The No-Deleting Theorem: The Other Side of Cloning
The no-deleting theorem shows that one of two copies of an unknown quantum state cannot be deleted against the other. Meaning and consequences.
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Tagged: Superposition
333 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.
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.
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 Information Spectrum Methods, Explained
Information spectrum methods handle quantum information tasks without assuming identical repeated uses of a channel. Concepts and applications.
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.
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 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.
The Holevo Bound: How Much a Qubit Can Carry
The Holevo bound, proved by Alexander Holevo in 1973, limits how much classical information can be read from qubits. Its statement and consequences.
Quantum Entropy: Measuring Uncertainty in a State
Quantum entropy measures uncertainty in a quantum state. Von Neumann entropy, its relation to classical entropy, and uses in physics and computing.
Quantum Network Security: Threats and Controls
Threats to network security from quantum computers and the controls available: QKD, post-quantum protocols and quantum hacking countermeasures.
