Universal and Operational Benchmarking of Quantum Memories

Quantum memory -- the capacity to store and faithfully recover unknown quantum states -- is essential for quantum-enhanced technology. There is thus a pressing need for operationally meaningful means to benchmark candidate memories across diverse physical platforms. Here we introduce a universal benchmark distinguished by its relevance across multiple key operational settings, exactly quantifying (1) the memory's robustness to noise, (2) the number of noiseless qubits needed for its synthesis, (3) its potential to speed up statistical sampling tasks, and (4) performance advantage in non-local games beyond classical limits. The measure is analytically computable for low-dimensional systems and can be efficiently bounded in experiment without tomography. We thus illustrate quantum memory as a meaningful resource, with our benchmark reflecting both its cost of creation and what it can accomplish. We demonstrate the benchmark on the five-qubit IBM Q hardware, and apply it to witness efficacy of error-suppression techniques and quantify non-Markovian noise. We thus present an experimentally accessible, practically meaningful, and universally relevant quantifier of a memory's capability to preserve quantum advantage.Comment: 30 page

Analysis of Contact Surface Wear Performance of O-Ring Dynamic Seal Based on Archard Model

With the development of hydraulic system to high pressure gradually, the leakage risk of sealing system increases, and it is necessary to confirm the performance parameters of sealing structure through analysis and calculation. The traditional analysis of the friction and wear performance of the seal ring is limited to the amount of wear, and cannot describe the surface wear characteristics of the O-ring in detail. Based on the Archard model, this paper constructs a model to analyse and calculate the friction and wear performance of the dynamic seal structure through the material characteristics and operating parameters, analyses the friction and wear characteristics of the O-ring seal structure under different compression ratio, medium pressure, relative slip velocity and temperature, and summarizes the influence of each single variable on the wear characteristics of the dynamic seal structure. According to the analysis in this paper, the increase of medium pressure of 5 MPa will cause the wear concentration area of the contact surface to move to the back pressure side, and the overall wear will be reduced, but the increase of contact area will lead to the weakening of sealing effect. By the action of 15 MPa, when the compression ratio is between 5% and 10%, the change of cumulative wear rate and the wear rate of each node is small

Dispersion and intersection of hydrothermal plumes in the Manus Back-Arc Basin, Western Pacific

The composition of hydrothermal plumes reflects the physical and chemical characteristics of seafloor hydrothermal fluids, which in turn reflects the host rock and subseafloor reaction conditions as well as the water column processes that act to alter the plumes as they disperse and age. Here, we show that the turbidity, current, pH value, dissolved Fe (dFe), and dissolved Mn (dMn) compositions of hydrothermal plumes can be used to understand the spatial distribution and source of hydrothermal systems in the submarine geological environment. Data were obtained from 18 hydrocast stations, among which the water column samples were collected at 8 stations during the MANUS cruise of R/V KEXUE in 2015. The results showed that the Satanic Mills plume and Fenway plume rose approximately 140 m and 220 m above the seafloor, respectively. In the Satanic Mills plume, dFe remained longer than dMn during lateral plume dispersal. There was a clear intersection of the Satanic Mills plume and Fenway plume between 1625 m and 1550 m in the PACMANUS hydrothermal field, and the varied dispersion trends of the mixed plumes were affected by current velocities at different depths. The physical and chemical properties of the seawater columns in the Manus Basin were affected by the input of high-Mn, high-Fe, and low-Mg vent fluids. The turbidity and dFe, dMn, and dissolved Mg concentrations in the sections of the plumes proximal to the Satanic Mills, Fenway, and Desmos vent sites were generally higher (turbidity, Mn, and Fe) and lower (Mg) than those in the sections of the plumes that were more distal from the vent sites. This implied that the plumes proximal to their vent fluid sources, which were interpreted to have relatively young ages, dispersed chemically over time, and their concentrations became more similar to those of the plumes that were more distal from their vent fluid sources

Experimental exploration of five-qubit quantum error correcting code with superconducting qubits

Quantum error correction is an essential ingredient for universal quantum computing. Despite tremendous experimental efforts in the study of quantum error correction, to date, there has been no demonstration in the realisation of universal quantum error correcting code, with the subsequent verification of all key features including the identification of an arbitrary physical error, the capability for transversal manipulation of the logical state, and state decoding. To address this challenge, we experimentally realise the $[\![5,1,3]\!]$ code, the so-called smallest perfect code that permits corrections of generic single-qubit errors. In the experiment, having optimised the encoding circuit, we employ an array of superconducting qubits to realise the $[\![5,1,3]\!]$ code for several typical logical states including the magic state, an indispensable resource for realising non-Clifford gates. The encoded states are prepared with an average fidelity of $57.1(3)\%$ while with a high fidelity of $98.6(1)\%$ in the code space. Then, the arbitrary single-qubit errors introduced manually are identified by measuring the stabilizers. We further implement logical Pauli operations with a fidelity of $97.2(2)\%$ within the code space. Finally, we realise the decoding circuit and recover the input state with an overall fidelity of $74.5(6)\%$, in total with $92$ gates. Our work demonstrates each key aspect of the $[\![5,1,3]\!]$ code and verifies the viability of experimental realization of quantum error correcting codes with superconducting qubits.Comment: 6 pages, 4 figures + Supplementary Material

Differential Expression of miRNAs in Response to Topping in Flue-Cured Tobacco (Nicotiana tabacum) Roots

Topping is an important cultivating measure for flue-cured tobacco, and many genes had been found to be differentially expressed in response to topping. But it is still unclear how these genes are regulated. MiRNAs play a critical role in post-transcriptional gene regulation, so we sequenced two sRNA libraries from tobacco roots before and after topping, with a view to exploring transcriptional differences in miRNAs.Two sRNA libraries were generated from tobacco roots before and after topping. Solexa high-throughput sequencing of tobacco small RNAs revealed a total of 12,104,207 and 11,292,018 reads representing 3,633,398 and 3,084,102 distinct sequences before and after topping. The expressions of 136 conserved miRNAs (belonging to 32 families) and 126 new miRNAs (belonging to 77 families) were determined. There were three major conserved miRNAs families (nta-miR156, nta-miR172 and nta-miR171) and two major new miRNAs families (nta-miRn2 and nta-miRn26). All of these identified miRNAs can be folded into characteristic miRNA stem-loop secondary hairpin structures, and qRT-PCR was adopted to validate and measure the expression of miRNAs. Putative targets were identified for 133 out of 136 conserved miRNAs and 126 new miRNAs. Of these miRNAs whose targets had been identified, the miRNAs which change markedly (>2 folds) belong to 53 families and their targets have different biological functions including development, response to stress, response to hormone, N metabolism, C metabolism, signal transduction, nucleic acid metabolism and other metabolism. Some interesting targets for miRNAs had been determined.The differential expression profiles of miRNAs were shown in flue-cured tobacco roots before and after topping, which can be expected to regulate transcripts distinctly involved in response to topping. Further identification of these differentially expressed miRNAs and their targets would allow better understanding of the regulatory mechanisms for flue-cured tobacco response to topping

A Cross-Scale Framework for Modelling Chloride Ions Diffusion in C-S-H: Combined Effects of Slip, Electric Double Layer and Ion Correlation

Water and chloride ions within pores of cementitious materials plays a crucial role in the damage processes of cement pastes, particularly in the binding material comprising calcium-silicate-hydrates (C-S-H). The migration mechanism of water and chloride ions restricted in C-S-H nanopores is complicated due to the presence of interfacial effects. The special mechanical properties of the solid–liquid interface determine the importance of boundary slip and Electric Double Layer (EDL) and ion diversity in pore solutions determines the difference of the EDL and the stability of water film slip. A cross-scale model covering slip effects, time-varying of EDL and ion correlation needs to be developed so that the interfacial effects concentrated at the pore scale can be extended to affect the overall diffusivity of C-S-H. The statistics of pore size distribution and fractal dimension were used to quantitatively compare the similarities between model and C-S-H structure, thus proving the reliability of cross-scale reconstructed C-S-H transmission model. The results show that the slip effect is the dominant factor affecting the diffusion ability of C-S-H, the contribution of the slip effect is up to 60% and the contribution rate of EDL time-varying only up to about 15%. Moreover, the slip effect is sensitive to both ion correlation and C-S-H inhomogeneity and EDL time-varying is almost insensitive to ion correlation changes. This quantification provides a necessary benchmark for understanding the destructiveness of cement-based materials in the salt rich environment and provides new insights into improving the durability of concrete by changing the solid–liquid interface on the micro-nanoscale