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Phys. Rev. Lett. 104, 080503 (2010) [4 pages]

Experimental Feedback Control of Quantum Systems Using Weak Measurements

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G. G. Gillett1,*, R. B. Dalton1,†, B. P. Lanyon1, M. P. Almeida1, M. Barbieri1,5, G. J. Pryde2, J. L. O’Brien3, K. J. Resch4, S. D. Bartlett6, and A. G. White1
1Department of Physics and Centre for Quantum Computer Technology, The University of Queensland, Brisbane 4072, Australia
2Centre for Quantum Dynamics and Centre for Quantum Computer Technology, Griffith University, Brisbane 4111, Australia
3Centre for Quantum Photonics, H. H. Wills Physics Laboratory and Department of Electrical and Electronic Engineering, University of Bristol, Bristol BS8 1UB, United Kingdom
4Institute for Quantum Computing and Department of Physics and Astronomy, University of Waterloo, Waterloo, Ontario, N2L 3G1 Canada
5Laboratoire Charles Fabry, Institut d’Optique, Palaiseau 91127, France
6School of Physics, The University of Sydney, Sydney 2006, Australia

Received 24 November 2009; published 26 February 2010

A goal of the emerging field of quantum control is to develop methods for quantum technologies to function robustly in the presence of noise. Central issues are the fundamental limitations on the available information about quantum systems and the disturbance they suffer in the process of measurement. In the context of a simple quantum control scenario—the stabilization of nonorthogonal states of a qubit against dephasing—we experimentally explore the use of weak measurements in feedback control. We find that, despite the intrinsic difficultly of implementing them, weak measurements allow us to control the qubit better in practice than is even theoretically possible without them. Our work shows that these more general quantum measurements can play an important role for feedback control of quantum systems.

© 2010 The American Physical Society

URL:
http://link.aps.org/doi/10.1103/PhysRevLett.104.080503
DOI:
10.1103/PhysRevLett.104.080503
PACS:
03.67.Pp, 02.30.Yy, 03.65.Ta, 42.50.Ex

*Corresponding author.

gillett@physics.uq.edu.au

†Corresponding author.

rohan.dalton@gmail.com

 
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