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Improving Accuracy of Estimating Two-Qubit States with Hedged Maximum Likelihood |
| Qi Yin1,2, Guo-Yong Xiang1,2**, Chuan-Feng Li1,2, Guang-Can Guo1,2 |
1Key Laboratory of Quantum Information, University of Science and Technology of China, Chinese Academy of Sciences, Hefei 230026
2Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Chinese Academy of Sciences, Hefei 230026
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| Cite this article: |
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Qi Yin, Guo-Yong Xiang, Chuan-Feng Li et al 2017 Chin. Phys. Lett. 34 030301 |
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Abstract As a widely used reconstruction algorithm in quantum state tomography, maximum likelihood estimation tends to assign a rank-deficient matrix, which decreases estimation accuracy for certain quantum states. Fortunately, hedged maximum likelihood estimation (HMLE) [Phys. Rev. Lett. 105 (2010) 200504] was proposed to avoid this problem. Here we study more details about this proposal in the two-qubit case and further improve its performance. We ameliorate the HMLE method by updating the hedging function based on the purity of the estimated state. Both performances of HMLE and ameliorated HMLE are demonstrated by numerical simulation and experimental implementation on the Werner states of polarization-entangled photons.
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Received: 05 December 2016
Published: 28 February 2017
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| PACS: |
03.67.-a
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(Quantum information)
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03.65.Wj
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(State reconstruction, quantum tomography)
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42.50.Dv
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(Quantum state engineering and measurements)
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| Fund: Supported by the National Natural Science Foundation of China under Grant Nos 11574291, 61108009 and 61222504. |
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