Quantum measurement

Reality is the state of everything that exists, not how they might be imagined. Different cultures and academic disciplines conceptualize it in various ways.

thought experiment

correlation between measurements of quantum subsystems, even when spatially separated

notation for conserved quantities in physics and chemistry

early and influential critique leveled against quantum mechanics

physical experiment that demonstrated the quantization of angular momentum

probabilistic interpretation of quantum mechanics involving wavefunction collapse

interpretation of quantum mechanics which denies the collapse of the wavefunction

in quantum physics, the theorem that locally causal hidden-variable theories cannot reproduce correlations predicted by quantum mechanics

process by which a quantum system takes on a definitive state

loss of quantum coherence due to interaction with the environment

set of statements which attempt to explain how quantum mechanics informs our understanding of nature

complex number whose squared absolute value is a probability

interpretation of quantum mechanics

physical principle that only immediate surroundings can influence an object

interaction of a quantum system with a classical observer

any theory of quantum mechanics where probabilistic outcomes are actually determined precisely by unobservable internal variables

in quantum mechanics, the rule that the probability of observing an eigenvalue is the square of the modulus of the inner product between the quantum state and the eigenstate corresponding to the eigenvalue

effect in quantum mechanics which disallows certain conditions in the decaying of a quantum state

in quantum mechanics, the problem of how or whether wave function collapse occurs during measurement

thought experiment in theoretical quantum physics

Series of public disputes between physicists Niels Bohr and Albert Einstein

quantum experiment in which photons are shone at a double-slit interferometer; whether interference patterns occur depends on whether the information about which slit the photon went through marked is erased or not

interpretation of quantum mechanics

quantum mechanics thought experiment that uses interaction-free measurements to verify that a bomb is functional without having to detonate it

Interpretation of quantum mechanics based on a consistency criterion that assigns probabilities to various alternative histories of a system

thought experiment in which one plays Russian roulette with the trigger connected to the Geiger counter measuring the decay of a radioactive atom

interpretation of quantum mechanics which treats the state of a quantum system as the relation between the observer and the system

physics experiment that combines the quantum eraser experiment with concepts in Wheeler's delayed-choice experiment

experiments in quantum mechanics

interpretation of quantum mechanics that considers the quantum state description to apply only to an ensemble of similarly prepared systems, rather than supposing that it exhaustively represents an individual physical system

quantum measurement that results in an observer obtaining very little information about the system on average, but also disturbs the state very little

theory of the emergence of classicality by environment-induced selection of quantum states

theory according to which wavefunction collapse happens under well-defined, objective conditions

In functional analysis and quantum information science, a positive operator-valued measure (POVM) is a measure whose values are positive semi-definite operators on a Hilbert space. POVMs are a generalization of projection-valued measures (PVM) and, correspondingly, quantum measurements described by POVMs are a generalization of quantum measurement described by PVMs (called projective measurements).

objective collapse theory in quantum mechanics

deviations from local realism characteristic of quantum mechanics

Controversial physics experiment

interpretation of quantum mechanics according to which retarded (forward in time) and advanced (backward in time) waves form a quantum interaction as a Wheeler–Feynman handshake

quantum mechanics experiment

non-invasive measurement of a quantum system

atomic clock with laser cooled single ions confined together in an electromagnetic ion trap

hidden-variable theory that is with local realism

no-go theorem in quantum information theory, forbidding some communication during measurement of entangled states

a wavefunction describing the quantum state of the entire universe

experiment proposed by Karl Popper to put to the test different interpretations of quantum mechanics

thought experiment in quantum mechanics in which a particle and its antiparticle may interact without annihilating each other

objective collapse theory that uncertainty in spacetime curvature causes collapse of the quantum state

testable implication of local hidden variable theories

theorem giving a justification of the Born rule in quantum mechanics

a set of orthonormal bases, where each vector of a given basis has the same overlap with all the vectors of other bases