Effect of Quantum Point Contact Measurement on Electron Spin State in Quantum Dots

We study the time evolution of two electron spin states in a double quantum-dot system, which includes a nearby quantum point contact (QPC) as a measurement device. We find that the QPC measurement induced decoherence is in the micrsecond timescale. We also find that the enhanced QPC measurement will trap the system in its initial spin states, which is consistent with the quantum Zeno effect.