A laser pulse lasting just a few femtoseconds can now grab hold of individual electrons and steer their motion inside atoms and molecules before the nuclei have time to budge. This matters because controlling electrons at their natural timescale—below one femtosecond—and at the atomic scale has been a fundamental goal of quantum physics. Until recently, laser pulses were too long or too unstable to exert this kind of precise, waveform-level control. The breakthrough of carrier-envelope phase-stabilised few-cycle pulses now provides a defined electric field waveform that can drive electron trajectories in a deterministic way, rather than relying on the pulse’s intensity envelope. If successful, this research could unlock new forms of quantum control with practical consequences. Selective bond cleaving via controlled electron recollision could lead to new chemical synthesis routes. Optimising coherent XUV and hard X-ray sources could improve imaging and spectroscopy for materials science. Spin-entangled electronic states might advance quantum information processing. Compact laser-phase detectors could simplify experimental setups. This is fundamentally curiosity-driven science. It does not promise an immediate product or treatment. But past work on strong-field laser physics has already enabled attosecond science, which now underpins real-world advances in ultrafast electronics and precision metrology.
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Intense, phase-stabilised, femtosecond laser pulses comprising only a few optical cycles ( few-cycle pulses) offer a unique new tool for the manipulation of electrons in matter The strong oscillating electric field of the pulse moves valence electrons in quasi-classical trajectories, but the interaction on the sub optical-cycle timescale is too brief for nuclear motion to occur. Thus the motion of the electrons in small quantum systems (e.g. atoms, molecules, clusters, surfaces, nanosystems) can be controlled whilst the nuclei are fixed in position. This proposal outlines an in-depth programme of research in this rapidly emerging area.The breakthrough of intense carrier envelope phase-stabilised (CEP stabilised), few-cycle pulses provides precisely defined strong electric field optical waveforms. These fully controlled few-cycle pulses permit, for the first time, the control of strongly driven electron motion down to the quantum limit with sub-optical period (< 1 fs) temporal resolution and near atomic scale (~10^-10m) spatial resolution. It is now possible to implement a new type of coherent control of strong field electron processes that are inherently sensitive to the CEP. It is important to stress that it is the electric field waveform, rather than the pulse intensity envelope , that is harnessed to control the system. Control of electrons is provided by these fields at the natural spatial and temporal scales relevant to electronic states in matter (i.e. < 10^-10m and < 10^-15s) - this opens up exciting new possibilities in quantum control. The control we will exercise isolates electron motion from the ion (nuclear) motion, the latter being effectively frozen on the timescale of the pulse duration. Thus the control of quasi-classical electron states within otherwise unaltered material will be feasible.This proposal concerns the development of these new optical techniques and their application to the investigation and control of electron processes in matter. The timeliness of this proposal is underlined by the growing interest in this field internationally with major efforts starting up, for instance in Sweden (Lund), France (Saclay), USA (Boulder, Berkeley, Ohio) and most notably in Germany (MPG-MPQ, Garching). The motivation for all these projects is the prospect of achieving the highest degree of quantum control in matter that can lead to new breakthroughs in chemical, material and optical sciences. Our project objectives include demonstration of selective bond cleaving via controlled electron recollision, optimisation of brightness and minimisation of pulse duration in coherent XUV and incoherent hard X-ray light sources, creation of spin entangled electronic states via ionisation of two-electron systems and development of compact detectors for laser phase.
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