high-performance computing


alongside their prototype soſtware simulation environments. ‘Topological materials could provide yet


another approach for quantum computation and this would be topologically protected; that is, basically decoherence-free,’ said Hakonen. Currently efforts are being made to


bridge graphene with silicon. Te European Graphene Flagship project is researching the integration with silicon circuits. Teir present objective is to produce components for optical communications using optical graphene detectors directly integrated with CMOS circuits. However, current CMOS technology still


➤


properties to handle decoherence issues that greatly hinder performance and information reliability of qubits. ‘Te advantage is that electrical charge


fluctuations in clean nanotubes are very small compared with silicon devices, and long enough coherence times may be achievable in nanotube systems,’ said Hakonen. Tis is important for information stability on qubits as error rates are far more prominent and impactful than in a classical CMOS transistor. Proof-of-concept devices have already


been created that have reliable contacts between the metallic lead and tube. Tis is due to the combination of CNTs with special superconducting alloys made of molybdenum and rhenium. However, measurements on CNT qubit devices have concentrated on noise properties so far. Te next step is to see how long


decoherence times can be reached in these novel qubits. Hakonen suspects that using superconducting nanowires instead could be a better approach, with lower component variation and easier to scale up. For example, a technique known as


molecular beam epitaxy enables the growth of thin films and wires of single crystals, or layers of semiconductors or other metals. Tese superconducting nanowires have already been grown and tested. Qubits with semiconductor nanowire Josephson junctions (two layers of superconductors separated by a thin insulating layer), known as a hybrid Gatemon two-qubit system, was demonstrated last year in the journal Physical Review Letters.


14 SCIENTIFIC COMPUTING WORLD THIS


DEMONSTRATION IS NOT ONLY GOOD NEWS FOR FUTURE FABRICATION SCALABILITY OF TRANSISTORS, BASED ON CARBON


NANOTUBES, BUT HAS THE POTENTIAL FOR BETTER MOBILE COMMUNICATION DEVICES


Both scientists Hakonen and Möttönen,


whose expertise resides in quantum information systems, know not to put all their qubit eggs in one basket when it comes to CNT technology. Certain computational problems will


always elude carbon nanotube-based computers. Only future large-scale quantum computers will be able to find ways to solve problems, such as computing the energy transport in novel drug molecules in a reasonable amount of time, instead of the thousands or millions of years it would take on today’s best supercomputers. For now, CNT technology investment is


still risky, as there is no guarantee of payback. For example, Microsoſt Research is focussing on designing ‘topological’ material qubits


has life in it yet. Te semiconductor industry is investing in techniques it knows probably will produce healthy returns from production. In late 2016, the large semiconductor manufacturer GlobalFoundries, based in California, announced their roll-out plan to deliver a new seven nanometre FinFET semiconductor technology, with trials running this year. FinFET stand for Fin Field Effect transistor or a ‘3D’ transistor. Intel just announced a $7 billion


investment in a next-generation semiconductor factory to target the seven nanometre manufacturing process in Arizona, which they advertise to be the most advanced semiconductor factory in the world. Te plan is for the plant to hire 3,000 high- tech engineering jobs and 10,000 long-term jobs to produce microprocessors to power data centres and hundreds of millions of smart and connected devices. Although Peng still believes that CNT


electronics will have a good chance to replace silicon CMOS technology at five nanometre nodes by 2022. ‘We are hoping to have more partners


working together to create a healthy industry environment for CNT chip fabrication, through co-operating with industries and government,’ said Peng. Whether or not carbon nanotubes will


replace silicon by 2022, all of these ongoing developments compliment advancement into next generation transistors. It appears likely that more advanced nanowires, or a hybrid-integration approach or even precise 3D printing of composite materials, will push CMOS transistor performance further. Tis is unless, of course, another novel breakthrough transports us to faster, more reliable and easily mass-produced quantum computing. l


Adrian Giordani is a freelance science writer who previously worked for CERN. Adrian specialises in science communications particularly in the fields of open science, computing, future technologies and HPC.


@scwmagazine l www.scientific-computing.com


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