TY - JOUR
T1 - Feedback control of quantum entanglement in a two-spin system
AU - Yamamoto, Naoki
AU - Tsumura, Koji
AU - Hara, Shinji
N1 - Funding Information:
This paper was not presented at any IFAC meeting. This paper was recommended for publication in revised form by Associate Editor Rene Boel under the direction of Editor Ian Petersen. This work is supported by The Ministry of Education, Science, Sport and Culture, Japan, under Grants 06693 and 17656137.
PY - 2007/6
Y1 - 2007/6
N2 - A pair of spins is the most simple quantum system that can exhibit entanglement: a nonclassical property that plays an essential role in quantum information technologies. In this paper, feedback control problems of a symmetric two-spin system conditioned on a continuous measurement are investigated. In order to make some useful formulas in stochastic control theory directly applicable, we first derive a two-dimensional representation of the system. We then prove that a feedback controller stabilizes an entangled state of the two spins almost globally with probability one. Furthermore, it is demonstrated that some entangled states, which correspond to nonequilibrium points of the dynamics, are globally stabilized via feedback in the sense that the mean distance from a target can be reduced to an arbitrarily small value.
AB - A pair of spins is the most simple quantum system that can exhibit entanglement: a nonclassical property that plays an essential role in quantum information technologies. In this paper, feedback control problems of a symmetric two-spin system conditioned on a continuous measurement are investigated. In order to make some useful formulas in stochastic control theory directly applicable, we first derive a two-dimensional representation of the system. We then prove that a feedback controller stabilizes an entangled state of the two spins almost globally with probability one. Furthermore, it is demonstrated that some entangled states, which correspond to nonequilibrium points of the dynamics, are globally stabilized via feedback in the sense that the mean distance from a target can be reduced to an arbitrarily small value.
KW - Feedback control
KW - Quantum systems
KW - Stochastic differential equation
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U2 - 10.1016/j.automatica.2006.12.008
DO - 10.1016/j.automatica.2006.12.008
M3 - Article
AN - SCOPUS:34247484349
SN - 0005-1098
VL - 43
SP - 981
EP - 992
JO - Automatica
JF - Automatica
IS - 6
ER -