Controlled dephasing of a quantum dot: from coherent to sequential tunneling

Area of Science:

• Quantum physics
• Condensed matter physics

Background:

• Resonant tunneling through identical barriers normally leads to transparency due to coherent quantum mechanical interference.
• Quantum dots (QDs) are nanoscale semiconductor structures that exhibit quantum mechanical properties.

Purpose of the Study:

• To investigate resonant tunneling phenomena in a quantum dot.
• To explore the effect of electron trajectory detection on quantum dot transparency.

Main Methods:

• Experiments were conducted in the integer quantum Hall regime.
• Tunneling electrons in an inner edge channel were coupled to detector electrons in a partitioned neighboring outer channel.

Main Results:

• Resonant tunneling, typically leading to transparency, was observed in the quantum dot.
• Detection of electron trajectories caused the quantum dot to become nearly insulating.
• Quantitative analysis revealed that a small number of detector electrons were sufficient to dephase the quantum dot.

Conclusions:

• Electron trajectory detection destroys the coherent interference necessary for resonant tunneling in quantum dots.
• The quantum Hall regime provides a platform to control and probe quantum coherence in mesoscopic systems.
• This work demonstrates a sensitive method for controlling quantum transport in nanostructures.