Novel Graphene Film Offers New Concept for Solar Energy and Solar Seawater Desalination


Ultrathin-graphene-film-for-solar-energy-image-img_assist-400x254

Researchers at Swinburne, the University of Sydney and Australian National University have collaborated to develop a solar absorbing, ultra-thin graphene-based film with unique properties that has great potential for use in solar thermal energy harvesting.

The 90 nanometre material is said to be a 1000 times finer than a human hair and is able to rapidly heat up to 160°C under natural sunlight in an open environment.

The team stated that this new graphene-based material may also open new avenues in:

  • thermophotovoltaics (the direct conversion of heat to electricity)
  • solar seawater desalination
  • infrared light source and heater
  • optical components: modulators and interconnects for communication devices
  • photodetectors
  • colorful display
  • It could possibly lead to the development of ‘invisible cloaking technology’ through developing large-scale thin films enclosing the objects to be ‘hidden’.

The researchers have developed a 2.5cm x 5cm working prototype to demonstrate the photo-thermal performance of the graphene-based metamaterial absorber. They have also proposed a scalable manufacturing strategy to fabricate the proposed graphene-based absorber at low cost.

“This is among many graphene innovations in our group,” says Professor Baohua Jia, Research Leader, Nanophotonic Solar Technology, in Swinburne’s Center for Micro-Photonics.

“In this work, the reduced graphene oxide layer and grating structures were coated with a solution and fabricated by a laser nanofabrication method, respectively, which are both scalable and low cost.”

‌‌“Our cost-effective and scalable graphene absorber is promising for integrated, large-scale applications that require polarisation-independent, angle insensitive and broad bandwidth absorption, such as energy-harvesting, thermal emitters, optical interconnects, photodetectors and optical modulators,” says first author of this research paper, Dr Han Lin, Senior Research Fellow in Swinburne’s Center for Micro-Photonics.

“Fabrication on a flexible substrate and the robustness stemming from graphene make it suitable for industrial use,” Dr Keng-Te Lin, another author, added.

“The physical effect causing this outstanding absorption in such a thin layer is quite general and thereby opens up a lot of exciting applications,” says Dr Bjorn Sturmberg, who completed his PhD in physics at the University of Sydney in 2016 and now holds a position at the Australian National University.

“The result shows what can be achieved through collaboration between different universities, in this case with the University of Sydney and Swinburne, each bringing in their own expertise to discover new science and applications for our science,” says Professor Martijn de Sterke, Director of the Institute of Photonics and Optical Science.

“Through our collaboration we came up with a very innovative and successful result. We have essentially developed a new class of optical material, the properties of which can be tuned for multiple uses.”

Source:  Swinburne
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New Technology from U Mass Lowell may hold key to ‘Mainstream’ Fuel Cell EV’s ~ “May be the ‘boost’ that Fuel Cell EV’s Need“


While EVs have come a long way — even Ford is making electric trucks — they’re still a far cry from perfect. One of the biggest complaints is that the batteries need to be plugged in and recharged, and even when they’re charged, they have a limited range. Fuel cell electric vehicles offer an alternative.

Their “battery” — actually a hydrogen/oxygen fuel cell — can be replenished with hydrogen gas. The biggest problem to-date has been that producing hydrogen isn’t an environmentally friendly process. We would also need the infrastructure to refuel with hydrogen. But, new technology from UMass Lowell could remove those barriers.

Researchers there have created a way to produce hydrogen on demand using water, carbon dioxide and cobalt. Theoretically, that would go directly into a fuel cell, where it would mix with oxygen to generate electricity and water. The electricity would then power the EV’s motor, rechargeable battery and headlights.

According to UMass Lowell, the hydrogen produced is 95 percent pure, and vehicles would not need to be refueled at a filling station. Instead, owners would replace canisters of the cobalt metal which would fuel the hydrogen generator.

Because the technology can produce hydrogen at low temperatures and pressures and because excess isn’t stored in the vehicle, it minimizes the risk of fire or explosion. While this isn’t a practical application yet, it could help make FCEVs a viable option.

In a statement from UMass Lowell’s Chemistry Department Chairman Professor David Ryan below said that vehicles would not be refueled at a fueling station.

The system that we have devised would not require the vehicle to be refueled at a hydrogen filling station.

Our technology would use canisters of the cobalt metal as the fuel to operate the hydrogen generator.

The canisters would be swapped out when expended. It’s really too early to tell, but the goal is typically to be able to travel up to 350 to 400 miles for most vehicles before “refueling.”

U of Maryland: Wang Group Develops Highly Reversible 5.3 V Battery ~ 720Wh/kg for 1k cycles ~ With graphite and Li-metal anodes ~ Game Changer?


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Over the last several years, increasing the energy density of batteries has been a top priority in battery technology development, congruent with increasing demands for faster mobile devices and longer-lasting electrIc vehicles.

The energy density of lithium-ion batteries can be enhanced by either increasing the capacity of electrodes, or by enhancing the cell voltage (V).

Extensive research has been devoted to exploring the pairing of various materials in the search for the most efficient cathode/anode mix, but until now, only limited advances have been achieved due to the narrow electrochemical stability window of traditional electrolyte.

Researchers at the University of Maryland (UMD) led by Chunsheng Wang – a professor with joint appointments in the Departments of Chemical & Biomolecular Engineering (ChBE), and Chemistry & Biochemistry – have developed a highly reversible 5.3 V battery offering a Mn3+-free LiCoMnO4 cathode, and graphite and Li-metal anodes.

A specially designed electrolyte was also created, which is stable to 5.5V for both the LiCoMnO4 cathode and (graphite and Li-metal) anodes. This resulted in a 5.3V Li-metal cell, delivering a high energy density of 720Wh/kg for 1k cycles.

What’s more, this battery chemistry boasts a Coulombic efficiency of >99%, offering new development opportunity for high-voltage and energy Li-ion batteries.

Long Chen – a ChBE post-doctoral research associate – and Xiulin Fan– a ChBE assistant research scientist – served as first authors on the corresponding research paper, published in Chem on February 28, 2019.

“We are pleased to announce that we have created a stable 5.3V battery,” said Long Chen.

“The key is the super electrolytes with an especially wide electrochemical windows of 0 – 5.5V – this is due to the formation of robust interfacial layer on the electrodes.”   

Said Wang, “The high voltage electrolytes enable us to use high voltage cathode and high capacity Si- and potential Li-metal anodes, which will significantly increase the cell energy density.

However, the Coulombic efficiency of >99% for 5.3V LiCoMnO4 still needs improvement to achieve a long cycle life.”

For additional information:

Chen, L., Fa, X., Hu, E., Ji, X., Chen, J., HouS., Deng, T., Li, J., Su, D., Yang, X., Wang, C. “Achieving High Energy Density through Increasing the Output Voltage:

A Highly Reversible 5.3 V Battery.” Chem, 28 February 2019. https://doi.org/10.1016/j.chempr.2019.02.003

Published March 6, 2019

Cost-effective method for hydrogen fuel production process discovered at U of A


NAno particles for hydrogen 190319121737_1_540x360

Researchers at the U of A have designed nanoparticles that act as catalysts, making the process of water electrolysis more efficient. Credit: Jingyi Chen, Lauren Greenlee and Ryan Manso

 

Nanoparticles composed of nickel and iron have been found to be more effective and efficient than other, more costly materials when used as catalysts in the production of hydrogen fuel through water electrolysis.

The discovery was made by University of Arkansas researchers Jingyi Chen, associate professor of physical chemistry, and Lauren Greenlee, assistant professor of chemical engineering, as well as colleagues from Brookhaven National Lab and Argonne National Lab.

The researchers demonstrated that using nanocatalysts composed of nickel and iron increases the efficiency of water electrolysis, the process of breaking water atoms apart to produce hydrogen and oxygen and combining them with electrons to create hydrogen gas.

Chen and her colleagues discovered that when nanoparticles composed of an iron and nickel shell around a nickel core are applied to the process, they interact with the hydrogen and oxygen atoms to weaken the bonds, increasing the efficiency of the reaction by allowing the generation of oxygen more easily. Nickel and iron are also less expensive than other catalysts, which are made from scarce materials.

This marks a step toward making water electrolysis a more practical and affordable method for producing hydrogen fuel. Current methods of water electrolysis are too energy-intensive to be effective.

Story Source:

Materials provided by University of ArkansasNote: Content may be edited for style and length.


Journal Reference:

  1. Ryan H. Manso, Prashant Acharya, Shiqing Deng, Cameron C. Crane, Benjamin Reinhart, Sungsik Lee, Xiao Tong, Dmytro Nykypanchuk, Jing Zhu, Yimei Zhu, Lauren F. Greenlee, Jingyi Chen. Controlling the 3-D morphology of Ni–Fe-based nanocatalysts for the oxygen evolution reactionNanoscale, 2019; DOI: 10.1039/C8NR10138H

A new strategy of fabricating p-n junction in single crystalline Si nanowires, twisting


anewstrategy
Illustration of the relative formation energy as function of twist rate γ of doped Si nanowire for Sb and B dopants at different atomic sites. The strain-free and twisted Si nanowires are shown at the axial view. Credit: ©Science China Press

Can single crystalline materials be used for low dimensional p-n junction design? This is an open and long-standing problem. Microscopic simulations based on the generalized Bloch theorem show that in single crystalline Si nanowires, an axial twist can lead to the separation of p-type and n-type dopants along the nanowire radial dimension, and thus realizes the p-n junction. A bond orbital analysis reveals that this is due to the twist-induced inhomogeneous shear strain in the nanowire.

If a semiconductor crystal is doped with  dopants in one region and with  dopants in another region, a p-n junction configuration is formed. P-n junctions are fundamental building units of light emitting diodes, solar cells and other semiconductor transistors. P-n junctions in nano-structures are also expected to be the fundamental units of next generation nano-devices.

However, due to the strong attraction between them, n-type dopants and p-type dopants tend to form neutral pairs. As a result, the p-n junction fails. To prevent such attraction between n-type dopants and p-type dopants, heterostructures are introduced, where one  is doped with n-type dopants while the other is doped with p-type dopants, and the interface between two different semiconductor materials acts as an  between n-type dopants and p-type dopants.

Indeed, the usage of heterostructures stands for a paradigm for the material design of p-n junction. Recently, similar  configurations are also possible for nanowire heterostructures such as co-axial core-shell nanowires. However, there are several limitations in nanowire heterostructures. For example, the synthesis of core-shell nanowires usually involves a two-step process, which costs extra expense. Often the shell of the obtained nanowire heterostructure is polycrystalline. Such imperfection goes ill with the transports of carriers. Furthermore, the interface between the core and shell also introduces detrimental deep centers that largely hinder the device efficiency.

Can we make p-n junctions with single crystalline nanowires? Frankly, the answer will be “No” if one thinks the problem intuitively. Indeed, similar to the bulk, p-type dopants and n-type dopants in a codoped single crystalline nanowire also feel strong Coulomb attraction. Without an interface, how can we overcome such attraction? It requires an effective modulation/control of the spatial occupation sites, i.e., spatial distribution, of dopants. In fact, this is one of the long-standing and fundamental issues regarding doping in semiconductor.

From the point of view of materials engineering, this can be attributed to the failure of conventional approaches such as hydrostatic, biaxial and uniaxial stresses on the modulation of the spatial distribution of dopants. However, since all these mentioned distortions are uniform, can we employ some inhomogeneous ones, such as twisting? In fact, twisting of structures represents a focus of recent condensed matter physics research in low dimensions.

In a new paper published in National Science Review, a team of scientists from Beijing Normal University, the Chinese University of Hong Kong, and Beijing Computational Science Research Center present their theoretical advances of codoped Si nanowire under twisting. They employ both microscopic simulations based on the generalized Bloch theorem and analytical modeling based on the bond orbital theory to conduct the study and deliver the physics behind.

Interestingly, twisting has substantial impact on distribution of dopants in . From the displayed figure, in a twisted Si nanowire, a  of larger atomic size (Such as Sb) has a lower formation energy if it occupies an atomic site closer to nanowire surface; On the opposite, a dopant of smaller atomic size (Such as B) has a lower formation energy if it occupies an atomicsites around the nanowire core. According to their calculations, it is possible to separate n-type and p-type dopants in the codoped nanowire with proper choices of codoping pairs, e.g., B and Sb. A bond orbital analysis reveals that it is the twist-induced inhomogeneous shear strain along nanowire radial dimension that drives the effective modulation. These findings are fully supported by density-functional tight-binding based generalized Bloch theorem simulations.

This new strategy largely simplifies the manufacturing process and lowers the manufacturing costs. If the twisting is applied when the device is in working mode, the recombination of different types of dopants is largely suppressed. Even if the twisting is removed when the device is in working mode, due to the limited diffusion, the recombination is still difficult.

 Explore further: Researchers decipher electrical conductivity in doped organic semiconductors

More information: Dong-Bo Zhang et al, Twist-Driven Separation of p-type and n-type Dopants in Single Crystalline Nanowires, National Science Review (2019). DOI: 10.1093/nsr/nwz014

 

UCLA School of Dentistry: New membrane class shown to regenerate tissue and bone, viable solution for periodontitis


newmembranecA multifunctional periodontal membrane is surgically inserted into the pocket between affected gums and tooth. This new membrane has shown to protect the site from further infection as well as to help regrow bone. Credit: UCLA School of Dentistry

Periodontitis affects nearly half of Americans ages 30 and older, and in its advanced stages, it could lead to early tooth loss or worse. Recent studies have shown that periodontitis could also increase risk of heart disease and Alzheimer’s disease.

A team of UCLA researchers has developed methods that may lead to more effective and reliable therapy for periodontal disease—ones that promote gum tissue and bone regeneration with biological and mechanical features that can be adjusted based on treatment needs. The study is published online in ACS Nano.

Periodontitis is a chronic, destructive disease that inflames the gums surrounding the tooth and eventually degrades the structure holding the tooth in place, forming infected pockets leading to bone and tooth loss. Current treatments include infection-fighting methods; application of molecules that promote tissue growth, also known as growth factors; and guided tissue regeneration, which is considered the optimal standard of care for the treatment of periodontitis.

Guided tissue regeneration, in the case of periodontitis, involves the use of a membrane or thin film that is surgically placed between the inflamed gum and the tooth. Membranes, which come in non-biodegradable and biodegradable forms, are meant to act not only as barriers between the infection and the gums, but also as a delivery system for drugs, antibiotics and growth factors to the gum tissue.

Unfortunately, results from guided tissue regeneration are inconsistent. Current membranes lack the ability to regenerate gum tissue directly and aren’t able to maintain their structure and stability when placed in the mouth. The membrane also can’t support prolonged drug delivery, which is necessary to help heal infected gum tissue. For non-biodegradable membranes, multiple surgeries are needed to remove the membrane after any drugs have been released—compromising the healing process.

“Given the current disadvantages with guided tissue regeneration, we saw the need to develop a new class of membranes, which have tissue and bone regeneration properties along with a flexible coating that can adhere to a range of biological surfaces,” said Dr. Alireza Moshaverinia, lead author of the study and assistant professor of prosthodontics at the UCLA School of Dentistry. “We’ve also figured out a way to prolong the drug delivery timeline, which is key for effective wound healing.”

The team started with an FDA-approved polymer—a large-scale synthetic molecule commonly used in biomedical applications. Because the polymer’s surface isn’t suitable for cell adhesion in periodontal treatment, the researchers introduced a polydopamine coating—a polymer that has excellent adhesive properties and can attach to surfaces in wet conditions. The other benefit of using such a coating is that it speeds up bone regeneration by promoting mineralization of hydroxyapatite, which is the mineral that makes up tooth enamel and bone.

After identifying an optimal combination for their new membrane, the researchers used electrospinning to bond the polymer with the polydopamine coating. Electrospinning is a production method that simultaneously spins two substances at a rapid speed with positive and negative charges, and fuses them together to create one substance. To improve their new membrane’s surface and structural characteristics, the researchers used metal mesh templates in conjunction with the electrospinning to create different patterns, or micro-patterning, similar to the surface of gauze or a waffle.

“By creating a micro pattern on the surface of the membrane, we are now able to localize cell adhesion and to manipulate the membrane’s structure,” said co-lead author Paul Weiss, UC presidential chair and distinguished professor of chemistry and biochemistry, bioengineering, and materials science and engineering at UCLA. “We were able to mimic the complex structure of periodontal tissue and, when placed, our membrane complements the correct biological function on each side.”

To test the safety and efficiency of their new membrane, the researchers injected rat models with gingival-derived human stem cells and human periodontal ligament stem cells. After eight weeks of evaluating the degradation of the membranes and the tissue’s response, they observed that the patterned, polydopamine-coated polymer membrane had higher levels of bone gain when compared to models with no membrane or a membrane with no coating.

In order to suit a wide range of medical and dental applications, the researchers also figured out a way to adjust the speed at which their membranes degraded when inserted in their models. They did this by adding and subtracting different oxidative agents or using lighter polymer bases before going through the electrospinning process. The ability to turn the degradation rates up or down helped the researchers control the timing of the delivery of drugs to the desired areas.

“We’ve determined that our membranes were able to slow down periodontal infection, promote bone and tissue regeneration, and stay in place long enough to prolong the delivery of useful drugs,” Moshaverinia said. “We see this application expanding beyond periodontitis treatment to other areas needing expedited wound healing and prolonged drug delivery therapeutics.”

The researchers’ next steps are to evaluate whether their membranes can deliver cells with growth factors in the presence or absence of stem cells.

 Explore further: Microscopic membrane could fight gum disease

More information: Mohammad Mahdi Hasani-Sadrabadi et al. Hierarchically Patterned Polydopamine-Containing Membranes for Periodontal Tissue Engineering, ACS Nano (2019). DOI: 10.1021/acsnano.8b09623

 

Visualizing the World’s EV Markets – Who is the World’s Undisputed Leader in EV Adoption?


It took five years to sell the first million electric cars. In 2018, it took only six months.

The Tesla Model 3 also passed a significant milestone in 2018, becoming the first electric vehicle (EV) to crack the 100,000 sales mark in a single year. The Nissan LEAF and BAIC EC-Series are both likely to surpass the 100,000 this year as well.

Although the electric vehicle market didn’t grow as fast as some experts initially projected, it appears that EV sales are finally hitting their stride around the world. Below are the countries where electric vehicles are a biggest part of the sales mix.

The EV Capital of the World

Norway, after amassing a fortune through oil and gas extraction, made the conscious decision to create incentives for its citizens to purchase electric vehicles. As a result, the country is the undisputed leader in EV adoption.

In 2018, a one-third of all passenger vehicles were fully electric, and that percentage is only expected to increase in the near future. The Norwegian government has even set the ambitious target of requiring all new cars to be zero-emission by 2025.

That enthusiasm for EVs is spilling over to other countries in the region, which are also seeing a high percentage of EV sales. However, the five countries in which EVs are the most popular – Norway, Iceland, Sweden, Netherlands, and Finland – only account for 0.5% of the world’s population. For EV adoption to make any real impact on global emissions, drivers in high-growth/high–population countries will need to opt for electric powered vehicles. (Of course power grids will need to get greener as well, but that’s another topic.)

China’s Supercharged Impact

One large economy that is embracing plug-in vehicles is China. 

The country leads the world in electric vehicle sales, with over a million new vehicles hitting the roads in 2018. Last year, more EVs were sold in Shenzhen and Shanghai than any country in the world, with the exception of the United States.

China also leads the world in another important metric – charging stations. Not only does China have the highest volume of chargers, many of them allow drivers to charge up faster.

Electric vehicle charging stations

Accelerating from the Slow Lane

In the United States, electric vehicle sales are rising, but they still tend to be highly concentrated in specific areas. In around half of states, EVs account for fewer than 1% of vehicle sales. On the other hand, California is approaching the 10% mark, a significant milestone for the most populous state.

Nationally, EV sales increasedthroughout 2018, with December registering nearly double the sales volume of the same month in 2017. Part of this surge in sales is driven by the Tesla’s Model 3, which led the market in the last quarter of 2018.

U.S. Electric vehicle sales

North of the border, in Canada, the situation is similar. EV sales are increasing, but not fast enough to meet targets set by the government. Canada aimed to have half a million EVs on the road by 2018, but missed that target by around 400,000 vehicles.

The big question now is whether the recent surge in sales is a temporary trend driven by government subsidies and showmanship of Elon Musk, or whether EVs are now becoming a mainstream option for drivers around the world.

Scientists ‘Reverse Time’ with a Quantum Computer


“Now the thing about time is that time isn’t really real.

It’s just your point of view, how does it feel to you?

Einstein said we could never understand it all … “

James Taylor ~ “The Secret of Life”

Researchers from the Moscow Institute of Physics and Technology teamed up with colleagues from the U.S. and Switzerland and returned the state of a quantum computer a fraction of a second into the past.

They also calculated the probability that an electron in empty interstellar space will spontaneously travel back into its recent past. The study is published in Scientific Reports.

“This is one in a series of papers on the possibility of violating the . That law is closely related to the notion of the arrow of time that posits the one-way direction of time from the past to the future,” said the study’s lead author Gordey Lesovik, who heads the Laboratory of the Physics of Quantum Information Technology at MIPT.

“We began by describing a so-called local perpetual motion machine of the second kind. Then, in December, we published a paper that discusses the violation of the second law via a device called a Maxwell’s demon,” Lesovik said. “The most recent paper approaches the same problem from a third angle: We have artificially created a state that evolves in a direction opposite to that of the thermodynamic arrow of time.”

What makes the future different from the past

Most laws of physics make no distinction between the future and the past. For example, let an equation describe the collision and rebound of two identical billiard balls. If a close-up of that event is recorded with a camera and played in reverse, it can still be represented by the same equation. Moreover, it is not possible to distinguish from the recording if it has been doctored. Both versions look plausible. It would appear that the billiard balls defy the intuitive sense of time.

However, imagine recording a cue ball breaking the pyramid, the billiard balls scattering in all directions. In that case, it is easy to distinguish the real-life scenario from reverse playback. What makes the latter look so absurd is our intuitive understanding of the second law of thermodynamics—an isolated system either remains static or evolves toward a state of chaos rather than order.

Most other laws of physics do not prevent rolling billiard balls from assembling into a pyramid, infused tea from flowing back into the tea bag, or a volcano from “erupting” in reverse.

But these phenomena are not observed, because they would require an isolated system to assume a more ordered state without any outside intervention, which runs contrary to the second law. The nature of that law has not been explained in full detail, but researchers have made great headway in understanding the basic principles behind it.

Read More: “Quantum Time Travel”

Spontaneous time reversal

Quantum physicists from MIPT decided to check if time could spontaneously reverse itself at least for an individual particle and for a tiny fraction of a second. That is, instead of colliding billiard balls, they examined a solitary electron in empty interstellar space.

“Suppose the electron is localized when we begin observing it. This means that we’re pretty sure about its position in space. The laws of quantum mechanics prevent us from knowing it with absolute precision, but we can outline a small region where the electron is localized,” says study co-author Andrey Lebedev from MIPT and ETH Zurich.

The physicist explains that the evolution of the electron state is governed by Schrödinger’s equation. Although it makes no distinction between the future and the past, the region of space containing the electron will spread out very quickly. That is, the system tends to become more chaotic. The uncertainty of the electron’s position is growing. This is analogous to the increasing disorder in a large-scale system—such as a billiard table—due to the second law of thermodynamics.

The four stages of the actual experiment on a quantum computer mirror the stages of the thought experiment involving an electron in space and the imaginary analogy with billiard balls. Each of the three systems initially evolves from order toward chaos, but then a perfectly timed external disturbance reverses this process. Credit: @tsarcyanide/MIPT

“However, Schrödinger’s equation is reversible,” adds Valerii Vinokur, a co-author of the paper, from the Argonne National Laboratory, U.S.

“Mathematically, it means that under a certain transformation called complex conjugation, the equation will describe a ‘smeared’ electron localizing back into a small region of space over the same time period.”

Although this phenomenon is not observed in nature, it could theoretically happen due to a random fluctuation in the cosmic microwave background permeating the universe.

The team set out to calculate the probability to observe an electron “smeared out” over a fraction of a second spontaneously localizing into its recent past. It turned out that even across the entire lifetime of the universe—13.7 billion years—observing 10 billion freshly localized electrons every second, the reverse evolution of the particle’s state would only happen once. And even then, the electron would travel no more than a mere one ten-billionth of a second into the past.

Large-scale phenomena involving billiard balls and volcanoes obviously unfold on much greater timescales and feature an astounding number of  and other particles. This explains why we do not observe old people growing younger or an ink blot separating from the paper.

Reversing time on demand

The researchers then attempted to reverse time in a four-stage experiment. Instead of an electron, they observed the state of a quantum computer made of two and later three basic elements called superconducting qubits.

  • Stage 1: Order. Each qubit is initialized in the ground state, denoted as zero. This highly ordered configuration corresponds to an electron localized in a small region, or a rack of billiard balls before the break.
  • Stage 2: Degradation. The order is lost. Just like the electron is smeared out over an increasingly large region of space, or the rack is broken on the pool table, the state of the qubits becomes an ever more complex changing pattern of zeros and ones. This is achieved by briefly launching the evolution program on the quantum computer. Actually, a similar degradation would occur by itself due to interactions with the environment. However, the controlled program of autonomous evolution will enable the last stage of the experiment.
  • Stage 3: Time reversal. A special program modifies the state of the quantum computer in such a way that it would then evolve “backwards,” from chaos toward order. This operation is akin to the random microwave background fluctuation in the case of the electron, but this time, it is deliberately induced. An obviously far-fetched analogy for the billiards example would be someone giving the table a perfectly calculated kick.
  • Stage 4: Regeneration. The evolution program from the second stage is launched again. Provided that the “kick” has been delivered successfully, the program does not result in more chaos but rather rewinds the state of the qubits back into the past, the way a smeared electron would be localized or the billiard balls would retrace their trajectories in reverse playback, eventually forming a triangle.

The researchers found that in 85 percent of the cases, the two-qubit quantum computer returned back into the initial state. When three qubits were involved, more errors happened, resulting in a roughly 50 percent success rate. According to the authors, these errors are due to imperfections in the actual quantum computer. As more sophisticated devices are designed, the error rate is expected to drop.

Interestingly, the time reversal algorithm itself could prove useful for making quantum computers more precise. “Our algorithm could be updated and used to test programs written for computers and eliminate noise and errors,” Lebedev explained.

More information: Scientific Reports(2019). DOI: 10.1038/s41598-019-40765-6

Provided by Moscow Institute of Physics and Technology

Explore further: Quantum Maxwell’s demon ‘teleports’ entropy out of a qubit

Graphene quantum dots for single electron transistors ~ Application for Future Electronics


The schematic structure of the devices

Scientists from Manchester University, the Ulsan National Institute of Science & Technology and the Korea Institute of Science and Technology have developed a novel technology, which combines the fabrication procedures of planar and vertical heterostructures in order to assemble graphene-based single-electron transistors.

In the study, it was demonstrated that high-quality graphene quantum dots (GQDs), regardless of whether they were ordered or randomly distributed, could be successfully synthesized in a matrix of monolayer hexagonal boron nitride (hBN).

Here, the growth of GQDs within the layer of hBN was shown to be catalytically supported by the platinum (Pt) nanoparticles distributed in-between the hBN and supporting oxidised silicon (SiO2) wafer, when the whole structure was treated by the heat in the methane gas (CH4). It was also shown, that due to the same lattice structure (hexagonal) and small lattice mismatch (~1.5%) of graphene and hBN, graphene islands grow in the hBN with passivated edge states, thereby giving rise to the formation of defect-less quantum dots embedded in the hBN monolayer.

Such planar heterostructures incorporated by means of standard dry-transfer as mid-layers into the regular structure of vertical tunnelling transistors (Si/SiO2/hBN/Gr/hBN/GQDs/hBN/Gr/hBN; here Gr refers to monolayer graphene and GQDs refers to the layer of hBN with the embedded graphene quantum dots) were studied through tunnel spectroscopy at low temperatures (3He, 250mK).

The study demonstrated where the manifestation of well-established phenomena of the Coulomb blockade for each graphene quantum dot as a separate single electron transmission channel occurs.

‘Although the outstanding quality of our single electron transistors could be used for the development of future electronics, “This work is most valuable from a technological standpoint as it suggests a new platform for the investigation of physical properties of various materials through a combination of planar and van der Waals heterostructures.” as explained study co-author Davit Ghazaryan, Associate Professor at the HSE Faculty of Physics, and Research Fellow at the Institute of Solid State Physics (RAS)

A Conversation with Professor (Sir) Kostya Novoselov, Co-Nobel Prize Winner in Physics 2019 ~ Research into “The Graphene Flagship” and other 2D materials


Talking with SciTech Europa, Professor Novoselov, co-awarded the 2019 Nobel Prize in Physics, for the discovery and isolation of a single atomic layer of carbon for the first time, explores the research into Graphene Flagship and other 2D materials.

At the University of Manchester, UK, in 2004, Professor Sir Kostya Novoselov, along with his colleague Professor Sir Andre Geim, discovered and isolated a single atomic layer of carbon for the first time. The pair received the Nobel Prize in Physics in 2010 in recognition of their breakthrough.

On 28 January 2013, the European Commission announced that, out of the six pilot preparatory actions put forward for the Future and Emerging Technology (FET) Flagships competition, the Graphene Flagship, along with the Human Brain Project, had been selected to receive €1bn in funding over the course of a decade, tasking it with bringing together academic and industrial researchers to take graphene from the realm of academic laboratories into European society, thereby generating economic growth, new jobs, and new opportunities.

In February, SciTech Europa attended the Mobile World Congress in Barcelona, Spain. This event is the world’s largest exhibition for the mobile industry, and where, for the fourth consecutive year, the Graphene Flagship hosted its Graphene Pavilion – this year showcasing over 20 different graphene-based working prototypes and devices that will transform future telecommunications.

At the pavilion, SEQ met with Professor Novoselov to discuss research into graphene and other two dimensional materials, as well as how the Flagship is working to bolster both fundamental research and applications stemming from these advanced materials.

What do you think have been the biggest, and latest, developments in graphene (and other 2D materials) research?

There has been a lot of progress in recent years and, indeed, we are no longer talking only about graphene, but also about many other two dimensional materials as well.

First of all – new applications of graphene is one example of recent developments – we see new applications emerging on an almost monthly basis. Second, there is still a lot of progress being made in fundamental research on graphene and 2D materials. And those fundamental results are being implemented in applications.

In terms of other new 2D materials, there is a lot of activity on ferromagnetic materials.

What potential is there now to move graphene forwards, and how would you describe the role of the Flagship in this?

The basic technology is in place, and so what is important now is for entrepreneurs and SMEs to convert those developments into commercial applications, and, indeed, we need to help them to do so.

The Flagship, of course, has now reached the half way stage, and we therefore need to carefully balance the amount of effort we place on applications with the effort we place on the development of fundamental science, which remains crucial.

Nevertheless, we also need to ensure we are helping companies and industry to introduce this material into real products, and that is actually much more difficult, not least because of the fact that this has not been done at this scale before, and so nobody knows how to do it yet.

Are you able to utilise EU instruments to help fund commercialisation activities?

It is not necessarily funding that is a problem in in Europe; the challenge comes more in the form of bringing together scientists, entrepreneurs, and funders in the same room, and it is still not clear how to achieve that. There is thus the argument that we need to work more closely with entrepreneurs and we need to grow those entrepreneurs who are working on advanced materials because this is a much more challenging area than, say, ‘.com’ applications.

What do you feel are the biggest barriers here?

It is perhaps the mentality that exists around risk taking that needs to change. Bringing together entrepreneurs, scientists, the technology and the money around the same table is a challenge and, as I have mentioned, it needs to be understood that bringing new materials, especially nanomaterials, to market is much more challenging than it is to bring, for example, new software to consumers.

And, of course, the level of required investment is also much larger. Whether we have enough people in Europe who are ready to take this risk is a good question.

Would you say that Europe is too risk averse when it comes to this type of investment in comparison to, for instance, the USA?

Perhaps; there is certainly a sense that Europe needs to work much harder than the USA or South-East Asia. And the reason for that is not only a lack of those willing to take enhanced risks, but also the level and mobility of the available money and, indeed, how soon financiers expect a return on their investment.

Could 2D materials research spark a ‘revolution’ in real world applications?

I am not sure that we will see a ‘revolution’; the growth in real world applications utilising graphene is, and will continue to be, a gradual introduction. That is not to say, however, that this gradual process won’t speed up a little over time.

And it is great to see that, when it comes to graphene, this introduction, although gradual, is already happening much faster than with any other advanced material that we have seen before. The purpose of the Flagship is to help speed up this process.

The Flagship is now investing in research into the safety of graphene. How important is that?

This is an example of the sort of issue where the Flagship should take the initiative, because it is not only about graphene; we need to realise that many new nanomaterials are going to play an increasing role in the everyday lives of people, and we need to be prepared for that.

There are a great many regulations which have to be passed when bringing such advanced materials to market, including health and safety and toxicology regulations, and very often these are not very well defined because, quite simply, we have never been in this situation before. It can also be quite expensive to run the necessary projects to investigate things like toxicology, and so it is important for projects like the Flagship to take the initiative and help businesses to overcome these barriers.

Where are your own research interests going to lie, moving forwards?

I do indeed conduct my own research, and within that graphene is not the largest part. I go beyond graphene and work on many other 2D materials and heterostructures, but it is nevertheless exciting to remember that it was graphene that made all the other materials possible as we work on those heterostructures towards new discoveries.

Professor Sir Kostya Novoselov
Nobel Laureate 
Director, National Graphene Institute at the University of Manchester
Member, Strategic Advisory Council, Graphene Flagship
Tweet @GrapheneCA @UoMGraphene

www.graphene.manchester.ac.uk/about/ngi
www.graphene-flagship.eu

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