Electron Charge Within Millisecond Coherence Time

Coherence stands as a pillar of effective communication, whether it is in writing, speaking or information processing. This principle extends to quantum bits, or qubits, the building blocks of quantum computing. A quantum computer could one day tackle previously insurmountable challenges in climate prediction, material design, drug discovery and more.  READ MORE...

A team led by the U.S. Department of Energy's (DOE) Argonne National Laboratory has achieved a major milestone toward future quantum computing. They have extended the coherence time for their novel type of qubit to an impressive 0.1 milliseconds—nearly a thousand times better than the previous record.

Quantum Computing 10 Times More Efficient

In the world of quantum error correction, an underdog is coming for the king.

Last week, new simulations from two groups reported that a rising class of quantum error-correcting codes is more efficient by an order of magnitude than the current gold standard, known as the surface code. 

The codes all work by transforming a horde of error-prone qubits into a much smaller band of “protected” qubits that rarely make mistakes. But in the two simulations, low-density parity check — or LDPC — codes could make protected qubits out of 10 to 15 times fewer raw qubits than the surface code. 

Neither group has implemented these simulated leaps in actual hardware, but the experimental blueprints suggest that these codes, or codes like them, could hasten the arrival of more capable quantum devices.

“It really looks like it’s coming to fruition,” said Daniel Gottesman of the University of Maryland, who studies LDPC codes but was not involved in the recent studies. “These [codes] could be practical things that can greatly improve our ability to make quantum computers.”

Classical computers run on bits that rarely misfire. But the particle-like objects — qubits — that power quantum computers lose their quantum mojo when just about anything jostles them out of their delicate state. 

To coax future qubits into usefulness, researchers plan to use quantum error correction, the practice of using extra qubits to redundantly encode information. It’s similar in spirit to protecting a message from static by speaking each word twice, spreading out the information among more characters.

The Canonical King
In 1998, Alexei Kitaev of the California Institute of Technology and Sergey Bravyi, then of the Landau Institute for Theoretical Physics in Russia, introduced the quantum error-correcting surface code. It organizes qubits into a square grid and executes something like a game of Minesweeper: Each qubit connects to four neighbors, so checking designated helper qubits allows you to discreetly snoop on four data-carrying qubits. 

Depending on whether the check returns a 0 or a 1, you can infer whether some of the neighbors have erred. By checking around the board, you can deduce where the errors are and fix them.  READ MORE...

A Quantum Enigma

Scientists have discovered that tantalum, a superconducting metal, significantly improves the performance of qubits in quantum computers. By using x-ray photoelectron spectroscopy, they found that the tantalum oxide layer on qubits was non-uniform, prompting further investigations on how to modify these interfaces to boost overall device performance.





Researchers decode the chemical profile of tantalum surface oxides to enhance understanding of loss mechanisms and to boost the performance of qubits.

Whether it’s baking a cake, constructing a building, or creating a quantum device, the caliber of the finished product is greatly influenced by the components or fundamental materials used. In their pursuit to enhance the performance of superconducting qubits, which form the bedrock of quantum computers, scientists have been probing different foundational materials aiming to extend the coherent lifetimes of these qubits.

Coherence time serves as a metric to determine the duration a qubit can preserve quantum data, making it a key performance indicator. A recent revelation by researchers showed that the use of tantalum in superconducting qubits enhances their functionality. However, the underlying reasons remained unknown – until now.


Scientists from the Center for Functional Nanomaterials (CFN), the National Synchrotron Light Source II (NSLS-II), the Co-design Center for Quantum Advantage (C2QA), and Princeton University investigated the fundamental reasons that these qubits perform better by decoding the chemical profile of tantalum.


The results of this work, which were recently published in the journal Advanced Science, will provide key knowledge for designing even better qubits in the future. CFN and NSLS-II are U.S. Department of Energy (DOE) Office of Science User Facilities at DOE’s Brookhaven National Laboratory. C2QA is a Brookhaven-led national quantum information science research center, of which Princeton University is a key partner.     READ MORE...

Hybrid Atomic Quantum Computers

Left: A hybrid array of cesium atoms (yellow) and rubidium atoms (blue). Right: The customizability of the researchers' technique enables them to place the atoms anywhere, allowing them to create this image of Chicago landmarks Willis Tower and the Cloud Gate. The scale bar in both images is 10 micrometers. Credit: Hannes Bernien

Qubits, the building blocks of quantum computers, can be made from many different technologies. One way to make a qubit is to trap a single neutral atom in place using a focused laser, a technique that won the Nobel Prize in 2018.


But to make a quantum computer out of neutral atom qubits, many individual atoms must be trapped in place by many laser beams. So far, these arrays have only been constructed from atoms of a single element, out of concern that making an array out of two elements would be prohibitively complex.

But for the first time, University of Chicago researchers have created a hybrid array of neutral atoms from two different elements, significantly broadening the system's potential applications in quantum technology. The results were funded in part by the NSF Quantum Leap Challenge Institute Hybrid Quantum Architectures and Networks (HQAN), and published in Physical Review X.

"There have been many examples of quantum technology that have taken a hybrid approach," said Hannes Bernien, lead researcher of the project and assistant professor in University of Chicago's Pritzker School of Molecular Engineering. "But they have not been developed yet for these neutral atom platforms. We are very excited to see that our results have triggered a very positive response from the community, and that new protocols using our hybrid techniques are being developed."

Double the potential
While manmade qubits such as superconducting circuits require quality control to stay perfectly consistent, neutral atoms made from a single element all have exactly the same properties, making them ideal, consistent candidates for qubits.

But since every atom in the array has the same properties, it's extremely difficult to measure a single atom without disturbing its neighbors—they're all on the same frequency, so to speak.  READ MORE...

Cryptocurrency's Computing Problem

Cryptocurrencies hold the potential to change finance, eliminating middlemen and bringing accounts to millions of unbanked people around the world. Quantum computers could upend the way pharmaceuticals and materials are designed by bringing their extraordinary power to the process.

Here's the problem: The blockchain accounting technology that powers cryptocurrencies could be vulnerable to sophisticated attacks and forged transactions if quantum computing matures faster than efforts to future-proof digital money.

Cryptocurrencies are secured by a technology called public key cryptography. The system is ubiquitous, protecting your online purchases and scrambling your communications for anyone other than the intended recipient. The technology works by combining a public key, one that anyone can see, with a private key that's for your eyes only.

If current progress continues, quantum computers will be able to crack public key cryptography, potentially creating a serious threat to the crypto world, where some currencies are valued at hundreds of billions of dollars. If encryption is broken, attackers can impersonate the legitimate owners of cryptocurrency, NFTs or other such digital assets.

"Once quantum computing becomes powerful enough, then essentially all the security guarantees will go out of the window," Dawn Song, a computer security entrepreneur and professor at the University of California, Berkeley, told the Collective[i] Forecast forum in October. "When public key cryptography is broken, users could be losing their funds and the whole system will break."

Quantum computers get their power by manipulating data stored on qubits, elements like charged atoms that are subject to the peculiar physics governing the ultrasmall. To crack encryption, quantum computers will need to harness thousands of qubits, vastly more than the dozens corralled by today's machines. The machines will also need persistent qubits that can perform calculations much longer than the fleeting moments possible right now.

But makers of quantum computers are working hard to address those shortcomings. They're stuffing ever more qubits into machines and working on quantum error correction methods to help qubits perform more-sophisticated and longer calculations.

"We expect that within a few years, sufficiently powerful computers will be available" for cracking blockchains open, said Nir Minerbi, CEO of quantum software maker Classiq Technologies.  READ MORE...