Magnetic flux detection with an Andreev quantum dot

The charge of the subgap state in an Andreev quantum dot (AQD) inserted into the superconducting loop is very sensitive to the magnetic flux threading the loop. Sensitivity is analyzed as a function of the AQD parameters in detail in the Δ → ∞ limit. Weak Coulomb interaction in the AQD is taken into account. The possibility of using this setup as a device to detect a weak magnetic field is discussed.