Floquet engineering of long-range p-wave superconductivity: Beyond the high-frequency limit

It has been shown that long-range {\it p}-wave superconductivity in a Kitaev chain can be engineered via an ac field with a high frequency [Benito et al., Phys. Rev. B 90, 205127 (2014)]. For its experimental realization, however, theoretical understanding of Floquet engineering with a broader range of driving frequencies becomes important. In this work, focusing on the ac-driven tunneling interactions of a Kitaev chain, we investigate effects from the leading correction to the high-frequency limit on the emergent {\it p}-wave superconductivity. Importantly, we find new engineered long-range {\it p}-wave pairing interactions that can significantly alter the ones in the high-frequency limit at long interaction ranges. We also find that the leading correction additionally generates nearest-neighbor {\it p}-wave pairing interactions with a renormalized pairing energy, long-range tunneling interactions, and in particular multiple pairs of Floquet Majorana edge states that are destroyed in the high- frequency limit.Comment: 13 pages, 8 figure

Incorporation of Inherent Safety and Environmental Aspects in Process Design and Supply Chain Optimization

The integration of inherently safer design and environmental aspects at the early phases of supply chain selection and process design provides significant benefits. It allows the highest ability to positively influence lifecycle safety, environmental impact, and cost of the project. Because of the preliminary nature of conceptual process design, it is crucial to have a simple yet effective approach to evaluate and compare the design alternatives based on the safety and environmental aspects at the early stage of the project when available engineering information and data are limited. This work proposes a framework to incorporating life-cycle safety measures in the supply chain design and the process technologies included in the supply chain. A hierarchical approach is developed for conceptual-phase engineering project to facilitate the inclusion of safety objectives in the process synthesis and supply chain design engineering work in a consistent manner. Design options are first generated and screened based on economic criteria. Next, safety metrics are used in addition to economic objectives to evaluate the various designs and transportation options. Findings from the hazard and risk assessment are used to generate design alternatives to improve the safety performance. Economic evaluation is updated for acceptable options to guide the decision making. To demonstrate the approach, a case study is solved for a conceptual design of a high density polyethylene (HDPE) supply chain from shale gas. Various conceptual design options that considered different elements such as process technology, manufacturing network and capacity were screened and evaluated per proposed framework. A high-level quantitative risk assessment approach was used for assessing the safety aspects of the design options

Incorporation of Inherent Safety and Environmental Aspects in Process Design and Supply Chain Optimization

The integration of inherently safer design and environmental aspects at the early phases of supply chain selection and process design provides significant benefits. It allows the highest ability to positively influence lifecycle safety, environmental impact, and cost of the project. Because of the preliminary nature of conceptual process design, it is crucial to have a simple yet effective approach to evaluate and compare the design alternatives based on the safety and environmental aspects at the early stage of the project when available engineering information and data are limited. This work proposes a framework to incorporating life-cycle safety measures in the supply chain design and the process technologies included in the supply chain. A hierarchical approach is developed for conceptual-phase engineering project to facilitate the inclusion of safety objectives in the process synthesis and supply chain design engineering work in a consistent manner. Design options are first generated and screened based on economic criteria. Next, safety metrics are used in addition to economic objectives to evaluate the various designs and transportation options. Findings from the hazard and risk assessment are used to generate design alternatives to improve the safety performance. Economic evaluation is updated for acceptable options to guide the decision making. To demonstrate the approach, a case study is solved for a conceptual design of a high density polyethylene (HDPE) supply chain from shale gas. Various conceptual design options that considered different elements such as process technology, manufacturing network and capacity were screened and evaluated per proposed framework. A high-level quantitative risk assessment approach was used for assessing the safety aspects of the design options

Backaction of a charge detector on a double quantum dot

We develop a master equation approach to study the backaction of quantum point contact (QPC) on a double quantum dot (DQD) at zero bias voltage. We reveal why electrons can pass through the zero-bias DQD only when the bias voltage across the QPC exceeds a threshold value determined by the eigenstate energy difference of the DQD. This derived excitation condition agrees well with experiments on QPC-induced inelastic electron tunneling through a DQD [S. Gustavsson et al., Phys. Rev. Lett. 99, 206804(2007)]. Moreover, we propose a new scheme to generate a pure spin current by the QPC in the absence of a charge current.Comment: 6 pages, 4 figure

Collective quantum phase slips in multiple nanowire junctions

Realization of robust coherent quantum phase slips represents a significant experimental challenge. Here we propose a new design consisting of multiple nanowire junctions to realize a phase-slip flux qubit. It admits good tunability provided by gate voltages applied on superconducting islands separating nanowire junctions. In addition, the gates and junctions can be identical or distinct to each other leading to symmetric and asymmetric setups. We find that the asymmetry can improve the performance of the proposed device, compared with the symmetric case. In particular, it can enhance the effective rate of collective quantum phase slips. Furthermore, we demonstrate how to couple two such devices via a mutual inductance. This is potentially useful for quantum gate operations. Our investigation on how symmetry in multiple nanowire junctions affects the device performance should be useful for the application of phase-slip flux qubits in quantum information processing and quantum metrology.Comment: 12 pages, 6 figure

Cooling a nanomechanical resonator by a triple quantum dot

We propose an approach for achieving ground-state cooling of a nanomechanical resonator (NAMR) capacitively coupled to a triple quantum dot (TQD). This TQD is an electronic analog of a three-level atom in $\Lambda$ configuration which allows an electron to enter it via lower-energy states and to exit only from a higher-energy state. By tuning the degeneracy of the two lower-energy states in the TQD, an electron can be trapped in a dark state caused by destructive quantum interference between the two tunneling pathways to the higher-energy state. Therefore, ground-state cooling of an NAMR can be achieved when electrons absorb readily and repeatedly energy quanta from the NAMR for excitations.Comment: 6 pages, 3 figure