### Abstract

A pair of spins is the most simple quantum system that can possess entanglement, a non-classical property playing an essential role in quantum information technologies. In this paper, feedback control problems of the two-spin system conditioned on a continuous measurement are considered. In order to make some useful formulas in stochastic control theory directly applicable, we first derive a two-dimensional description 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 shown that another entangled state, which corresponds to a non-equilibrium point of the dynamics, is stabilized via feedback in the sense that the expectation of the distance from the target can be made arbitrarily small.

Original language | English |
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Title of host publication | Proceedings of the 44th IEEE Conference on Decision and Control, and the European Control Conference, CDC-ECC '05 |

Pages | 3182-3187 |

Number of pages | 6 |

Volume | 2005 |

DOIs | |

Publication status | Published - 2005 |

Externally published | Yes |

Event | 44th IEEE Conference on Decision and Control, and the European Control Conference, CDC-ECC '05 - Seville, Spain Duration: 2005 Dec 12 → 2005 Dec 15 |

### Other

Other | 44th IEEE Conference on Decision and Control, and the European Control Conference, CDC-ECC '05 |
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Country | Spain |

City | Seville |

Period | 05/12/12 → 05/12/15 |

### Fingerprint

### ASJC Scopus subject areas

- Engineering(all)

### Cite this

*Proceedings of the 44th IEEE Conference on Decision and Control, and the European Control Conference, CDC-ECC '05*(Vol. 2005, pp. 3182-3187). [1582651] https://doi.org/10.1109/CDC.2005.1582651

**Feedback control of quantum entanglement in a two-spin system.** / Yamamoto, Naoki; Tsumura, Koji; Hara, Shinji.

Research output: Chapter in Book/Report/Conference proceeding › Conference contribution

*Proceedings of the 44th IEEE Conference on Decision and Control, and the European Control Conference, CDC-ECC '05.*vol. 2005, 1582651, pp. 3182-3187, 44th IEEE Conference on Decision and Control, and the European Control Conference, CDC-ECC '05, Seville, Spain, 05/12/12. https://doi.org/10.1109/CDC.2005.1582651

}

TY - GEN

T1 - Feedback control of quantum entanglement in a two-spin system

AU - Yamamoto, Naoki

AU - Tsumura, Koji

AU - Hara, Shinji

PY - 2005

Y1 - 2005

N2 - A pair of spins is the most simple quantum system that can possess entanglement, a non-classical property playing an essential role in quantum information technologies. In this paper, feedback control problems of the two-spin system conditioned on a continuous measurement are considered. In order to make some useful formulas in stochastic control theory directly applicable, we first derive a two-dimensional description 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 shown that another entangled state, which corresponds to a non-equilibrium point of the dynamics, is stabilized via feedback in the sense that the expectation of the distance from the target can be made arbitrarily small.

AB - A pair of spins is the most simple quantum system that can possess entanglement, a non-classical property playing an essential role in quantum information technologies. In this paper, feedback control problems of the two-spin system conditioned on a continuous measurement are considered. In order to make some useful formulas in stochastic control theory directly applicable, we first derive a two-dimensional description 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 shown that another entangled state, which corresponds to a non-equilibrium point of the dynamics, is stabilized via feedback in the sense that the expectation of the distance from the target can be made arbitrarily small.

UR - http://www.scopus.com/inward/record.url?scp=33847192510&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=33847192510&partnerID=8YFLogxK

U2 - 10.1109/CDC.2005.1582651

DO - 10.1109/CDC.2005.1582651

M3 - Conference contribution

SN - 0780395689

SN - 9780780395688

VL - 2005

SP - 3182

EP - 3187

BT - Proceedings of the 44th IEEE Conference on Decision and Control, and the European Control Conference, CDC-ECC '05

ER -