20 terms for understanding quantum technology

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.

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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