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A Greek rho with a circumflex, a state that may be a mixture.
Also known as: Density operator, Rho hat, Statistical operator
The density matrix describes a quantum state that may be a statistical mixture rather than a single wavefunction. Its diagonal entries are probabilities and its off-diagonal entries are coherences — and decoherence is literally the off-diagonal entries going to zero.
Denotes the density operator, representing a quantum state that may be mixed rather than pure.
Contexts: Laboratory
Carries populations on its diagonal and coherences off it; decoherence is the decay of the off-diagonal elements.
Contexts: Laboratory
Describes a pure state exactly when its square equals itself, which is the formal test for purity.
Contexts: Laboratory
A Greek lowercase rho with a small inverted-V accent set directly above it.