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Filtering noise in quantum systems

Presented by: 
M Biercuk University of Sydney
Date: 
Friday 8th August 2014 - 09:45 to 10:25
Venue: 
INI Seminar Room 1
Abstract: 
Co-authors: Alex Soare (ARC Centre for Engineered Quantum Systems, University of Sydney), Harrison Ball (ARC Centre for Engineered Quantum Systems, University of Sydney), David Hayes (ARC Centre for Engineered Quantum Systems, University of Sydney), Xinglong Zhen (ARC Centre for Engineered Quantum Systems, University of Sydney), MC Jarratt (ARC Centre for Engineered Quantum Systems, University of Sydney), Jarrah Sastrawan (ARC Centre for Engineered Quantum Systems, University of Sydney)

Instabilities due to extrinsic interference are routinely faced in systems engineering, and a common solution is to rely on a broad class of filtering techniques in order to afford stability to intrinsically unstable systems. For instance, electronic systems are frequently designed to incorporate electrical filters composed of, e.g. RLC components, in order to suppress the effects of out-of-band fluctuations that interfere with desired performance. Quantum coherent systems are now moving to a level of complexity where challenges associated with realistic time-dependent noise are coming to the fore. In this talk we present work using the theory of quantum control engineering and experiments with trapped ions to demonstrate the construction of noise filters which are specifically designed to mitigate the effect of realistic time-dependent fluctuations on qubits during useful operations. Starting with desired filter characteristics and the Walsh basis functions, we use a com bination of analytic design rules and numeric search to construct time-domain noise filters tailored to a desired state transformation. We describe experiments validating the generalized filter-transfer function framework for arbitrary quantum control operations, and demonstrate that it can be leveraged as an effective tool for developing robust control protocols. We describe how these filtering approaches can be extended to multi-qubit gates and even complex quantum control tasks at the algorithmic level.
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