\Bra{\phi}The \Bra{\phi} notation is used in quantum mechanics to denote a bra vector, which is an element of the dual space associated with a given vector space. In the context of Dirac notation, a bra is the Hermitian conjugate of a ket vector, represented as \Ket{\phi}. The bra-ket notation is a standard notation for describing quantum states and their inner products.
Inner product of bra \Bra{\phi} and ket \Ket{\psi}, representing a complex number.
\Bra{\phi} \Ket{\psi}Expectation value of operator A in the state described by ket \Ket{\psi} and bra \Bra{\phi}.
\Bra{\phi} A \Ket{\psi}The bra \Bra{\phi} is the Hermitian conjugate of the ket \Ket{\phi}.
\Bra{\phi} = (\Ket{\phi})^\dagger