Entanglement Witnesses: Detecting Entanglement
Entanglement witnesses are observables that detect entanglement without full tomography. How they are built and used in experiments.
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Tagged: Bell's Theorem
20 articles
Quantum Symmetric States and Permutation Invariance
Symmetric states are unchanged when their particles are permuted. Their structure, entanglement properties and uses in computing and cryptography.
The No-Broadcasting Theorem for Mixed States
The no-broadcasting theorem extends no-cloning to mixed states: non-commuting states cannot be broadcast. Its statement, proof and uses.
Quantum Entanglement: What It Is and What It Is Not
What quantum entanglement is and what it is not: its history, Bell tests, applications, and why it cannot be used to send signals faster than light.
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.
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 Entropy: Measuring Shared Information
Entanglement entropy measures how entangled one part of a system is with the rest. Definition, calculation and meaning in physics.
Device-Independent QKD: Security Without Trust
Device-independent QKD bases its security on Bell inequality violations, so users need not trust their devices. Principles and experiments.
Entanglement Complexity: Measuring How Tangled
How entanglement is quantified: entanglement entropy, witnesses and other measures, plus experiments, swapping, teleportation and networks.
Quantum Non-Local Games and What They Prove
Non-local games such as CHSH and the magic square game show that entangled players can beat classical ones. What they prove and how they are used.
The Kochen-Specker Theorem and Contextuality
The Kochen-Specker theorem shows that quantum outcomes cannot all be fixed in advance independent of context. Proofs, experiments and meaning.
Bell’s Theorem: The Experiment That Settled It
Bell’s theorem shows that no local hidden-variable theory can match quantum predictions. The inequality, the experiments and what they settled.
