Search

Conventional theoretical studies on the ground-state laser cooling of a trapped ion have mostly focused on the weak sideband coupling (WSC) regime, where the cooling rate is inverse proportional to the linewidth of the excited state. In a recent work [New J. Phys.23, 023018 (2021)10.1088/1367-2630/abe273], we proposed a theoretical framework to study the ground state cooling of a trapped ion in the strong sideband coupling (SSC) regime, under the assumption of a vanishing carrier transition. Here we extend this analysis to more general situations with nonvanishing carrier transitions, where we show that by properly tuning the coupling lasers a cooling rate proportional to the linewidth can be achieved. Our theoretical predictions closely agree with the corresponding exact solutions in the SSC regime, which provide an important theoretical guidance for sideband cooling experiments.

We have developed a simple time-bin phase encoding quantum key distribution system, using the optical injection locking technique. This setup incorporates both the merits of simplicity and stability in encoding, and immunity to channel disturbance. We have demonstrated the field implementation of quantum key distribution over long-distance deployed aerial fiber automatically. During the 70-day field test, we achieved approximately a 1.0 kbps secure key rate with stable performance. Our work takes an important step toward widespread implementation of QKD systems in diverse and complex real-life scenarios.

In this work, we present a new time-bin phase-encoding quantum key distribution (QKD), where the transmitter utilizes an inherently stable Sagnac-type interferometer, and has comparable electrical requirements to existing polarization or phase encoding schemes. This approach does not require intensity calibration and is insensitive to environmental disturbances, making it both flexible and high-performing. We conducted experiments with a compact QKD system to demonstrate the stability and secure key rate performance of the presented scheme. The results show a typical secure key rate of 6.2 kbps@20 dB and 0.4 kbps@30 dB with channel loss emulated by variable optical attenuators. A continuous test of 120-km fiber spool shows a stable quantum bit error rate of the time-bin basis within 0.4%∼0.6% over a consecutive 9-day period without any adjustment. This intrinsically stable and compatible scheme of time-bin phase encoding is extensively applicable in various QKD experiments, including BB84 and measurement-device-independent QKD.

The reference-frame-independent quantum key distribution (RFI-QKD) has the advantage of tolerating reference frames that slowly vary. It can generate secure keys between two remote users with slowly drifted and unknown reference frames. However, the drift of reference frames may inevitably compromise the performance of QKD systems. In the paper, we employ the advantage distillation technology (ADT) to the RFI-QKD and the RFI measurement-device-independent QKD (RFI MDI-QKD), and we then analyze the effect of ADT on the performance of decoy-state RFI-QKD and RFI MDI-QKD in both asymptotic and nonasymptotic cases. The simulation results show that ADT can significantly improve the maximum transmission distance and the maximum tolerable background error rate. Furthermore, the performance of RFI-QKD and RFI MDI-QKD in terms of the secret key rate and maximum transmission distance are still greatly improved when statistical fluctuations are taken into account. Our work combines the merits of the ADT and RFI-QKD protocols, which further enhances the robustness and practicability of QKD systems.

Proteomic tools were used to identify the key proteins that might be associated with bronchial asthma(BA). Firstly, the serum samples from healthy adults and asthmatic patients were collected. Tandem Mass Tag~(TM)(TMT), which removes high-abundance structures and nonspecific proteins, was employed to identify the differentially expressed proteins between asthmatic patients and healthy adults. Gene Ontology(GO) annotation and Kyoto Encyclopedia of Genes and Genomes(KEGG) pathway enrichment analysis were carried out for the differentially expressed proteins. The core proteins in the asthma group were screened out by protein-protein interaction(PPI) analysis. Then the core proteins were verified by Western blot for 3 patients with bronchial asthma and 3 healthy adults. A total of 778 differentially expressed proteins were screened out, among which 32 proteins contained quantitative information, including 18 up-regulated proteins and 14 down-regulated proteins. The differentially expressed proteins were enriched in 28 KEGG signaling pathways. The PPI analysis showed that 10 proteins(GDN, 1433 Z, VWF, HEMO, CERU, A1 AT, TSP1, G3 P, IBP7, and KPYM) might be involved in the pathogenesis of bronchial asthma. Compared with those in healthy adults, the expression levels of SLC25 A4, SVEP1, and KRT25 in the sera of asthmatic patients were up-regulated(P<0.05). Therefore, it is hypothesized that a variety of immune signaling pathways and differentially expressed proteins play a role in the pathogenesis of BA, which provides potential target information for the treatment of BA.

Sending-or-not sending twin-field quantum key distribution (SNS TF-QKD) has the advantage of tolerating large amounts of misalignment errors, and its key rate can exceed the linear bound of repeaterless quantum key distribution. However, the weak randomness in a practical QKD system may lower the secret key rate and limit its achievable communication distance, thus compromising its performance. In this paper, we analyze the effects of the weak randomness on the SNS TF-QKD. The numerical simulation shows that SNS TF-QKD can still have an excellent performance under the weak random condition: the secret key rate can exceed the PLOB boundary and achieve long transmission distances. Furthermore, our simulation results also show that SNS TF-QKD is more robust to the weak randomness loopholes than the BB84 protocol and the measurement-device-independent QKD (MDI-QKD). Our results emphasize that keeping the randomness of the states is significant to the protection of state preparation devices.

Quantum key distribution (QKD) has attracted much attention due to its unconditional security. High-dimensional quantum key distribution (HD-QKD) is a brand-new type of QKD protocol that has many excellent advantages. Nonetheless, practical imperfections in realistic devices that are not considered in the theoretical security proof may have an impact on the practical security of realistic HD-QKD systems. In this paper, we research the influence of a realistic intensity modulator on the practical security of HD-QKD systems with the decoy-state method and finite-key effects. We demonstrate that there is a certain impact in the secret key rate and the transmission distance when taking practical factors into security analysis.

Scaling up to a large number of qubits with high-precision control is essential in the demonstrations of quantum computational advantage to exponentially outpace the classical hardware and algorithmic improvements. Here, we develop a two-dimensional programmable superconducting quantum processor, Zuchongzhi, which is composed of 66 functional qubits in a tunable coupling architecture. To characterize the performance of the whole system, we perform random quantum circuits sampling for benchmarking, up to a system size of 56 qubits and 20 cycles. The computational cost of the classical simulation of this task is estimated to be 2-3 orders of magnitude higher than the previous work on 53-qubit Sycamore processor [Nature 574, 505 (2019)NATUAS0028-083610.1038/s41586-019-1666-5. We estimate that the sampling task finished by Zuchongzhi in about 1.2 h will take the most powerful supercomputer at least 8 yr. Our work establishes an unambiguous quantum computational advantage that is infeasible for classical computation in a reasonable amount of time. The high-precision and programmable quantum computing platform opens a new door to explore novel many-body phenomena and implement complex quantum algorithms.

Twin-field quantum key distribution (TF-QKD) has attracted considerable attention and developed rapidly due to its ability to surpass the fundamental rate-distance limit of QKD. However, the device imperfections may compromise its practical implementations. The goal of this paper is to make it robust against the state preparation flaws (SPFs) and side channels at the light source. We adopt the sending or not-sending (SNS) TF-QKD protocol to accommodate the SPFs and multiple optical modes in the emitted states. We analyze that the flaws of the phase modulation can be overcome by regarding the deviation of the phase as phase noise and eliminating it with the post-selection of phase. To overcome the side channels, we extend the generalized loss-tolerant (GLT) method to the four-intensity decoy-state SNS protocol. Remarkably, by decomposing of the two-mode single-photon states, the phase error rate can be estimated with only four parameters. The practical security of the SNS protocol with flawed and leaky source can be guaranteed. Our results might constitute a crucial step towards guaranteeing the practical implementation of the SNS protocol.

Recent advances on quantum computing hardware have pushed quantum computing to the verge of quantum supremacy. Here, we bring together many-body quantum physics and quantum computing by using a method for strongly interacting two-dimensional systems, the projected entangled-pair states, to realize an effective general-purpose simulator of quantum algorithms. The classical computing complexity of this simulator is directly related to the entanglement generation of the underlying quantum circuit rather than the number of qubits or gate operations. We apply our method to study random quantum circuits, which allows us to quantify precisely the memory usage and the time requirements of random quantum circuits. We demonstrate our method by computing one amplitude for a 7×7 lattice of qubits with depth (1+40+1) on the Tianhe-2 supercomputer.

Aim of Study: To further evaluate the influence of glutathione S-transferase M1 (GSTM1) and glutathione S-transferase T1 (GSTT1) null genotypes on bladder cancer risk, we conducted a meta-analysis in the Chinese population., Materials and Methods: PubMed and Chinese databases were electronically searched through April 2016., Results: Nine studies were included for our meta-analysis, involving 1646 bladder cancer cases and 1938 controls. In general, our findings indicated that a significant association existed between GSTM1-null genotype and the risk of bladder cancer in the studied Chinese population (odds ratio = 1.56, 95% confidence interval: 1.36-1.79). However, no significant association between GSTT1 polymorphism and bladder cancer was found. After stratification of the subgroup analyses by source of controls and geographical areas, a substantially elevated risk was revealed between GSTM1-null genotype and bladder cancer in the population-based studies and those conducted in South China and North China., Conclusion: Our meta-analysis suggested that GSTM1-null genotype is associated with an increased bladder cancer risk in the Chinese individuals., Competing Interests: None

Boson sampling is strongly believed to be intractable for classical computers but solvable with photons in linear optics, which raises widespread concern as a rapid way to demonstrate the quantum supremacy. However, due to its solution is mathematically unverifiable, how to certify the experimental results becomes a major difficulty in the boson sampling experiment. Here, we develop a statistical analysis scheme to experimentally certify the collision-free boson sampling. Numerical simulations are performed to show the feasibility and practicability of our scheme, and the effects of realistic experimental conditions are also considered, demonstrating that our proposed scheme is experimentally friendly. Moreover, our broad approach is expected to be generally applied to investigate multi-particle coherent dynamics beyond the boson sampling.

The device-independent (DI) quantum key distribution (QKD) protocol requires minimal assumptions about the devices and its security relies on the violation of Bell inequalities, making it hard to realize in real world. Semi-device-independent (SDI) QKD protocol confines quantum state within finite dimensional Hilbert space, thus easier for implementation with existing experimental technology. In this paper, we propose a practical SDI prepare-and-measure BB84 protocol. By introducing min entropy for security proof, we obtain a security bound under the practical condition with finite resources. Numerical simulations imply the finite-key effect can not be ignored in the forthcoming SDI QKD experiment.

Recently, a novel protocol named round-robin differential phase-shift (RRDPS) quantum key distribution [Nature 509, 475(2014)] has been proposed. It can estimate information leakage without monitoring bit error rate. In this paper, we study the performance of RRDPS using heralded single photon source (HSPS) without and with decoy-state method, then compare it with the performance of weak coherent pulses (WCPs). From numerical simulation, we can see that HSPS performs better especially for shorter packet and higher bit error rate. Moreover, we propose a general theory of decoy-state method for RRDPS protocol based on only three decoy states and one signal state. Taking WCPs as an example, the three-intensity decoy-state protocol can distribute secret keys over a distance of 128 km when the length of pulses packet is 32, which confirms great practical interest of our method.

In spite of the advances in the diagnosis and treatment of bladder cancer, the prognosis of bladder cancer remains relatively poor. As a result, it is vital to identify novel diagnostic and prognostic marker of bladder cancer. A growing volume of literature has implicated the vital role of long noncoding RNA in the development of cancer. GHET1, a recently identified lncRNA, was initially characterized in gastric cancer. However, its role in bladder cancer remains largely unknown. In this study, we demonstrated that GHET1 was upregulated in bladder cancer tissues compared to adjacent normal tissues and its over-expression correlates with tumor size, advanced tumor and lymph node status, and poor survival. GHET1 knockdown suppressed the proliferation and invasion of bladder cancer cells in vitro. In the meantime, inhibition of GHET1 reversed the epithelial-mesenchymal-transition in bladder cancer cell line. Taken together, our study suggests that the potential use of GHET1 as a prognostic marker and therapeutic target of bladder cancer.

We have developed an improved three-dimensional (3D) percolation model to investigate the effect of the alignment of carbon nanotubes (CNTs) on the electrical conductivity of nanocomposites. In this model, both intrinsic and contact resistances are considered, and a new method of resistor network recognition that employs periodically connective paths is developed. This method leads to a reduction in the size effect of the representative cuboid in our Monte Carlo simulations. With this new technique, we were able to effectively analyze the effects of the CNT alignment upon the electrical conductivity of nanocomposites. Our model predicted that the peak value of the conductivity occurs for partially aligned rather than perfectly aligned CNTs. It has also identified the value of the peak and the corresponding alignment for different volume fractions of CNTs. Our model works well for both multi-wall CNTs (MWCNTs) and single-wall CNTs (SWCNTs), and the numerical results show a quantitative agreement with existing experimental observations.

Considering electron-impurity and electron-phonon scattering, we present a balance-equation-based theoretical examination of thermoelectric power (TEP) in a two-dimensional single-layer graphene away from the carrier neutrality point. Both the boundary scattering and phonon-phonon interaction in phonon relaxation processes are taken into account. We find that, at temperatures T > 10 K, the contribution to TEP mainly comes from diffusive processes and the phonon-drag effect can be ignored. However, at T ≤ 10 K, the phonon-phonon interaction leads to a phonon-drag peak in the temperature dependence of TEP. We also compare our results with experiments.

Considering electron-impurity, electron-acoustic-phonon and electron-optical-phonon scatterings, the nonlinear steady-state transport properties of graphene are studied theoretically by means of the balance equation approach. We find that the conductivity as a function of electric field strength, E, exhibits strongly nonlinear behavior for E larger than a critical value, E(c)≈0.1 kV cm(-1). With the increase of E from zero, the conductivity first decreases slowly and then it falls rapidly when E>E(c). The dependence of electron temperature on E is also demonstrated.

Aim: To investigate the influence of Ginkgo biloba extract (GbE) on cardiomyocytes damaged by H2O2., Methods: Cultured rat cardiomyocytes were divided into 3 groups randomly: control group; H2O2 (2.5 mmol.L-1) group; H2O2 2.5 mmol.L-1 + GbE 150 mg.L-1 group. The cardiomyocytes were cultured in MEM (Eagle's) at 37 degrees C in the presence of 5% CO2 for 4 h. Lactate dehydrogenase (LDH) was assayed by colorimetric method. Lipid peroxidation was determined by measuring thiobarbituric acid-reactive substances. Ultrastructure was viewed under transmission electron microscope., Results: Compared with the control group, LDH leakage and malondialdehyde (MDA) content increased in H2O2 group, LDH increased from (2166 +/- 247) U.L-1 to (5180 +/- 648) U.L-1, MDA increased from (3.5 +/- 0.2) nmol/10(6) cells to (7.2 +/- 0.4) nmol/10(6) cells (P < 0.01). The ultrastructure was damaged seriously. GbE inhibited the increase of LDH leakage and MDA content induced by H2O2. In this group, LDH decreased from (5180 +/- 648) U.L-1 to (3496 +/- 386) U.L-1, MDA decreased from (7.2 +/- 0.4) nmol/10(6) cells to (4.8 +/- 0.9) nmol/10(6) cells (P < 0.01). Ultrastructure of cells was also protected by GbE., Conclusion: GbE protected the cardiomyocyte against H2O2 injury, the protective action was attributed to its antiperoxidative effect.