QLC: EAGER: Collaborative Research: Dissecting many-body correlations in matter by quantum process tomography

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One of the most fundamentally important problems in chemistry is to understand how electrons behave in molecules. Chemists often exploit the interaction of light with such electrons to deduce this information. Interaction with light may also provide profound information on how molecules interact each other in liquids and solids. For example, inter-molecular interactions dictate how fast electrons lose the energy transferred to them by light, and how fast they forget about the process of light absorption. Nevertheless, the details of how these properties depend on electronic interactions with all other electrons in liquids and solids is not always easily extractable using light that can be completely described with classical physics. In this project funded by the Chemical Structure Dynamics and Mechanism (CSDM-A) program of the Chemistry Division, Professors Carlos Silva of the Georgia Institute of Technology and Eric Bittner of the University of Houston are developing techniques that take advantage of light that obeys quantum mechanics to overcome these limitations. Specifically, they exploit entanglement of exactly two light particles (photons) at a time. Entanglement means that it is fundamentally impossible to distinguish between the properties of identical particles, regardless of how far they are from each other. The properties of the two entangled photons are measured after one of the two interacts with electrons in molecules. This approach provides new tools for chemists to understand the details on how electrons in different molecules talk to each other in order to dictate important collective behavior in liquids and solids. In addition to the scientific and technical innovations involved in this research, it serves as a training platform to contribute to the intellectual capital and scientific infrastructure of the US, in which quantum technologies is growing in significance. Technical description: Quantum process tomography is developed as a novel materials optical probe, with clear potential to isolate details of many-body and multi-quantum interactions with unique selectivity with respect to classical nonlinear spectroscopy and contemporary quantum spectroscopies. After one photon in a polarization-entangled pair interacts with a sample, the change in entanglement entropy the degree to which the initially pure state becomes a mixed quantum state is quantified. This change is driven by nonlinear processes in the sample. The objectives for this project are (i) to implement a versatile time-tagged quantum-process tomography setup to investigate multi-quantum processes in conjugated molecules and polymers, and (ii) to develop a theoretical formalism invoking the quantum-optical nature of the technique and the effect on the entangled biphoton state of the many-body physics intrinsic to the material.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.