Until now, this has been the situation for the bits of hardware that make up a silicon quantum computer, a type of quantum computer with the potential to be cheaper and more versatile than today’s versions.
Now a team based at Princeton University has overcome this limitation and demonstrated that two quantum-computing components, known as silicon “spin” qubits, can interact even when spaced relatively far apart on a computer chip. The study was published in the journal Nature.
“The ability to transmit messages across this distance on a silicon chip unlocks new capabilities for our quantum hardware,” said Jason Petta, the Eugene Higgins Professor of Physics at Princeton and leader of the study. “The eventual goal is to have multiple quantum bits arranged in a two-dimensional grid that can perform even more complex calculations. The study should help in the long term to improve communication of qubits on a chip as well as from one chip to another.”
Quantum computers have the potential to tackle challenges beyond the capabilities of everyday computers, such as factoring large numbers. A quantum bit, or qubit, can process far more information than an everyday computer bit because, whereas each classical computer bit can have a value of 0 or 1, a quantum bit can represent a range of values between 0 and 1 simultaneously.
To realize quantum computing’s promise, these futuristic computers will require tens of thousands of qubits that can communicate with each other. Today’s prototype quantum computers from Google, IBM and other companies contain tens of qubits made from a technology involving superconducting circuits, but many technologists view silicon-based qubits as more promising in the long run.
Silicon spin qubits have several advantages over superconducting qubits. The silicon spin qubits retain their quantum state longer than competing qubit technologies. The widespread use of silicon for everyday computers means that silicon-based qubits could be manufactured at low cost.
The challenge stems in part from the fact that silicon spin qubits are made from single electrons and are extremely small.
“The wiring or ‘interconnects’ between multiple qubits is the biggest challenge towards a large scale quantum computer,” said James Clarke, director of quantum hardware at Intel, whose team is building silicon qubits using using Intel’s advanced manufacturing line, and who was not involved in the study. “Jason Petta’s team has done great work toward proving that spin qubits can be coupled at long distances.”
To accomplish this, the Princeton team connected the qubits via a “wire” that carries light in a manner analogous to the fiber optic wires that deliver internet signals to homes. In this case, however, the wire is actually a narrow cavity containing a single particle of light, or photon, that picks up the message from one qubit and transmits it to the next qubit.
The two qubits were located about half a centimeter, or about the length of a grain of rice, apart. To put that in perspective, if each qubit were the size of a house, the qubit would be able to send a message to another qubit located 750 miles away.
The key step forward was finding a way to get the qubits and the photon to speak the same language by tuning all three to vibrate at the same frequency. The team succeeded in tuning both qubits independently of each other while still coupling them to the photon. Previously the device’s architecture permitted coupling of only one qubit to the photon at a time.
“You have to balance the qubit energies on both sides of the chip with the photon energy to make all three elements talk to each other,” said Felix Borjans, a graduate student and first author on the study. “This was the really challenging part of the work.”
Each qubit is composed of a single electron trapped in a tiny chamber called a double quantum dot. Electrons possess a property known as spin, which can point up or down in a manner analogous to a compass needle that points north or south. By zapping the electron with a microwave field, the researchers can flip the spin up or down to assign the qubit a quantum state of 1 or 0.
“This is the first demonstration of entangling electron spins in silicon separated by distances much larger than the devices housing those spins,” said Thaddeus Ladd, senior scientist at HRL Laboratories and a collaborator on the project. “Not too long ago, there was doubt as to whether this was possible, due to the conflicting requirements of coupling spins to microwaves and avoiding the effects of noisy charges moving in silicon-based devices. This is an important proof-of-possibility for silicon qubits because it adds substantial flexibility in how to wire those qubits and how to lay them out geometrically in future silicon-based ‘quantum microchips.'”
The communication between two distant silicon-based qubits devices builds on previous work by the Petta research team. In a 2010 paper in the journal Science, the team showed it is possible to trap single electrons in quantum wells. In the journal Nature in 2012, the team reported the transfer of quantum information from electron spins in nanowires to microwave-frequency photons, and in 2016 in Science they demonstrated the ability to transmit information from a silicon-based charge qubit to a photon. They demonstrated nearest-neighbor trading of information in qubits in 2017 in Science. And the team showed in 2018 in Nature that a silicon spin qubit could exchange information with a photon.
Jelena Vuckovic, professor of electrical engineering and the Jensen Huang Professor in Global Leadership at Stanford University, who was not involved in the study, commented: “Demonstration of long-range interactions between qubits is crucial for further development of quantum technologies such as modular quantum computers and quantum networks. This exciting result from Jason Petta’s team is an important milestone towards this goal, as it demonstrates non-local interaction between two electron spins separated by more than 4 millimeters, mediated by a microwave photon. Moreover, to build this quantum circuit, the team employed silicon and germanium—materials heavily used in the semiconductor industry.”
This hot super-Earth has temperatures of 800°F and rivers of glowing lava – Digital Trends
No day or night, heat intense enough to melt lead, and glowing rivers of lava: This hellish landscape is a typical day on Gliese 486b, a recently discovered exoplanet orbiting the nearby star Gliese 486. The planet is rocky and around three times the mass of Earth, making it a type called a super-Earth. But it is so hot that the conditions there are quite different from what we’re used to.
The planet is so close to its star that a year there lasts only 1.5 Earth days. Though the star is fainter and cooler than our sun, the planet orbits just 1.5 million miles away and it is tidally locked, meaning one side of the planet always faces the star. This drives temperatures up even higher, reaching a surface temperature of 700 Kelvin (800 degrees Fahrenheit).
The researchers who made the discovery believe this means the planet would appear more like Venus than like Earth, with a hot and dry landscape and rivers of glowing lava. There is probably little atmosphere there, as the heat from the star would act to evaporate it away, but the planet’s gravity likely helps it to retain some atmosphere.
The potential existence of a thin but present atmosphere makes this planet an excellent candidate for research as it allows scientists to test their theories on atmospheric models for rocky planets. “The discovery of Gliese 486b was a stroke of luck,” said José A. Caballero of the Centro de Astrobiología in Spain, co-author of the paper, in a statement. “A hundred degrees hotter and the planet’s entire surface would be lava. Its atmosphere would consist of vaporized rocks. On the other hand, if Gliese 486b were a hundred degrees colder, it would have been unsuitable for follow-up observations.”
The researchers now want to use upcoming next-generation telescopes to study the planet further and to try to peer into its atmosphere to see its composition. “The proximity of this exoplanet is exciting because it will be possible to study it in more detail with powerful telescopes such as the upcoming James Webb Space Telescope and the future Extremely Large Telescopes,” said lead author Trifon Trifonov of the Max Planck Institute for Astronomy.
“We can hardly wait for the new telescopes to become available. The results will help us to understand how well rocky planets can hold their atmospheres, what they are made of, and how they influence the energy distribution on the planets.”
In Oregon, Scientists Find a Virus Variant With a Worrying Mutation – Yahoo News
Scientists in Oregon have spotted a homegrown version of a fast-spreading variant of the coronavirus that first surfaced in Britain — but now it’s combined with a mutation that may make the variant less susceptible to vaccines.
The researchers have so far found just a single case of this formidable combination, but genetic analysis suggested that the variant had been acquired in the community and did not arise in the patient.
“We didn’t import this from elsewhere in the world — it occurred spontaneously,” said Brian O’Roak, a geneticist at Oregon Health and Science University who led the work. He and his colleagues participate in the Centers for Disease Control and Prevention’s effort to track variants, and they have deposited their results in databases shared by scientists.
The variant originally identified in Britain, called B.1.1.7, has been spreading rapidly across the United States, and accounts for at least 2,500 cases in 46 states. This form of the virus is both more contagious and more deadly than the original version, and it is expected to account for most U.S. infections in a few weeks.
The new version that surfaced in Oregon has the same backbone, but also a mutation — E484K, or “Eek” — seen in variants of the virus circulating in South Africa, Brazil and New York City.
Lab studies and clinical trials in South Africa indicate that the Eek mutation renders the current vaccines less effective by blunting the body’s immune response. (The vaccines still work, but the findings are worrying enough that Pfizer-BioNTech and Moderna have begun testing new versions of their vaccines designed to defeat the variant found in South Africa.)
The B.1.1.7 variant with Eek also has emerged in Britain, designated as a “variant of concern” by scientists. But the virus identified in Oregon seems to have evolved independently, O’Roak said.
O’Roak and his colleagues found the variant among coronavirus samples collected by the Oregon State Public Health Lab across the state, including some from an outbreak in a health care setting. Of the 13 test results they analyzed, 10 turned out to be B.1.1.7 alone, and one the combination.
Other experts said the discovery was not surprising, because the Eek mutation has arisen in forms of the virus all over the world. But the mutation’s occurrence in B.1.1.7 is worth watching, they said.
In Britain, this version of the variant accounts for a small number of cases. But by the time the combination evolved there, B.1.1.7 had already spread through the country.
“We’re at the point where B.1.1.7 is just being introduced” into the United States, said Stacia Wyman, an expert in computational genomics at the University of California, Berkeley. “As it evolves, and as it slowly becomes the dominant thing, it could accumulate more mutations.”
Viral mutations may enhance or weaken one another. For example, the variants identified in South Africa and Brazil contain many of the same mutations, including Eek. But the Brazilian version has a mutation, K417N, that is not present in the version from South Africa.
In a study published Thursday in Nature, researchers compared antibody responses to all three variants of concern — the ones identified in Britain, South Africa and Brazil. Consistent with other studies, they found that the variant that pummeled South Africa is most resistant to antibodies produced by the immune system.
But the variant circulating in Brazil was not as resistant, even though it carried the Eek mutation. “If you have the second mutation, you don’t see as bad an effect,” said Michael Diamond, a viral immunologist at Washington University in St. Louis, who led the study.
It’s too early to say whether the variant in Oregon will behave like the ones in South Africa or Brazil. But the idea that other mutations could weaken Eek’s effect is “excellent news,” Wyman said.
Overall, she said, the Oregon finding reinforces the need for people to continue to take precautions, including wearing a mask, until a substantial portion of the population is immunized.
“People need to not freak out but to continue to be vigilant,” she said. “We can’t let down our guard yet while there’s still these more transmissible variants circulating.”
This article originally appeared in The New York Times.
© 2021 The New York Times Company
NASA rover Perseverance takes first spin on surface of Mars – Global News
NASA’s Mars rover Perseverance has taken its first, short drive on the surface of the red planet, two weeks after the robot science lab’s picture-perfect touchdown on the floor of a massive crater, mission managers said on Friday.
The six-wheeled, car-sized astrobiology probe put a total of 6.5 meters (21.3 feet) on its odometer on Thursday during a half-hour test spin within Jezero Crater, site of an ancient, long-vanished lake bed and river delta on Mars.
Taking directions from mission managers at NASA’s Jet Propulsion Laboratory (JPL) near Los Angeles, the rover rolled 4 meters (13.1 feet) forward, turned about 150 degrees to its left and then drove backward another 2.5 meters (8.2 feet).
“It went incredibly well,” Anais Zarifian, a JPL mobility test engineer for Perseverance, said during a teleconference briefing with reporters, calling it a “huge milestone” for the mission.
NASA displayed a photo taken by the rover showing the wheel tread marks left in the reddish, sandy Martian soil after its first drive.
Perseverance rover: Scientist on when we can expect samples back from Mars
Another vivid image of the surrounding landscape shows a rugged, ruddy terrain littered with large, dark boulders in the foreground and a tall outcropping of rocky, layered deposits in the distance – marking the edge of the river delta.
Some additional, short-distance test driving is planned for Friday. Perseverance is capable of averaging 200 meters of driving per day.
But JPL engineers still have additional equipment checks to run on the rover‘s many instruments before they will be ready to send the robot on a more ambitious journey as part of its primary mission to search for traces of fossilized microbial life.
So far, Perseverance and its hardware, including its main robot arm, appear to be operating flawlessly, said Robert Hogg, deputy mission manager. The team has yet to conduct post-landing tests of the rover‘s sophisticated system to drill and collect rock samples for return to Earth via future Mars missions.
NASA announced it has named the site of Perseverance’s Feb. 18 touchdown as the “Octavia E. Butler Landing,” in honor of the award-winning American science-fiction writer. Butler, a native of Pasadena, California, died in 2006 at age 58.
(Reporting by Steve Gorman, Editing by Rosalba O’Brien)
© 2021 Reuters
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