分类： 光学 >> 量子光学 提交时间： 2023-02-19
Xiaodong Zheng
Peiyu Zhang
Renyou Ge
Liangliang Lu
Guanglong He
Qi Chen
Fangchao Qu
Labao Zhang
Xinlun Cai
Yanqing Lu
Shining Zhu
Peiheng Wu
Xiao-Song Ma
摘要： Integrated photonics provides a route both to miniaturize quantum key distribution (QKD) devices and to enhance their performance. A key element for achieving discrete-variable QKD is a single-photon detector. It is highly desirable to integrate detectors onto a photonic chip to enable the realization of practical and scalable quantum networks. We realize an integrated heterogeneous superconducting-silicon-photonic chip. Harnessing the unique high-speed feature of our optical waveguide-integrated superconducting detector, we perform the first optimal Bell-state measurement (BSM) of time-bin encoded qubits generated from two independent lasers. The optimal BSM enables an increased key rate of measurement-device-independent QKD, which is immune to all attacks against the detection system, and hence provides the basis for a QKD network with untrusted relays. Together with the time-multiplexed technique, we have enhanced the sifted key rate by almost one order of magnitude. With a 125 MHz clock rate, we obtain a secure key rate of 6.166 kbps over 24.0 dB loss, which is comparable to the state-of-the-art MDI-QKD experimental results with GHz clock rate. Combined with integrated QKD transmitters, a scalable, chip-based and cost-effective QKD network should become realizable in the near future.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
Ming-Hao Jiang
Wenyi Xue
Qian He
Yu-Yang An
Xiaodong Zheng
Wen-Jie Xu
Wenjun Wen
Yu-Bo Xie
Yanqing Lu
Shining Zhu
Xiao-Song Ma
摘要： The quantum internet -- in synergy with the internet that we use today -- promises an enabling platform for next-generation information processing, including exponentially speed-up distributed computation, secure communication, and high-precision metrology. The key ingredients for realizing such a global network are the distribution and storage of quantum entanglement. As quantum networks are likely to be based on existing fibre networks, telecom-wavelength entangled photons and corresponding quantum memories are of central interest. Recently, ${\rm ^{167}Er^{3+}}$ ions have been identified as a promising candidate for an efficient, broadband quantum memory at telecom wavelength. However, to date, no storage of entangled photons, the crucial step of quantum memory using these ions, has been reported. Here, we demonstrate the storage and recall of the entangled state of two telecom photons generated from an integrated photonic chip based on silicon nitride. Combining the natural narrow linewidth of the entangled photons and long storage time of ${\rm ^{167}Er^{3+}}$ ions, we achieve storage time of 400 ns, more than one order of magnitude longer than in previous works. Successful storage of entanglement in the crystal is certified by a violation of an entanglement witness by more than 12 standard deviations (-0.161 $\pm$ 0.012) at 400 ns storage time. These results pave the way for realizing quantum networks based on solid-state devices.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： The interference of quanta lies at the heart of quantum physics. The multipartite generalization of single-quanta interference creates entanglement, the coherent superposition of states shared by several quanta. Entanglement allows non-local correlations between many quanta and hence is a key resource for quantum information technology. Entanglement is typically considered to be essential for creating non-local correlations, manifested by multipartite interference. Here, we show that this is not the case and demonstrate multiphoton non-local quantum interference without entanglement of any intrinsic properties of the photons. We harness the superposition of the physical origin of a four-photon product state, which leads to constructive and destructive interference of the photons' mere existence. With the intrinsic indistinguishability in the generation process of photons, we realize four-photon frustrated quantum interference. We furthermore establish non-local control of multipartite quantum interference, in which we tune the phase of one undetected photon and observe the interference of the other three photons. Our work paves the way for fundamental studies of non-locality and potential applications in quantum technologies.
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