Qubit energy tuner based on single flux quantum circuits

A device called the qubit energy tuner (QET), based on single flux quantum (SFQ) circuits, has been proposed for Z control of superconducting qubits. The QET is created by improving flux digital-to-analog converters (flux DACs). It can set the energy levels or frequencies of qubits, particularly flux-tunable transmons, and perform gate operations requiring Z control. The circuit structure of the QET is elucidated, consisting of an inductor loop and flux bias units for coarse or fine-tuning. The key feature of the QET is analyzed to understand how SFQ pulses change the inductor loop current, which provides external flux for qubits. Three simulations were performed to verify QET functionality. The first simulation verified the responses of the inductor loop current to SFQ pulses, showing a relative deviation of approximately 4.259% between the analytical solutions of the inductor loop current and the solutions from the WRSpice time-domain simulation. The second and third simulations, using QuTip, demonstrated how to perform a Z gate and an iSWAP gate using the QET, respectively, with corresponding fidelities of 99.99884% and 99.93906% for only one gate operation to specific initial states. These simulations indicate that the SFQ-based QET could act as an efficient component of SFQ-based quantum–classical interfaces for digital Z control of large-scale superconducting quantum computers

Assessing ecosystem service dynamics and drivers for sustainable management in the Agro-pastoral ecotone of northern China: A spatiotemporal analysis

To achieve regional ecological management and sustainable socio-economic development, it is essential to comprehend the intricate and interdependent relationships among various ecosystem services. The Agro-pastoral ecotone of northern China is a typical ecologically vulnerable area. There is limited research on managing multiple ecosystem services to maximize supply based on understanding the complex relationships among ecosystem services. This study used the InVEST model to quantify habitat quality (HQ), soil conservation (SC), carbon sequestration (CS), and water yield (WY) in the Agro-pastoral ecotone of northern China in 2000, 2010, and 2020 at the 5 km grid and county scales. Their trade-off and synergistic effects were explored using Spearman correlation analysis and the Geographically Weighted Regression (GWR) model. In addition, self-organizing mapping was employed to identify ecosystem service bundles at two scales, whereas the geodetector was employed to determine the primary social-ecological drivers of ES. Finally, management strategies are proposed based on the research results to promote regional ecological sustainability. The results indicate that: (1) The four ESs exhibited an increasing trend during the study period. Except for WY, the other three ES demonstrated a similar spatial distribution while remaining relatively stable over time; (2) there is a synergistic effect between CS, HQ, and SC, whereas WY-related ES show trade-off effects; (3) six ES bundles were identified at the 5 km grid scale, and four ES bundles were identified at the county scale; (4) precipitation is a major driving factor for WY and an important driving factor for CS, HQ, and SC. In summary, natural factors have a greater impact on ES than socio-economic factors. Based on the differences in ecosystem service bundles and drivers at different scales, and in conjunction with China’s existing environmental policies, corresponding ecological management strategies were proposed, potentially providing a reference for sustainable development of the Agro-pastoral ecotone in northern China