Kvanttitieto

Kvanttitieto, or quantum information, is the study of how information can be encoded, processed, transmitted and stored using quantum mechanical systems. The core resource is the quantum bit, or qubit, which can exist in superpositions of states and become entangled with other qubits, enabling information processing tasks beyond classical limits.

In quantum information theory, information is represented by quantum states described by vectors in Hilbert space or density operators; measurements produce probabilistic outcomes and generally disturb the state; the no-cloning theorem prohibits exact copying of unknown quantum states; quantum channels model transmission. Quantum operations are unitary evolutions plus measurements and noise.

Major subfields include quantum computation, which uses quantum logic gates to perform computations; notable results include algorithms that can factor integers (Shor) and search unsorted databases (Grover). Quantum communication covers entanglement-enabled protocols like teleportation and dense coding, and quantum key distribution providing cryptographic security. Quantum error correction and fault-tolerant designs protect information against noise, enabling scalable quantum computation. Theoretical aspects also include channel capacities and the Holevo bound.

History and status: the field originated in the 1980s–1990s with foundational work by Bennett, Brassard, Shor and others. Experimental progress has demonstrated basic qubits and elementary algorithms in photonics, superconducting circuits, trapped ions, and solid-state systems. Practical quantum computers and networks are under active development, with anticipated impacts in cryptography, simulation of quantum systems and optimization.

In Finland and elsewhere, Kvanttieto is used to refer to this area of science and technology, spanning physics, computer science, and information theory.