November 2020
Abstracts of the QSIT Lunch Seminar, Thursday, November 5, 2020
Demonstrating the power of state-of-the-art quantum computers
Elisa Bäumer - Quantum Information Theory (Renner group), ETH Zurich
Increasingly sophisticated quantum computers motivate the exploration of their abilities in certifying genuine quantum phenomena. In this talk, I will give an overview of state-of-the-art IBM quantum computers and demonstrate their power in correlation experiments inspired by quantum networks. Our experiments feature up to 12 qubits and require the implementation of paradigmatic Bell-State Measurements for scalable entanglement-swapping. Our results demonstrate the ability of quantum computers to outperform classical limitations and certify scalable entangled measurements.
Metrological complementarity reveals the Einstein-Podolsky-Rosen paradox
Matteo Fadel - Quantum Optics Lab (Treutlein group), University of Basel
The Einstein-Podolsky-Rosen (EPR) paradox is typically associated with the possibility of predicting the results of non-commuting measurements with a precision that seems to violate the uncertainty principle. This apparent contradiction to complementarity is made possible by nonclassical correlations stronger than entanglement, called steering. Quantum information recognises steering as an essential resource for a number of tasks but, contrary to entanglement, its role for metrology has so far remained unclear. In this talk I will present a formulation of the EPR paradox in the framework of quantum metrology, showing that it enables the precise estimation of a local phase shift and of its generating observable. Employing a stricter formulation of quantum complementarity, we derive a criterion based on the quantum Fisher information that detects steering in a larger class of states than well-known uncertainty-based criteria. Our result identifies useful steering for quantum enhanced precision measurements and allows one to uncover steering of non-Gaussian states in state-of-the-art atomic and optical experiments.