Ultrashort pulse two-photon coherent control of a macroscopic phenomena: light-induced current from channelrhodopsin-2 in live brain cells

Abstract

Coherent control is extended to macroscopic processes under continuous pulsed laser irradiation. Here, this approach is used to analyze the experimentally measured two-photon phase control of currents emanating from a living brain cells expressing channelrhodopsin-2, a light-gated ion channel. In particular, a mechanism is proposed that encompasses more than 15 orders magnitude in time, from the ultrafast dynamics of retinal in channelrhodopsin-2 to the slow dynamics of the neuron current.Implications for other photochemical processes are discussed.

Considerations regarding one-photon phase control

“…the population of photoisomers, are dynamical only over timescales much longer than typical ultrafast excitations. 14 Therefore, there are no a priori contradictions 7 between the dynamical nature of control and the long-lived phase control reported in some experiments and simulations. [27][28][29][30][31] Yet it is also profoundly unsatisfying, from a physical point of view, that the steady state would be defined only at the t → ∞ limit -what constitutes the "steady state" with respect to control should be related to physical timescales (e.g.…”

“…6 Thus, phase control in the linear regime is never due to a phase-dependent change in the absorption probability, as may be the case in multiphoton absorption. 13,14 This phase insensitive absorption probability greatly simplifies the interpretation of one-photon phase control. Consider, for example, the cis-trans isomerization of retinal.…”

“…In contrast, multiphoton absorption is phase-dependent 16 -a change in the isomerization yield in a multiphoton experiment might reflect phase control over the absorption with no change in the isomerization dynamics. 13,14,17,18 Experimental and numerical demonstrations of one-photon phase control lead to the development of formal conditions under which such control is possible. In the control of molecular photodissociation, it was shown that the cross-section of a photochemical reaction (a steady-state quantity) triggered by a one-photon excitation is independent of the phase of the excitation.…”

“…32 Steady-state onephoton phase control has been shown to be impossible for certain classes of open quantum systems, 9 as it is for closed systems. 7 In addition, it has been demonstrated that multiphoton effects can create large contribution even in the linear absorption regime, 14,[33][34][35] which might lead to multiphoton phase control in seemingly one-photon experiments.…”

Differentiable Molecular Simulations for Control and Learning

“…Computational and theoretical analysis of control can explain and motivate experimental control protocols. [32,33,34,35] In Ref. [34], for example, an experimental control protocol was reproduced computationally and explained theoretically.…”