Proposal for a loophole-free Bell test based on spin-photon interactions in cavities

We present a scheme to demonstrate loophole-free Bell inequality violation where the entanglement between photon pairs is transferred to solid state (spin) qubits mediated by cavity QED interactions. As this transfer can be achieved in a heralded way, our scheme is basically insensitive to losses on the channel. This makes it appealing for the implementation of quantum information protocols based on nonlocality, such as device-independent quantum key distribution. We consider potential experimental realisations of our scheme using single atom, colour centre and quantum dot cavity systems.Comment: 7 pages, 4 figure

Interference between distinguishable photons

Two-photon interference (TPI) lies at the heart of photonic quantum technologies. TPI is generally regarded as quantum interference stemming from the indistinguishability of identical photons, hence a common intuition prevails that TPI would disappear if photons are distinguishable. Here we disprove this perspective and uncover the essence of TPI. We report the first demonstration of TPI between distinguishable photons with their frequency separation up to $10^4$ times larger than their linewidths. We perform time-resolved TPI between an independent laser and single photons with ultralong coherence time ($>10\ \mu$s). We observe a maximum TPI visibility of $72\%\pm 2\%$ well above the $50\%$ classical limit indicating the quantum feature, and simultaneously a broad visibility background and a classical beat visibility of less than $50\%$ reflecting the classical feature. These visibilities are independent of the photon frequency separation and show no difference between distinguishable and indistinguishable photons. Based on a general wave superposition model, we derive the cross-correlation functions which fully reproduce and explain the experiments. Our results reveal that TPI as the fourth-order interference arises from the second-order interference of two photons within the mutual coherence time and TPI is not linked to the photon indistinguishability. This work provides new insights into the nature of TPI with great implications in both quantum optics and photonic quantum technologies.Comment: 7 pages, 5 figures. Comments are welcome. arXiv admin note: substantial text overlap with arXiv:2404.0515

Quantum and Classical Two-photon Interference of Single Photons with Ultralong Coherence Time

Two-photon interference (TPI) is a fundamental phenomenon in quantum optics and plays a crucial role in quantum information science and technology. TPI is commonly considered as quantum interference with an upper bound of $100\%$ for both the TPI visibility and the beat visibility in contrast to its classical counterpart with a maximum visibility of $50\%$. However, this is not always the case. Here we report a simultaneous observation of quantum and classical TPI of single photons with ultralong coherence time which is longer than the photon correlation time by five orders of magnitude. We observe a TPI visibility of $94.3\%\pm 0.2\%$ but a beat visibility of $50\%$. Besides an anti-bunching central dip due to single-photon statistics, we observe two bunching side peaks in cross-correlation curves for indistinguishable photons. Using either classical wave superposition theory or quantum field approach, we derive the same expressions for the cross-correlation functions which reproduce and explain the experiments well. We conclude that quantum TPI with a stream of single photons is equivalent to classical TPI, both of which are the fourth-order interference arising from the second-order interference occurring on the time scale of photon coherence time.Comment: 7 pages, 4 figures, Comments are welcom

Highly discriminative and adaptive feature extraction method based on NMF-MFCC for event recognition of Φ-OTDR

To enhance the capability of phase-sensitive optical time domain reflectometers (Φ-OTDR) to recognize disturbance events, an improved adaptive feature extraction method based on NMF-MFCC is proposed, which replaces the fixed filter bank used in the traditional method to extract the mel-frequency cepstral coefficient (MFCC) features by a spectral structure obtained from the Φ-OTDR signal spectrum using nonnegative matrix factorization (NMF). Three typical events on fences are set as recognition targets in our experiments, and the results show that the NMF-MFCC features have higher distinguishability, with the corresponding recognition accuracy reaching 98.47%, which is 7% higher than that using the traditional MFCC features.</p

Hotspots and frontiers of the relationship between gastric cancer and cancer-associated fibroblasts: a bibliometric analysis

BackgroundCancer-Associated Fibroblasts (CAFs) are pivotal stromal constituents within the Tumor Microenvironment (TME), characterized by marked heterogeneity and plasticity. Over the past two decades, a notable association between Gastric Cancer (GC) and CAFs has been established. Despite this, there remains a paucity of comprehensive data to guide researchers in understanding the prevalence and potential research trajectories concerning GC and CAFs.MethodsThis study conducted an extensive literature search within the Web of Science Core Collection database from January 1, 2003, to December 31, 2023. Bibliometric analysis and visualization were performed using VOSviewer, CiteSpace, R software, and Microsoft Excel.ResultsA total of 1170 articles were included. These articles were disseminated across 200 journals and incorporated 1800 distinct keywords. A notable surge in publications has been observed from 2011 to 2023. China emerged as the leading contributor to both article count and citations. Prominent research institutions in this domain include Osaka City University, Shanghai Jiaotong University, and National Cancer Research Center Hospital. Notable researchers, such as Masakazu Yashiro and Kosei Hirakawa from Osaka City University and Zhenggang Zhu from Shanghai Jiaotong University, were among the most productive and highly cited authors. FRONTIERS IN ONCOLOGY boasts the highest number of publications, whereas ONCOGENE ranks as the most cited journal. The primary research foci within the realm of CAFs and GC encompass the impact of CAFs on GC cell proliferation, angiogenesis, invasion, metastasis, epithelial-mesenchymal transition, immunosuppression, drug resistance, and the interplay between CAFs and GC.ConclusionUsing bibliometric analysis, this study presents a panoramic view of the research landscape of CAFs and GC from 2003 to 2023. It highlights prominent research areas and anticipates future directions with the aim of offering valuable insights and strategic recommendations for future endeavors in this field

Sidelobe Suppression Method with Improved CLEAN Algorithm for Pulse Compression OTDR

Although pulse compression optical time domain reflectometry (PC-OTDR) exhibits high performance in spatial resolution and dynamic range, it inevitably introduces auto-correlation sidelobes, potentially impacting measurement accuracy. In this letter, an improved CLEAN algorithm is proposed to efficiently suppress sidelobes and enhance the peak-to-sidelobe ratio (PSLR) of signals in PC-OTDR. The proposed method introduces an adaptive step factor instead of the traditional fixed factor to reduce the number of iterations. Compared to the traditional method, the proposed method achieves a 2.87 dB improvement of PSLR from a 10 km sensing fiber. In addition, the computation time cost is significantly reduced, which is 1.92 s less than that of the traditional CLEAN algorithm