MPS/CHE-EPSRC: Attosecond Photoelectron Imaging with Quantum Light

With support from the Division of Chemistry, Professors Philip Bucksbaum and Mohammed Hassan of Stanford University and the University of Arizona, respectively, along with their United Kingdom collaborators from the University College London, are investigating electron-ion entanglement in the photoionization of small molecules by extremely intense laser pulses of squeezed quantum light. Entanglement is a quantum mechanical phenomenon where two particles, such as the ion and its departing electron, exhibit correlated behavior, even when they are separated by large distances. However, entanglement is difficult to create and detect, and the ionization process happens extremely quickly. Professors Bucksbaum, Hassan, and their UK collaborators, will detect the directions and velocities of electrons emitted from atoms and molecules when they are ionized by squeezed fields derived from ultrafast laser pulses. Their discoveries could reveal quantum entanglement between the ion and its departing electron, potentially leading to a deeper understanding of the role quantum fields play in chemical dynamics. The project will also provide research opportunities for graduate students in quantum information science and thus contribute to the development of a quantum-enabled workforce. This award is made under the NSF-UKRI lead agency opportunity. The team will create bright squeezed vacuum (BSV) fields capable of affecting photoionization using near-infrared or visible coherent pulsed laser sources that then undergo nonlinear optical conversion by collinear degenerate parametric down-conversion or degenerate four-wave mixing. Nanojoule pulse energies are expected, and the nonclassical squeezing parameter will be measured using several standard methods, including autocorrelation measurements as well as pulse height histograms. These BSV fields will then be used to ionize chemical target molecules such as hydrogen, nitrogen, and water. The electron momentum distribution will be measured in a velocity-map imager (VMI). The well-known strong-field ionization patterns observed using classical fields should be altered in the presence of BSV. Holographic features, which have been observed using field ionization by classical fields, may be reduced in non-classical fields and could provide insight into ion-electron entanglement. Quantum mechanical models will be used to predict the patterns of electrons and guide the choice of targets and analysis methods. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.