IQUIST Special Seminar: Prineha Narang, University of California, Los Angeles  

Abstract: Quantum information technologies are expected to enable transformative technologies with wide-ranging global impact. Towards realizing this tremendous promise, efforts have emerged to pursue quantum architectures capable of supporting distributed quantum computing, networks and quantum sensors. Quantum architecture at scale would consist of interconnected physical systems, many operating at their individual classical or quantum limit. Such scalable quantum architecture requires modeling that accurately describes these mesoscopic hybrid phenomena. By creating predictive theoretical and computational approaches to study dynamics, decoherence and correlations in quantum matter, our work could enable such hybrid quantum technologies1,2. In this talk, I will present examples from my research group on describing, from first principles, the microscopic dynamics, decoherence and optically-excited collective phenomena in matter at finite temperature to quantitatively link predictions with 3D atomic-scale imaging, quantum spectroscopy, and macroscopic behavior. Capturing these dynamics poses unique theoretical and computational challenges. The simultaneous contribution of processes that occur on many time and length-scales have remained elusive for state-of-the-art calculations and model Hamiltonian approaches alike, necessitating the development of new methods in computational physics3–5. I will show selected examples of our approach in ab initio design of active defects in quantum materials6–8, and control of collective phenomena to link these active defects9,10. Building on this, in the second part of my seminar, I will present promising physical mechanisms and device architectures for coupling (transduction) to other qubit platforms via dipole-, phonon-, and  magnon-mediated  interactions9–12. In a molecular context, will discuss approaches to entangling molecules in the strong coupling regime. Being able to control molecules at a quantum level gives us access to degrees of freedom such as the vibrational or rotational degrees to the internal state structure. Entangling those degrees of freedom offers unique opportunities in quantum information processing, especially in the construction of quantum memories. In particular, we look at two identical molecules spatially separated by a variable distance within a photonic environment such as a high-Q optical cavity. By resonantly coupling the effective cavity mode to a specific vibrational frequency of both molecules, we theoretically investigate how strong light-matter coupling can be used to control the entanglement between vibrational quantum states of both molecules. Linking this with detection of entanglement and quantifying the entanglement with an appropriate entanglement measure, we use quantum tomographic techniques to reconstruct the density matrix of the underlying quantum state. Taking this further, I will present some of our recent work in capturing non-Markovian dynamics in open quantum systems (OQSs) built on the ensemble of Lindblad's trajectories approach 13–16. Finally, I will present ideas in directly emulating quantum systems, particularly addressing the issues of model abstraction and scalability, and connect with the various quantum algorithm efforts underway.

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