**Quantum mechanics is central to much of the technology we use every day. But what exactly is it? The 11**^{th} Fondation Mines-Télécom booklet explores the origins of quantum technology, revealing its practical applications by offering a better understanding of the issues. To clarify the concepts addressed, the booklet includes a glossary, from which this list is taken.

^{th}Fondation Mines-Télécom booklet explores the origins of quantum technology, revealing its practical applications by offering a better understanding of the issues. To clarify the concepts addressed, the booklet includes a glossary, from which this list is taken.

**Black-body radiation** – Thermal radiation of an ideal object absorbing all the electromagnetic energy it receives.

**Bra-ket notation** (*from the word bracket*) – Formalism that facilitates the writing of equations in quantum mechanics.

**Coherent detectors** – Equipment used to detect photons based on amplitude and the phase of the electromagnetic signal rather than interactions with other particles.

**Decoherence** – Each possibility of a quantum superposition state interacts with its environment at a degree of complexity that makes the different possibilities incoherent and unobservable.

**Entanglement **– Phenomenon in which two quantum systems present quantum states that are dependent on one another, regardless of the distance separating them.

**Locality** (*principle of*) – The idea that two distant objects cannot directly influence each other.

**Momentum** – Product of the mass and velocity vector of a hypothetical object in time.

**NISQ (Noisy Intermediate-Scale Quantum)** – Current class of quantum computers

**Observable** (*noun*) – Concept in the quantum world comparable to a physical value (position, momentum, etc.) in the classical world.

**Quanta** – The smallest indivisible unit (of energy, momentum, etc.)

**Quantum Hall effect** – classical Hall effect refers to the phenomenon of voltage created by an electric current flowing through material immersed in a magnetic field. According to the conditions, this voltage increases in increments. This is the quantum Hall effect.

**Quantum state** – A concept that differs from a classical physical system, in which measured physical values like position and speed are sufficient in defining the system. A quantum state provides a probability distribution for each observable of the quantum system to which it refers.

**Quantum system** – Refers to an object studied in a context in which its quantum properties are interesting, such as a photon, mass of particles, etc.

**Qubit **– Refers to a quantum system in which a given observable (the spin for example) is the superposition of two independent quantum states.

**Spin** – Like the electric charge, one of the properties of particles.

**Superposition principle **– Principle that a same quantum state can have several values for one of its given observables.

**The Schrödinger wave function** – A fundamental concept of quantum mechanics, a mathematical function representing the quantum state of a quantum system.

**Uncertainty Principle** – Mathematical inequality that expresses a fundamental limit to the level of precision with which two physical properties of a same particle can be simultaneously known.

**Wave function collapse** – Fundamental concept of quantum mechanics that states that after a measurement, a quantum system’s state is reduced to what was measured.

**Wave-particle duality** (*or wave-corpuscle duality*) – The principle that a physical object sometimes has wave properties and sometimes corpuscular properties.

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