The Quantum Source Coding Theorem and Compression
Schumacher’s quantum source coding theorem shows quantum data can be compressed down to its von Neumann entropy. History, concepts and uses.
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Quantum Information Theory
Entropy, channel capacity, teleportation, complexity classes and the theorems that define what quantum information can and cannot do.
155 articles
The Quantum Channel Coding Theorem, Explained
The quantum channel coding theorem sets how much information noisy quantum channels can carry reliably. Foundations, codes and implications.
The Quantum Chernoff Bound for State Discrimination
The quantum Chernoff bound gives the best error exponent for telling two quantum states apart with many copies. Definition and applications.
Quantum Fisher Information and Measurement Precision
Quantum Fisher information sets the best possible precision for estimating a parameter. Its definition, the Cramér-Rao bound and metrology uses.
The Quantum Hamming Bound on Code Parameters
The quantum Hamming bound limits the parameters of non-degenerate quantum codes. Its derivation, examples and implications for code design.
Superdense Coding: Two Bits From One Qubit
Superdense coding, proposed by Bennett and Wiesner in 1992, sends two classical bits with one qubit using a shared entangled pair. How it works.
Entanglement of Formation and the Cost of Correlation
The entanglement of formation is the minimum entanglement needed to create a given state. Its definition, formulas for two qubits and uses.
Entanglement Entropy: Measuring Shared Information
Entanglement entropy measures how entangled one part of a system is with the rest. Definition, calculation and meaning in physics.
Quantum Discord: Correlation Without Entanglement
Quantum discord captures non-classical correlations that can exist even without entanglement. Its definition, measurement and possible uses.
Quantum Coherence: The Resource Behind Interference
Quantum coherence is the ability of a state to show interference. Where it comes from, how it is lost and why computing and sensing depend on it.
Quantum Fidelity: How Close Two States Are
Fidelity measures how close two quantum states are. How it is computed and why it is used to judge gates, error correction and protocols.
Quantum Information Distance Between States
Measures of distance between quantum states and channels, such as trace distance, fidelity and diamond norm, and where each is used.
