Séminaire spécialisé proposé par Geneviève Fleury

Both metaphysical and practical considerations intrigued generations of scientists to devise and implement time-inversion protocols – in particular the Hahn echo [1], different forms of “time mirrors” for classical waves (see e.g. [2]), and recently an instantaneous time mirror for water waves [3]. With our proposal for an instantaneous Quantum Time Mirror [4], we showed the possibility to extend the family of time reversal protocols to continuous quantum systems, more precisely to wave packets in Dirac-cone systems, by changing the propagation direction with a short, time-dependent pulse.

As examples, we discuss the effect on the Quantum Time Mirror of both, a static, out-of-plane magnetic field, which breaks time-reversal symmetry, and band structures other than the Dirac cone, e.g. the valence and conduction bands in direct gap semi-conductors. Moreover, we show that applying the time-dependent pulse periodically, we can devise effectively a discrete quantum walk with tunable "coin" parameters.

[1] E. L. Hahn, Spin echoes. Phys. Rev.. 80, 580 (1950)
[2] M. Fink, IEEE Trans. Ultrason. Ferroelectr. Freq. Control, 39, 555, (1992)
[3] V. Bacot, et al., Nat. Phys. 12, 972–977 (2016)
[4] P. Reck, et al., Phys. Rev. B 95, 165421 (2017)