Taking tomographic measurements for photonic qubits 88 ns before they are created
Zhibo Hou(侯志博)1,2, Qi Yin(殷琪)1,2, Chao Zhang(张超)1,2, Han-Sen Zhong(钟翰森)1,2, Guo-Yong Xiang(项国勇)1,2,†, Chuan-Feng Li(李传锋)1,2, Guang-Can Guo(郭光灿)1,2, Geoff J. Pryde3, and Anthony Laing4,‡
1 Key Laboratory of Quantum Information, University of Science and Technology of China, CAS, Hefei 230026, China; 2 Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei 230026, China; 3 Centre for Quantum Computation and Communication Technology (CQC2T) and Centre for Quantum Dynamics, Griffith University, Brisbane, 4111, Australia; 4 Quantum Engineering and Technology Laboratories, School of Physics and Department of Electrical and Electronic Engineering, University of Bristol, UK
Abstract We experimentally demonstrate that tomographic measurements can be performed for states of qubits before they are prepared. A variant of the quantum teleportation protocol is used as a channel between two instants in time, allowing measurements for polarization states of photons to be implemented 88 ns before they are created. Measurement data taken at the early time and later unscrambled according to the results of the protocol's Bell measurements, produces density matrices with an average fidelity of 0.900.01 against the ideal states of photons created at the later time. Process tomography of the time reverse quantum channel finds an average process fidelity of 0.840.02. While our proof-of-principle implementation necessitates some post-selection, the general protocol is deterministic and requires no post-selection to sift desired states and reject a larger ensemble.
Fund: Project supported by the National Key Research and Development Program of China (Grant No. 2018YFA0306400) and the National Natural Science Foundation of China (Grant Nos. 61905234, 11974335, 11574291, and 11774334). GP acknowledges support from the US Army Research Office (ARO) Grant No. W911NF-14-1-0133, and the Australian Research Council (DP140100648, CE170100012). Fellowship support from EPSRC is acknowledged by A.L. (EP/N003470/1).
Zhibo Hou(侯志博), Qi Yin(殷琪), Chao Zhang(张超), Han-Sen Zhong(钟翰森), Guo-Yong Xiang(项国勇), Chuan-Feng Li(李传锋), Guang-Can Guo(郭光灿), Geoff J. Pryde, and Anthony Laing Taking tomographic measurements for photonic qubits 88 ns before they are created 2021 Chin. Phys. B 30 040304
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