Quantum Information
Quantum information is information represented and processed using quantum systems, with the qubit as its basic unit.
Concept hubs
Quantum topics
Each hub gives a short definition first, then an overview, a recommended learning sequence, FAQs and related subjects.
Qubits
A qubit is a two-level quantum system used as the basic unit of quantum information.
Superposition
Superposition is a quantum state formed by combining other states, each carrying an amplitude.
Entanglement
Entanglement is a link between quantum systems in which the whole has a definite description while its parts do not.
Quantum Measurement
Measurement extracts a definite classical outcome from a quantum system, with probabilities given by squared amplitudes.
Quantum Gates and Circuits
A quantum gate is a reversible operation on qubits; a quantum circuit is a time-ordered sequence of gates ending in measurement.
Quantum Algorithms
A quantum algorithm is a procedure that uses quantum operations and interference to solve a problem, often with fewer steps than the best known classical method.
Quantum Error Correction
Quantum error correction encodes a logical qubit across many physical qubits so errors can be detected and corrected without reading the stored information.
Quantum Communication
Quantum communication transmits quantum states between locations, usually encoded in photons over fibre or free space.
Quantum Cryptography
Quantum cryptography uses quantum physics — chiefly the disturbance caused by measurement — to secure tasks such as key exchange.
Quantum Teleportation
Quantum teleportation transfers a quantum state between locations using shared entanglement and two classical bits.
Quantum Sensors
Quantum sensors exploit the sensitivity of quantum systems to measure time, fields, gravity, and rotation with very high precision.
Quantum Hardware
Quantum hardware comprises the physical systems and control electronics that implement and manipulate qubits.