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Background: Melanocytic nevi (MN) can be classified into three subtypes according to the depth of the nests of nevus cells which is important for management. High‐frequency ultrasound (HF‐US) can clearly reveal the lesion size, contour, depth, and internal structures. However, the HF‐US studies of MN according to subtypes are limited. We aimed to describe the HF‐US features of MN and explore its value in accurate classification. Materials and methods: This retrospective study was conducted from January 2018 to November 2019. Eighty‐five patients with MN were included and examined by 50 and 20 MHz HF‐US. The HF‐US features were recorded including morphological flatness, depth, shape, boundary, internal echogenicity, hyperechoic spots, lateral acoustic shadow, posterior echoic patterns, mushroom signs, and straw‐hat signs. Each image was evaluated by two physicians independently, and the consistency was tested. Results: Eleven lesions could not be detected by HF‐US. The rest 74 lesions underwent ultrasonic analysis. MN appeared as strip‐shaped or oval, hypoechoic areas localized in the epidermis and dermis under ultrasonography. A strong consistency between HF‐US and dermoscopy of determining the lesion depth was achieved (κ = 0.935, p < 0.001). The hyperechoic spots were found in 57.6% intradermal nevi. The mushroom signs were seen in 34.8% intradermal nevi, and the straw‐hat signs were seen in all the compound nevi. Conclusion: MN can be correctly classified using HF‐US, and it had a strong correlation with dermoscopic and clinical classification. HF‐US could further reveal the internal morphological features of MN, which may support more precise classification and management. [ABSTRACT FROM AUTHOR]

Based on quantum information splitting and reconstruction, we present a quantum private comparison (QPC) protocol, enabling two distrustful parties (Alice and Bob) to compare the equality of their information without revealing the information content. In this protocol, the information carriers are split into two wave packets by a beam splitter (BS), which is owned by a semi-honest third party Trent, and then they are sent to Alice and Bob, respectively. Alice and Bob encodes their secret information on the received wave packets. Only the superimposition of the two wave packets in Trent's site can reveal the compared result. Compared with the QPC protocols using entangled states, the information carriers used in our protocol is single-photon pulse, which reduces the difficulty of realization in practical. In addition, our protocol is feasible with the present techniques since only linear optical components, BS, single-photon detector, phase shifter (PS) and switcher (SWT) are required. The security of the protocol is ensured by principles on the phenomenon of quantum interference. And through the security analysis it shows that the protocol is secure and resists against the well-known attacks. [ABSTRACT FROM AUTHOR]