We demonstrate experimentally the feasibility of continuous variable quantum key distribution (CV-QKD) in dense-wavelength-division multiplexing networks (DWDM), where QKD will typically have to coexist with several co-propagating (forward or backward) C-band classical channels whose launch power is around 0 dBm. We have conducted experimental tests of the coexistence of CV-QKD multiplexed with an intense classical channel, for different input powers and different DWDM wavelengths. Over a 25 km fiber, a CV-QKD operated over the 1530.12 nm channel can tolerate the noise arising from up to 11.5 dBm classical channel at 1550.12 nm in the forward direction (9.7 dBm in backward). A positive key rate (0.49 kbits s −1 ) can be obtained at 75 km with classical channel power of respectively −3 and −9 dBm in forward and backward. Based on these measurements, we have also simulated the excess noise and optimized channel allocation for the integration of CV-QKD in some access networks. We have, for example, shown that CV-QKD could coexist with five pairs of channels (with nominal input powers: 2 dBm forward and 1 dBm backward) over a 25 km WDM-PON network. The obtained results demonstrate the outstanding capacity of CV-QKD to coexist with classical signals of realistic intensity in optical networks.Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence.Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.1 The notion of 'distance limitation of QKD ' is, as such, ill-defined. If one wants to establish a comparison between the performance of different QKD systems, a large number of parameters have to be jointly considered, starting with the security model and the secure key rate, together with important more 'practical' parameters that include channel loss, noise environment and the photodetector technology. The numbers we indicate are approximative estimates of the maximum distance at which QKD could be operated with state-of-the art QKD systems, ten years ago [6] and now [7], with a key rate of at least 100 bits s −1 sufficient for practical key renewal, on a standard dark fiber (loss 0.25 dB km −1 ) and for QKD systems operating without He-cooled detectors, under conservative security model (coherent attacks including finite-size effect, even if such analysis was not yet performed 10 years ago). © 2015 IOP Publishing Ltd and Deutsche Physikalische Gesellschaft allow to deploy QKD on lit fiber. This would boost the compatibility of quantum communications with existing optical infrastructures and lead to a significant improvement in terms of cost-effectiveness and addressable market for QKD.However, coexistence with intense classical channels raises new challenges for QKD. The optical power used on optical classical channels is orders of magnitude higher than for quantum communication. Multiplexing classical and quantum signals on a single fiber can result in very important additional noise for the quant...

We identify and study a new security loophole in continuous-variable quantum key distribution (CV-QKD) implementations, related to the imperfect linearity of the homodyne detector. By exploiting this loophole, we propose an active side-channel attack on the Gaussian-modulated coherent state CV-QKD protocol combining an intercept-resend attack with an induced saturation of the homodyne detection on the receiver side (Bob). We show that an attacker can bias the excess noise estimation by displacing the quadratures of the coherent states received by Bob. We propose a saturation model that matches experimental measurements on the homodyne detection and use this model to study the impact of the saturation attack on parameter estimation in CV-QKD.We demonstrate that this attack can bias the excess noise estimation beyond the null key threshold for any system parameter, thus leading to a full security break. If we consider an additional criteria imposing that the channel transmission estimation should not be affected by the attack, then the saturation attack can only be launched if the attenuation on the quantum channel is sufficient, corresponding to attenuations larger than approximately 6 dB. We moreover discuss the possible counter-measures against the saturation attack and propose a new countermeasure based on Gaussian post-selection that can be implemented by classical post-processing and may allow to distill secret key when the raw measurement data is partly saturated.

We propose an efficient strategy to attack a continuous-variable quantum key distribution (CV-QKD) system, that we call homodyne detector blinding. This attack strategy takes advantage of a generic vulnerability of homodyne receivers: a bright light pulse sent on the signal port can lead to a saturation of the detector electronics. While detector saturation has already been proposed to attack CV-QKD, the attack we study in this paper has the additional advantage of not requiring an eavesdropper to be phase locked with the homodyne receiver. We show that under certain conditions, an attacker can use a simple laser, incoherent with the homodyne receiver, to generate bright pulses and bias the excess noise to arbitrary small values, fully comprising CV-QKD security. These results highlight the feasibility and the impact of the detector blinding attack. We finally discuss how to design countermeasures in order to protect against this attack.

In this paper, we report the utility of a colorimetric polymer stabilized cholesteric liquid crystal (PSCLC) array for detecting vaporous amines. The PSCLC with various polymer concentrations (5-20% w/w) is made into an array which shows distinct color changes upon exposure to 400 parts-permillion (ppm) octylamine vapor at 23-35 degrees C. Interestingly, PSCLC shows stronger response to primary amine over secondary amine, tertiary amine, ester, aldehyde, and alkane having similar molecular weights. PSCLCs also give detection limits as low as 2 ppmv for decylamine. Because PSCLC is transparent at room temperature and changes color upon exposure to amine vapors, it can be coated on windows or safety goggles to offer protection against amine vapors.

A compact asymmetric coplanar strip (ACS)-fed ultra-wideband (UWB) monopole antenna with extra Bluetooth band for various wireless applications is presented. The proposed antenna is composed of a modified ACS-fed structure and a staircase-shaped patch for covering the UWB band (3.1-10.6 GHz), which occupies a very compact size of 32.5 × 10 mm 2. By etching a snake-shaped slot in the staircaseshaped patch, an additional band can be realised covering the Bluetooth band (2.4-2.484 GHz). Furthermore, the proposed antenna has been fabricated and measured, and good results obtained. The proposed antenna shows nearly omnidirectional radiation characteristics, relatively consistent group delays and stable gains in the operating bands. The simple feeding structure, compact size and uniplanar design make it easy to be integrated within portable devices for wireless communication.

Standard plane localization is crucial for ultrasound (US) diagnosis. In prenatal US, dozens of standard planes are manually acquired with a 2D probe. It is time-consuming and operator-dependent. In comparison, 3D US containing multiple standard planes in one shot has the inherent advantages of less user-dependency and more efficiency. However, manual plane localization in US volume is challenging due to the huge search space and large fetal posture variation. In this study, we propose a novel reinforcement learning (RL) framework to automatically localize fetal brain standard planes in 3D US. Our contribution is twofold. First, we equip the RL framework with a landmark-aware alignment module to provide warm start and strong spatial bounds for the agent actions, thus ensuring its effectiveness. Second, instead of passively and empirically terminating the agent inference, we propose a recurrent neural network based strategy for active termination of the agent's interaction procedure. This improves both the accuracy and efficiency of the localization system. Extensively validated on our in-house large dataset, our approach achieves the accuracy of 3.4mm/9.6 • and 2.7mm/9.1 • for the transcerebellar and transthalamic plane localization, respectively. Our proposed RL framework is general and has the potential to improve the efficiency and standardization of US scanning.

A compact asymmetric coplanar strip (ACS)-fed ultra-wideband (UWB) antenna for diversity applications is presented. The proposed antenna is composed of two circular radiating elements and orthogonal ACS-fed mechanisms to achieve diversity performance across the UWB from 2.66 to 11.08 GHz, and occupies a very compact size of 28.5 × 28.5 mm 2. By introducing a rectangular stub diagonally between the two circular radiating elements, an interport isolation better than 15 dB is achieved. Furthermore, the proposed antenna shows nearly omnidirectional radiation patterns, stable gains and a low envelope correction coefficient. The simple feeding structure, compact size and uniplanar design make it easy to be integrated within the portable device for wireless communications with diversity operations.

Polymeric composite microspheres consisting of a poly(D,L-lactic-co-glycolic acid) (PLGA) core surrounded by a poly(D,L-lactic acid) (PDLLA) shell layer were successfully fabricated by coaxial electrohydrodynamic atomization (CEHDA) process. Process conditions, including nozzle voltage and polymer solution flow rates, as well as solution parameters, such as polymer concentrations, were investigated to ensure the formation of composite microspheres with a doxorubicin-loaded PLGA core surrounded by a relatively drug-free PDLLA shell layer. Various microsphere formulations were fabricated and characterized in terms of their drug distribution, encapsulation efficiency and in vitro release. Numerical simulation of CEHDA process was performed based on a computational fluid dynamics (CFD) model in Fluent by employing the process conditions and fluid properties used in the experiments. The simulation results were compared with the experimental work to illustrate the capability of the CFD model to predict the production of consistent compound droplets, and hence, the expected core-shell structured microspheres.