Technology

Quantum systems can be manipulated with extremely high precision, but not perfectly. Researchers in the Department of Physics at ETH Zurich have now demonstrated how to monitor and correct errors that occur during such operations.

The field of quantum computation has seen tremendous progress in recent years. Increasingly, quantum devices are challenging conventional computers, at least at a handful of selected tasks. Current advances notwithstanding, today’s quantum information processors still struggle to cope with errors, which inevitably occur in any calculation. This inability to rectify errors efficiently hinders efforts toward sustained, large-scale processing of quantum information. Now, a set of experiments by the group of Jonathan Home at the Institute for Quantum Electronics has, for the first time, integrated a range of elements needed for performing quantum error correction in a single experiment. These results have been published today in the journal Nature.

Making imperfection tolerable

Just like their classical counterparts, quantum computers are built from imperfect components, and they are far more sensitive to disturbances from the outside. This leads inescapably to errors as calculations are executed. For conventional computers, there exists a well-established toolkit for detecting and correcting such errors. Quantum computers will rely even more on locating and fixing errors. This requires conceptually different approaches that take into account the fact that information is encoded in quantum states. In particular, reading out quantum information repeatedly without disturbing it, a requirement for detecting errors, and reacting in real time to reverse these errors pose considerable challenges.

Repeat performance

The Home group encodes quantum information in the quantum states of single ions that are strung together in a trap. Typically, these strings contain ions of only one species. But Ph.D. students Vlad Negnevitsky and Matteo Marinelli, together with postdoc Karan Mehta and further colleagues, have now created strings in which they trapped two different species—two beryllium ions (9Be+) and one calcium ion (40Ca+). Such mixed-species strings have been produced before, but the team has used them in novel ways.

They made use of the distinctly different properties that the two species possess. In particular, in their experiments, they manipulated and measured beryllium and calcium ions using different colours of light. This opens up an avenue for working on one species without disturbing the other. At the same time, the ETH researchers found ways to let the unlike ions interact with one another such that measurements on the calcium ion yield information about the quantum states of the beryllium ions, without corrupting those fragile states. Importantly, the physicists monitored the beryllium ions repeatedly as they were subjected to imperfections and errors. The team performed 50 measurements on the same system, whereas in previous experiments (where only calcium ions were used), such repeated readout has been limited to only a few rounds.

Corrective action

Spotting errors is one thing; taking action to rectify them another. To do the latter, the researchers developed a powerful control system for repeatedly nudging the beryllium ions depending on how much they strayed away from the target state. Bringing the ions back on track required complex information processing on the timescale of microseconds. As the system uses classical control electronics, the approach now demonstrated should be useful also for quantum computation platforms based on information carriers other than trapped ions.

Importantly, Negnevitsky, Marinelli, Mehta and their co-workers demonstrated these techniques can also be used to stabilize states in which the two beryllium ions share entangled quantum states, which have no direct equivalent in classical physics. Entanglement is one ingredient that endows quantum computers with unique capabilities. Moreover, entanglement can also be used to enhance the accuracy of precision measurements. Ingredients for error correction such as the ones now demonstrated can make these states last longer—providing intriguing prospects not only for quantum computation but also for metrology.

Scientists are working to dramatically speed up the development of fusion energy in an effort to deliver power to the electric grid soon enough to help mitigate impacts of climate change. The arrival of a breakthrough technology—high-temperature superconductors, which can be used to build magnets that produce stronger magnetic fields than previously possible—could help them achieve this goal. Researchers plan to use this technology to build magnets at the scale required for fusion, followed by construction of what would be the world’s first fusion experiment to yield a net energy gain.

The effort is a collaboration between Massachusetts Institute of Technology’s Plasma Science & Fusion Center and Commonwealth Fusion Systems, and they will present their work at the American Physical Society Division of Plasma Physics meeting in Portland, Ore.

Fusion power is generated when nuclei of small atoms combine into larger ones in a process that releases enormous amounts of energy. These nuclei, typically heavier cousins of hydrogen called deuterium and tritium, are positively charged and so feel strong repulsion that can only be overcome at temperatures of hundreds of millions of degrees. While these temperatures, and thus fusion reactions, can be produced in modern fusion experiments, the conditions required for a net energy gain have not yet been achieved.

One potential solution to this could be increasing the strength of the magnets. Magnetic fields in fusion devices serve to keep these hot ionized gases, called plasmas, isolated and insulated from ordinary matter. The quality of this insulation gets more effective as the field gets stronger, meaning that one needs less space to keep the plasma hot. Doubling the magnetic field in a fusion device allows one to reduce its volume—a good indicator of how much the device costs—by a factor of eight, while achieving the same performance. Thus, stronger magnetic fields make fusion smaller, faster and cheaper.

A breakthrough in superconductor technology could allow fusion power plants to come to fruition. Superconductors are materials that allow currents to pass through them without losing energy, but to do so they must be very cold. New superconducting compounds, however, can operate at much higher temperatures than conventional superconductors. Critical for fusion, these superconductors function even when placed in very strong magnetic fields.

While originally in a form not useful for building magnets, researchers have now found ways to manufacture high-temperature superconductors in the form of “tapes” or “ribbons” that make magnets with unprecedented performance. The design of these magnets is not suited for fusion machines because they are much too small. Before the new fusion device, called SPARC, can be built, the new superconductors must be incorporated into the kind of large, strong magnets needed for fusion.

Once the magnet development is successful, the next step will be to construct and operate the SPARC fusion experiment. SPARC will be a tokamak fusion device, a type of magnetic confinement configuration similar to many machines already in operation (Figure 1).

As an accomplishment analogous to the Wright brothers’ first flight at Kitty Hawk, demonstrating a net energy gain, the aim of fusion research for more than 60 years, could be enough to put fusion firmly into national energy plans and launch commercial development. The goal is to have SPARC operational by 2025.

 

To evaluate in vivo physiological functions, electrophysiological signals must be monitored with high precision and high spatial or temporal resolution. Ultraflexible, multielectrode arrays (MEAs) were recently fabricated to establish conformal contact on the surfaces of organs and to measure electrophysiological signal propagation at high spatial-temporal resolution. However, plastic substrates with a high Young’s modulus incorporated in the process caused difficulties during implantation due to dynamic movement-based hemodynamics at the surface of the heart. In a new study published in Science Advances, Wonryung Lee and colleagues have developed an active MEA fabricated to demonstrate nonthrombogenicity, stretchability and stability. The arrays allowed long-term electrocardiographic (ECG) monitoring in the beating hearts of rats, even with capillary bleeding. The measured ECG signals exhibited a high signal-to-noise (SNR) ratio of 52 dB as a result of the active data reading.

In the study, the novel stretchable MEA was carefully designed using state-of-the-art engineering techniques. The methods combined extraordinarily high gain organic electrochemical transistors (OECTs) processed on microgrid substrates with a poly(3-methoxypropyl acetate) (PMC3A) coating. The process facilitated significant antithrombotic properties while maintaining excellent ionic conductivity.

Typically, multielectrode arrays (MEAs) are used to investigate the position of active/inactive cells, propagation of neural signals and networking among multiple neurons. The arrays can also be used to diagnose and treat disease by measuring biological signals at multiple points. The first reported in vitro MEA was fabricated on flat glass to measure cellular excitement in cultured myocardium, neuronal cells and propagation of signal from heart and brain slices. The recently developed noninvasive in vivo MEA arrays were fabricated on flexible plastic foil with the ability to contact soft and moving living tissues. During the engineering process, the device flexibility should be increased to facilitate MEAs onto complex structures in the body during implantation.

Conformal contact on wrinkled brain surfaces, for instance, can be achieved by reducing the device thickness below two µm. Similarly, ECG measurements can be conducted on the skin close to the heart via passive MEAs on 3 µm polyimide substrates. The ultraflexible properties of active MEAs were demonstrated via smooth contact to muscle cells, cerebral cortex as well as electromyography (EMG) and electrocorticography (ECoG) measurements. A stretchable and blood-compatible active MEA is yet to be realized due to two main limitations. At the onset, device degradation due to blood clots from surgical bleeding as a result of a high Young’s modulus was seen with polyimide or parylene polymers despite their high compatibility. Thereafter, it is also difficult to engineer high-performance active elements with stretchability to measure biological signals. The active elements also required high amplification factors and low drive voltages.

In the study, Lee et al. engineered an ultrathin, stretchable grid-patterned active OECT (organic electrochemical transistor) matrix to measure the distribution of ECG signals with a signal-to-noise ratio (SNR) of 52 dB via direct contact on the beating rat heart. The active 4 x 4 OECT array was fabricated with a total thickness of 2.6 µm and high transconductance. The device was entirely coated with 100 nm thick poly (3-methoxypropyl acetate) (PMC3A) to impart antithrombotic properties while maintaining excellent ionic conductivity. An ECG was mapped from the heart surface of a rat to determine feasibility of the 4 x 4, ultrathin, stretchable, antithrombotic and active OECT array. Due to high conformability of the grid structure, artifact noise caused by dynamic moving did not appear in the recorded data. In addition, due to its antithrombotic property, the device was capable of stable measurements across long periods of time, even in an implant environment with consistent bleeding.

The stretchable MEA containing OECTS and grid substrates were fabricated on 1.2 µm parylene substrates. The active layers of a thin poly(3,4-ethylenedioxythiophene)polystyrene sulfonate (PEDOT:PSS) system and the wiring were achieved on a honeycomb grid substrate. The honeycomb grid structure enabled mechanical stability and structural stretchability, previously investigated experimentally and via simulation. The outermost PMC3A [poly(3-methoxypropyl acetate)] layer enabled high blood compatibility to maintain antithrombogenicity. The device stretchability enabled dynamic movement on biological substrates.

Prior to conducting biological experiments in vivo, the authors systematically assessed the electrical and mechanical character of the device. The electrical performance was measured relative to transconductance of the array, which indicated sufficiently large quantities to measure the ECoG or EMG signals of rats. The thickness and water contact angle of the PMC3A surfaces showed consistent results to previous studies. Hemocompatibility studies on PMC3A were conducted using platelet adhesion by dipping samples in platelet suspensions extracted from human blood. The response time (τ) of OECTs before and after PMC3A coating was measured after a gate voltage pulse was applied with a duration of one millisecond, indicating that the dipping process of the PMC3A did not change the OECT electrical properties. The OECT coated PMC3As also confirmed long-term electric stability.

The researchers then conducted in vivo studies in a rat model in which the feasibility of the stretchable and hemocompatible OECT arrays were performed via ECG measurements on heart surfaces. The physiological signals were measured using the 4 x 4 array of stretchable and hemocompatible OECTs by attaching them to the exposed surface of the heart. The honeycomb holes in the ultrathin substrate allowed conformal contact between the device film and the heart surface.

The signal-to-noise ratio of the PMC3A-coated OECT recorded at 51 dB 30 min after attachment was similar to the value recorded right after attachment. The millisiemens order of transconductance observed in the study was due to the water permeability of PEDOT:PSS. As a result, the transconductance of OECT was a 100 x higher than that of the Si field-effect-transistors (FET).

The researchers also demonstrated ECG mapping signals using the OECT array when the device was placed on a rat heart surface covering the left and right ventricle areas. The load impedance was designed to be 0 ohm to substantially suppress the cross-talk in OECT array as previously demonstrated. Spatial voltage maps of all nodes at four sequential timepoints were visualized. Based on the sensor location, the anatomical signals showed different shapes. The stretchable and blood-compatible OECT arrays successfully recorded spatial-temporal distribution of ECGs on rat heart surfaces with multiplexing.

In the study, a high SNR of 52 dB was achieved due to two reasons; first, since the authors succeeded in using OECTs with high transconductance in the order of millisiemen. Higher by a factor of 10 compared to single crystal Si FET in the presence of surgical bleeding, while the PMC3A coating simultaneously maintained high ionic conductivity. Second, the motion artefact noise was suppressed by the high conformability of the microgrid architecture: the device can adhere to the dynamic target during motion of the heart. The stretchable and active MEAs with non-thrombogenic PMC3A coating will enable measurements of ECG, ECoG or EMG signals with higher accuracy in further preclinical studies.

Japan’s biotechnology company euglena is to start mass production of bio jet fuel and biodiesel out of algae and waste oil, with the aim of being the first company to fuel green commercial flights out of Japan.

The company announced the completion of its refinery plant in Yokohama on Friday. The site can produce 125 kiloliters of bio jet fuel and biodiesel per year, and it plans to raise the production capacity to 250,000 kiloliters by 2025.

The cost of biofuels, which has been one of the major obstacles to their commercialization, is expected to drop from the current 10,000 yen ($88.6) per liter to 100 yen by 2025. This will be close to the current price of petroleum-based jet fuel at about 70 yen.

The company has partnered with aviation group ANA Holdings in the venture, with the aim of fueling their commercial international flights departing from Japan by 2020. Euglena is also planning to offer bio jet fuel to other companies taking off from Japan. ANA will support euglena to develop the airport infrastructure to supply aircraft.

Mitsuru Izumo, euglena’s chief executive, said he expected the demand to expand along with the growing Asian aviation industry. “We want [low-cost carriers] and oversea flights to try using our biofuel,” particularly from Southeast Asia where bio jet fuel is still rare, he said.

In Japan, no airline has yet carried out a green commercial flight, while there have been nearly 150,000 flights worldwide, according to euglena. Aircraft manufacturer Airbus has so far conducted programs in places including Australia and Brazil, and partnered with China’s Tsinghua University to develop bio jet fuel in China. Airlines including Cathay Pacific Airways and Qatar Airways have supported efforts to commercialize bio jet fuel production.

“Environmental requirements surrounding the aviation industry are being increasingly strengthened,” said Chikako Miyata, who is responsible for the promotion of corporate social responsibility at ANA Holdings. With passenger numbers on international flights increasing by 5% every year, improving aircraft and fuel efficiency was not enough to meet industry goals, she said.

Euglena’s bio jet fuel is expected to qualify for ASTM certification, an international standard for bio jet fuel, by next spring.

The biofuel will also be used in automobiles. The company has been partnering with Isuzu Motors to test the fuel’s quality, which is now on a par with that of petroleum and does not have to be mixed with other types of fuel, according to Isuzu.

Euglena will start selling biodiesel produced in the new refinery from next summer. “The price will be negotiated with clients since it is still in the testing phase,” a spokesperson said.

The company has invested 6 billion yen in the development of the Yokohama refinery. Companies including Isuzu, engineering group Chiyoda and energy trading company Itochu Enex have invested in euglena, as well as provided their experience to build and operate the plant. US oil group Chevron also provided technology for the refinery.

One of Japan’s leading oil companies, JXTG Holdings, also owns a stake in euglena and is expected to provide infrastructure support as production is scaled up. Izumo said that by 2030, the plan was to create three more new refinery plants to produce 1 million kiloliters of the fuel in total. He said that the locations could be in Japan or abroad.

Biofuel is a renewable alternative to petroleum-based fuels that is made from algae and results in lower greenhouse gas emissions. Algae, like other plants, consume carbon dioxide as they grow. In response to concerns about climate change, the International Air Transport Association set a goal of reducing CO2 emissions by 50% by 2050 relative to 2005 levels.

Euglena has the technology to grow a species of algae called “euglena,” and makes its profits largely from the sale of related supplements, food products and cosmetics.

After the announcement, euglena’s shares rose by 2% to close at 673 yen on Friday. The share price has been decreasing since its peak in 2013 and a report by Well Investments Research published last year cast doubt on the growth potential of its energy business. The report noted that the share price of TerraVia, a U.S. biotech company that produces biofuel, had been negatively affected when oil prices fell.

Algae is widely considered as a potential source of biofuel because it does not compete with food resources. Japan’s IHI also announced last year that it would test development of algae-based bio jet fuel with Thailand’s Siam Cement Public Company.

According to Makoto Watanabe, specially appointed professor at the University of Tsukuba, countries such as the Philippines and Indonesia have been “recently strengthening the development of algae-based fuels” at research level.

Oregon State University scientists have found a resource to increase agricultural production on dry, unirrigated farmland—solar panels.

In a study published Thursday in the journal PLOS One, a research team in OSU’s College of Agricultural Sciences found that grasses favored by sheep and cattle thrive in the shade of a solar array installed in a pasture on the OSU campus.

The results of the OSU study indicate that locating solar panels on pasture or agricultural fields could increase crop yields, said corresponding author Chad Higgins, an associate professor in the Department of Biological and Ecological Engineering.

“There are some plants that are happier in shaded environments,” he said. “The amount of water that went into the making those plants is tremendously smaller than in the open field. You get double the yield, less water and all the solar energy.”

The concept of co-developing the same area of land for both solar photovoltaic power and conventional agriculture, known as agrivoltaics, dates to the early 1980s. Ground-mounted solar arrays typically aren’t placed on farms with the intent to grow crops.

“The idea of locating solar panels on farm isn’t new,” Higgins said. “The difference here is that this solar array was installed without the intent to influence plant production. It was by accident. Nobody engineered this system. Now we’re trying to develop a deeper understanding of how we can engineer the system to be technically feasible, environmentally sound and economically viable.”

OSU has solar project sites in Corvallis covering 10 acres that have the capacity to generate 2.6 million kilowatt-hours of power per year. This study focused on the 35th Street Solar Array installed in 2013 on the west side of the OSU campus.

Walking past the array one day, Higgins and colleagues noticed green grass growing in the shade of the panels. In May 2015, they installed microclimate research stations that recorded mean air temperature, relative humidity, wind speed, wind direction and soil moisture. By August, the instrumentation revealed the areas under the solar panels maintained higher soil moisture throughout the three-month period.

The result was striking, Higgins said. The areas under the array produced double the amount of plant material than the unshaded areas, including an increase in in nutritional value of plants. The researchers also noted a significant increase in late-season plant growth.

“It’s like a tortoise and a hare race,” Higgins said. “The plants that experience the full brunt of the sun use their water resources as quickly as possible. They grow to the extent they can and then they die. On the other hand, the plants in the shade take sips of water because they are less stressed, and they keep chugging along.”

The next step is to test the effect of solar panel placement on certain high-value crops that are suitable to shady conditions, Higgins said.

UK energy company Cuadrilla said Friday it has extracted a small but “encouraging” amount of shale gas for the first time since resuming fracking in Britain less than three weeks ago.

The 11-year-old private firm has borne the brunt of protests for trying to test whether fracking—a process in which water and chemicals are used to blast apart rock formations—can unlock natural gas deposits in the UK.

The method has transformed the global energy market but is only developing slowly in Europe.

Cuadrilla released a 12-second clip showing a bright yellow flame light up inside one of the chimney-like structures that stand over a web of pipes drilled deep into the ground.

The gas flare was Cuadrilla’s evidence that fracking at the site was possible. The company said the question now was whether the entire process was commercially viable.

“The volumes of gas returning to surface at this stage are small,” Cuadrilla chief executive Francis Egan said in a statement.

“However it provides early encouragement that the Bowland Shale can provide a significant source of natural gas to heat Lancashire and UK homes and offices and reduce our ever growing reliance on expensive foreign imports.”

Cuadrilla produced small amounts of shale gas at the same site in 2011.

It was then forced to halt operations because two small earthquakes were soon registered in the northwestern part of England where its operations are based.

It resumed work on October 15 after adopting more stringent safety and regulatory measures that environmentalists said were still insufficient.

The company has since been forced to briefly halt drilling on three occasions because minor tremors began being detected deep underground.

Cuadrilla stressed at the time that none of them could either be felt or cause physical damage on the surface.

“This Preston New Road site is being monitored to an unprecedented level,” Egan said in Friday’s statement.

“If we are able to fully test these wells, without compromising on safety, we have the potential to make a major difference to UK energy supply, security and economic prosperity.”

The company said on its website that its tests from 2011 suggest that it can produce 6.5 billion cubic feet (185 million cubic metres) of gas from the Bowland Shale well over 30 years.