[QIP-Sem] QIP seminar, Mon 5/9, 4:00, 36-428, Steve Flammia

[Peter Shor]

MIT Quantum Information Processing seminar
Monday 5/9 at 4:00 in 36-428
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Steve Flammia (California Institute of Technology)

Verification and Characterization of Quantum States and Processes

Abstract:

Recent years have witnessed tremendous progress in laboratory experiments which prepare highly entangled states of quantum many-body systems. As the complexity of these states increases, however, so too does the difficultly in verifying the quality of the experiment by some objective measure, and in characterizing any undesired noise processes therein. In this talk I will discuss several new methods which address both tasks -- verification and characterization -- using far fewer resources than traditional methods. I will show how ideas from compressed sensing can be adapted to learn a nearly pure quantum state or nearly unitary quantum process using quadratically fewer measurement settings than traditional methods, an improvement which is provably optimal. Next, I will show how ideas from quantum information theory and condensed matter physics allow us to efficiently learn the ground states of local Hamiltonians of gapped one-dimensional interacting quantum systems in polynom
 ial time in the number of systems. Finally, I will show how to directly verify the quality of an experiment (as quantified by the fidelity or process fidelity with respect to some ideal process) using only a constant number of measurement settings, independent of the size of the system.

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