ABSTRACT

Nontechnical description: Quantum-information science promises to revolutionize computation and communication, as well as our fundamental understanding of complex quantum systems. Qubits, the fundamental units of quantum computation, are the quantum analogs of the binary states of classical computers. A fundamental requirement of qubits is that the time over which they retain the encoded information, known as lifetime, is long compared to the operations that manipulate them. Here, the research team proposes a method to dramatically increase qubit lifetimes in specialized two-dimensional semiconductor materials. The main mechanism by which information in a qubit is lost is through interactions of the system and its environment, much like a pendulum is slowed down by friction at its suspension point. A common approach to increasing qubit lifetime is to isolate the system, analogous to lubricating the point of suspension of the pendulum, but this is highly impractical for many quantum information applications. The approach proposed here is to periodically decouple the system from its environment using various external controls. In this way, qubit lifetime is extended even at room temperature, greatly expanding the range of materials that can be used for quantum information applications. These research aims are naturally integrated with an educational plan that seeks to advance undergraduate, graduate, and postdoctoral training. The mechanism of this program is the development of online tutorial courses and outreach work that promotes science learning to a broad audience.

Technical description: A major challenge in quantum information sciences has been the prevalence of short-lived coherences between quantum states, which impede practical utilization of quantum phenomena. This is especially problematic at room temperature where the environment causes large energy fluctuations that greatly accelerate decoherence. Here, the research team proposes a method to dramatically increase electronic coherence times in quantum-confined two-dimensional (2D) semiconductors at room temperature. The approach is multi-faceted: 1) perform 'single' particle measurements to minimize heterogeneous broadening, 2) identify transient excitonic states that are well-below the bandgap of the materials, and 3) create unique decoherence-free subspaces by optical driving fields that decouple the excitons from strongly coupled phonons, thereby giving rise to long-lived coherences among electronic states of matter. The proposed platform based on highly tunable 2D organic-inorganic perovskite crystals is used to create robust quantum states far from thermal equilibrium for applications in quantum sensing, quantum transport, and quantum information processing. 2D perovskites are ideal materials for this purpose because they exhibit a large manifold of transient and strongly-coupled exciton states that can be used as qubits in quantum information processing and sensing. The approach combines ideas from magnetic resonance, quantum chemistry, coherent spectroscopy, and quantum optics in order to create long-lived coherences with orders-of-magnitude longer electronic coherence times than currently possible in condensed-phase molecular systems under ambient conditions. The work proposed here enables understanding of how structural and chemical changes to the system, as well as modifications of the bath through external perturbations, affect decoherence far from thermal equilibrium. This project incorporates an educational component that advances undergraduate and graduate training through the creation of online tutorial courses that disseminate the research findings and the scientific background necessary to understand them. These courses are made available to a wide audience of students and teachers at the K-12 levels.

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.

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