Cady Feng - Academia.edu (original) (raw)
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Papers by Cady Feng
Zenodo (CERN European Organization for Nuclear Research), Feb 28, 2022
buildings 2% industry 1% transportation 6% non-CO2 GHGs 0.01% 2030 emissions gap 91% buildings 7%... more buildings 2% industry 1% transportation 6% non-CO2 GHGs 0.01% 2030 emissions gap 91% buildings 7% industry 7% power 48% transportation 26% non-CO2 GHGs 12% buildings 7% industry 12% power 34% transportation 26% non-CO2 GHGs 12% 2030 emissions gap 9% 6 BBBA (Nov '21) BBBA (Sept '21) IIJÂ-CO2-e calculations use 100 year global warming potential equivalence as per EPA Inventory of Greenhouse Gas Emissions. Gross emissions exclude net changes in land carbon sinks. Target for gross emissions reductions by 2030 assumes 100 MMT CO2-e increase in net land carbon sinks, bringing net GHG emissions to 50% below 2005 levels. See p. 15 for additional details. 2030 Contributions to Gross U.S. Greenhouse Gas Emissions Reductions Needed to Reach U.S. Climate Targets percentage of gross emissions reductions relative to Frozen Policy Benchmark consistent with a target of 50% below 2005 levels for net emissions (-1,405 MMT CO 2 e)T he House-passed BBBA (Nov '21) version delivers less emissions reductions in electricity (due to removal of the Clean Electricity Performance Program) and more in industry (due to the increase in 45Q tax credit for CCUS) than the originally introduced BBBA (Sept '21) version, leaving a net gap of ~180 MMT CO 2 e to meet 2030 emissions goals The IIJA achieves only 9% of the emissions reductions relative to Frozen Policy necessary to reach 2030 U.S. emissions goals BBBA (Nov '21)
arXiv (Cornell University), Jan 18, 2023
Superconducting qubits are a leading system for realizing large scale quantum processors, but ove... more Superconducting qubits are a leading system for realizing large scale quantum processors, but overall gate fidelities suffer from coherence times limited by microwave dielectric loss. Recently discovered tantalum-based qubits exhibit record lifetimes exceeding 0.3 ms. Here we perform systematic, detailed measurements of superconducting tantalum resonators in order to disentangle sources of loss that limit state-of-the-art tantalum devices. By studying the dependence of loss on temperature, microwave photon number, and device geometry, we quantify materials-related losses and observe that the losses are dominated by several types of saturable two level systems (TLSs), with evidence that both surface and bulk related TLSs contribute to loss. Moreover, we show that surface TLSs can be altered with chemical processing. With four different surface conditions, we quantitatively extract the linear absorption associated with different surface TLS sources. Finally, we quantify the impact of the chemical processing at single photon powers, the relevant conditions for qubit device performance. In this regime we measure resonators with internal quality factors ranging from 5 to 15 × 10 6 , comparable to the best qubits reported. In these devices the surface and bulk TLS contributions to loss are comparable, showing that systematic improvements in materials on both fronts will be necessary to improve qubit coherence further.
Zenodo (CERN European Organization for Nuclear Research), Feb 28, 2022
buildings 2% industry 1% transportation 6% non-CO2 GHGs 0.01% 2030 emissions gap 91% buildings 7%... more buildings 2% industry 1% transportation 6% non-CO2 GHGs 0.01% 2030 emissions gap 91% buildings 7% industry 7% power 48% transportation 26% non-CO2 GHGs 12% buildings 7% industry 12% power 34% transportation 26% non-CO2 GHGs 12% 2030 emissions gap 9% 6 BBBA (Nov '21) BBBA (Sept '21) IIJÂ-CO2-e calculations use 100 year global warming potential equivalence as per EPA Inventory of Greenhouse Gas Emissions. Gross emissions exclude net changes in land carbon sinks. Target for gross emissions reductions by 2030 assumes 100 MMT CO2-e increase in net land carbon sinks, bringing net GHG emissions to 50% below 2005 levels. See p. 15 for additional details. 2030 Contributions to Gross U.S. Greenhouse Gas Emissions Reductions Needed to Reach U.S. Climate Targets percentage of gross emissions reductions relative to Frozen Policy Benchmark consistent with a target of 50% below 2005 levels for net emissions (-1,405 MMT CO 2 e)T he House-passed BBBA (Nov '21) version delivers less emissions reductions in electricity (due to removal of the Clean Electricity Performance Program) and more in industry (due to the increase in 45Q tax credit for CCUS) than the originally introduced BBBA (Sept '21) version, leaving a net gap of ~180 MMT CO 2 e to meet 2030 emissions goals The IIJA achieves only 9% of the emissions reductions relative to Frozen Policy necessary to reach 2030 U.S. emissions goals BBBA (Nov '21)
arXiv (Cornell University), Jan 18, 2023
Superconducting qubits are a leading system for realizing large scale quantum processors, but ove... more Superconducting qubits are a leading system for realizing large scale quantum processors, but overall gate fidelities suffer from coherence times limited by microwave dielectric loss. Recently discovered tantalum-based qubits exhibit record lifetimes exceeding 0.3 ms. Here we perform systematic, detailed measurements of superconducting tantalum resonators in order to disentangle sources of loss that limit state-of-the-art tantalum devices. By studying the dependence of loss on temperature, microwave photon number, and device geometry, we quantify materials-related losses and observe that the losses are dominated by several types of saturable two level systems (TLSs), with evidence that both surface and bulk related TLSs contribute to loss. Moreover, we show that surface TLSs can be altered with chemical processing. With four different surface conditions, we quantitatively extract the linear absorption associated with different surface TLS sources. Finally, we quantify the impact of the chemical processing at single photon powers, the relevant conditions for qubit device performance. In this regime we measure resonators with internal quality factors ranging from 5 to 15 × 10 6 , comparable to the best qubits reported. In these devices the surface and bulk TLS contributions to loss are comparable, showing that systematic improvements in materials on both fronts will be necessary to improve qubit coherence further.