GSTDTAP

浏览/检索结果: 共63条,第1-10条 帮助

限定条件                    
已选(0)清除 条数/页:   排序方式:
Scaling up zero-deforestation initiatives through public-private partnerships: A look inside post-conflict Colombia 期刊论文
GLOBAL ENVIRONMENTAL CHANGE-HUMAN AND POLICY DIMENSIONS, 2020, 62
作者:  Furumo, Paul R.;  Lambin, Eric F.
收藏  |  浏览/下载:13/0  |  提交时间:2020/07/02
Agenda setting  Global forest governance  Low-emissions rural development  Post-conflict  REDD  Sustainable supply chains  
Scalar capital as ingredient of success in conservation governance: evidence from Melanesia 期刊论文
GLOBAL ENVIRONMENTAL CHANGE-HUMAN AND POLICY DIMENSIONS, 2020, 62
作者:  Cheok, Jessica;  Weeks, Rebecca;  Morrison, Tiffany H.;  Pressey, Robert L.
收藏  |  浏览/下载:6/0  |  提交时间:2020/07/02
Multiscale governance  Scalar capital  Environmental governance  Social-ecological systems  Conservation planning  
Scale-Dependent Evanescence of River Dunes During Discharge Extremes 期刊论文
GEOPHYSICAL RESEARCH LETTERS, 2020, 47 (6)
作者:  Nagshband, S.;  Hoitink, A. J. F.
收藏  |  浏览/下载:0/0  |  提交时间:2020/07/02
Operation of a silicon quantum processor unit cell above one kelvin 期刊论文
NATURE, 2020, 580 (7803) : 350-+
作者:  Han, Kyuho;  Pierce, Sarah E.;  Li, Amy;  Spees, Kaitlyn;  Anderson, Grace R.;  Seoane, Jose A.;  Lo, Yuan-Hung;  Dubreuil, Michael;  Olivas, Micah;  Kamber, Roarke A.;  Wainberg, Michael;  Kostyrko, Kaja;  Kelly, Marcus R.;  Yousefi, Maryam;  Simpkins, Scott W.;  Yao, David
收藏  |  浏览/下载:10/0  |  提交时间:2020/07/03

Quantum computers are expected to outperform conventional computers in several important applications, from molecular simulation to search algorithms, once they can be scaled up to large numbers-typically millions-of quantum bits (qubits)(1-3). For most solid-state qubit technologies-for example, those using superconducting circuits or semiconductor spins-scaling poses a considerable challenge because every additional qubit increases the heat generated, whereas the cooling power of dilution refrigerators is severely limited at their operating temperature (less than 100 millikelvin)(4-6). Here we demonstrate the operation of a scalable silicon quantum processor unit cell comprising two qubits confined to quantum dots at about 1.5 kelvin. We achieve this by isolating the quantum dots from the electron reservoir, and then initializing and reading the qubits solely via tunnelling of electrons between the two quantum dots(7-9). We coherently control the qubits using electrically driven spin resonance(10,11) in isotopically enriched silicon(12 28)Si, attaining single-qubit gate fidelities of 98.6 per cent and a coherence time of 2 microseconds during '  hot'  operation, comparable to those of spin qubits in natural silicon at millikelvin temperatures(13-16). Furthermore, we show that the unit cell can be operated at magnetic fields as low as 0.1 tesla, corresponding to a qubit control frequency of 3.5 gigahertz, where the qubit energy is well below the thermal energy. The unit cell constitutes the core building block of a full-scale silicon quantum computer and satisfies layout constraints required by error-correction architectures(8),(17). Our work indicates that a spin-based quantum computer could be operated at increased temperatures in a simple pumped He-4 system (which provides cooling power orders of magnitude higher than that of dilution refrigerators), thus potentially enabling the integration of classical control electronics with the qubit array(18,19).


  
Coherent electrical control of a single high-spin nucleus in silicon 期刊论文
NATURE, 2020, 579 (7798) : 205-+
作者:  Dedoussi, Irene C.;  Eastham, Sebastian D.;  Monier, Erwan;  Barrett, Steven R. H.
收藏  |  浏览/下载:10/0  |  提交时间:2020/07/03

Nuclear spins are highly coherent quantum objects. In large ensembles, their control and detection via magnetic resonance is widely exploited, for example, in chemistry, medicine, materials science and mining. Nuclear spins also featured in early proposals for solid-state quantum computers(1) and demonstrations of quantum search(2) and factoring(3) algorithms. Scaling up such concepts requires controlling individual nuclei, which can be detected when coupled to an electron(4-6). However, the need to address the nuclei via oscillating magnetic fields complicates their integration in multi-spin nanoscale devices, because the field cannot be localized or screened. Control via electric fields would resolve this problem, but previous methods(7-9) relied on transducing electric signals into magnetic fields via the electron-nuclear hyperfine interaction, which severely affects nuclear coherence. Here we demonstrate the coherent quantum control of a single Sb-123 (spin-7/2) nucleus using localized electric fields produced within a silicon nanoelectronic device. The method exploits an idea proposed in 1961(10) but not previously realized experimentally with a single nucleus. Our results are quantitatively supported by a microscopic theoretical model that reveals how the purely electrical modulation of the nuclear electric quadrupole interaction results in coherent nuclear spin transitions that are uniquely addressable owing to lattice strain. The spin dephasing time, 0.1 seconds, is orders of magnitude longer than those obtained by methods that require a coupled electron spin to achieve electrical driving. These results show that high-spin quadrupolar nuclei could be deployed as chaotic models, strain sensors and hybrid spin-mechanical quantum systems using all-electrical controls. Integrating electrically controllable nuclei with quantum dots(11,12) could pave the way to scalable, nuclear- and electron-spin-based quantum computers in silicon that operate without the need for oscillating magnetic fields.


  
Time-Dependent Production Functions of Lunar Simple Craters on Layered Targets With Consideration of Topographic Degradation 期刊论文
GEOPHYSICAL RESEARCH LETTERS, 2019
作者:  Xie, Minggang;  Xiao, Zhiyong;  Xu, Aoao
收藏  |  浏览/下载:5/0  |  提交时间:2019/11/27
target properties  production function  topographic degradation  chronology  regolith  impact craters  
Quantitative assessment of microbial necromass contribution to soil organic matter 期刊论文
GLOBAL CHANGE BIOLOGY, 2019, 25 (11) : 3578-3590
作者:  Liang, Chao;  Amelung, Wulf;  Lehmann, Johannes;  Kaestner, Matthias
收藏  |  浏览/下载:12/0  |  提交时间:2019/11/27
amino sugar  ecosystem sustainability  microbial anabolism  microbial biomarker  microbial residue  soil organic carbon  
Linking forest growth with stand structure: Tree size inequality, tree growth or resource partitioning and the asymmetry of competition 期刊论文
FOREST ECOLOGY AND MANAGEMENT, 2019, 447: 139-157
作者:  Forrester, David, I
收藏  |  浏览/下载:6/0  |  提交时间:2019/11/27
Asymmetric competition  Climate change  Continuous cover forestry  Growth dominance  Mixed species  Multi-aged  Size heterogeneity  Uneven-aged  
Significant feedbacks of wetland methane release on climate change and the causes of their uncertainty 期刊论文
ENVIRONMENTAL RESEARCH LETTERS, 2019, 14 (8)
作者:  Gedney, N.;  Huntingford, C.;  Comyn-Platt, E.;  Wiltshire, A.
收藏  |  浏览/下载:6/0  |  提交时间:2019/11/27
wetlands  methane  climate  feedback  
Terrestrial gross primary production: Using NIRV to scale from site to globe 期刊论文
GLOBAL CHANGE BIOLOGY, 2019, 25 (11) : 3731-3740
作者:  Badgley, Grayson;  Anderegg, Leander D. L.;  Berry, Joseph A.;  Field, Christopher B.
收藏  |  浏览/下载:8/0  |  提交时间:2019/11/27
carbon cycle  near-infrared reflectance  photosynthesis  remote sensing  terrestrial gross primary production