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Geometric phases and dissipation in quantum devices

... assessing the role of geometric manipulations for quantum information processing

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Project Description

This project is part of the EU STREP project

"GEOMDISS - Geometric phases, pumping, and dissipation in quantum devices"

with the aim to assess the role of geometric manipulations in quantum solid-state devices for future ICT applications and in metrological applications under realistic conditions.

One of the most intriguing aspects of quantum dynamics is the adiabatic geometric evolution. It allows for manipulation of the state of a quantum system by slowly varying the system's parameters along a contour in parameter space. Robustness of this technique motivated proposals of, e.g., geometric manipulations (gates) of quantum bits for quantum computing or geometric pumping of charge for setting the standard of current. Since all realistic solid-state devices suffer from dissipation due to their coupling to the environment, it is crucial to understand how geometric effects are modified and whether they are still useful.

The objective of our part of the project is to investigate geometric phase effects as a promising approach for the implementation of robust quantum gates in the circuit QED architecture. In a previous experiment we have already observed Berry's adiabatic geometric phase [Leek et al. Science 318, 1889 (2007)] and demonstrated the presence of geometric dephasing. Since adiabatic, infinitely slow manipulations are impractical in solid-state devices, we will explore the adiabatic limit separating adiabatic and non-adiabatic regimes of evolution. By adding artificial noise, we will characterize dissipative corrections to the geometric phase for noise with different characteristics and further determine the nature of intrinsic noise sources. We will perform comparative experiments on geometric and traditional single and two qubit operations and study possible implementations of holonomic quantum gates.

Stefan Filipp
Andreas Wallraff

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