Taking tomographic measurements for photonic qubits 88 ns before they are created

• 作者: Zhibo Hou Qi Yin Chao Zhang Han-Sen Zhong Guo-Yong Xiang Chuan-Feng Li Guang-Can Guo Geoff J.Pryde Anthony Laing
• 来源期刊: 中国物理B（英文版）
• 年，卷（期）: 2021,（4）
• 所属期刊栏目: SPECIAL TOPIC—Quantum computation and quantum simulation
• 页码范围: 59-65
• 页数: 7页
• 语种: 英文
• DOI: 10.1088/1674-1056/abe29c

摘要

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 0.90±0.01 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 0.84±0.02.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.