Attosecond imaging—capturing electron motion in billionths of a billionth of a second—currently uses only classical light, leaving the potential of quantum light largely untapped. This project will build a source of intense “squeezed” light, where quantum noise is reduced in one property at the cost of increasing it in another, and use it to image photoelectrons. The goal is to see whether non-classical light can sharpen holographic images of electron trajectories, reveal quantum entanglement between electrons and ions, and give researchers finer control over electron motion during chemical reactions. If successful, the work could improve the precision of ultrafast imaging used in attochemistry and condensed-matter physics, and provide practical insights into maintaining quantum coherence—a core challenge for quantum computing and sensing. It also supports the UK National Quantum Strategy by developing quantum-enhanced measurement tools. This is primarily fundamental science. The project explores a largely uncharted regime where quantum optics meets attosecond physics. Past fundamental work on squeezed light, for example, now underpins gravitational-wave detectors; similar long-term payoffs could emerge from controlling electron dynamics at the quantum level.
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This project integrates quantum optics into ultrafast imaging, bridging quantum optics, attosecond science, and photochemistry. It aims to refine photoelectron momentum distributions, enhance holographic resolution, and improve control over quantum coherence in electron motion. Selectively enhancing quantum features like entanglement and non-classical correlations could unlock new opportunities in attochemistry and quantum technologies. Attosecond science (10?¹8 s) explores extreme non-equilibrium conditions, where laser fields rival atomic binding forces—some of the shortest time scales in nature. This regime holds promise for overcoming decoherence in quantum technologies. However, attosecond imaging mainly relies on classical light, leaving the potential of non-classical light largely unexplored. Most attosecond quantum optics studies focus on high-order harmonic generation (HHG), for which macroscopic effects like phase matching are important. In contrast, photoelectrons provide a single-emitter response, making them ideal for detecting quantum correlations. Experiments suggest that squeezed states can dramatically modify electron trajectories, suppress interference, and enhance resolution. Additionally, field properties transfer to emitted electrons, offering new ways to control electron motion at the quantum level. The project will: Develop a quantum electrodynamic path-integral model to describe photoelectron momentum distributions in strong laser fields, fully incorporating electron-ion and electron-light entanglement. This extends the UCL-developed Coulomb Quantum Orbit Strong-Field Approximation (CQSFA) to include quantum electrodynamical (QED) effects and shaped light fields. By treating binding potentials and external laser fields equally, the CQSFA has advanced our understanding of holographic interference and multipath electron dynamics. The refined QED-CQSFA model will incorporate quantum entanglement and be benchmarked against advanced atomic physics simulations like R-matrix with time dependence. Generate high-intensity squeezed light (>10¹² W/cm²) with tunable frequencies, time profiles, and polarizations, developing a bright squeezed vacuum (BSV) source via four-wave mixing to produce intense phase- and amplitude-squeezed states. Perform high-precision holographic measurements to analyze electron-ion entanglement in attosecond photoemission, using high-fidelity momentum imaging and shaped squeezed light to manipulate holographic spectra. This will explore quantum advantages beyond classical methods in attosecond imaging. Identify and measure quantum correlations between electron pathways, electron-ion entanglement, and light-matter interactions. Time-correlation filtering techniques will help separate distinct quantum pathways, employing the QED-CQSFA alongside quantum optics and quantum information tools. Develop and test pump-probe schemes with intense squeezed light to create and control quantum superpositions relevant to bond breaking and chemical reactivity. Theoretical proposals will be followed by experimental realizations, initially targeting atoms and small molecules. These studies will explore an uncharted domain, as ultrafast pump-probe schemes typically use weak conventional light. This project could drive breakthroughs in: Quantum-enhanced imaging, improving precision in electron dynamics for attochemistry and condensed matter physics. Quantum information science, providing insights into coherence and entanglement control in ultrafast processes. Photonics and sensing, advancing high-precision spectroscopy using squeezed light. Additionally, this research aligns with the UK National Quantum Strategy, aiding the integration of quantum-enhanced sensing into emerging technologies. It also supports UKRI’s Grand Challenges in Quantum Physics for New Technologies and Physics Far from Equilibrium. The project will train the next generation of researchers through: Interdisciplinary collaboration in quantum optics, attoscience, and photochemistry. Technical skills development in ultrafast spectroscopy, quantum field theory, and computational physics. Public engagement via Quantum Battles in Attoscience and Atto Fridays. By merging quantum light control with attosecond imaging, this project will pioneer new approaches to ultrafast electron dynamics, unlocking new ways to manipulate quantum coherence, entanglement, and chemical reactivity.
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