80 articles
Quantum Rényi entropy
The quantum Rényi entropy is a one-parameter family of entropy measures on quantum states that generalizes the von Neumann entropy, recovering it as α approaches 1.
Quantum resource theory
Quantum resource theory is a quantum information framework that treats properties like entanglement and coherence as quantifiable resources, defined by free states and free operations.
Quantum state tomography
Quantum state tomography is a set of measurement and estimation procedures that reconstructs the density matrix of a quantum system from repeated measurements on identical copies.
Quantum switch
The quantum switch is a quantum process in which two operations act in a superposition of their two possible orders, with no definite causal order between them.
Quantum thermodynamics
Quantum thermodynamics extends thermodynamics to systems small enough that fluctuations, coherence, and correlations matter, redefining work and heat and asking whether quantum effects improve heat engines.
Qubit
A qubit, or quantum bit, is the basic unit of quantum information: a two-level quantum system that, unlike a classical bit, can exist in a superposition of states.
Rényi entropy
Rényi entropy, also called Rényi information, is a one-parameter family of information measures introduced by Alfréd Rényi that generalizes Shannon entropy and reduces to it as its order approaches 1.
Resource inequalities (quantum information theory)
Resource inequalities are bookkeeping statements in quantum information theory that protocols convert among classical bits, qubit channels, and shared entanglement, with teleportation and superdense coding as unit examples.
Ryu–Takayanagi conjecture
The Ryu–Takayanagi conjecture is a proposal in the AdS/CFT correspondence equating a region's entanglement entropy to a bulk minimal surface's area, proposed by Shinsei Ryu and Tadashi Takayanagi in 2006.
Schmidt decomposition
The Schmidt decomposition is a theorem of quantum information theory stating that any bipartite pure state can be written with paired orthonormal bases and real, non-negative coefficients.
Separable state
A separable state, or separable quantum state, is a quantum state of a composite system that can be written as a convex combination of product states, containing only classical correlations rather than entanglement.
Shannon capacity of a graph
The Shannon capacity of a graph, denoted Θ(G), is a graph parameter introduced by Claude Shannon in 1956 that measures the maximum rate of zero-error communication over a noisy channel.
Spin qubit
A spin qubit is a quantum bit encoding information in the spin of a confined electron in a semiconductor quantum dot, proposed by Loss and DiVincenzo in 1998.
Steane code
The Steane code is a [[7,1,3]] quantum error-correcting code proposed by Andrew Steane in 1996 that encodes one logical qubit in seven physical qubits and corrects any single-qubit error.
Stinespring dilation theorem
The Stinespring dilation theorem, proved by W. Forrest Stinespring in 1955, states that every completely positive map is a compression of a -homomorphism on a larger Hilbert space.
Strong subadditivity of quantum entropy
Strong subadditivity of quantum entropy (SSA) is a fundamental inequality for the von Neumann entropy of composite quantum systems, proved by Lieb and Ruskai in 1973.
Tsallis entropy
Tsallis entropy, also called nonextensive entropy, is a one-parameter family of entropies proposed by Constantino Tsallis in 1988, generalizing Boltzmann–Gibbs–Shannon entropy and underpinning nonextensive statistical mechanics.
Von Neumann entropy
The von Neumann entropy is the quantum analog of Shannon entropy, defined as S(ρ) = −tr(ρ log ρ), introduced by John von Neumann in 1932.
W state
The W state is a genuinely tripartite-entangled quantum state of three qubits, sharing one excitation equally, and, unlike the GHZ state, keeps entanglement when a qubit is lost.
Zero-error capacity of quantum channels
The zero-error capacity of a quantum channel is the rate, in bits per channel use, at which messages can be sent with error probability exactly zero, analyzed via noncommutative graphs.