Core terms
Qubit — the basic unit of quantum information, analogous to a classical bit but able to exist in superposition.
Superposition — a qubit's ability to represent a combination of 0 and 1 simultaneously until measured.
Entanglement — a correlation between qubits that cannot be explained classically; the resource behind much of quantum computing's power.
Engineering terms
Algorithmic qubit — a qubit available for computation, after accounting for the physical qubits used for error correction.
Gate fidelity — how reliably a quantum operation executes; a key quality metric.
Error correction / surface code — techniques that spread quantum information across many physical qubits so errors can be detected and corrected.
Fault tolerance — the ability of a system to keep computing correctly even when individual components fail.
Market terms
Quantum advantage — the point at which a quantum computer solves a useful problem faster or better than the best classical alternative.
Pure-play — a company whose business is focused almost entirely on quantum technology.