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New studies on particle entanglement dynamics in graphene for alternative quantum computing protocols

Posted By Graphene Council, Thursday, September 10, 2020
Quantum properties of matter as entanglement, which can allow controlling quantum states of physical systems, are key to the development of quantum computing and higher-performance information processing. Entanglement usually defines a nonlocal correlation between two or more particles, such that the quantum state of each of them cannot be described independently of the state of the others, even when particles become separated by an extremely large distance. Entanglement can be also observed between internal degrees of freedom of a single particle, which are independent parameters describing the state of a system, as physical coordinates define the position of a point in space. The comprehension of these phenomena, called inter- and intra-particle entanglement, can lead to manipulating the quantum states of physical systems, including materials as graphene and topological matter as a whole. 

In a paper recently published in Physical Review B as a Rapid Communication, researchers from the ICN2 Theoretical and Computational Nanoscience group, led by ICREA Prof. Stephan Roche, present a study on the origin, dynamics and magnitude of intra-particle entanglement between various degrees of freedom of electrons propagating in graphene. In particular, they explore the quantum correlations between the spin, defined as the intrinsic angular momentum of particles, and the pseudo-spin, which is a property analogous to spin that emerges in lattice structures and depends on their specific geometrical symmetries.

The authors of this study show that large intra-particle entanglement is a general feature of graphene supported onto a substrate and that its generation and evolution is independent of the initial state of the system. In addition, it may be robust to disorder and dephasing, which means that, if an interaction compromised the intra-particle entanglement, it would regenerate. This research also suggests that the properties of intra-particle entanglement in graphene should be relevant to the dynamic of inter-particle entanglement between pairs of electrons: in fact, the evolution of the first phenomenon is reflected in the second. Because of this, intra-particle entanglement might be detected indirectly in experiments via inter-particle correlations.

These results unveil unexplored paths to understanding and manipulating entanglement phenomena in a family of materials, called Dirac materials, which includes graphene: this name is due to the fact that they are systems that can be described by the Dirac equation of relativistic quantum mechanics. The ability to detect and manipulate entanglement in such materials could become an unprecedented resource for future research on the application of this phenomenon to quantum information processing.

Tags:  Graphene  ICN2  ICREA  quantum materials  Stephan Roche 

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New investors for INBRAIN to develop graphene-based implants against brain disorders

Posted By Graphene Council, Friday, June 12, 2020
INBRAIN Neuroelectronics, a spin-off of the Catalan Institute of Nanoscience and Nanotechnology and ICREA, receives funding from Sabadell Asabys and Alta Life Sciences, as well as ICF and Finaves, which will allow the company to speed up the development of novel graphene-based implants to optimise the treatment of brain disorders, such as Parkinson's and epilepsy.

According to a 2010 study commissioned by the European Brain Council, the cost of brain disorders in Europe alone reaches approximately 800 billion euros a year, with more than one-third of the population affected. The high incidence of brain-related diseases worldwide and their huge social cost call for greater investments in basic research in this field, with the aim of developing new and more efficient therapeutic and diagnostic tools.

INBRAIN Neuroelectronics, a spin-off of the Catalan Institute of Nanoscience and Nanotechnology (ICN2) and ICREA, was established in 2019 with the mission to develop brain-implants based on graphene technology for application in patients with epilepsy, Parkinson’s and other neuronal diseases. These smart devices, built around an innovative graphene electrode, will decode with high fidelity neural signals from the brain and produce a therapeutic response adapted to the clinical condition of the specific patient.

Additional resources have been recently injected into this endeavour by new investors — in particular Asabys and Alta Life Sciences, through the Sabadell-Asabys funds, followed by the Institut Català de Finances (ICF) and Finaves (fund promoted and managed by IESE Business School) — and other existing shareholders, such as the ICN2 and ICREA themselves. It will allow INBRAIN to accelerate the development of these novel intracranial implants for patients affected by brain disorders.

The company is designing the least invasive and smartest neural interface on the market that, powered by artificial intelligence and the use of Big Data, will have the ability to read and modulate brain activity, detect specific biomarkers and trigger adaptive responses to deliver optimal results in personalised neurological therapies. So far, the technology has been validated in in-vitro and in-vivo biocompatibility and toxicity tests and it has been successfully used to complete studies on small animals. Recently, INBRAIN has begun tests on large animals with the aim of ensuring that these graphene devices are safe, as well as superior to current solutions based on metals such as platinum and iridium. The company also plans to start soon human studies.

INBRAIN was founded, among others, by ICREA Prof. Jose Garrido, leader of the ICN2 Advanced Electronic Materials and Devices Group, Prof. Kostas Kostarelos, leader of the ICN2 Nanomedicine Group, and Dr Anton Guimerà, a researcher at the Spanish National Centre of Microelectronics (IMB-CNM). "Within the framework of the Graphene Flagship, which is a European macroproject”, explains Prof. Garrido, "we were able to develop this novel graphene-based technology that will allow measuring and stimulating neuronal activity in the brain with a resolution much higher than that of current commercial technologies”. During 2019, the incorporation of INBRAIN was a priority project for the ICN2 Business and Innovation Department, which coordinated the technology transfer process and successfully orchestrated the licensing of this high-potential technology.

“Minimally invasive electronic therapies represent a revolutionary alternative with less potential cost for health systems,” comments Carolina Aguilar, CEO of INBRAIN and a former global executive at Medtronic in the field of neuro-stimulation. "In our case, the application of new 2D materials such as graphene represents a real opportunity to understand how the brain works in order to optimise and personalise the treatment.”

Tags:  Carolina Aguilar  Graphene  ICN2  ICREA  IMB-CNM  INBRAIN 

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Layered heterostructures put a spin on magnetic memory devices

Posted By Graphene Council, Thursday, January 9, 2020
Graphene is a unique material with great potential for the long-distance transportation of spin information. However, spin-to-charge interconversion (SCI) in graphene and graphene-based heterostructures to date could not be performed at room temperature. But now, researchers at Graphene Flagship partners ICN2 and Universitat Autònoma de Barcelona, Spain, and the University of Groningen, the Netherlands, have achieved efficient room temperature SCI in graphene-based structures, and devised a way to make this process tuneable using an external electric field. The findings, published in Nature Materials and Nano Letters, could allow scientists to use layered heterostructures for ultra-compact, low-power consumption magnetic memory devices.

Spintronics is a branch of electronics which uses electrons' spin to store, manipulate and transfer information. Spintronics could benefit many emerging markets, like motion sensing and next-generation memory devices. Developing efficient and versatile spin-based technologies requires both high-quality materials for long-distance spin transfer, and suitable engineering methods to generate and manipulate spin currents, to ensure electrons move in a controlled way with their spins oriented along a given direction.

Generally, spin currents are generated and detected using ferromagnetic contacts. But as an alternative, spin-orbit interactions could enable spin currents to be controlled entirely by an electric field, resulting in a far more versatile tool to be implemented in large-scale spin devices. Now, Graphene Flagship researchers ICREA Prof. Sergio O. Valenzuela, ICREA Prof. Stephan Roche, and colleagues have exploited the unique spin properties of graphene to transport spin information across long distances in large-scale SCI electronics. Additionally, by interfacing graphene with transition metal dichalcogenides (TMDs), another family of layered materials with strong spin-orbit coupling, they were able to precisely control spin transport in these devices. "Thanks to this research, the Graphene Flagship's Spintronics Work Package has made a major step towards the engineering of SCI in quantum devices, with genuine potential for spintronics applications," explains Roche.

By fabricating a high-quality device and using very sensitive detection techniques to evaluate the spin Hall and inverse spin Galvanic effects – focusing in particular on spin precession and non-local measurements – they demonstrated experimentally that the SCI in graphene–TMD heterostructures is in good agreement with theoretical models. Furthermore, using these techniques, Graphene Flagship researchers not only demonstrated the spin-related character of the signals, but also tailored the efficiency of their SCI and sign using electrostatic gating. This important feature directly showcases their ability to manipulate spin information in the heterostructures with an electric field, and this could soon lead to new applications in magnetic memory devices. Most notably, they found that the room temperature SCI efficiencies were just as high as the best results using other materials.

"We're very excited to report the first unambiguous evidence of large and tuneable SCI in van der Waals heterostructures at room temperature," comments Valenzuela, from Graphene Flagship partner ICN2. "This is a significant step forward towards the long sought-after goal of electrostatic control of spin information," he continues. Additionally, Prof. Bart van Wees, from Graphene Flagship partner the University of Groningen, elaborates: "It is difficult to imagine how complex it is to fabricate spin devices combining various types of magnetic and non-magnetic materials, graphene, boron nitride, and strong spin-orbit coupling materials such as TMDs. Thanks to this work, the Spintronics Work Package has developed a unique expertise in realizing operational spin devices which really show the full potential of layered materials."

Kevin Garello, Graphene Flagship Work Package Leader for Spintronics, comments: "Devices involving the spin–orbit torque phenomenon, such as the spin Hall effect and the spin Galvanic effect, are great candidates for future spintronics applications as they require low power input and are capable of ultra-fast performance. It is great to see that spin-orbit torques can be electrically manipulated and improved by the smart engineering of layered materials, which has now been unequivocally confirmed independently by two experimental teams in Work Package Spintronics. This opens the door for new and exciting perspectives and strategies to manipulate spin information and further advance applications in spintronics based on layered materials."

The success of these studies is the result of the joint effort between experimental and theoretical researchers working closely together in the EU-funded Graphene Flagship framework. The results provide valuable insights for the spintronics and layered materials communities, and the researchers hope that their findings will enable scientists to explore new theoretical models and further experiments in the future.

Andrea C. Ferrari, Science and Technology Officer of the Graphene Flagship and Chair of its Management Panel, adds: "The Graphene Flagship has invested in spintronics research since the very beginning. The great potential of graphene and related materials in this area has been showcased by world-leading work done in the Flagship. These results indicate that we are getting close to the point where the fundamental work can be translated into useful applications, as foreseen in our science and technology and innovation roadmaps."

Tags:  Andrea C. Ferrari  Electronics  Graphene  Graphene Flagship  ICN2  ICREA  Kevin Garello  Sergio O. Valenzuela  Stephan Roche  Universitat Autònoma de Barcelona  University of Groningen 

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