Efficient decomposition of unitary matrices in quantum circuit compilers

Unitary decomposition is a widely used method to map quantum algorithms to an arbitrary set of quantum gates. Efficient implementation of this decomposition allows for translation of bigger unitary gates into elementary quantum operations, which is key to executing these algorithms on existing quantum computers. The decomposition can be used as an aggressive optimization method for the whole circuit, as well as to test part of an algorithm on a quantum accelerator. For selection and implementation of the decomposition algorithm, perfect qubits are assumed. We base our decomposition technique on Quantum Shannon Decomposition which generates O((3/4)*4^n) controlled-not gates for an n-qubit input gate. The resulting circuits are up to 10 times shorter than other methods in the field. When comparing our implementation to Qubiter, we show that our implementation generates circuits with half the number of CNOT gates and a third of the total circuit length. In addition to that, it is also up to 10 times as fast. Further optimizations are proposed to take advantage of potential underlying structure in the input or intermediate matrices, as well as to minimize the execution time of the decomposition.Comment: 13 page

Efficient parameterised compilation for hybrid quantum programming

Near term quantum devices have the potential to outperform classical computing through the use of hybrid classical-quantum algorithms such as Variational Quantum Eigensolvers. These iterative algorithms use a classical optimiser to update a parameterised quantum circuit. Each iteration, the circuit is executed on a physical quantum processor or quantum computing simulator, and the average measurement result is passed back to the classical optimiser. When many iterations are required, the whole quantum program is also recompiled many times. We have implemented explicit parameters that prevent recompilation of the whole program in quantum programming framework OpenQL, called OpenQL_PC, to improve the compilation and therefore total run-time of hybrid algorithms. We compare the time required for compilation and simulation of the MAXCUT algorithm in OpenQL to the same algorithm in both PyQuil and Qiskit. With the new parameters, compilation time in OpenQL is reduced considerably for the MAXCUT benchmark. When using OpenQL_PC, compilation of hybrid algorithms is up to two times faster than when using PyQuil or Qiskit

Calcium sensor kinase activates potassium uptake systems in gland cells of Venus flytraps

The Darwin plant Dionaea muscipula is able to grow on mineral-poor soil, because it gains essential nutrients from captured animal prey. Given that no nutrients remain in the trap when it opens after the consumption of an animal meal, we here asked the question of how Dionaea sequesters prey-derived potassium. We show that prey capture triggers expression of a K+ uptake system in the Venus flytrap. In search of K+ transporters endowed with adequate properties for this role, we screened a Dionaea expressed sequence tag (EST) database and identified DmKT1 and DmHAK5 as candidates. On insect and touch hormone stimulation, the number of transcripts of these transporters increased in flytraps. After cRNA injection of K+-transporter genes into Xenopus oocytes, however, both putative K+ transporters remained silent. Assuming that calcium sensor kinases are regulating Arabidopsis K+ transporter 1 (AKT1), we coexpressed the putative K+ transporters with a large set of kinases and identified the CBL9-CIPK23 pair as the major activating complex for both transporters in Dionaea K+ uptake. DmKT1 was found to be a K+-selective channel of voltage-dependent high capacity and low affinity, whereas DmHAK5 was identified as the first, to our knowledge, proton-driven, high-affinity potassium transporter with weak selectivity. When the Venus flytrap is processing its prey, the gland cell membrane potential is maintained around -120 mV, and the apoplast is acidified to pH 3. These conditions in the green stomach formed by the closed flytrap allow DmKT1 and DmHAK5 to acquire prey-derived K+, reducing its concentration from millimolar levels down to trace levels

Shard scheduler: object placement and migration in sharded account-based blockchains

We propose Shard Scheduler, a system for object placement and migration in account-based sharded blockchains. Our system calculates optimal placement and decides on object migrations across shards. It supports complex multi-account transactions caused by smart contracts. Placement and migration decisions made by Shard Scheduler are fully deterministic, verifiable, and can be made part of the consensus protocol. Shard Scheduler reduces the number of costly cross-shard transactions, ensures balanced load distribution and maximizes the number of processed transactions for the blockchain as a whole. To this end, it leverages a novel incentive model motivating miners to maximize the global throughput of the entire blockchain rather than the throughput of a specific shard. In our simulations, Shard Scheduler can reduce the number of costly cross-shard transactions by half while ensuring equal load and increasing throughput more than 2 fold when using 60 shards. We also implement and evaluate Shard Scheduler on Chainspace, more than doubling its throughput and reducing user-perceived latency by 70% when using 10 shards

Proof-of-Prestige: A Useful Work Reward System for Unverifiable Tasks

As cryptographic tokens and altcoins are increasingly being built to serve as utility tokens, the notion of useful work consensus protocols is becoming ever more important. With useful work consensus protocols, users get rewards after they have carried out some specific tasks useful for the network. While in some cases the proof of some utility or service can be provided, the majority of tasks are impossible to verify reliably. To deal with such cases, we design “Proof-of-Prestige” (PoP)—a reward system that can run directly on Proof-of-Stake (PoS) blockchains or as a smart contract on top of Proof-of-Work (PoW) blockchains. PoP introduces “prestige,” which is a volatile resource that, in contrast to coins, regenerates over time. Prestige can be gained by performing useful work, spent when benefiting from services, and directly translates to users minting power. Our scheme allows us to reliably reward decentralized workers while keeping the system free for the end-users. PoP is resistant against Sybil and collusion attacks and can be used with a vast range of unverifiable tasks. We build a simulator to assess the cryptoeconomic behavior of the system and deploy a full prototype of a content dissemination platform rewarding its participants. We implement the blockchain component on both Ethereum (PoW) and Cosmos (PoS), provide a mobile application, and connect it with our scheme with a negligible memory footprint. Finally, we adapt a fair exchange protocol allowing us to atomically exchange files for rewards also in scenarios where not all the parties have Internet connectivity. Our evaluation shows that even for large Ethereum traces, PoP introduces sub-millisecond computational overhead for miners in Cosmos and less than 0.013$ smart contract invocation cost for users in Ethereum

SeHCAT [tauroselcholic (selenium-75) acid] for the investigation of bile acid malabsorption and measurement of bile acid pool loss

Background The principal diagnosis/indication for this assessment is chronic diarrhoea due to bile acid malabsorption (BAM). Diarrhoea can be defined as the abnormal passage of loose or liquid stools more than three times daily and/or a daily stool weight > 200 g per day and is considered to be chronic if it persists for more than 4 weeks. The cause of chronic diarrhoea in adults is often difficult to ascertain and patients may undergo several investigations without a definitive cause being identified. BAM is one of several causes of chronic diarrhoea and results from failure to absorb bile acids (which are required for the absorption of dietary fats and sterols in the intestine) in the distal ileum. Objective For people with chronic diarrhoea with unknown cause and in people with Crohn's disease and chronic diarrhoea with unknown cause (i.e. before resection): (1) What are the effects of selenium-75-homocholic acid taurine (SeHCAT) compared with no SeHCAT in terms of chronic diarrhoea, other health outcomes and costs? (2) What are the effects of bile acid sequestrants (BASs) compared with no BASs in people with a positive or negative SeHCAT test? (3) Does a positive or negative SeHCAT test predict improvement in terms of chronic diarrhoea, other health outcomes and costs? Data sources A systematic review was conducted to summarise the evidence on the clinical effectiveness of SeHCAT for the assessment of BAM and the measurement of bile acid pool loss. Search strategies were based on target condition and intervention, as recommended in the Centre for Reviews and Dissemination (CRD) guidance for undertaking reviews in health care and the Cochrane Handbook for Diagnostic Test Accuracy Reviews. The following databases were searched up to April 2012: MEDLINE; MEDLINE In-Process & Other Non-Indexed Citations; EMBASE; the Cochrane Databases; Database of Abstracts of Reviews of Effects; Health Technology Assessment (HTA) Database; and Science Citation Index. Research registers and conference proceedings were also searched. Review methods Systematic review methods followed the principle

Decentralised Edge-Computing and IoT through Distributed Trust

The emerging Internet of Things needs edge-computing - this is an established fact. In turn, edge computing needs infrastructure decentralisation. What is not necessarily established yet is that infrastructure decentralisation needs a distributed model of Internet governance and decentralised trust schemes. We discuss the features of a decentralised IoT and edge-computing ecosystem and list the components that need to be designed, as well the challenges that need to be addressed

Wandering permanent pacemaker generators in children: a case series

<p>Abstract</p> <p>Introduction</p> <p>Epicardial permanent pacemaker generators are implanted some times in the abdominal wall in pediatric age groups.</p> <p>Case presentation</p> <p>Three permanent epicardial pacemakers that migrated in an unusual manner producing intraabdominal complications are reported.</p> <p>Conclusion</p> <p>The different clinical presentations of pacemaker migration in the pediatric age groups are highlighted and a few suggestions are made for avoiding such a complication.</p

Inclusion of carer health-related quality of life in national institute for health and care excellence appraisals

Objectives Health interventions for patients can have effects on their carers too. For consistency, decision makers may wish to specify whether carer outcomes should be included. One example is the National Institute for Health and Care Excellence (NICE), whose reference case specifies that economic evaluations should include direct health effects for patients and carers where relevant. We aimed to review the methods used in including carer health-related quality of life (HRQL) in NICE appraisals. Methods We reviewed all published technology appraisals (TAs) and highly specialized technologies (HSTs) to identify those that included carer HRQL and discussed the methods and data sources. Results Twelve of 414 TAs (3%) and 4 of 8 HSTs (50%) included carer HRQL in cost-utility analyses. Eight were for multiple sclerosis, the remainder were each in a unique disease area. Twelve of the 16 appraisals modeled carer HRQL as a function of the patient’s health state, 3 modeled carer HRQL as a function of the patient’s treatment, and 1 included family quality-adjusted life year (QALY) loss. They used 5 source studies: 2 compared carer EQ-5D scores with controls, 2 measured carer utility only (1 health utilities index and 1 EQ-5D), and 1 estimated family QALY loss from a child’s death. Two used disutility estimates not from the literature. Including carer HRQL increased the incremental QALYs and decreased incremental cost-effectiveness ratios in all cases. Conclusions The inclusion of carer HRQL in NICE appraisals is relatively uncommon and has been limited by data availability

Measuring Health Spillovers for Economic Evaluation:A Case Study in Meningitis

The health of carers and others close to the patient will often be relevant to economic evaluation, but it is very rarely considered in practice. This may reflect a lack of understanding of how the spillover effect of illness can be appropriately quantified. In this study we used three different approaches to quantify health spillovers resulting from meningitis. We conducted a survey of 1218 family networks affected by meningitis and used regression modelling to estimate spillover effects. The findings show that meningitis had long-term effects on family members' health, particularly affecting the likelihood of family members reporting anxiety and depression. These effects extended beyond a single close family member. These findings suggest that vaccinating against meningitis will bring significant health benefits not just to those that might have contracted the illness but also to their family networks. In methodological terms, different approaches for quantifying health spillovers provided broadly consistent results. The choice of method will be influenced by the ease of collecting primary data from family members in intervention contexts