Magic-State Functional Units: Mapping and Scheduling Multi-Level Distillation Circuits for Fault-Tolerant Quantum Architectures

Quantum computers have recently made great strides and are on a long-term path towards useful fault-tolerant computation. A dominant overhead in fault-tolerant quantum computation is the production of high-fidelity encoded qubits, called magic states, which enable reliable error-corrected computation. We present the first detailed designs of hardware functional units that implement space-time optimized magic-state factories for surface code error-corrected machines. Interactions among distant qubits require surface code braids (physical pathways on chip) which must be routed. Magic-state factories are circuits comprised of a complex set of braids that is more difficult to route than quantum circuits considered in previous work [1]. This paper explores the impact of scheduling techniques, such as gate reordering and qubit renaming, and we propose two novel mapping techniques: braid repulsion and dipole moment braid rotation. We combine these techniques with graph partitioning and community detection algorithms, and further introduce a stitching algorithm for mapping subgraphs onto a physical machine. Our results show a factor of 5.64 reduction in space-time volume compared to the best-known previous designs for magic-state factories.Comment: 13 pages, 10 figure

Resource Optimized Quantum Architectures for Surface Code Implementations of Magic-State Distillation

Quantum computers capable of solving classically intractable problems are under construction, and intermediate-scale devices are approaching completion. Current efforts to design large-scale devices require allocating immense resources to error correction, with the majority dedicated to the production of high-fidelity ancillary states known as magic-states. Leading techniques focus on dedicating a large, contiguous region of the processor as a single "magic-state distillation factory" responsible for meeting the magic-state demands of applications. In this work we design and analyze a set of optimized factory architectural layouts that divide a single factory into spatially distributed factories located throughout the processor. We find that distributed factory architectures minimize the space-time volume overhead imposed by distillation. Additionally, we find that the number of distributed components in each optimal configuration is sensitive to application characteristics and underlying physical device error rates. More specifically, we find that the rate at which T-gates are demanded by an application has a significant impact on the optimal distillation architecture. We develop an optimization procedure that discovers the optimal number of factory distillation rounds and number of output magic states per factory, as well as an overall system architecture that interacts with the factories. This yields between a 10x and 20x resource reduction compared to commonly accepted single factory designs. Performance is analyzed across representative application classes such as quantum simulation and quantum chemistry.Comment: 16 pages, 14 figure

Vacuum Infusion Process Development for Conformal Ablative Thermal Protection System Materials

Conformal ablators are low density composite materials comprised of a flexible carbon felt based fibrous substrate and a high surface area phenolic matrix. These materials are fabricated to near net shape by molding the substrate, placing in a rigid matched mold and infusing with liquid resin through a vacuum assisted process. The open mold process, originally developed for older rigid substrate ablators, such as PICA, wastes a substantial amount of resin. In this work, a vacuum infusion process a type of liquid composite molding where resin is directly injected into a closed mold under vacuum is advanced for conformal ablators. The process reduces waste over the state-of-the-art technique. Small, flat samples of Conformal Phenolic Impregnated Carbon Ablator are infused using the new approach and subjected to a range of curing configurations and conditions. Resulting materials are inspected for quality and compared to material produced using the standard process. Lessons learned inform subsequent plans for process scale up

Trauma, Depression, and Burnout in the Human Rights Field: Identifying Barriers and Pathways to Resilient Advocacy

Human rights advocates often confront trauma and stress in their work. They are exposed to testimony about heinous abuses; work in insecure locations; visit physical sites of abuse; review forensic, photographic, and video evidence; directly witness abuses; experience threats; and can also suffer detention, be attacked, or be tortured themselves. Such exposure risks adversely impacting the wellbeing and mental health of advocates. While the human rights field is diverse and work varies widely, most – if not all – advocates are likely directly or indirectly exposed to potentially traumatic events or material in the course of their work. The degree and type of exposure to human rights violations and insecurity can vary considerably among advocates: they work on human rights issues ranging from genocide to the right to water, in the midst of extreme poverty or armed conflict, as well as in countries experiencing relative peace and economic advantage. Some human rights advocates live and work in the same community, documenting abuses close to home. Others take up positions in national, regional, or international organizations, traveling to the scene of violations for defined periods. Many advocates have a wide variety of experiences over the course of a lifetime. One constant is that human rights advocates are likely to work in environments with abusive, violent, threatening, or otherwise distressing materials that can pose risks to advocates’ mental health and wellbeing. Yet many human rights advocates have little education in or support for the potential mental health impacts of their work, there is very little research in this area in either the human rights or psychology fields, and there is limited evidence-based guidance for promoting resilience and sustainable advocacy practices. This Article is part of an effort to close these gaps and to document the mental health of human rights advocates, who, in the pursuit of the rights of others, may neglect their own wellbeing. The Article is also part of an effort to understand the causes and dynamics of both positive and adverse wellbeing among advocates, with a view to improving how advocates are prepared for and conduct their work. It is crucial to identify specific factors that might place human rights advocates at risk for negative mental health impacts, as well as those factors that may help them develop resilience and ensure sustainable work practices, at both the individual and the institutional levels

Pre-Pandemic Ethics: Triage and Discrimination

UK COVID-19 death rates are disproportionately high among Black African, Black Caribbean, Bangladeshi, Pakistani, and Indian people in the UK, as well as among care home residents, carers, essential workers, and people living with disabilities and pre-existing conditions. The effects of the pandemic demonstrate the systemic social disparities of life and death in the UK. This is the context in which the authors consider Christian pandemic ethics, and this calls for a shift of focus away from pandemic ethics to what we term ‘pre-pandemic ethics’

Optimized Surface Code Communication in Superconducting Quantum Computers

Quantum computing (QC) is at the cusp of a revolution. Machines with 100 quantum bits (qubits) are anticipated to be operational by 2020 [googlemachine,gambetta2015building], and several-hundred-qubit machines are around the corner. Machines of this scale have the capacity to demonstrate quantum supremacy, the tipping point where QC is faster than the fastest classical alternative for a particular problem. Because error correction techniques will be central to QC and will be the most expensive component of quantum computation, choosing the lowest-overhead error correction scheme is critical to overall QC success. This paper evaluates two established quantum error correction codes---planar and double-defect surface codes---using a set of compilation, scheduling and network simulation tools. In considering scalable methods for optimizing both codes, we do so in the context of a full microarchitectural and compiler analysis. Contrary to previous predictions, we find that the simpler planar codes are sometimes more favorable for implementation on superconducting quantum computers, especially under conditions of high communication congestion.Comment: 14 pages, 9 figures, The 50th Annual IEEE/ACM International Symposium on Microarchitectur

Serotonin signaling through the 5-HT1B receptor and NADPH oxidase 1 in pulmonary arterial hypertension

Objective: Serotonin can induce human pulmonary artery smooth muscle cell (hPASMC) proliferation through reactive oxygen species (ROS), influencing the development of pulmonary arterial hypertension (PAH). We hypothesise that in PASMCs, serotonin induces oxidative stress through NADPH-oxidase-derived ROS generation and reduced Nrf-2 anti-oxidant systems, promoting vascular injury. Approach and Results: HPASMCs from controls and PAH patients, and PASMCs from Nox1-/- mice, were stimulated with serotonin in the absence/presence of inhibitors of Src kinase, the 5-HT1B receptor and NADPH oxidase 1 (Nox1). Markers of fibrosis were also determined. The pathophysiological significance of our findings was examined in vivo in serotonin transporter overexpressing (SERT+) female mice, a model of pulmonary hypertension (PH). We confirmed serotonin increased superoxide and H2O2 production in these cells. For the first time, we show that serotonin increased oxidized protein tyrosine phosphatases and peroxiredoxin-SO3H and decreased Nrf-2 and catalase activity in hPASMCs. ROS generation was exaggerated, and dependent on c-Src, 5-HT1B receptor and the serotonin transporter in PAH-hPASMCs. Proliferation and extracellular matrix remodeling were exaggerated in PAH-hPASMCs and dependent on 5-HT1B receptor signaling and Nox1, confirmed in PASMCs from Nox1-/- mice. In SERT+ mice, SB216641, a 5-HT1B receptor antagonist, prevented development of PH in a ROS-dependent manner. Conclusions: Serotonin can induce c-Src-regulated Nox1-induced ROS and Nrf-2 dysregulation, contributing to increased post-translational oxidative modification of proteins, activation of redox-sensitive signaling pathways in hPASMCs; associated with mitogenic responses. 5-HT1B receptors contribute to experimental PH by inducing lung ROS production. Our results suggest 5-HT1B receptor-dependent c-Src-Nox1-pathways contribute to vascular remodeling in PAH

Faculty Showcase Recital

This is the program for the faculty showcase recital featuring the following artists (in order of performance): pianist Adam Haas; soprano Margaret Garrett accompanied by pianist Louis Menendez; tenor Jon Secrest accompanied by Louis Menendez; horn player Heather Thayer accompanied by pianist Susan Monroe; soprano Glenda Secrest accompanied by Louis Menendez; soprano Robin Williams, mezzo soprano Suzetta Glenn, and baritone John Alec Briggs accompanied by Louis Menendez; pianist Louis Menendez; trombonist Justin Isenhour and percussionist Ryan Lewis; Glenda Secrest and Jon Secrest accompanied by Louis Menendez; John Briggs; pianist Cai Lei; and sopranos Glenda Secrest and Robin Williams; altos Margaret Garrett and Suzetta Glenn, tenors Jon Secrest and David Stanley, and bass John Alec Briggs accompanied on duo pianos by Louis Menendez and Phyllis Walker. This recital took place on September 17, 1998, in the W. Francis McBeth Recital Hall