  We characterize the quantum entanglement of the realistic two-qubit signals
that are sensitive to charge noises. Our working example is the time response
generated from a silicon double quantum dot (DQD) platform, where a
single-qubit rotation and a two-qubit controlled-NOT operation are conducted
sequentially in time to generate arbitrary entangled states. In order to
characterize the entanglement of two-qubit states, we employ the marginal
operational quasiprobability (OQ) approach that allows negative values of the
probability function if a given state is entangled. While the charge noise,
which is omnipresent in semiconductor devices, severely affects logic
operations implemented in the DQD platform, causing huge degradation in
fidelity of unitary operations as well as resulting two-qubit states, the
pattern in the OQ-driven entanglement strength turns out to be quite invariant,
indicating that the resource of quantum entanglement is not significantly
broken though the physical system is exposed to noise-driven fluctuations in
exchange interaction between quantum dots.
