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Sortition is one fairness-preserving decision-making method, whereby each of the involved legitimate users can obtain a completely random but mutually different message. Here, using the fantastic high-dimension multi-particle singlet states as the random lot pool, we propose the first authenticated quantum sortition protocol in theory with some desirable properties of privacy, fairness, and uniqueness, which shows particular function glamour over to the classical sortitions. The proposed protocol also can expand to solve some related problems, defined as “picking at random”. Any effective attacks from an outside eavesdropper, semi-honest designated authority, and inside malicious user will be detected by honest participants, and thus guarantee the security. This work to sortition theory helps elucidate how quantum mechanics can be harnessed for secure strategic advantage.

The nonlocality research of quantum entanglement plays an important role in the development of quantum mechanics theory and quantum information technology. As multipartite entangled state is a rare quantum resource, its nonlocality research has always been an important subject in the study of quantum theory. In this paper, we focus on N entangled states composed of N copies of an entangled state. First, a new Bell test with respect to N entangled states is presented, and lifting Bell inequalities are applied to certify nonlocality. Second, we obtain the nonlocality certification standard of N entangled states by parity binning lifting Bell inequality. Third, we prove the conjecture that N + 2 entangled states must be local if N entangled states are local certified by parity binning lifting Bell inequality. The research will promote the theoretical research progress of quantum coherence, and provide theoretical basis and technical support for the multipartite entangled states application in quantum cryptographic protocols.

Quantum random access codes (QRACs) have attracted much attention because of their different properties from random access codes. How to explore and verify optimal QRAC strategies is an important research topic in quantum cryptography. In this paper, we focus on optimal $$n\rightarrow 1$$ QRACs using single 3-level systems. Here, we present a general upper bound of maximum guess probability of $$n\rightarrow 1$$ QRACs using a generalized Bloch sphere representation, and the maximum guess probability is an important indicator to verify whether it is the optimal QRAC. Furthermore, the optimal $$2\rightarrow 1$$ and $$3\rightarrow 1$$ QRACs are obtained through analytical methods. Finally, tight upper bounds of the maximum guess probability of $$2\rightarrow 1$$ and $$3\rightarrow 1$$ QRACs are acquired. These results will improve QRAC-based quantum cryptography protocols, such as quantum key distributions, quantum random number generations.

Recently, entanglement-assisted state discrimination has attracted much attention. However, most of the relevant results are about the bipartite quantum states and very little is known about the multipartite case. In this paper, considering the nonlocal orthogonal product states constructed by Jiang and Xu [Phys. Rev. A 102, 032211 (2020)], we first present one protocol to locally distinguish a set of orthogonal product states in $$3\otimes 3 \otimes 3$$ by using a $$2\otimes 2$$ maximally entangled state. Then, we generalize the distinguishing method for the class of nonlocal of orthogonal product states in $$\otimes _{j=1}^n{\mathbb {C}}^{d_j}$$ , where $$n\geqslant 3, d_j\geqslant 2, j=1,2,\ldots ,n$$ . Furthermore, for another class of orthogonal product states in $$\otimes _{j=1}^n{\mathbb {C}}^{d_j}$$ , where $$n\geqslant 3, d_j\geqslant 3, j=1,2,\ldots ,n$$ , we prove that these states can also be distinguished by LOCC with a $$3\otimes 3$$ maximally entangled state or two copies of $$2\otimes 2$$ maximally entangled states. The above results can let us better understand how to use entanglement resource more efficiently in multipartite quantum systems and also reveal the phenomenon of less nonlocality with more entanglement.

Dimensionality reduction (DR) algorithms, which reduce the dimensionality of a given data set while preserving the information of the original data set as well as possible, play an important role in machine learning and data mining. Duan \emph{et al}. proposed a quantum version of the A-optimal projection algorithm (AOP) for dimensionality reduction [Phys. Rev. A 99, 032311 (2019)] and claimed that the algorithm has exponential speedups on the dimensionality of the original feature space $n$ and the dimensionality of the reduced feature space $k$ over the classical algorithm. In this paper, we correct the time complexity of Duan \emph{et al}.'s algorithm to $O(\frac{\kappa^{4s}\sqrt{k^s}} {\epsilon^{s}}\mathrm{polylog}^s (\frac{mn}{\epsilon}))$, where $\kappa$ is the condition number of a matrix that related to the original data set, $s$ is the number of iterations, $m$ is the number of data points and $\epsilon$ is the desired precision of the output state. Since the time complexity has an exponential dependence on $s$, the quantum algorithm can only be beneficial for high dimensional problems with a small number of iterations $s$. To get a further speedup, we propose an improved quantum AOP algorithm with time complexity $O(\frac{s \kappa^6 \sqrt{k}}{\epsilon}\mathrm{polylog}(\frac{nm}{\epsilon}) + \frac{s^2 \kappa^4}{\epsilon}\mathrm{polylog}(\frac{\kappa k}{\epsilon}))$ and space complexity $O(\log_2(nk/\epsilon)+s)$. With space complexity slightly worse, our algorithm achieves at least a polynomial speedup compared to Duan \emph{et al}.'s algorithm. Also, our algorithm shows exponential speedups in $n$ and $m$ compared with the classical algorithm when both $\kappa$, $k$ and $1/\epsilon$ are $O(\mathrm{polylog}(nm))$., Comment: 11 pages, 2 figures

Nowadays, identity protection has turned into a fundamental demand for online activities. Currently, the present quantum anonymous communication protocols mostly rely on multi-entanglement. In this paper, we propose an anonymous communication protocol for anonymous sender by using single-particle states. The protocol can be extended to a communication protocol where the sender and receiver are fully anonymous with the message kept secret. In terms of security, our protocol is designed to comply with the technique of collective detection. Compared to the step-by-step detection, collective detection, in which the participants perform detection only once, reduces the complexity of the protocol to some extent. Moreover, we analytically demonstrate the security of the protocol in the face of active attacks. Any active attack employed by an external or internal attacker cannot reveal any useful information about the sender’s identity. Meanwhile, any malicious behavior will be detected by honest participants.

Anonymous voting is often one decision-making choice in many democracies. Facing the security threats from quantum computers, classical anonymous voting protocols based on computational complexity hypothesis have innovated to quantum anonymous voting protocols based on quantum mechanics. In this paper, we propose a quantum anonymous voting protocol by using high-dimension single particles. With the help of EA and T, the construction of our protocol makes each legitimate voter cast only one ballot, and all ballots open in a quite random rearrangement. Each voter can anonymously trace his/her vote by a private position index, thus our protocol achieving the precious properties of eligibility, privacy, no-reusability, verifiability and fairness. We also analyze that the protocol can successfully resist attacks from external eavesdroppers and internal participants, ensuring that our voting protocol is secure under ideal conditions. Designing mature quantum anonymous voting protocols is challenging.

In this paper, two multi-party quantum private comparison (MQPC) protocols are proposed in distributed mode and traveling mode, respectively. Compared with the first MQPC protocol, which pays attention to compare between arbitrary two participants, our protocols focus on the comparison of equality for $$n$$n participants with a more reasonable assumption of the third party. Through executing our protocols once, it is easy to get if $$n$$n participants' secrets are same or not. In addition, our protocols are proved to be secure against the attacks from both outside attackers and dishonest participants.

Influenza A (H7N9) virus infections were first observed in China in March 2013. This type virus can cause severe illness and deaths, the situation raises many urgent questions and global public health concerns. Our purpose was to investigate bedside chest radiography findings for patients with novel influenza A (H7N9) virus infections and the followup appearances after short-time treatment.Eight hospitalized patients infected with the novel influenza A (H7N9) virus were included in our study. All of the patients underwent bedside chest radiography after admission, and all had follow-up bedside chest radiography during their first ten days, using AXIOM Aristos MX and/or AMX-IV portable X-ray units. The exposure dose was generally 90 kV and 5 mAs, and was slightly adjusted according to the weight of the patients. The initial radiography data were evaluated for radiological patterns (ground glass opacity, consolidation, and reticulation), distribution type (focal, multifocal, and diffuse), lung zones involved, and appearance at follow-up while the patients underwent therapy.All patients presented with bilateral multiple lung involvement. Two patients had bilateral diffuse lesions, three patients had unilateral diffuse lesions of the right lobe with multifocal lesions of the left lobe, and the remaining three had bilateral multifocal lung lesions. The lesions were present throughout bilateral lung zones in three patients, the whole right lung zone in three patients with additional involvement in the left middle and/or lower lung zone(s), both lower and middle lung zones in one patient, and the right middle and lower in combination with the left lower lung zones in one patient. The most common abnormal radiographic patterns were ground glass opacity (8/8), and consolidation (8/8). In three cases examined by CT we also found the pattern of reticulation in combination with CT images. Four patients had bilateral and four had unilateral pleural effusion. After a short period of treatment the pneumonia in one patient had significantly improved and three cases demonstrated disease progression. In four cases the severity of the pneumonia fluctuated.In patients with influenza A (H7N9) virus infection, the distribution of the lung lesions are extensive, and the disease usually involves both lung zones. The most common imaging findings are a mixture of ground glass opacity and consolidation. Pleural effusion is common. Most cases have a poor short-time treatment response, and seem to have either rapid progressive radiographic deterioration or fluctuating radiographic changes. Chest radiography is helpful for evaluating patients with severe clinical symptoms and for follow-up evaluation.

We present the first quantum secure communication protocol for an anonymous receiver without the assistance of anonymous entanglement. In previous works, if a public sender wants to send quantum messages to a chosen receiver while protecting the identity of the receiver from others, all participants should cooperate first to construct the entanglement between the sender and the anonymous receiver. This is the most important process in anonymous quantum communications. With anonymous entanglement, the sender can communicate quantum messages to the anonymous receiver by applying teleportation protocols. In contrast, our protocol is novel and achieves communication of quantum messages directly from the public sender to the anonymous receiver based on the quantum one-time pad and current achievements. Notably, the anonymity of the receiver, as well as the privacy of the quantum messages, is perfectly protected with the exception of an exponentially small probability in our protocol.