  We propose a scheme to measure the quantum state of photons in a cavity. The
proposal is based on the concept of quantum weak values and applies equally
well to both the solid-state circuit and atomic cavity quantum electrodynamics
(QED) systems. The proposed scheme allows us to access directly the
superposition components in Fock state basis, rather than the Wigner function
as usual in phase space. Moreover, the separate access feature held in the
direct scheme does not require a global reconstruction for the quantum state,
which provides a particular advantage beyond the conventional method of quantum
state tomography.
