Quantum Emulation of Coherent Backscattering in a System of Superconducting Qubits

In condensed matter systems, coherent backscattering and quantum interference in the presence of time-reversal symmetry lead to well-known phenomena, such as weak localization (WL) and universal conductance fluctuations (UCFs). Here we use multipass Landau-Zener transitions at the avoided crossing of a highly coherent superconducting qubit to emulate these phenomena. The average and standard deviations of the qubit transition rate exhibit a dip and peak when the driving waveform is time-reversal symmetric, analogous to WL and UCFs, respectively. The higher coherence of this qubit enabled the realization of both effects, in contrast to the earlier work by Gustavsson et al. [Phys. Rev. Lett. 110, 016603 (2013)], who successfully emulated UCFs, but did not observe WL. This demonstration illustrates the use of nonadiabatic control to implement quantum emulation with superconducting qubits.