Optical nonlinearities can be engineered into high-speed optical gates when a probe signal is switched coherently and fast by an optical control pulse through various nonlinear effects for switching. In semiconductors, a strong light–matter interaction can also excite many electrons to interact with each other, which can deteriorate switching through Coulomb-induced dephasing. Here, we demonstrate that optical transmission of carbon nanotubes can be switched reversibly hundreds of times via detuned Rabi splitting, faster than 200 fs via nonresonant but strong control pulses. Our detailed experiment–theory analysis identifies that quantum memory in Coulombic scattering restores reversibility while simultaneously reducing undesirable pure dephasing of coherences. This capability creates new possibilities for ultrafast quantum optoelectronic processing in quantum materials.

Reversible, 200 fs optical switching of carbon nanotubes is demonstrated by utilizing Coulombic many-body effects, strong exciton binding and quantum memory in Coulombic scattering which together eliminate pure dephasing of coherences.

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