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Atomically Thin Materials Significantly Shrink Qubits

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Quantum computing is a devilishly complex technology, with many technical hurdles impacting its development. Of these challenges two critical issues stand out: miniaturization and qubit quality.

IBM has adopted the superconducting qubit road map of reaching a 1,121-qubit processor by 2023, leading to the expectation that 1,000 qubits with today’s qubit form factor is feasible. However, current approaches will require very large chips (50 millimeters on a side, or larger) at the scale of small wafers, or the use of chiplets on multichip modules. While this approach will work, the aim is to attain a better path toward scalability.

Now researchers at MIT have been able to both reduce the size of the qubits and done so in a way that reduces the interference that occurs between neighboring qubits. The MIT researchers have increased the number of superconducting qubits that can be added onto a device by a factor of 100.

“We are addressing both qubit miniaturization and quality,” said William Oliver, the director for the Center for Quantum Engineering at MIT. “Unlike conventional transistor scaling, where only the number really matters, for qubits, large numbers are not sufficient, they must also be high-performance. Sacrificing performance for qubit number is not a useful trade in quantum computing. They must go hand in hand.”

The key to this big increase in qubit density and reduction of interference comes down to the use of two-dimensional materials, in particular the 2D insulator hexagonal boron nitride (hBN). The MIT researchers demonstrated that a few atomic monolayers of hBN can be stacked to form the insulator in the capacitors of a superconducting qubit.

Just like other capacitors, the capacitors in these superconducting circuits take the form of a sandwich in which an insulator material is sandwiched between two metal plates. The big difference for these capacitors is that the superconducting circuits can operate only at extremely low temperatures—less than 0.02 degrees above absolute zero (-273.15 °C).

Golden dilution refrigerator hanging vertically
Superconducting qubits are measured at temperatures as low as 20 millikelvin in a dilution refrigerator.Nathan Fiske/MIT

In that environment, insulating materials that are available for the job, such as PE-CVD silicon oxide or silicon nitride, have quite a few defects that are too lossy for quantum computing applications. To get around these material shortcomings, most superconducting circuits use what are called coplanar capacitors. In these capacitors, the plates are positioned laterally to one another, rather than on top of one another.

As a result, the intrinsic silicon substrate below the plates and to a smaller degree the vacuum above the plates serve as the capacitor dielectric. Intrinsic silicon is chemically pure and therefore has few defects, and the large size dilutes the electric field at the plate interfaces, all of which leads to a low-loss capacitor. The lateral size of each plate in this open-face design ends up being quite large (typically 100 by 100 micrometers) in order to achieve the required capacitance.

In an effort to move away from the large lateral configuration, the MIT researchers embarked on a search for an insulator that has very few defects and is compatible with superconducting capacitor plates.

“We chose to study hBN because it is the most widely used insulator in 2D material research due to its cleanliness and chemical inertness,” said colead author Joel Wang, a research scientist in the Engineering Quantum Systems group of the MIT Research Laboratory for Electronics.

On either side of the hBN, the MIT researchers used the 2D superconducting material, niobium diselenide. One of the trickiest aspects of fabricating the capacitors was working with the niobium diselenide, which oxidizes in seconds when exposed to air, according to Wang. This necessitates that the assembly of the capacitor occur in a glove box filled with argon gas.

While this would seemingly complicate the scaling up of the production of these capacitors, Wang doesn’t regard this as a limiting factor.

“What determines the quality factor of the capacitor are the two interfaces between the two materials,” said Wang. “Once the sandwich is made, the two interfaces are “sealed” and we don’t see any noticeable degradation over time when exposed to the atmosphere.”

This lack of degradation is because around 90 percent of the electric field is contained within the sandwich structure, so the oxidation of the outer surface of the niobium diselenide does not play a significant role anymore. This ultimately makes the capacitor footprint much smaller, and it accounts for the reduction in cross talk between the neighboring qubits.

“The main challenge for scaling up the fabrication will be the wafer-scale growth of hBN and 2D superconductors like [niobium diselenide], and how one can do wafer-scale stacking of these films,” added Wang.

Wang believes that this research has shown 2D hBN to be a good insulator candidate for superconducting qubits. He says that the groundwork the MIT team has done will serve as a road map for using other hybrid 2D materials to build superconducting circuits.

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How to watch AMD, Nvidia, and Microsoft’s Computex 2022 keynotes

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Computex is just hours away and will feature keynotes from some of the biggest names in tech, including AMD, Nvidia, and Microsoft. There will almost certainly be some exciting announcements from each brand, but since Computex takes place in Taipei, Taiwan, the keynotes don’t occur at the most convenient times (at least for those of us in North America).

Microsoft and AMD’s keynotes will have you staying up into the wee hours of the morning tonight, while Nvidia’s keynote doesn’t take place until late tomorrow evening. Here’s how and when to tune into each keynote:

How to watch AMD’s keynote

AMD CEO Lisa Su is set to speak in a keynote titled “AMD Advancing the High-Performance Computing Experience,” which is set to highlight AMD’s latest innovations in laptop and desktop performance. The chip company is rumored to reveal Ryzen 7000 series desktop CPUs that use the new Zen 4 core architecture, as well as its X670E, X670, and B650 motherboards that support the next-gen AM5 platform.

You can watch the keynote on YouTube when it goes live early tomorrow morning on Monday, May 23rd at 2AM ET, 11PM PT, or 2PM local time in Taipei. If you’re unsure what time that is for where you live, you can check out this handy time conversion chart AMD posted to Twitter.

How to watch Nvidia’s keynote

Nvidia’s keynote will feature six different speakers, including Ian Buck, the company’s vice president of accelerated computing; Jeff Fisher, the senior vice president of GeForce; and Michael Kagan, the CTO of Nvidia. The keynote is set to cover a range of topics, such as accelerated computing, gaming, content creation, and data center solutions.

You can watch the keynote from Nvidia’s YouTube livestream tomorrow night, May 23rd at 11PM ET / 8PM PT, or 11AM on local Taipei time.

How to watch Microsoft’s keynote

Microsoft’s keynote includes a talk from Panos Panay, the chief product officer behind Windows and Microsoft Surface devices, as well as Nicole Dezen, Microsoft’s corporate vice president. The keynote is simply titled “A Conversation About Windows 11 with Panos Panay and Nicole Dezen.”

You can watch the 30-minute keynote from YouTube early tomorrow morning on May 23rd at 3:30AM ET / 12:30AM PT, or 3:30PM local time in Taipei.

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Paytm, whose share price has dropped 57% so far this year, reports Q4 revenue of ~$200M, up 89% YoY, and a net loss of ~$98M, up 72% YoY due to higher expenses (Reuters)

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Reuters:

Paytm, whose share price has dropped 57% so far this year, reports Q4 revenue of ~$200M, up 89% YoY, and a net loss of ~$98M, up 72% YoY due to higher expenses  —  India’s One 97 Communications Ltd (PAYT.NS), the parent of fintech firm Paytm, on Friday reported a wider fourth-quarter loss due …

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Doctor Strange 2 Surpasses 800 Million at the Box Office

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Image: Marvel Studios

As the weekend winds down, news has come out from The Wrap that Doctor Strange in the Multiverse of Madness, directed by Sam Raimi, has earned over 800 million dollars officially passing The Batman’s theatrical runs, the last big superhero flick to hit the theaters. Doctor Strange 2 is still a decent chunk of change away from the last Marvel outing–Spider-Man: No Way Home earned 1.89 billion dollars during its release.

The Northman continues to draw audiences, although its release to VOD has made it so that there will likely be little more movement after this weekend. To date the Robert Eggers-directed historical action film earned about 64 million. The film stars Alexander Skarsgård and Anya Taylor-Joy as they attempt to seek revenge and escape the clutches of a dismal fate.

This weekend also saw the first returns for Downton Abbey: A New Era, which brought in 16 million after its opening weekend. Universal Pictures, a specialty production from Universal Studios, released the sequel to 2019’s Downton Abbey, which in turn was a follow-up to the hit television series that ran from 2010 to 2015 and became an international phenomenon. The show follows the aristocratic Crawley family and their domestic help across six seasons and fifty-two episodes.

Alex Garland’s horror film of “toxic masculinity,” aptly titled Men, had a solid opening weekend as well (Entertainment Weekly). While 3.3 million might seem modest compared to the big releases, the film is a challenging and divisive watch distributed by the indie darling A24. For a better comparison we can look at the opening numbers for Everything Everywhere All at Once, another A24-distributed film, which netted 3.2 million on its opening weekend.


Want more io9 news? Check out when to expect the latest Marvel and Star Wars releases, what’s next for the DC Universe on film and TV, and everything you need to know about House of the Dragon and Lord of the Rings: The Rings of Power.

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