Continuous variable quantum key distribution based on simultaneous quantum and classical communication in the terahertz band.

Continuous variable quantum key distribution (CVQKD) based on a simultaneous quantum and classical communication (SQCC) protocol can use a single coherent communication system for multiple purposes. In this paper, we propose an inter-satellite SQCC-CVQKD scheme in the terahertz (THz) band. This scheme performs classical modulation at the sending end, followed by quantum Gaussian modulation operations. At the receiving end, an amplifier is used to amplify and demultiplex the received signal, and, finally, a homodyne detector or heterodyne detector is selected for decoding. We have demonstrated the security of the SQCC-CVQKD system in the THz band, and a performance analysis of the scheme is given in the finite-size regime. The simulation results show that this scheme has a higher secret key rate and stronger anti-interference ability in practice. This work provides an effective way to construct wireless quantum communication networks.

Composable security for inter-satellite continuous-variable quantum key distribution in the terahertz band.

Continuous-variable quantum key distribution (CVQKD) can be effectively compatible with off-the-shelf communication systems and has been proven to be the security against collective attacks in the finite-size regime and composability. In this paper, we classify three different trust levels for the loss and noise experienced by the sender and receiver. Based on these trust levels, we derive the composable finite-size security bounds of inter-satellite CVQKD in the terahertz (THz) band. We also show how these trust levels can nontrivially increase the composable secret key rates of THz-CVQKD and tolerate higher loss. Furthermore, the numerical simulations strongly support the feasibility of inter-satellite THz-CVQKD even in the worst trust level. This work provides an efficient path for building an inter-satellite quantum communication network.

FL-QKD based on optical-THz biphotons generated by spontaneous parametric downconversion in inter-satellite wireless communication.

Floodlight quantum key distribution (FL-QKD) is a new QKD protocol that can achieve a 2 Gbps secret key rate (SKR) in a 50 km fiber link without multiplexing technology [Q. Zhuang et al., Phys. Rev. A94, 012322 (2016)PLRAAN1050-294710.1103/PhysRevA.94.012322]. In this paper, we propose a wireless FL-QKD at terahertz bands (THz-FL-QKD) in inter-satellite links. THz-FL-QKD is the two-way protocol that sends quantum signals in the forward channel, modulates and amplifies the received signals at the receiver, and then returns to the transmitter through the backward channel for homodyne detection and decoding. We analyze the security of THz-FL-QKD against individual attacks and optimum collective attacks. Numerical simulations show that THz-FL-QKD is capable of a 50 Mbps SKR at 10 THz frequency in a 200 km inter-satellite wireless link. We expect this work will provide an efficient path to build a high-speed global quantum communication network.

FL-QKD based on optical-THz biphotons generated by spontaneous parametric downconversion in inter-satellite wireless communication: publisher's note.

This publisher's note serves to identify a correction in Appl. Opt.60, 7362 (2021)APOPAI0003-693510.1364/AO.430898.

Continuous-Variable Quantum Secret Sharing Based on Thermal Terahertz Sources in Inter-Satellite Wireless Links.

We propose a continuous-variable quantum secret sharing (CVQSS) scheme based on thermal terahertz (THz) sources in inter-satellite wireless links (THz-CVQSS). In this scheme, firstly, each player locally preforms Gaussian modulation to prepare a thermal THz state, and then couples it into a circulating spatiotemporal mode using a highly asymmetric beam splitter. At the end, the dealer measures the quadrature components of the received spatiotemporal mode through performing the heterodyne detection to share secure keys with all the players of a group. This design enables that the key can be recovered only by the whole group players' knowledge in cooperation and neither a single player nor any subset of the players in the group can recover the key correctly. We analyze both the security and the performance of THz-CVQSS in inter-satellite links. Results show that a long-distance inter-satellite THz-CVQSS scheme with multiple players is feasible. This work will provide an effective way for building an inter-satellite quantum communication network.

[Clinical and pathological characteristics of intracranial haemangioblastoma].

OBJECTIVE: To analyze and summarize the clinical and pathological characteristics of intracranial haemangioblastoma and to improve surgery effect. METHOD: Seventy-two patients with intracranial haemangioblastoma who were proven by operation and pathology from 1970 to 1988 were analyzed retrospectively. RESULTS: Intracranial haemangioblastoma tends to occur in the hemisphere of cerebellum (83 tumours, 87%) and the age of them ranged from 20 to 40 years (47 cases, 58.3%) mostly. The ratio of men (46 cases) was higher than women (26 cases). The diagnosis of the disease depends on CT and MR substantive haemangioblastoma. The most effective and reliable treatment of intracranial haemangioblastoma is surgical resection. CONCLUSION: Intracranial haemangioblastoma is benign tumour which can be, cured by total surgical resection. The key recurrence factors include the young age of initial onset, mistaken exploration and incomplete extirpation of tumour.