  In this letter, we present a new procedure to determine completely the
complex modular values of arbitrary observables of pre- and post-selected
ensembles, which works experimentally for all measurement strengths and all
post-selected states. This procedure allows us to discuss the physics of
modular and weak values in interferometric experiments involving a qubit meter.
We determine both the modulus and the argument of the modular value for any
measurement strength in a single step, by controlling simultaneously the
visibility and the phase in a quantum eraser interference experiment. Modular
and weak values are closely related. Using entangled qubits for the probed and
meter systems, we show that the phase of the modular and weak values has a
topological origin. This phase is completely defined by the intrinsic physical
properties of the probed system and its time evolution. The physical
significance of this phase can thus be used to evaluate the quantumness of weak
values.
