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A spark for young minds

first_imgAt the Harvard Allston Education Portal, China Cardriche ’16 was happily inspiring impressionable children — with explosions.“Nothing inspires first-graders more than blowing things up,” Cardriche said, picking up a balloon covered in small, dark marks. “A regular balloon explodes when you light it on fire. But if you fill a balloon with a little bit of water, the water acts as a shield and it warms before the balloon pops … so it actually burns the balloon instead of popping it.”Cardriche and other Harvard undergrads were on hand Dec. 7 to help showcase work that was accomplished over the past 10 weeks as part of the Ed Portal’s mentoring program. In a service that is free to Allston-Brighton residents, 26 Harvard undergrads mentor 102 local students from first through 12th grade in fields such as math, creative writing, and science.“Inspiring children is one of the best takeaways,” said Cardriche, an applied math concentrator who facilitated a science club for first-graders at the Ed Portal.Nearby, Allston resident Priscilla Anderson and her 9-year-old daughter, Dora Capobianco, watched one of three computer animations Capobianco designed while enrolled in the Ed Portal’s new Scratch programming mentoring option.“She’s certainly never programmed anything before,” said Anderson, adding that her daughter had been involved with the mentoring program since first grade. “She’s learning a new skill, and she has a lot of fun — it’s fun learning.”Robert Lue, director of Life Sciences education, faculty director of HarvardX, and faculty director of the Harvard Allston Ed Portal, said he always enjoys attending the mentoring showcase, and seeing how students’ imaginations have been “sparked” by the program.“Being here gives you an idea of how much of an impact working with the mentors has had,” he said. “The undergraduate students here have a long history of being socially engaged, but we’re seeing the growing realization that it’s a mutually enriching exchange. It’s a learning opportunity for everyone involved. What we may have traditionally thought of as service becomes much more of a partnership.”Speaking of her work in writing and the visual arts with sixth- and eighth-graders, mentor Ujunwa Nwosu ’17 echoed that sentiment.“I learned a lot from my students — just about teaching and how to connect with someone,” said Nwosu, a neurobiology concentrator. “This was my first semester doing it, and it was a great experience. I’m definitely coming back because I loved it so much.”Such learning opportunities will expand dramatically when the Ed Portal moves into its new facility in February. The new digs at 224 Western Ave. in Allston will include flexible-use spaces, creating opportunities for performing arts events, an art gallery, and deeper programming. The new space will also expand the relationship between HarvardX and the Ed Portal and build upon the new educational initiative HarvardX for Allston.“The iStudio at the Ed Portal will take the best of what we know about digital learning, and bring people together in the local community,” Lue said. “We’ll take everything we’ve learned about digital resources and media, and bring that to the community as a re-imagining of what a community space can be like — a 21st-century version of that communal space. We’ve experimented with it here, in this space, but I think that will really be quite something.”last_img read more

The Latest on the Election

first_imgSeveral other races remain too close to call, including in Maine, where Senator Susan Collins leads the Democratic nominee, Sara Gideon. In a special Senate election in Georgia, the incumbent Kelly Loeffler is headed to a January runoff against the Democrat Raphael Warnock. Democrats’ struggled to match their 2016 margins among Hispanic voters. We’ve covered that theme in some detail in this newsletter, and it hurt Biden, especially in Florida and Texas. If Biden holds onto his lead in Nevada and Wisconsin, he would need to win only one of three states — Georgia, Michigan or Pennsylvania — to secure a majority of electoral votes (and could still lose North Carolina). “The vote-counting happening now is…. exactly what we knew and reported would happen. This is legitimate vote-counting, of ballots that were returned before or on Election Day.” — Scott Detrow, NPR Make something comfortingCornbread tamale pie, a recipe from The Joy of Cooking, is a crowd-pleasing classic. It elevates a beef chili by baking it with a simple cornbread batter on top.DiversionsGames Democratic Senate candidates were running slightly behind Biden in several states, making it difficult for the party to retake Senate control. The outstanding ballots are mostly mail-in ballots, which are likely to favor Biden, because more Democrats than Republicans voted early this year. He leads in the current vote count in Nevada and Wisconsin, while Trump leads in the remaining four. “I don’t think people have fully internalized how Democratic these mail and absentee ballots will be in MI/PA/WI,” Nate wrote. Joe Biden is now the favorite to win the presidency, and Republicans are favored to keep Senate control — but both results are far from certain. And Democrats failed to win the resounding victory that pre-election polls had suggested they could.- Advertisement – Many of the state polls were wrong and underestimated support for Republicans — again. A big question in coming days will be why: Did polls again fail to include enough working-class white voters, as was the case in 2016? Or was it something else? Democrats needed to win at least five of the 14 competitive Senate races and have so far won only two. Six races remain up in the air. The only incumbent Republicans to have lost are Martha McSally in Arizona and Cory Gardner in Colorado. Even with Biden’s seeming advantages at this point, the country has never experienced an election with such heavy voting by mail, which creates significant uncertainty. It is entirely possible that Trump will retain his lead in the states where he now leads and win the election. The pangram from yesterday’s Spelling Bee was chantey. Today’s puzzle is above — or you can play online if you have a Games subscription. In Iowa, Senator Joni Ernst, a Republican, won re-election. Republicans also won races in Montana, South Carolina — where Lindsey Graham held on to his seat — and Texas. “Biden’s the favorite, even if narrowly, just about everywhere,” Nate Cohn of The Times tweeted, listing five of the six states above (all but North Carolina). Sean Trende of RealClearPolitics agreed: “Would probably rather be Biden than Trump.” The situation in the Senate is different — and more favorable to Republicans. They appear to be in a strong position to retain Senate control, which would give them a veto over nearly all of a President Biden’s legislative plans. Biden, addressing supporters after midnight, urged patience. “We believe we’re on track to win this election,” he said. “We’re going to have to be patient until the hard work of tallying the votes is finished. And it ain’t over until every vote is counted, every ballot is counted.” Subscribers make our reporting possible, so we can help you make sense of the moment. If you’re not a subscriber, please consider becoming one today.PLAY, WATCH, EAT, BAKE You can visit The Times all day for the latest coverage. Want to get The Morning by email? Here’s the sign-up.Good morning. There is no presidential winner yet. Biden appears to be in a better position than Trump, and Republicans seem in better shape to hold Senate control. The outcome is unclear in six swing states — Georgia, Michigan, Nevada, North Carolina, Pennsylvania and Wisconsin — and all are still counting votes. We may get some final vote counts today, while others could take a few days. “This is an extremely flammable situation and the president just threw a match into it,” Chris Wallace said on Fox News, after Trump’s remarks. “He hasn’t won these states.”“Donald Trump called it a ‘fraud’ to continue to count votes. This does not sound like a democracy.” — Olivia Nuzzi, New York Magazine“What Trump did tonight is shocking, even though he’s been telegraphing this for some time. He’s primed his supporters to believe any result that doesn’t involve him winning is fraud.” — Rosie Gray, BuzzFeed News“Trump may indeed win. But he certainly hasn’t yet. And, he doesn’t get to say that your vote shouldn’t be counted.” — S.E. Cupp, CNN“Every single serious analysis I read of this election said that it would be long and drawn out, and that Trump would try to steal the election by trying to discount late-arriving Biden votes. And now that it’s happening…everyone seems shocked.” — Anne Applebaum, The Atlantic “Incredible how competitive Trump is with 230K+ covid deaths and kids being locked in cages and everything else. Even if Biden wins he will have to govern in a Trump country. This is who America is.” — Gabriel Sherman, Vanity Fair“In any normal presidential democracy, this would not be a close election right now. It is only close because of our strange Electoral College.” — Lee Drutman, New America think tank“A key question moving forward is whether public opinion polling is irreparably broken or if polling is just broken in elections with Trump on the ballot.” — Nathan Gonzales of Inside Elections.“Biden POTUS with GOP Senate is a recipe for a horrifically nasty politics next year.” — Matt Glassman, Georgetown political scientist“Democrats had hoped for a massive, unequivocal repudiation of Donald Trump for his mishandling of the pandemic, his raging White House incompetence, and his disdain for the rule of law. Instead, there was the sobering message that Trump’s support in key states like Florida was, in truth, greater than the polls had predicted.” — Walter Shapiro of The New Republic.The Senate Democrats flipped two seats: John Hickenlooper defeated Gardner in Colorado, and Mark Kelly defeated McSally in Arizona. Further down, you’ll find information on some of this year’s other races — including more detail on the Senate, as well as the latest on state ballot initiatives. First, though, I want to give you a selection of commentary on the national scene.Election Commentary Republicans flipped one seat: Tommy Tuberville beat the Democrat Doug Jones in Alabama. Gary Peters, the Democratic incumbent in Michigan, is locked in a close race with his Republican challenger, John James; it will depend on the outstanding votes. – Advertisement – Trump falsely declared himself the winner around 2:30 a.m. Eastern. He said he would call on the Supreme Court to stop counting ballots in states where he led, while urging more counting in states where he was behind. He claimed “fraud” (for which there is no evidence) and he called the election an “embarrassment to the country.” – Advertisement – Here’s where we stand after a topsy-turvy election night, in which the situation shifted multiple times: The counting of ballots seems likely to be slowest in Michigan and Pennsylvania. Officials in Pennsylvania have said they expect all votes to be counted by Friday. – Advertisement –last_img read more

A strike of workers in Croatia Airlines has been announced for Thursday

first_imgHowever, the workers’ organization Croatia Airlines (ORCA) announced a strike.After the meeting held with the Prime Minister of the Republic of Croatia, Mr. Andrej Plenković, on July 06.07.2018, 20, an agreement was reached with the Prime Minister’s promise that the necessary conditions will be created soon, primarily the appointment of a new and competent Management Board. a collective agreement that is the foundation of all civilized western airlines, including Croatia Airlines.After that, the start of the strike was postponed, but as they point out from ORCA, unfortunately for them, the Prime Minister did not fulfill his side of the agreement and they were forced to announce the strike of the day again. 08.08.2018. starting at 6 p.m. morning. “We would like to emphasize once again that this was the last option for us, but after not even the last agreement resulted in any reaction from the owner’s representatives, unfortunately for all of us, we were forced to take this step.. ” conclude from ORCA.The reason for the strike is poor working conditions, too many working hours and low wages, especially in the context of competition and at the level of the profession in Europe.Croatia Airlines: ORCA union strike to cause losses of up to EUR 800.000 on each day of strikeThe CA management also reacted to the announced strike, and in the manner of the claim concept, warned that the loss for the company would amount to EUR 800.000 per day of the strike, that the strike would affect almost 7000 passengers only on the first announced day of the strike union demands, represented an increase in wage and benefit costs of more than 30 percent, or about $ 53 million annually.By the way, Croatia Airlines ended the first half of this year with the best financial result in the last four years. In the first six months of 2018, a total of 949.007 passengers were transported, which is 5 percent more than in the same period in 2017, with a achieved passenger occupancy factor (PLF) of 70,9 percent, which is an increase of 1,3 percentage points.In 2018, Croatia Airlines started flying to two new destinations, Mostar throughout the year and Dublin during the summer season, and new seasonal routes were introduced from Dubrovnik to Munich and from Split to Copenhagen. In addition to the new routes, this year’s summer flight schedule also increased the number of weekly flights on some existing routes. Croatia Airlines aircraft also fly to all eight new European destinations, ie on all seasonal routes introduced during 2016 and 2017 – from Zagreb to Stockholm, Oslo, Helsinki, Bucharest, Lisbon, Milan, Prague and St. Petersburg.During the summer flight schedule, Croatia Airlines today connects Croatia with 40 destinations in 23 European countries in regular international traffic, and in cooperation with partners from the Star Alliance and the whole world.last_img read more

PREMIUMGovernment’s plan to empower MSMEs through omnibus bill faces backlash

first_imgLOG INDon’t have an account? Register here Facebook Google Forgot Password ? Topics : The government’s plan to empower micro, small and medium enterprises (MSME) and cooperatives through the omnibus bill on job creation is facing backlash from stakeholders.Association of Indonesian MSMEs (Akumindo) chairman Ikhsan Ingratubun said the plan would harm micro and small businesses.“The President said during his inauguration speech in 2019 that the government would empower MSMEs. However, the bill may actually harm businesses,” Ikhsan told The Jakarta Post on Wednesday.“The bill does not set a maximum threshold for businesses that could be considered an MSME, this could lead to big businesses claiming to be MSMEs.”Ikhsan said the bill could lead to multiple interpretations, calling on the government and stakeholders to review it.According to Article 94 of the draft bill, an MSME is defined by several criterial, namely its net wo… Indonesia omnibus-bill-on-job-creation MSMEs-cooperatives criteria license financing Log in with your social account Linkedinlast_img read more

Chelsea youngster set to complete Birmingham loan move

first_imgChelsea youngster Ben Gordon is expected to complete a loan move to Birmingham City in the coming days.The left-back was scheduled to make the move to St Andrew this week but the deal was held up because he has been carrying an injury.Gordon, 21, was wanted by a number of clubs in the Championship and League One.Follow West London Sport on TwitterFind us on Facebooklast_img

Antibiotic resistance found with little or no exposure to human activity

first_imgShare Facebook Twitter Google + LinkedIn Pinterest Since the 1940s, antibiotics have effectively treated certain bacterial diseases. But over the years, some bacteria have developed resistance to the antibiotics that once killed them.Each year, about 2 million people in the United States are infected with bacteria that are resistant to antibiotics, according to the Centers for Disease Control and Prevention. While antibiotic resistance is commonly viewed as a result of antibiotic overuse in humans and animals, this isn’t always the case. Lisa Durso, a microbiologist at the Agricultural Research Service (ARS) Agroecosystem Management Research Unit in Lincoln, Neb., recently found antibiotic-resistant bacteria in prairie soils that had little or no exposure to human or animal activity.Durso belongs to a nationwide network of ARS scientists investigating agriculture-related antibiotic resistance, sharing critical information, and developing solutions. Their research involves examining antibiotic resistance as it relates to food safety, animal production and protection, and the environment.When it comes to resistance, scientists typically measure three things: drugs (antibiotics people take or give to animals), “bugs” (bacteria that might be resistant), and genes (DNA instructions in the bacteria that code for resistance). Genes are usually in the cells, though not always, Durso explains. After a cell dies, the genes can persist in the soil.“Antibiotic-resistant bacteria and genes occur naturally,” Durso said. “Studies have shown antibiotic resistance in soil samples dating back to the time of woolly mammoths. This is because antibiotics, such as penicillin, came originally from fungi or other bacteria-found naturally in soil.”One obstacle to identifying the source of antibiotic resistance on farms and in the environment is measurement, according to Durso. Antibiotic-resistant bacteria and antibiotic-resistant genes found in soils where manure has been added (by animals or by spreading) provide valuable information on what is currently present in a sample site, such as a feedlot. A concern is that even if bacteria in manure are dead, their genes can persist in soils. If baseline levels of antibiotic resistance aren’t collected, scientists will have a difficult time sorting out resistance caused by human antibiotic use from resistance that occurs naturally.“To determine the impact of food-animal antibiotic use on resistance, it’s essential that baseline levels of resistance be considered and subtracted out when measuring resistance in agroecosystems,” Durso said.To address this problem, Durso and her team examined native prairie soils that had little human impact and no animal grazing for the past 20 years. The team worked with a number of partners — including landowners, academia, and staff from state game and parks commissions — to identify 20 native prairies in southeast Nebraska meeting these criteria.Soil samples were collected from the sites and screened for antibiotic-resistant bacteria. All the samples contained bacteria resistant to tetracycline and cefotaxime, and nearly half of the bacteria isolated from prairie soils were resistant to two or more antibiotics.“We actually measured total soil DNA and isolated all of the DNA, which we believe mostly came from living cells,” Durso said.The findings also included a type of sulfonamide-resistant gene in 91% of the samples. Considered a marker of human activity, the gene was present despite a lack of human activity at those sites.“Other research has suggested that sulfonamide resistance genes are associated with human activities and could be a base for measurement,” Durso said. “However, our findings suggest that if we see sulfonamide genes in Nebraska feedlots, we cannot conclude that it is due to human activity, because we saw them in fairly high numbers in these prairies.”There is a great need to reduce antibiotic resistance in agricultural settings, Durso said. One of the first things scientists need to determine is a realistic target for reduction-how low can they measure? These findings provide a basis for answering those questions and implementing a strategy to reduce antibiotic resistance in agricultural productions.“It would be unrealistic to say we want zero antibiotic resistance on farms, because even in natural settings, you see resistance,” Durso said. “We’re able to use this data to set a baseline for what’s occurring naturally. It gives us a starting point for figuring out how best to manage antibiotic resistance on agricultural lands.”This study was published in the Journal of Environmental Quality in March 2016 and “Prairies Yield Clues for Antibiotic Resistance” was published in the September 2016 issue of AgResearch Magazine.last_img read more

How the Stack Effect Can Defeat Your Winterizing Efforts

first_imgRELATED ARTICLESStupid Energy-Saving TipsMore Energy MythsA Plague of Bad Energy-Saving Tips Caulk your windows. Weatherstrip your doors. It’s that time of year again.No, I don’t mean the time of year when you should do those things. I mean it’s the time of year when all the news stories that include this ineffective advice start appearing. There’s a lot of bad advice included in those articles, but let’s just look at why the caulking and weatherstripping advice will provide minimal relief.The first problem with caulking and weatherstrippingI’ve written about this topic a number of times. Most recently, it was my article about bad energy saving tips on Clark Howard’s website. I covered a number of their bad tips but gave only a cursory answer to the caulking and weatherstripping issue:Why? Because doing this will reduce your total air leakage by a small amount. The bigger leaks are in your crawl space or basement and in your attic.That is Reason Number 1 that caulking and weatherstripping aren’t going to help a whole lot. When you’ve got really big holes in the ceiling or floor, the gaps around the windows and doors pale in comparison. For example, there’s the bathtub hole in the floor, as shown in Image #2 at the bottom of this page. The open chase to the attic is another biggie (Image #3, below). The mechanical closet in the photo had no ceiling.Occasionally contractors or homeowners put really crazy holes in the ceiling. My in-laws had a hole cut in their kitchen ceiling (Image #4, below), and the best I could figure was that the remodeling contractor who did their kitchen a few years earlier thought their refrigerator needed to be vented to the attic.Another crazy hole found in someone’s home was the one shown in Image #5. It’s open at the top to the attic and connected to a louvered grille at the ceiling below. Stuart Perkin of Airtight Energy Inspections sent me this one and said it was one of three in that Colorado home. Even worse, he said it was installed by the builder, not a DIY homeowner.The other problem with caulking and weatherstrippingI mention the other problem with caulking and weatherstripping just about every time I teach a class that includes understanding air leakage. Somehow, though, I don’t think I’ve ever put it here in the blog. Before I reveal what it is, let’s review the fundamentals of air leakage.For air to leak across the building enclosure, you need two things: a pressure difference and a pathway.Pressure differences are created by wind, the stack effect, and mechanical systems.For every cubic foot of air that leaks (or is blown) out of a home, another cubic foot leaks in somewhere else.If you live in a windy place, wind can be a significant factor. You can’t control that pressure difference, so the best way to prevent it from stealing conditioned air from your home is to seal up the leaks. Go for all the big leaks you can find first.Mechanical systems can create pressure differences, too. One of the hidden sources of this type of pressure difference is unbalanced duct leakage. Exhaust fans, including your clothes dryer, are another. You have some control here, and if you do things right, you shouldn’t have big pressure differences from the equipment in your home.That leaves the stack effect. Warm air rises inside the home because it’s less dense than cold air. (Actually, it’s pushed upward by cold, dense air leaking in at the bottom, but let’s not get into all that controversial stuff right now.) Because of the different air densities, you end up different pressures in the house. As you see in the diagram below, you get positive pressure (inside higher than outside) at the top and negative pressure at the bottome of the house.Air leaks when you have a pressure difference and a pathway, so you’ll get a lot more air leaking at the bottom and the top of the house than you do in the middle. In fact, you could even have an open window in the middle and get very little air leakage if you’re at what’s called the neutral pressure plane.The last photo below shows the stack effect working its magic on a building under construction in Boston. The plastic is getting sucked in at the bottom because of negative pressure and pushed out at the top by the positive pressure.The stack effect increases with building height and temperature difference between inside and out. Tall buildings on cold days get it the worst, but a two or three story home can experience significant air leakage due to the stack effect, too.Should you caulk and weatherstrip?The common advice for winterizing your home isn’t incorrect. Well, not completely anyway. It’s just that it’s likely to be ineffective because of two reasons:The big holes are in the floor and ceiling.The big pressure differences are at the top and bottom of the house.Air leakage is one of the biggest problems with homes, so it’s absolutely worth going after it. Just be smart about it and go for the big leaks. Those standard tips for winterizing a home may give you a warm and fuzzy feeling but won’t give you a warm and cozy house. Allison Bailes of Decatur, Georgia, is a speaker, writer, energy consultant, RESNET-certified trainer, and the author of the Energy Vanguard Blog. Check out his in-depth course, Mastering Building Science at Heatspring Learning Institute, and follow him on Twitter at @EnergyVanguard.last_img read more

Premier gets feisty calls on employers to be fair to locals

first_imgFacebook Twitter Google+LinkedInPinterestWhatsApp Recommended for you Bishop says peace & prosperity is everybody’s responsibility at Law Enforcers Church Service Facebook Twitter Google+LinkedInPinterestWhatsAppProvidenciales, 20 Feb 2015 – One day after being put on blast by former Premier Michael Misick and the TCI sees a warning from the current Premier to employers in the country to hire his people and pay his people. The statement is already being criticized as baseless and the country’s leader: playing politics. Premier Rufus Ewing in a press release yesterday talks about the boom in the economy thanks to the tourism and hospitality industry surging by 24% and then gets on the case of companies in that sector saying he is not satisfied, for example, that the level of growth is being felt in local businesses. Another point for the Premier, I quote him here: “…ensure that Turks and Caicos Islanders employed within your establishments receive fair opportunities for promotions and fair compensation, comparative to that which any foreign worker would have otherwise received had they been employed in those positions.” He said on the one hand there are companies hiring and fairly compensating natives, but to those which are not, the Premier leveled this warning: “This practice of overlooking my people stops here and it will no longer be business as usual. Moving forward, I will expect your efforts to employ, train, retain, promote and pay Turks and Caicos Islanders to be genuine, earnest, strategic and meaningful, and this expectation applies to all businesses, public, private and statutory.” The leader in the PNP Administration in that statement also claims that the unemployment rate has been reduced since they took office. The comments from Hon Rufus Ewing come one day after former Premier Michael Misick blasted the current PNP for veering off of the PNP Manifesto promises and losing touch with the people, and just hours before Cabinet revealed that a minimum wage increase starts on April 1, 2015. Magnetic Media asked the Office of the Premier to provide statistics on the unemployment rate in 2012 vs 2015, to provide the figure on how many jobs have been created in the private sector and to provide the number of jobs created in the public sector. Up to news time, that information was not yet issued. Beaches puts former Premier on blast about controversial pier Related Items:employers, islanders, premier rufus ewing Row over Grand Turk infrastructure reaches fever pitch in Parliamentlast_img read more

Towards a global quantum network Photoelectron trapping in double quantum dots

first_img Citation: Towards a global quantum network: Photoelectron trapping in double quantum dots (2013, July 31) retrieved 18 August 2019 from https://phys.org/news/2013-07-global-quantum-network-photoelectron-dots.html Journal information: Physical Review Letters © 2013 Phys.org. All rights reserved. More information: Nondestructive Real-Time Measurement of Charge and Spin Dynamics of Photoelectrons in a Double Quantum Dot, Physical Review Letters 110, 266803 (2013), doi:10.1103/PhysRevLett.110.266803 Researchers entangle a single electron spin to a single photon in a quantum dot Explore further (color online). (a) A scanning electron micrograph of the typical lateral DQD device. The surface gates for dot formation have Tið10 nmÞ=Auð20 nmÞ metal thickness. A 60 nm thick Al2O3 insulating layer was formed on top of them by atomic layer deposition. (b) A Tið30 nmÞ=Auð220 nmÞ mask was fabricated on the surface above the DQD with an aperture of 400 nm diameter. (c) Band profile of the HEMT structure. The excitation laser energy is tuned just above the GaAs band gap. The excited electron-hole pair is separated due to the intrinsic electric field. Copyright © doi:10.1103/PhysRevLett.110.266803 To successfully address these challenges, Fujita explains, the scientists relied on a small number of key insights and innovations. “A significant innovation was to introduce an additional infrared laser beam so that persistent photoconductivity would be erased. This was an innovative scheme because it made it possible to continuously experiment with photon irradiation single-shot single photon detection and obtain series of data.” Another technique, he continues, was to form different kinds of charge sensors to improve the signals in DC measurements.Several other interesting results were achieved in this study, one being that the researchers’ approach offers a novel method to study the multielectron dynamics which are strongly affected by the Coulomb interaction in a multidot system. “Photoexcitation can create multiple electrons within the pulse duration, and the excited spins depend thoroughly upon the incident polarization,” Fujita points out. “This allows initialization of multiple spins and multiple coupled dot experiments.”The demonstrated results can also be regarded as excited state spectroscopy, in that they correspond to a spin excitation over the ground state of the dot, which is an excited state. “Excited states reflect the configuration of the quantum dot which could be modified by tuning the gate voltages,” Fujita notes. “Using our scheme we can investigate energy and spin correlations of excited states using photoelectrons through interdot interactions.”The paper also reports that fast initialization of the excited states can be realized by controlling the incident photon number, energy, and polarization. “Photon number could be tuned with the laser power, energy with the wavelength, and spin polarization with the photon polarization,” Fujita explains. “The photon configurations are tuned in the optics and excitation could be realized fast within the laser pulse width. If we compare this with electrical initialization by tunneling from the leads, the initialization time is limited by the tunneling rate and exact spins are currently difficult to inject.”Using the resonant interdot tunneling in the DQDs, the researchers’ technique would also open a way to high fidelity photon counting. “Our technique to keep the photoelectrons from escaping is an advantage for counting multiple photoelectrons,” Fujita says. “We’ve shown that tunneling rates could be properly tuned in a desired range. This enables us to tune the tunneling of each electron number to a good tunneling rate so that every electron tunneling could be resolved and give us a higher fidelity.”Fujita also comments on the relationship between their findings and the no-cloning theorem, which he points out holds that quantum communication becomes perfectly safe – but on the other hand, there’s also no way to amplify a quantum state to extend the communication length. This therefore restricts the length of quantum information transfer with a single photon. “Quantum repeaters would shorten each photon propagation,” Fujita notes, “thus making it possible to connect between more distant places – and we’ve demonstrated a scheme that brings us closer to the realization of a quantum repeater.”More specifically, in the current study a quantum repeater is shown as a solution for extending the quantum communication length. “We think our demonstrated nondestructive single-shot single photon detection in lateral quantum dots is a good candidate for one of the ingredients of this repeater,” Fujita tells Phys.org. “In the future it could realize determination and storage of the arrived photons to immediately create entanglement at its convenience to raise the entanglement creation rate. Further integration of quantum operations in our quantum dot would possibly move the establishment of information network forward, and thereby impact the establishment of a global quantum information network.””We’ve demonstrated the detection of photoelectron spin configuration using two electron spin correlation, namely the spin blockade, so next we’ll detect single photoelectron spin by correctly initializing the prepared spin.” Fujita adds. “Our next step is to combine our photoelectron spin detection scheme with heavy hole excitations to verify angular momentum transfer,” In terms their continued research, Fujita says that the researchers would like to verify the angular momentum transfer to the electron spins. “This requires selective excitation of electron hole spin states, so a wavelength-tunable single shot irradiation setup is needed. Another development,” he continues, “would be to increase the photon absorption rate at a scale that would permit realizing sufficient entanglement between photons and electron spins.” The scientists are also thinking of embedding Bragg reflectors inside the wafer.Over the next decade, Fujita continues, their research would lead to the entanglement between distant solid state qubits by trapping entangled photon pairs. “After the verification of coherent angular momentum transfer, experiments on trapping entangled photon pairs will be demonstrated to verify the entanglement between photons and electron spins. The advantage of our lateral quantum dot is that 2-spin qubit operations could be done,” Fujita concludes. “This will be then demonstrated in two trapped photons to create entanglement between distant entangled photon pairs.” Recently, however, scientists at The University of Tokyo, Princeton University, Ruhr-Universität Bochum, and RIKEN found that nondestructive measurement is feasible using gallium arsenide double quantum dots (DQDs), thereby taking a significant step towards long distance entanglement distribution. Moreover, the importance of using a lateral dot is that these have a possibility to store and manipulate the photoelectrons – and while previous studies show detection of photocurrents or photoelectron signals, the scientists state that to their knowledge, none of them performed experiments demonstrating the possibility of further photoelectron storage or manipulation. Lastly, although the researchers have not yet demonstrated the spin manipulation of photoelectrons, their double dot structure shows repetitive tunneling of single photoelectrons, and so satisfies the photoelectron spin manipulation condition.Researcher Takafumi Fujita discussed the research he, Prof. Seigo Tarucha, and their colleagues conducted with Phys.org. “The main challenge in demonstrating the trapping of single photons and interdot tunneling of the photogenerated electrons in a nondestructive manner using double quantum dots was to stabilize our quantum dot while performing single-shot single photon detection experiments,” Fujita tells Phys.org. “Conventional lateral quantum dot devices can change their condition upon irradiation. We had to fine-tune and maintain the resonant interdot tunneling condition while performing irradiation experiments. The photon responses do not recover immediately so repetition of the irradiation sequence also had to be tuned to wait for photoconductivity to relax.”Regarding the use of resonant tunneling, Fujita explains, the idea of using a double dot was to use spin blockade, but the researchers also had to clearly distinguish photoelectron trapping signals from the noise. Rather than using a single-step signal – which can be difficult to distinguish in photon irradiation measurements – they decided to use iterative bi-stable charge tunneling signals in the double dot to clearly discriminate single photoelectron trapping events from noise. “With iterative bi-stable charge tunneling to determine the number of trapped photoelectrons,” Fujita adds, “we had to wait in order to be certain that there were no other electrons left in the dot. However, we found that the resonant interdot tunneling would give us an immediate response of the last remaining electron.” In addition, says Fujita, to infer photoelectron spin states, the scientists thought that they needed a large number of data samples – but once again, interdot resonance proved to be an advantage. (Phys.org) —While the journey from today’s fledgling quantum computers to a global quantum information network may seem daunting, researchers are continually, and at an accelerating pace, making progress towards that goal. One key element essential to that progress is the transfer of quantum information between single photons and solid-state quanta – and the properties of semiconductor quantum dots (QDs) make them excellent candidates for photon-electron quantum coupling. One historical stumbling block has been that although quantum circuits require nondestructive transfer between separate dots, using single QDs usually fails due to destructive transfer in which photoelectrons are immediately lost upon measurement. This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.last_img read more