergodic scar states, embedded in an otherwise thermalizing spectrum, that yield coherent revivals, first observed in Bernien and colleagues' 51-atom 2017 experiment.

Quantum master equation

A quantum master equation is an evolution equation for the reduced density matrix of an open quantum system, describing non-unitary dynamics under dissipation and decoherence.

Quantum matrix operations and trace estimation

Quantum matrix operations are subroutines that multiply, power, invert, or apply functions to matrices and estimate traces like Tr(e^A), serving as building blocks for larger quantum algorithms.

Quantum mechanics

Quantum mechanics, also called quantum physics, is the branch of physics describing matter and light at the atomic scale, where objects show both particle and wave behavior.

Quantum memory

A quantum memory is a device that stores the quantum state of a photon or other qubit and releases it on demand with high fidelity, enabling quantum repeaters that extend entanglement over long distances.

Quantum memory for light

A quantum memory for light is a device that stores the quantum state of a photon in an atomic ensemble and retrieves it later without destroying the quantum information.

Quantum meruit

Quantum meruit, Latin for "as much as one has deserved," is a legal doctrine allowing recovery of the reasonable value of services when no contract sets a price.

Quantum metamaterials

A quantum metamaterial is an engineered structure whose optical properties are governed by the quantum coherent state of its artificial atoms, such as superconducting qubits.

Quantum metasurface

A quantum metasurface is an ultrathin planar array of subwavelength nanostructures engineered to generate, manipulate, and detect non-classical light, including single photons and entangled photon pairs.

Quantum metric

The quantum metric is a Riemannian metric on the space of quantum states, measuring the distance between nearby states, and forms the real part of the quantum geometric tensor.

Quantum metrology

Quantum metrology uses superposition and entanglement to estimate physical parameters with precision beyond classical limits, finding use in atomic clocks, magnetic sensing, and gravitational-wave detection.

Quantum microscopy

Quantum microscopy is a class of imaging techniques using nonclassical light, such as squeezed light and entangled photons, or quantum sensors, to improve microscope sensitivity and resolution.

Quantum mind

Quantum mind, or quantum brain, is a contested theory suggesting consciousness relies on quantum processes, like the Orch OR proposal by Hameroff and Penrose in the mid-1990s.

Quantum Monte Carlo

Quantum Monte Carlo (QMC) is a family of computational methods that use random sampling to solve the quantum many-body Schrödinger equation, valued for accuracy in electron correlation and energy predictions.

Quantum Motion Technologies

Quantum Motion Technologies is a London quantum computing company founded in 2017 as a UCL and Oxford spin-out, building silicon transistor spin qubits with CMOS fabrication.

Quantum Mpemba effect

The quantum Mpemba effect is a relaxation phenomenon in quantum systems where a state initially farther from equilibrium reaches equilibrium faster than one starting closer.

Quantum mutual information

Quantum mutual information measures the total correlations, classical and quantum, shared between two parts of a quantum system, generalizing classical mutual information using von Neumann entropy.

Quantum natural language processing

Quantum natural language processing (QNLP) is a research field that runs NLP models on quantum computers; its main framework, DisCoCat, maps grammar onto quantum circuits.