Words before formulas

Quantum Learning glossary

Short definitions written for a first encounter. Each term links to the lesson that introduces it.

50 terms shown.

algorithm: A precise sequence of steps for completing a task.
Introduced in Simplified quantum algorithms
amplitude: A signed or phased calculation component whose squared magnitude gives probability.
Introduced in Interference and quantum search
analyse: Use a later operation and measurement to reveal a state feature.
Introduced in Why instruction order matters
Bell state: A maximally entangled two-qubit state; this lesson prepares (|00⟩+|11⟩)/√2.
Introduced in Entanglement
bit: An ordinary information unit recorded as 0 or 1.
Introduced in Ordinary computer bits and quantum information
checkpoint: A calculated state or probability view after a circuit step.
Introduced in Why instruction order matters
circuit: An ordered set of instructions applied to qubits.
Introduced in Simple quantum instructions and circuits
classical channel: An ordinary communication path that carries classical bits.
Introduced in What quantum teleportation really transfers
coherence: The controlled phase relationships needed for quantum interference.
Introduced in Noise, errors and reliable scientific evidence
controlled-X (CX): A two-qubit gate that applies X to a target when its control is in the relevant basis state.
Introduced in Quantum gates and circuits
correction: An X, Z, both or neither operation chosen from the two classical results.
Introduced in What quantum teleportation really transfers
correlation: A pattern in which two recorded variables are statistically related.
Introduced in Linked quantum systems
diffusion step: The Grover operation that uses interference to amplify the marked amplitude.
Introduced in Interference and quantum search
entanglement: A property of some joint quantum states that cannot be described as separate independent qubit states.
Introduced in Entanglement
error mitigation: Methods that reduce some error effects in estimated results without fully correcting every error.
Introduced in Noise, errors and reliable scientific evidence
fresh preparation: Preparing the same intended state again before another trial.
Introduced in Measurement and probability
gate: A controlled quantum instruction represented by a box on a circuit wire.
Introduced in Simple quantum instructions and circuits
Hadamard gate (H): A gate that can create or analyse equal-probability states.
Introduced in Quantum gates and circuits
histogram: A chart whose bars show outcome counts or percentages.
Introduced in Repeated experiments and result patterns
hybrid: Combining classical and quantum processing in one workflow.
Introduced in Quantum and classical problem-solving
independent: Prepared so one result pattern does not depend on the other.
Introduced in Linked quantum systems
input: The data or starting condition supplied to an algorithm.
Introduced in Simplified quantum algorithms
instruction order: The left-to-right sequence in which circuit operations act.
Introduced in Why instruction order matters
joint system: Two or more systems described and measured together.
Introduced in Linked quantum systems
ket and reference-state notation: A ket is a state label written with a vertical bar and angle bracket; the reference-state label |0⟩ is read ‘ket zero’.
Introduced in Introductory qubit models
limitation: A boundary on what an experiment or conclusion establishes.
Introduced in Simplified quantum algorithms
logical qubit: A qubit role in the intended circuit, which software later assigns to a physical qubit learned about in Lesson 11.
Introduced in How circuits are fitted to quantum chips
measurement: A physical process that produces a classical recorded result.
Introduced in Ordinary computer bits and quantum information
no-signalling: The rule that entanglement cannot be used to send a chosen usable message faster than light.
Introduced in Entanglement
noise: Unwanted changes or uncertainty introduced by a device and its environment.
Introduced in Noise, errors and reliable scientific evidence
oracle: A circuit component that marks the desired choice by changing its phase.
Introduced in Interference and quantum search
outcome: The classical result recorded in one measurement.
Introduced in Measurement and probability
phase: A feature of a quantum state that can change how later instructions combine possible outcomes.
Introduced in Introductory qubit models
phase and Z gate: Phase is a state feature that affects later combinations; Z is a gate that changes relative phase.
Introduced in Quantum gates and circuits
physical qubit: A particular engineered qubit available on a selected QPU.
Introduced in Quantum simulators and physical hardware
probability: A number from 0 to 1 that describes the predicted chance of an outcome.
Introduced in Introductory qubit models
proposal: A suggested future possibility that still requires evidence and development.
Introduced in Future quantum technologies and study pathways
prototype: An early working version used to test an idea.
Introduced in Future quantum technologies and study pathways
quantum advantage: A demonstrated performance benefit for a defined task and fair comparison, not a general slogan.
Introduced in Quantum and classical problem-solving
quantum processing unit (QPU): Physical hardware engineered to operate qubits.
Introduced in Quantum simulators and physical hardware
quantum technology field: One area of work: quantum computing processes information, quantum sensing measures physical quantities, quantum communication transmits or protects quantum information, and materials/devices work builds the physical systems.
Introduced in Future quantum technologies and study pathways
quantum teleportation: A protocol that reconstructs a quantum state elsewhere using shared entanglement, measurement and classical communication.
Introduced in What quantum teleportation really transfers
qubit: A quantum system used as a unit of quantum information.
Introduced in Ordinary computer bits and quantum information
seed: A chosen starting value that makes a pseudorandom demonstration repeatable.
Introduced in Repeated experiments and result patterns
shot: One preparation-and-measurement run of an experiment.
Introduced in Repeated experiments and result patterns
simulator: Classical software that calculates or samples a quantum model.
Introduced in Quantum simulators and physical hardware
SWAP: An operation sequence used to exchange two qubit states for routing.
Introduced in How circuits are fitted to quantum chips
transpilation: Adapting and rearranging a circuit so a selected machine can execute it.
Introduced in How circuits are fitted to quantum chips
workflow: An ordered set of stages used to complete and check a task.
Introduced in Quantum and classical problem-solving
X gate: A gate that exchanges |0⟩ and |1⟩ in the reference-state examples.
Introduced in Simple quantum instructions and circuits