Finite-key analysis for quantum key distribution with discrete phase randomization

Quantum key distribution(QKD) allows two remote parties to share information-theoretic secret keys. Many QKD protocols assume the phase of encoding state can be continuous randomized from 0 to 2 pi, which, however, may be questionable in experiment. This is particularly the case in the recently proposed twin-field(TF) QKD, which has received a lot of attention, since it can increase key rate significantly and even beat some theoretical rate-loss limits. As an intuitive solution, one may introduce discrete phase-randomization instead of continuous one. However, a security proof for a QKD protocol with discrete phase-randomization in finite-key region is still missing. Here we develop a technique based on conjugate measurement and quantum state distinguishment to ana-lyze the security in this case. Our result shows that TF-QKD with reasonable number of discrete random phases, e.g. 8 phases from {0, pi/4, pi/2, ..., 7pi/4}, can achieve satisfactory performance. More importantly, as a the first proof for TF-QKD with discrete phase-randomization in finite-key region, our method is also applicable in other QKD protocols.Comment: 1 figures,20 page

Twin-field quantum key distribution with partial phase postselection

Quantum key distribution (QKD) allows two remote parties to share information-theoretically secure keys. In recent years, a revolutionary breakthrough called twin-field (TF) QKD has been developed to overcome the linear key-rate constraint and greatly increases the achievable distance. Phase-randomization and subsequent postselection play important roles in its security proof. Later, no-phase-postselection TF-QKD was proposed and became a popular variant, since the removal of phase postselection leads to a higher key rate. However, the achievable distance is decreased compared to the original one. Here, we propose a TF-QKD protocol with partial phase postselection. Namely, its code mode is still free from global phase randomization and postselection to make sure the advantage of the high key rate remains. On other hand, phase postselection is introduced in the decoy mode to improve the performance. Applying an operator dominance condition, we prove universal security of the proposed protocol in the finite-key case under coherent attacks, and numerical simulations confirm its potential advantages in terms of key rate and achievable distance

Ethanol exposure leads to disorder of blood island formation in early chick embryo

Ethanol’s effect on embryonic vasculogenesis and its underlying mechanism is obscure. Using VE-cadherin in situ hybridization, we found blood islands formation was inhibited in area opaca, but abnormal VE-cadherin+ cells were seen in area pellucida. We hypothesise ethanol may affect blood island progenitor cell migration and differentiation. DiI and in vitro experiments revealed ethanol inhibited cell migration, Quantitative PCR analysis revealed that ethanol exposure enhanced cell differentiation in area pellucida of HH5 chick embryos and repressed cell differentiation in area pellucida of HH8 chick embryos. By exposing to 2,2′-azobis-amidinopropane dihydrochloride, a ROS inducer, which gave a similar anti-vasculogenesis effect as ethanol and this anti-vasculogenesis effect could be reversed by vitamin C. Overall, exposing early chick embryos to ethanol represses blood island progenitor cell migration but disturbed differentiation at a different stage, so that the disorder of blood island formation occurs through excess ROS production and altered vascular-associated gene expression

Differential sensitivity of membrane-associated pyrophosphatases to inhibition by diphosphonates and fluoride delineates two classes of enzyme

Abstract1,1-Diphosphonate analogs of pyrophosphate, containing an amino or a hydroxyl group on the bridge carbon atom, are potent inhibitors of the H+-translocating pyrophosphatases of chromatophores prepared from the bacterium Rhodospirillum rubrum and vacuolar membrane vesicles prepared from the plant Vigna radiata. The inhibition constant for aminomethylenediphosphonate, which binds competitively with respect to substrate, is below 2 μM. Rat liver mitochondrial pyrophosphatase is two orders of magnitude less sensitive to this compound but extremely sensitive to imidodiphosphate. By contrast, fluoride is highly effective only against the mitochondrial pyrophosphatase. It is concluded that the mitochondrial pyrophosphatase and the H+-pyrophosphatases of chromatophores and vacuolar membranes belong to two different classes of enzyme

Effect of dispersion on indistinguishability between single-photon wave-packets

With propagating through a dispersive medium, the temporal-spectral profile of laser pulses should be inevitably modified. Although such dispersion effect has been well studied in classical optics, its effect on a single-photon wave-packet, i.e., the matter wave of a single-photon, has not yet been entirely revealed. In this paper, we investigate the effect of dispersion on indistinguishability of single-photon wave-packets through the Hong-Ou-Mandel (HOM) interference. By dispersively manipulating two indistinguishable single-photon wave-packets before interfering with each other, we observe that the difference of the second-order dispersion between two optical paths of the HOM interferometer can be mapped to the interference curve, indicating that (1) with the same amount of dispersion effect in both paths, the HOM interference curve must be only determined by the intrinsic indistinguishability between the wave-packets, i.e., dispersion cancellation due to the indistinguishability between Feynman paths; (2) unbalanced dispersion effect in two paths cannot be cancelled and will broaden the interference curve thus providing a way to measure the second-order dispersion coefficient. Our results suggest a more comprehensive understanding of the single-photon wave-packet and pave ways to explore further applications of the HOM interference

Robust single divacancy defects near stacking faults in 4H-SiC under resonant excitation

Color centers in silicon carbide (SiC) have demonstrated significant promise for quantum information processing. However, the undesirable ionization process that occurs during optical manipulation frequently causes fluctuations in the charge state and performance of these defects, thereby restricting the effectiveness of spin-photon interfaces. Recent predictions indicate that divacancy defects near stacking faults possess the capability to stabilize their neutral charge states, thereby providing robustness against photoionization effects. In this work, we present a comprehensive protocol for the scalable and targeted fabrication of single divacancy arrays in 4H-SiC using a high-resolution focused helium ion beam. Through photoluminescence emission (PLE) experiments, we demonstrate long-term emission stability with minimal linewidth shift ($\sim$ 50 MHz over 3 hours) for the single c-axis divacancies within stacking faults. By measuring the ionization rate for different polytypes of divacancies, we found that the divacancies within stacking faults are more robust against resonant excitation. Additionally, angle-resolved PLE spectra reveal their two resonant-transition lines with mutually orthogonal polarizations. Notably, the PLE linewidths are approximately 7 times narrower and the spin-coherent times are 6 times longer compared to divacancies generated via carbon-ion implantation. These findings highlight the immense potential of SiC divacancies for on-chip quantum photonics and the construction of efficient spin-to-photon interfaces, indicating a significant step forward in the development of quantum technologies.Comment: 11 pages, 4 figure

Design & Optimization of the HV divider for JUNO 20-inch PMT

The Jiangmen Underground Observatory (JUNO) is a 20-kton liquid scintillator detector that employs 20,000 20-inch photomultiplier tubes (PMTs) as photon sensors, with 5,000 dynode-PMTs from HAMAMATSU Photonics K.K. (HPK), and 15,000 MCP-PMTs from North Night Vision Technology (NNVT) installed in pure water. JUNO aims to provide long-lasting and the best performance operation by utilizing a high-transparency liquid scintillator, high detection efficiency PMTs, and specially designed electronics including water-proof potting for the high voltage (HV) dividers of PMTs. In this paper, we present a summary of the design and optimization of HV dividers for both types of 20-inch PMTs, which includes collection efficiency, charge resolution, HV divider current, pulse shape, and maximum amplitude restriction. We have developed and finalized four schemes of the HV divider for different scenarios, including the final version selected by JUNO. All 20,000 20-inch PMTs have successfully undergone production and burning tests.Comment: 14pages,28figure