Coherent backscattering and forward-scattering peaks in the quantum kicked rotor

Abstract

Abstract. We propose and analyze an experimental scheme using the quantum kicked rotor to observe the newly-predicted coherent forward scattering peak together with its long-known twin brother, the coherent backscattering peak. Contrary to coherent backscattering, which arises already under weak-localization conditions, coherent forward scattering is only triggered by Anderson or strong localization. So far, coherent forward scattering has not been observed in conservative systems with elastic scattering by spatial disorder. We propose to turn to the quantum kicked rotor, which has a long and succesful history as an accurate experimental platform to observe dynamical localization, i.e., Anderson localization in momentum space. We analyze the coherent forward scattering effect for the quantum kicked rotor by extensive numerical simulations, both in the orthogonal and unitary class of disordered quantum systems, and show that an experimental realization involving phase-space rotation techniques is within reach of state-of-the-art cold-atom experiments.arXiv:1612.02091v1 [cond-mat.quant-gas] 7 Dec 2016Coherent back and forward scattering peaks in the quantum kicked rotor 2

Coherent forward scattering as a signature of Anderson metal-insulator transitions

“…The same conclusion and similar quantitative results, although a bit more noisy, are obtained if one uses C F only as the critical quantity. In a system where time-reversal symmetry is broken [22], the CFS peak is still present, but the CBS peak disappears. In such a situation, one has to use directly C F to characterize the transition.…”

“…Indeed, the CBS peak relies on time-reversal symmetry (TRS) [19] and exists on both sides of the MIT, with no discontinuous behavior as the mobility edge is crossed [20]. In marked contrast, CFS requires Anderson localization to show up (it is absent in the metallic phase) and is present whether or not TRS is broken [21,22]. While the experimental observation of CBS in momentum space has been recently achieved with cold atoms [23], no observation of CFS has been reported so far.…”

Controlling symmetry and localization with an artificial gauge field in a disordered quantum system

“…This interference is visible, in our system, in a mixed momentum/configuration space representation ( p 1 , x 2 ), in which the initial state is localized. Starting with the initial conditions p 1 ( t = 0) ≈ 0 and x 2 ( t = 0) = + φ , a CBS peak should be observed around p 1 = 0 at x 2 = − φ (in the presence of the PT -symmetry) and a CFS peak around p 1 = 0 at x 2 = + φ 19 . Because of the time-dependence of x 2 ( t ) = x 2 (0) + 2 πt / N , we thus expect to observe CBS and CFS at different times, depending on the initial phase φ of the modulation (see Methods).…”

Prethermalization and wave condensation in a nonlinear disordered Floquet system

“…A similar situation happens when an initial plane wave propagates in a disordered nonlinear medium, disorder inducing the required wave randomization [4]. This configuration is particularly interesting because (i) it is the natural setting to observe the coherent backscattering (CBS) [70][71][72][73] and coherent forward scattering (CFS) effects [74][75][76][77][78][79][80] when interactions are absent and (ii) it allows to control the initial energy of the wave and thus the route to wave condensation in nonlinear systems.…”

“…(3) allows to evolve systems of large sizes N ∼ 10 5 up to large times t ∼ 10 6 at low numerical cost. Without interaction, localization occurs in p-space and CBS and CFS take place in θ-space [78]. Starting from an initial rotor angle θ 0 , ψ + 0 (p) = Following the analogy with thermalization and condensation predicted in disordered nonlinear systems [4], we consider the effect of interactions on these peaks.…”