Noisy quantum devices: Theory and realizations

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Quantum technologies promise transformative applications in computing, communication, information storage and sensing. In the present paradigm, quantum devices rely on pure, quantum coherent (unitary) dynamics, assuming perfect isolation of the system from its surroundings. However, quantum systems are never perfectly isolated from their environment, leading to phase decoherence and energy dissipation, resulting in a degraded operation. In this program, we will advance a radically distinct paradigm for quantum devices: We will develop the theory, concepts, and applications of room-temperature noisy (dissipative) quantum systems whose operation is based on the synergy between quantum coherent and incoherent effects. The program includes three thrusts, to be advanced simultaneously. (i) Formulating and evolving the dynamics of externally-controlled quantum dissipative many-body systems pose a significant theoretical and computational challenge. We will develop theoretical tools to describe the dynamics of these rich quantum systems. Our semi-analytic methods will offer a balance between computationally-massive numerically exact tools and inaccurate yet intuitive perturbative methods. (ii) We will advance the theory of quantum thermodynamics. Focusing on heat engines, we will devise rational and machine-learned quantum control schemes for optimizing performance of these noisy devices utilizing strong system-bath coupling effects and uncovering cost-precision tradeoff relations. (iii) We will put our methods to work and propose noisy quantum devices in different platforms: atomic-scale and molecular electronic conductors and hybrid superconducting qubits. Concretely, we will study noisy quantum effects in charge, energy, and spin transport in molecules and within hybrid devices. In our work, we will formulate minimal models to gain insights, perform simulations of molecular systems to identify candidate systems, and collaborate with experimental groups to test our predictions. Specific intriguing topics to be examined include: (i) Unconventional charge transport behavior in nanostructures, e.g. electrical conductance that increases with molecular length. (ii) The origin, mitigation, and harnessing of current noise in nanoscale conductors. (iii) Role of quantum coherence in spin transport through chiral molecules. (iv) Quantum control of (noisy) heat machines and proposals for realizations in superconducting qubits. The program will be tackled by a diverse group of postdoctoral fellows, graduate students and undergraduates with backgrounds in chemistry, physics, and engineering. Efforts will be made to reach out to groups traditionally under-represented in Theoretical Chemistry and involve them in this research endeavor. Our research will contribute to the advancement of knowledge with the development of approaches for treating driven quantum many-body effects in complex systems, and to new technologies: room-temperature, noisy quantum devices.