The continuous-variable version of quantum key distribution (QKD) offers the advantages (over discrete-variable systems) of higher secret key rates in metropolitan areas, as well as the use of standard telecom components that can operate at room temperature. An important step in the real-world adoption of continuous-variable QKD is the deployment of field tests over commercial fibers. Here we report two different field tests of a continuousvariable QKD system through commercial fiber networks in Xi'an and Guangzhou over distances of 30.02 km (12.48 dB) and 49.85 km (11.62 dB), respectively. We achieve secure key rates two orders-of-magnitude higher than previous field test demonstrations by employing an efficient calibration model with one-time evaluation. This accomplishment is also realized by developing a fully automatic control system which stabilizes system noise, and by applying a rate-adaptive reconciliation method which maintains high reconciliation efficiency with high success probability in fluctuated environments. Our results pave the way to deploy continuousvariable QKD in metropolitan settings.

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Because of its extreme toxicity, the determination of Hg2+ in aqueous solution is an important subject for human health and environmental monitoring. In this study, a novel UIO-66-type metal–organic framework (MOF) doped with Eu3+ (isophthalic acid and 2,6-pyridinedicarboxylic acid and zirconium chloride served as the organic connectors and metal precursor, respectively) was prepared by a hydrothermal method and postsynthetic modification. The obtained lanthanide MOFs exhibited good photothermal and fluorescence stability in aqueous solution. As a luminescent probe, dispersions of the material can specifically recognize Hg2+ in many ions and have a detection limit of 8.26 nM. This novel lanthanide MOF shows great potential applications for biosensing, imaging, environmental analysis, and so on.

Balanced homodyne detector (BHD) that can measure the field quadratures of coherent states has been widely used in a range of quantum information technologies. Generally, the BHD tends to suffer from narrow bands and an expanding bandwidth behavior usually traps into a compromise with the gain, electronic noise, and quantum to classical noise ratio, etc. In this paper, we design and construct a wideband BHD based on radio frequency and integrated circuit technology. Our BHD shows bandwidth behavior up to 1.2 GHz and its quantum to classical noise ratio is around 18 dB. Simultaneously, the BHD has a linear performance with a gain of 4.86k and its common mode rejection ratio has also been tested as 57.9 dB. With this BHD, the secret key rate of continuous-variable quantum key distribution system has a potential to achieve 66.55 Mbps and 2.87 Mbps respectively at the transmission distance of 10 km and 45 km. Besides, with this BHD, the generation rate of quantum random number generator could reach up to 6.53Gbps.Index Terms: Balanced homodyne detector, bandwidth, quantum to classical noise ratio, common mode rejection ratio, continuous-variable quantum key distribution, quantum random number generator.Vol. , No. ,