Average shot-noise power via a diagrammatic method

In this work we use a diagrammatic method for integration over the unitary group to obtain a quantum correction to the average shot-noise power of a chaotic cavity with non-ideal contacts. We present maximally crossed diagrams representing the physical modes of the system responsible for the dominant quantum correction. We demonstrate with explicit calculations that the suppression--amplification effect reported in Ramos et al (2008 Phys. Rev. B 78 235305) occurs both for systems in the presence of time-reversal (TR) and spin-rotation (SR) symmetries and for systems with broken SR symmetry but in the presence of TR symmetry.