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Time-reversal symmetry and universal conductance fluctuations in a driven two-level system

S. Gustavsson ; Jonas Bylander (Institutionen för mikroteknologi och nanovetenskap, Kvantkomponentfysik) ; W.D. Oliver
Physical Review Letters (0031-9007). Vol. 110 (2013), 1, p. 016603.
[Artikel, refereegranskad vetenskaplig]

In the presence of time-reversal symmetry, quantum interference gives strong corrections to the electric conductivity of disordered systems. The self-interference of an electron wave function traveling time-reversed paths leads to effects such as weak localization and universal conductance fluctuations. Here, we investigate the effects of broken time-reversal symmetry in a driven artificial two-level system. Using a superconducting flux qubit, we implement scattering events as multiple Landau-Zener transitions by driving the qubit periodically back and forth through an avoided crossing. Interference between different qubit trajectories gives rise to a speckle pattern in the qubit transition rate, similar to the interference patterns created when coherent light is scattered off a disordered potential. Since the scattering events are imposed by the driving protocol, we can control the time-reversal symmetry of the system by making the drive waveform symmetric or asymmetric in time. We find that the fluctuations of the transition rate exhibit a sharp peak when the drive is time symmetric, similar to universal conductance fluctuations in electronic transport through mesoscopic systems. © 2013 American Physical Society.



Denna post skapades 2016-07-27. Senast ändrad 2016-08-15.
CPL Pubid: 239578

 

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