bra-ket

Meaning

Noun

• The product of two vectors (and optionally an operator), in Hilbert space, where the left vector is a bra and the right is a ket. Symbolised by ⟨...|...〉 (bra and ket only) or ⟨...|...|...〉 (bra, operator, ket).

Origin

• Concatenation of the terms bra and ket, which were introduced in 1939 and in turn derive from the splitting of the English word bracket.