  We solve the master equations of two charged qubits measured by two serially
coupled quantum point contacts (QPCs). We describe two-qubit dynamics by
comparing entangled states with product states, and show that the QPC current
can be used for reading out results of quantum calculations and providing
evidences of two-qubit entanglement. We also calculate the concurrence of the
two qubits as a function of dephasing rate that originates from the
measurement. We conclude that coupled charge qubits can be effectively detected
by a QPC-based detector.
