Quantum interferences and their classical limit in laser driven coherent control scenarios

An Approach To “Quantumness” In Coherent Control

“…This is not the case for the 1 vs. 2 control process, which retains its wavelike interference behavior in the classical limit. Indeed, as we have explained elsewhere [35], the primary difference between the YDS and coherent phase control is that the latter occurs due to external driving, i.e., E(t), whereas the former requires no such external influence. This result is in full agreement with the nonlinear response description in Sec.…”

“…For example [6,35,82], a classical, two-color cw driving field with frequency components ω and 2ω of the form E(t) = E 1 (t) + E 2 (t) = ε 1 cos(ωt + φ 1 ) + ε 2 cos(2ωt + φ 2 ) can induce an asymmetry in the position or momentum distribution of a single charged particle trapped in a symmetric potential with quartic anharmonicity. The asymmetry is controllable by changing the relative phase φ = 2φ 1 − φ 2 of the two field components.…”

“…Such an approach to analyzing quantum control scenarios and their possible classical analog, formulates the issue in terms of nonlinear perturbative response [35,41]. Non-linear response provides an infinite series expansion for the time-dependent ensemble average of the outcome of a measurement performed on a material system that is subject to an external (and here for simplicity, scalar-valued) driving signal E(t).…”

“…However, phase sensitivity and nonadditivity can also be of classical origin arising, for example, in transport processes [34]. Hence, one can ask [35,36] whether 1 vs. N phase control can also be viewed as a classical interference phenomenon or, for example, as a system's collective response to shaped incident laser fields [37,38]. Related concerns are raised by a number of additional studies [39][40][41] that consider 1 vs. 2 photon phase control as an intrinsically classical phenomenon.…”

Certifying the quantumness of a generalized coherent control scenario

“…Here, reliance on an interpretation of the interference of quantum pathways as described above (and as originally put forth 12,13 by one of the authors of this paper) is commonly accepted. But the issue of the extent to which nontrivial quantum features are central to phenomena such as coherent control needs to be reconsidered in light of developments in Bell-like tests to certify unique quantum features [14][15][16][17][18][19][20] and recent reports that identify distinct classical mechanisms as a possible source of control 5,[8][9][10][21][22][23] .…”