Pauli matrix

noun1

1. •
   Any one of three complex matrices that arise in Wolfgang Pauli's treatment of spin in quantum mechanics.

   • The first Pauli matrix is like a reflection about the "y=x" line. The third Pauli matrix is like a reflection about the "x axis". The second Pauli matrix is like a 90° counterclockwise rotation and scalar multiplication by the imaginary unit (which rotates the two complex components by 90° counterclockwise in their own "phasor spaces", as it were).
   • The eigenspinors are eigenvectors of the Pauli matrices in the case of a single spin 1/2 particle. —Wikipedia