February, 11 (2008) at 4pm

Kicheon Kang
Chonnam National University, South Korea

According to Bohr's complementarity principle, a particle shows wave-like behavior only when the different paths the particle may take are indistinguishable. In many cases the suppression of interference can either be understood as obtaining the path information or as unavoidable 'disturbance' by the detector. In this talk, I present three different examples of mesoscopic interferometers which can address this issue: (1) Aharonov-Bohm interferometer in closed-loop geometry with a detector[1,2], (2) Charge qubit coupled to a detector composed of a quantum-point-contact beam collider[3] (3) Coupled double electronic Mach-Zehnder interferometers[4,5]. Our study demonstrates that care must be taken in understanding the complementarity as disturbance, and that an acquisition of information is of prime importance for quantum mechanical complementarity. [1] G. L. Khym and Kicheon Kang, Charge Detection in a Closed-Loop Aharonov-Bohm Interferometer, Phys. Rev. B 74, 153309 (2006). [2] D. I. Chang et al., Quantum mechanical complementarity probed in a closed-loop Aharonov-Bohm interferometer, Nature Physics, in press (2008). [3] Y. Lee, G. L. Khym, and K. Kang, Nonlocality of dephasing in a charge qubit interacting with a quantum point contact beam collider, arXiv: 0712.0211. [4] Kicheon Kang, Electronic Mach-Zehnder Quantum Eraser, Phys. Rev. B 75, 125326 (2007). [5] Kicheon Kang and K. H. Lee, Violation of Bell's inequality in electronic Mach-Zehnder interferometers, Physica E (2007), doi: 10.1016/j.physe.2007.09.124.