Abstract

Entangled systems with large quantum Fisher information (QFI) can be used to outperform the standard quantum limit of the separable systems in quantum metrology. However, the interaction between the system and the environments inevitably leads to decoherence and decrease of the QFI, and it is not clear whether the entanglement systems can be a better resource than separable systems in the realistic physical condition. In this work, we study the steady QFI of two driven and collectively damped qubits with homodyne-mediated feedback. We show that the steady QFI can be significantly enhanced both in the cases of symmetric feedback and nonsymmetric feedback, and the shot-noise limit of separable states can be surpassed in both cases. The QFI can even achieve the Heisenberg limit for appropriate feedback parameters and initial conditions in the case of symmetric feedback. We also show that an initial-condition-independent steady QFI can be obtained by using nonsymmetric feedback.

© 2016 Optical Society of America

Real-time shot-noise-limited differential photodetection for atomic quantum control

F. Martin Ciurana, G. Colangelo, Robert J. Sewell, and Morgan W. Mitchell
Opt. Lett. 41(13) 2946-2949 (2016)

Broad-bandwidth near-shot-noise-limited intensity noise suppression of a single-frequency fiber laser

Qilai Zhao, Shanhui Xu, Kaijun Zhou, Changsheng Yang, Can Li, Zhouming Feng, Mingying Peng, Huaqiu Deng, and Zhongmin Yang
Opt. Lett. 41(7) 1333-1335 (2016)

Single logical qubit information encoding scheme with the minimal optical decoherence-free subsystem

Li Dong, Jun-Xi Wang, Qing-Yang Li, Hong-Zhi Shen, Hai-Kuan Dong, Xiao-Ming Xiu, and Ya-Jun Gao
Opt. Lett. 41(5) 1030-1033 (2016)

Few-photon scattering in dispersive waveguides with multiple qubits

Şükrü Ekin Kocabaş
Opt. Lett. 41(11) 2533-2536 (2016)

Simultaneous all-optical phase noise mitigation and automatically locked homodyne reception of an incoming QPSK data signal

Amirhossein Mohajerin-Ariaei, Morteza Ziyadi, Ahmed Almaiman, Yinwen Cao, Fatemeh Alishahi, Mohammad Reza Chitgarha, Ahmad Fallahpour, Jeng-Yuan Yang, Changjing Bao, Peicheng Liao, Bishara Shamee, Youichi Akasaka, Motoyoshi Sekiya, Joseph D. Touch, Moshe Tur, Carsten Langrock, Martin M. Fejer, and Alan E. Willner
Opt. Lett. 41(20) 4779-4782 (2016)