UOW’s Institute for Superconducting and Electronic Materials (ISEM) has successfully pioneered a way to construct a flexible, foldable and lightweight energy storage device that provides the building blocks for next-generation batteries needed to power wearable electronics and implantable medical devices (, "Self-Assembled Multifunctional Hybrids: Toward Developing High-Performance Graphene-Based Architectures for Energy Storage Devices"). The conundrum researchers have faced in developing miniature energy storage devices, such as batteries and supercapacitors, has been figuring out how to increase the surface area of the device, to store more charge, without making it larger. “Among all modern electronic devices, portable electronics are some of the most exciting,” ISEM PhD student Monirul Islam said. “But the biggest challenge is to charge storage in a small volume as well as being able to deliver that charge quickly on demand.” To solve this problem, a team of PhD students, led by Dr Konstantin Konstantinov under the patronage of ISEM Director Professor Shi Xue Dou and with the support of Professor Hua Kun Liu, the head of ISEM Energy Storage Division, have developed a three-dimensional structure using a flat-pack self-assembly of three components: graphene, a conductive polymer and carbon nanotubes, which are atom-thick lattice-like networks of carbon formed into cylinders. Graphene, made from single atom-thick layers of graphite, was a suitable candidate due its electronic performance and mechanical strength. “We knew in theory that if you can make a sort of carbon skeleton you have a greater surface area and greater surface area means more charge,” Dr Konstantinov said. “If we could efficiently separate the layers of carbon we could then use both surfaces of each layer for charge accumulation. The problem we faced was that fabricating these 3D shapes in practice, not just theory, is a challenging, if not impossible task.” The solution was to flat-pack the components by building the 3D shape layer-by-layer, much like a miniature exercise in cake decoration. The graphene in liquid form was mixed with the conductive polymer and reduced to solid and the carbon nanotubes carefully inserted between the graphene layers to form a self-assembled flat-packed, wafer-thin supercapacitor material. “The real challenge was how to assemble these three components into a single structure with the best use of the space available,” PhD student Monirul Islam said. “Getting the proportions or ratios of the components appropriately in order to obtain a composite material with maximum energy storage performance was another challenge.” Wrong proportions of either ingredient result in a lumpy mess, or a 3D shape that isn’t strong enough to retain the needed flexibility as well as the charge storage ability. There’s also elegance in the simplicity of the team’s design: the researchers dispersed the components in liquid crystalline, which enabled natural chemical interactions to prevent the graphene layers clumping together. The result was a 3D shape with, thanks to the carbon nanotubes, a massive surface area, excellent charge capacity that is also foldable. It can also be cheaply and easily fabricated without the need for expensive vacuum chambers or sophisticated equipment. “Our graphene-based flexible composite is highly conductive, lightweight, is able to fold like a roll or stack like a paper in electronic devices to store a huge amount of charge,” Monirul said. “This material can store charge in a second and deliver the charge in superfast speed and will be more lightweight than traditional batteries used in present day’s electronics.” The ISEM study has been financially supported by the Automotive Australia 2020 CRC as part of its research into electric vehicles. ISEM is the program leader for electrification and plays crucial role for design of next generation electric vehicles A key to unlocking the electric vehicle’s capability is a lightweight and powerful battery pack. “Our simple fabrication method of eco-friendly materials with increased performance has great potential to be scaled up for use supercapacitor and battery technology. Our next step is to use this material to fabricate flexible wearable supercapacitors with high power density and energy density as well as large scale supercapacitors for electric vehicles.”
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Superconducting qubit and magnetic sphere hybrid
Researchers at the University of Tokyo have demonstrated that it is possible to exchange a quantum bit, the minimum unit of information used by quantum computers, between a superconducting quantum-bit circuit and a quantum in a magnet called a magnon ("Coherent coupling between a ferromagnetic magnon and a superconducting qubit"). This result is expected to contribute to the development of quantum interfaces and quantum repeaters. Magnets, often used in our daily life, exert a magnetic force produced by a large number of microscopic magnets – the spins of individual electrons – that are aligned in the same orientation. The collective motions of the ensemble of spins are called spin waves. A magnon is a quantum of such excitations, similar to a photon as a quantum of light, i.e., the electromagnetic wave. At room temperature the motions of electron spins can be largely affected by heat. The properties of individual magnons have not been studied at low temperatures corresponding to the “quantum limit” where all thermally-induced spin fluctuations vanish. 
Illustration of magnet-qubit coupled system. A magnet (ytterium iron garnet; YIG) and a superconducting qubit are placed with a separation of 4 cm. The electric field in the cavity interacts with the qubit, while the magnetic field interacts with the magnet. At an extremely low temperature of around -273 degrees centigrade, magnons, i.e., quanta of the fluctuations in the magnet, coherently couple with the qubit through the electromagnetic field of the cavity. (Image: Yutaka Tabuchi) The research group of Professor Yasunobu Nakamura at the University of Tokyo Research Center for Advanced Science and Technology has succeeded for the first time to couple a magnon in a magnet to a photon in a microwave cavity at an ultralow temperature near absolute zero (-273.14 degrees centigrade). They observed coherent interaction between a magnon and a microwave photon by placing a millimeter-sized ferromagnetic sphere made of yttrium iron garnet in a centimeter-scale microwave cavity. The research group furthermore demonstrated coherent coupling of a magnon to a superconducting quantum-bit circuit. The latter is known as a well-controllable quantum system and as one of the most promising building blocks for quantum processors. The group placed the magnet together with the superconducting qubit in a cavity and demonstrated exchange of information between the magnon and superconducting qubit mediated by the microwave cavity. The results will stimulate research on the quantum behavior of magnons in spintronics devices and open a path toward realization of quantum interfaces and quantum repeaters.
read more "Superconducting qubit and magnetic sphere hybrid"
Illustration of magnet-qubit coupled system. A magnet (ytterium iron garnet; YIG) and a superconducting qubit are placed with a separation of 4 cm. The electric field in the cavity interacts with the qubit, while the magnetic field interacts with the magnet. At an extremely low temperature of around -273 degrees centigrade, magnons, i.e., quanta of the fluctuations in the magnet, coherently couple with the qubit through the electromagnetic field of the cavity. (Image: Yutaka Tabuchi) The research group of Professor Yasunobu Nakamura at the University of Tokyo Research Center for Advanced Science and Technology has succeeded for the first time to couple a magnon in a magnet to a photon in a microwave cavity at an ultralow temperature near absolute zero (-273.14 degrees centigrade). They observed coherent interaction between a magnon and a microwave photon by placing a millimeter-sized ferromagnetic sphere made of yttrium iron garnet in a centimeter-scale microwave cavity. The research group furthermore demonstrated coherent coupling of a magnon to a superconducting quantum-bit circuit. The latter is known as a well-controllable quantum system and as one of the most promising building blocks for quantum processors. The group placed the magnet together with the superconducting qubit in a cavity and demonstrated exchange of information between the magnon and superconducting qubit mediated by the microwave cavity. The results will stimulate research on the quantum behavior of magnons in spintronics devices and open a path toward realization of quantum interfaces and quantum repeaters.
Superfast fluorescence sets new speed record
Researchers have developed an ultrafast light-emitting device that can flip on and off 90 billion times a second and could form the basis of optical computing. At its most basic level, your smart phone's battery is powering billions of transistors using electrons to flip on and off billions of times per second. But if microchips could use photons instead of electrons to process and transmit data, computers could operate even faster. But first engineers must build a light source that can be turned on and off that rapidly. While lasers can fit this requirement, they are too energy-hungry and unwieldy to integrate into computer chips. Duke University researchers are now one step closer to such a light source. In a new study, a team from the Pratt School of Engineering pushed semiconductor quantum dots to emit light at more than 90 billion gigahertz. This so-called plasmonic device could one day be used in optical computing chips or for optical communication between traditional electronic microchips. 
A nanoscale view of the new superfast fluorescent system using a transmission electron microscope. The silver cube is just 75-nanometers wide. The quantum dots (red) are sandwiched between the silver cube and a thin gold foil. (Image: Maiken Mikkelsen, Duke University) The study was published online on July 27 in ("Ultrafast Spontaneous Emission Source Using Plasmonic Nanoantennas"). "This is something that the scientific community has wanted to do for a long time," said Maiken Mikkelsen, an assistant professor of electrical and computer engineering and physics at Duke. "We can now start to think about making fast-switching devices based on this research, so there's a lot of excitement about this demonstration." The new speed record was set using plasmonics. When a laser shines on the surface of a silver cube just 75 nanometers wide, the free electrons on its surface begin to oscillate together in a wave. These oscillations create their own light, which reacts again with the free electrons. Energy trapped on the surface of the nanocube in this fashion is called a plasmon. The plasmon creates an intense electromagnetic field between the silver nanocube and a thin sheet of gold placed a mere 20 atoms away. This field interacts with quantum dots -- spheres of semiconducting material just six nanometers wide -- that are sandwiched in between the nanocube and the gold. The quantum dots, in turn, produce a directional, efficient emission of photons that can be turned on and off at more than 90 gigahertz. "There is great interest in replacing lasers with LEDs for short-distance optical communication, but these ideas have always been limited by the slow emission rate of fluorescent materials, lack of efficiency and inability to direct the photons," said Gleb Akselrod, a postdoctoral research in Mikkelsen's laboratory. "Now we have made an important step towards solving these problems." "The eventual goal is to integrate our technology into a device that can be excited either optically or electrically," said Thang Hoang, also a postdoctoral researcher in Mikkelsen's laboratory. "That's something that I think everyone, including funding agencies, is pushing pretty hard for." The group is now working to use the plasmonic structure to create a single photon source -- a necessity for extremely secure quantum communications -- by sandwiching a single quantum dot in the gap between the silver nanocube and gold foil. They are also trying to precisely place and orient the quantum dots to create the fastest fluorescence rates possible. Aside from its potential technological impacts, the research demonstrates that well-known materials need not be limited by their intrinsic properties. "By tailoring the environment around a material, like we've done here with semiconductors, we can create new designer materials with almost any optical properties we desire," said Mikkelsen. "And that's an emerging area that's fascinating to think about."
read more "Superfast fluorescence sets new speed record"
A nanoscale view of the new superfast fluorescent system using a transmission electron microscope. The silver cube is just 75-nanometers wide. The quantum dots (red) are sandwiched between the silver cube and a thin gold foil. (Image: Maiken Mikkelsen, Duke University) The study was published online on July 27 in ("Ultrafast Spontaneous Emission Source Using Plasmonic Nanoantennas"). "This is something that the scientific community has wanted to do for a long time," said Maiken Mikkelsen, an assistant professor of electrical and computer engineering and physics at Duke. "We can now start to think about making fast-switching devices based on this research, so there's a lot of excitement about this demonstration." The new speed record was set using plasmonics. When a laser shines on the surface of a silver cube just 75 nanometers wide, the free electrons on its surface begin to oscillate together in a wave. These oscillations create their own light, which reacts again with the free electrons. Energy trapped on the surface of the nanocube in this fashion is called a plasmon. The plasmon creates an intense electromagnetic field between the silver nanocube and a thin sheet of gold placed a mere 20 atoms away. This field interacts with quantum dots -- spheres of semiconducting material just six nanometers wide -- that are sandwiched in between the nanocube and the gold. The quantum dots, in turn, produce a directional, efficient emission of photons that can be turned on and off at more than 90 gigahertz. "There is great interest in replacing lasers with LEDs for short-distance optical communication, but these ideas have always been limited by the slow emission rate of fluorescent materials, lack of efficiency and inability to direct the photons," said Gleb Akselrod, a postdoctoral research in Mikkelsen's laboratory. "Now we have made an important step towards solving these problems." "The eventual goal is to integrate our technology into a device that can be excited either optically or electrically," said Thang Hoang, also a postdoctoral researcher in Mikkelsen's laboratory. "That's something that I think everyone, including funding agencies, is pushing pretty hard for." The group is now working to use the plasmonic structure to create a single photon source -- a necessity for extremely secure quantum communications -- by sandwiching a single quantum dot in the gap between the silver nanocube and gold foil. They are also trying to precisely place and orient the quantum dots to create the fastest fluorescence rates possible. Aside from its potential technological impacts, the research demonstrates that well-known materials need not be limited by their intrinsic properties. "By tailoring the environment around a material, like we've done here with semiconductors, we can create new designer materials with almost any optical properties we desire," said Mikkelsen. "And that's an emerging area that's fascinating to think about."
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