Quantum Channel Degradability and Capacity Formulas
Degradable channels have simple capacity formulas because the environment gets less than the receiver. Definitions, examples and uses.
BasicsAlgorithmsHardwareError CorrectionCryptographyMachine LearningInformation TheoryPhysics & SimulationApplicationsIndustry & Careers
All Articles
Every explainer on QuantumExplainer.com, newest first. Use the pillars above to jump straight to a topic.
739 articles
Quantum Key Rates: From Raw Bits to Secret Bits
How QKD systems turn raw detections into a secret key, what sets the final key rate, and how distance and error rates affect it.
Quantum Information Inequalities and Strong Subadditivity
Key inequalities of quantum information: strong subadditivity, data processing, uncertainty relations, Bell inequalities and Tsirelson’s bound.
Quantum Information Measures, Compared
The main quantum information measures compared: entropy, mutual information, relative entropy, entanglement and correlation measures.
Coherent Information and the Quantum Capacity
Coherent information measures how much quantum information survives a channel, and its regularized maximum gives the quantum capacity.
Quantum Zero-Error Capacity and Perfect Transmission
Zero-error capacity asks how much information a channel can send with no errors at all. How quantum effects and entanglement change the answer.
Entanglement-Assisted Classical Capacity Explained
Entanglement-assisted classical capacity is the rate at which a channel carries classical bits when sender and receiver share entanglement.
Quantum Broadcast Channels and Their Capacities
Quantum broadcast channels send quantum information from one sender to several receivers. Architecture, capacities and applications.
Quantum State Merging and Negative Information
Quantum state merging transfers one party’s share of a state to another, and its cost can be negative, meaning entanglement is gained.
Quantum Process Tomography: Characterising a Gate
Quantum process tomography reconstructs the full description of a quantum operation from measurements. Methods, costs, challenges and uses.
Quantum Hypothesis Testing: Deciding Between States
Quantum hypothesis testing decides between quantum states using measurements. Binary and multiple hypotheses, error exponents and the Chernoff bound.
Quantum Information Spectrum Methods, Explained
Information spectrum methods handle quantum information tasks without assuming identical repeated uses of a channel. Concepts and applications.