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.”
HPC helps identify new, cleaner source for white light – EurekAlert
When early humans discovered how to harness fire, they were able to push back against the nightly darkness that enveloped them. With the invention and widespread adoption of electricity, it became easier to separate heat from light, work through the night, and illuminate train cars to highways. In recent years, old forms of electric light generation such as halogen lightbulbs have given way to more energy efficient alternatives, further cheapening the costs to brighten our homes, workplaces, and lives generally.
Unfortunately, however, white light generation by newer technologies such as light-emitting diodes (LEDs) is not straightforward and often relies on a category of materials called “rare-earth metals,” which are increasingly scarce. This has recently led scientists to look for ways to produce white light more sustainably. Researchers at Giessen University, the University of Marburg, and Karlsruhe Institute of Technology have recently uncovered a new class of material called a “cluster glass” that shows great potential for replacing LEDs in many applications.
“We are witnessing the birth of white-light generation technology that can replace current light sources. It brings all the requirements that our society asks for: availability of resources, sustainability, biocompatibility,” said Prof. Dr. Simone Sanna, Giessen University Professor and lead computational researcher on the project. “My colleagues from the experimental sciences, who observed this unexpected white light generation, asked for theoretical support. Cluster glass has an incredible optical response, but we don’t understand why. Computational methods can help to understand those mechanisms. This is exactly the challenge that theoreticians want to face.”
Sanna and his collaborators have turned to the power of high-performance computing (HPC), using the Hawk supercomputer at the High-Performance Computing Center Stuttgart (HLRS) to better understand cluster glass and how it might serve as a next-generation light source. They published their findings in Advanced Materials.
Clear-eyed view on cluster glass formation
If you are not a materials scientist or chemist, the word glass might just mean the clear, solid material in your windows or on your dinner table. Glass is actually a class of materials that are considered “amorphous solids;” that is, they lack an ordered crystalline lattice, often due to a rapid cooling process. At the atomic level, their constituent particles are in a suspended, disordered state. Unlike crystal materials, where particles are orderly and symmetrical across a long molecular distance, glasses’ disorder at the molecular level make them great for bending, fragmenting, or reflecting light.
Experimentalists from the University of Marburg recently synthesized a particular of glass called a “cluster glass.” Unlike a traditional glass that almost behaves as a liquid frozen in place, cluster glass, as the name implies, is a collection of separate clusters of molecules that behave as a powder at room temperature. They generate bright, clear, white light upon irradiation by infrared radiation. While powders cannot easily be used to manufacture small, sensitive electronic components, the researchers found a way to re-cast them in glass form: “When we melt the powder, we obtain a material that has all the characteristics of a glass and can be put in any form needed for a specific application,” Sanna said.
While experimentalists were able to synthesize the material and observe its luminous properties, the group turned to Sanna and HPC to better understand how cluster glass behaves the way it does. Sanna pointed out that white light generation isn’t a property of a single molecule in a system, but the collective behaviors of a group of molecules. Charting these molecules’ interactions with one another and with their environment in a simulation therefore means that researchers must both capture the large-scale behaviors of light generation and also observe how small-scale atomic interactions influence the system. Any of these factors would be computationally challenging. Modeling these processes at multiple scales, however, is only possible using leading HPC resources like Hawk.
Collaboration between experimentalists and theoreticians has become increasingly important in materials science, as synthesizing many iterations of a similar material can be slow and expensive. High-performance computing, Sanna indicated, makes it much faster to identify and test materials with novel optical properties. “The relationship between theory and experiment is a continuous loop. We can predict the optical properties of a material that was synthesized by our chemist colleagues, and use these calculations to verify and better understand the material’s properties,” Sanna said. “We can also design new materials on a computer, providing information that chemists can use to focus on synthesizing compounds that have the highest likelihood of being useful. In this way, our models inspire the synthetization of new compounds with tailored optical properties”
In the case of cluster glass, this approach resulted in an experiment that was verified by simulation, with modelling helping to show the researchers the link between the observed optical properties and the molecular structure of their cluster glass material and can now move forward as a candidate to replace light sources heavily reliant on rare-earth metals.
HPC expedites R&D timelines
HPC plays a major role in helping researchers accelerate the timeline between new discovery and new product or technology. Sanna explained that HPC drastically cut down on the time to get a better understanding of cluster glass. “We spend a lot of time doing simulation, but it is much less than characterizing these materials in reality,” he said. “The clusters we model have a diamond-shaped core with 4 ligands (molecular chains) attached to it. Those ligands can be made of any number of things, so doing this in an experiment is time consuming.”
Sanna pointed out that the team is still limited by how long they can perform individual runs for their simulations. Many research projects on supercomputers can divide a complex system into many small parts and run calculations for each part in parallel. Sanna’s team needs to pay special attention to long-distance particle interactions across large systems, so they are limited by how much they can divide their simulation across computer nodes. He indicated that having regular access to longer run times—more than a day straight on a supercomputer—would allow the team to work more quickly.
In ongoing studies of cluster glass Sanna’s team hopes to thoroughly understand the origin of its light generating properties. This could help to identify additional new materials and to determine how best to apply cluster glass in light generation.
Sanna explained that HPC resources at HLRS were essential for his team’s basic science research, which he hopes will lead to new products that can benefit society. “The main computational achievement in this journal article was only possible through our access to the machine in Stuttgart,” he said.
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Cluster-Glass for Low-Cost White-Light Emission
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The sun is dying: Here’s how long it has before exhausting its fuel – Firstpost
A new study has estimated the sun’s evolutionary process will continue for billions of more years before it runs out of its fuel and turns into a red giant. It has revealed the past and future of the sun, how the sun will behave at what stage and when it will enter the dusk of its life
The sun is very likely going through its middle age, a recent study published in June this year by the European Space Agency (ESA), based on the observations from its Gaia spacecraft, has revealed.
The ESA’s Gaia telescope has revealed information that could help determine when the sun will die, which was formed around 4.57 billion years ago.
The study has estimated the sun’s evolutionary process to continue for billions of more years before it runs out of its fuel and turns into a red giant. The study has revealed the past and future of the sun, how the sun will behave at what stage and when it will enter the dusk of its life.
What has the ESA study revealed?
According to the report made public on 13 June, 2022, at the age of around 4.57 billion years, our sun is currently in its ”comfortable middle age, fusing hydrogen into helium and generally being rather stable; staid even”.
However, it will not be the case forever. The sun will eventually die. The information by ESA’s Gaia observatory has also revealed the process of its decay.
“As the hydrogen fuel runs out in its core, and changes begin in the fusion process, we expect it to swell into a red giant star, lowering its surface temperature in the process.”
Exactly how this happens depends on how much mass a star contains and its chemical composition.
To deduce this, astronomer Orlagh Creevey, Observatoire de la Côte d’Azur, France, and collaborators from Gaia’s Coordination Unit 8, and colleagues combed the data looking for the most accurate stellar observations that the spacecraft could offer.
“We wanted to have a really pure sample of stars with high precision measurements,” says Orlagh.
When will the sun die?
The study found that the sun will reach a maximum temperature of approximately 8 billion years of age, before starting to cool down and increase in size.
“It will become a red giant star around 10–11 billion years of age. The Sun will reach the end of its life after this phase, when it eventually becomes a dim white dwarf.”
A white dwarf is a former star that has exhausted all its hydrogen that it once used as it central nuclear fuel and lost its outer layers as a planetary nebula.
“If we don’t understand our own Sun – and there are many things we don’t know about it – how can we expect to understand all of the other stars that make up our wonderful galaxy,” Orlagh said.
By identifying similar stars to the sun, but this time with similar ages, the observational gap can be bridged in how much we know about the sun compared to other stars in the universe.
To identify these ‘solar analogues’ in the Gaia data, Orlagh and colleagues looked for stars with temperatures, surface gravities, compositions, masses and radii that are all similar to the present-day Sun. They found 5863 stars that matched their criteria.
With inputs from agencies
SLS ready to roll to LC-39B for launch, teams prepare for multiple launch trajectories – NASASpaceFlight.com – NASASpaceflight.com
NASA’s Space Launch System (SLS) rocket has completed all pre-launch preparations inside the Vehicle Assembly Building at the Kennedy Space Center in Florida and is ready for its 4.2-mile (6.7-km) journey to Launch Complex 39B.
The multi-hour rollout process is currently set to begin at 9 PM EDT on Tuesday, August 16 (01:00 UTC on Wednesday, August 17), weather permitting – which should result in a sunrise arrival at the pad.
The rollout is the last major milestone ahead of launch, which will differ from most recent missions in that the rocket’s needed azimuth — or flight path — will continuously change through each day’s launch window.
Launching to the Moon
Launching into a rendezvous orbit with a satellite or station in low Earth orbit can be relatively simplified as needing to launch directly into the plane – and therefore the same orbital inclination – of the target’s orbit.
For example, when launching to the International Space Station from Florida, the azimuth the rocket follows is 44.98°. This does not change based on when within the daily window liftoff occurs.
However, the same is not true when trying to launch into an intercept trajectory with the Moon.
As related by Artemis 1 Ascent/Entry Flight Director Judd Frieling to NASASpaceflight during Artemis Day events in Mission Control at the Johnson Space Center, the Moon’s motion in its orbit coupled with its constantly-changing relative inclination to the launch site complicates the needed launch azimuth for SLS.
On each launch day, the azimuth SLS must fly moves incrementally, second-by-second, throughout the window to match the movement of the Moon relative to the Earth for the translunar injection (TLI) burn.
According to NASA, for SLS and Artemis 1, the azimuth at the opening of the window on all three launch attempts on August 29, September 2, and September 5 is 62°, resulting in a 38° inclination orbit.
At the end of each window, the azimuth flown would be 108° into a 32° inclination orbit.
But before SLS can be readied for its roll onto course on launch day, it must first arrive at the pad.
Rolling out for launch
The Artemis 1 launch rollout will mark the first time since May 31, 2011, that a vehicle will emerge from the Vehicle Assembly Building (VAB) at the Kennedy Space Center for launch operations.
As it has twice already for its wet dress rehearsal campaigns, the SLS rocket for Artemis 1 will make the journey to LC-39B atop crawler-transporter 2, one of two crawler-transporters owned by NASA and the only one modified to carry the full stack Artemis/SLS vehicle to the pad.
The upgrades were necessary due to the crawler’s age and the increased mass of the SLS vehicle with its combined Mobile Launcher (ML).
The combined SLS/ML weight is approximately 15 million pounds (6.8 million kg) and is significantly heavier than the previous record holder in the Space Shuttle at 12 million pounds (5.4 million kg).
Upgrades included a rating to handle 18 million pounds (8.1 million kg), a 50% greater load than was originally envisioned, as well as a new 1,500-kilowatt electrical power generator, parking and service brakes, redesigned and upgraded roller bearings, and several other modifications for the Artemis program.
Like the crawlers, their purpose-built road, the crawlerway, also underwent upgrades between Shuttle and SLS.
Beginning in 2013, the crawlerway’s foundations were repaired with new lime rock to return them to their original condition and ready them for the Block 1B SLS, presently scheduled for later this decade, which will be heavier than the Block 1 SLS used for Artemis 1.
Additionally, 30,000 tons of new Alabama river rock were added to return the crawlerway to its optimal depth.
For Launch Complex 39B, which was used for Apollo, Skylab, Apollo-Soyuz, Space Shuttle, and Ares I-X missions, the pad was slowly modified in stages, beginning in the final years of the Shuttle program, into a clean pad configuration with three, 600-foot (183 m) lightning towers connected with catenary wires.
The clean pad is without the Shuttle-era fixed and rotating service structures that serviced the Shuttle stack.
The sound suppression system, flame trench, cabling, and other systems were also upgraded during the transition to SLS. Work on Pad 39B has also included a new 1.25 million gallon liquid hydrogen tank, though this is not yet complete and will not be used for Artemis 1.
Pad 39B’s clean pad configuration was designed to be able to handle different types of rockets as part of a multi-user spaceport emphasis. To date, only Northrop Grumman expressed interest in the pad share for their now-canceled OmegA rocket.
Artemis 1 is scheduled to spend 13 days at Pad 39B after the August 16 rollout. During this time, the ML will be hooked up to the plumbing servicing the rocket with liquid oxygen, liquid hydrogen, helium, and liquid nitrogen.
Other round systems required for the launch will also be activated while teams conduct system checks on the SLS and Orion. Should all go well, the stage will be set for the 60th overall launch — and the second flight to the Moon after Apollo 10 — from Pad 39B.
The Artemis 1 countdown is currently scheduled to begin with Call To Stations at 9:53 AM EDT (13:53 UTC) on August 27. Fueling would begin early in the morning of August 29 for a two-hour launch window opening at 8:33 AM EDT (12:33 UTC).
Overall, Artemis 1 has 25 days to launch after the flight termination system (FTS) testing on the launch vehicle was completed on August 12.
Should Artemis 1 not be able to launch on August 29, launch windows for September 2 and 5 are available.
The two-hour September 2 launch window starts at 12:48 PM EDT (16:48 UTC) while the September 5 window lasts for 90 minutes, starting at 5:12 PM EDT (21:12 UTC).
Should Artemis 1 not be able to make any of the launch windows, crawler-transporter 2 would return to Pad 39B to roll the stack back to the VAB for FTS replacement and any other work the vehicle or ML might need before the next available launch window, most likely October 17 through 31.
Wide-angle photo showing the enormous Vehicle Assembly Building, standing 525 ft. tall. The crawler-transporter 2 is now in place under @NASA_SLS and @NASA_Orion and ready for tomorrow’s roll out to Launch Pad 39B. pic.twitter.com/fCDGS0wouf
— NASA’s Exploration Ground Systems (@NASAGroundSys) August 15, 2022
Together, the first two SLS/Orion Artemis missions will pave the way for the first human lunar landing since 1972 on Artemis 3, currently scheduled for no earlier than late 2025.
Artemis 3 will use the SLS and Orion to ferry astronauts to lunar orbit, where a waiting SpaceX Starship lander procured under the HLS contract will transport them to and from the surface near the Moon’s south pole.
Just under 50 years after humanity last left the Moon in December 1972, Artemis 1 stands ready to begin our return journey. This time, to stay.
(Lead photo: SLS basking in the morning sun at LC-39B. Credit: Stephen Marr for NSF)
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