Negative result measurements in mesoscopic systems

We investigate measurement of electron transport in quantum dot systems by using single-electron transistor as a non-invasive detector. It is demonstrated that such a detector can operate in the 'negative-result measurement' regime. In this case the measured current is not distorted, providing that it is a non-coherent one. For a coherent transport, however, the possibility of observing a particular state out of coherent superposition leads to distortion of a measured current even in the 'negative-result measurement' regime. The corresponding decoherence rate is obtained in the framework of quantum rate equations