Tiny quantum computing processors built from silicon have finally surpassed 99 percent fidelity in certain logic operations (“gates”). Quantum computers store information in the quantum state of a physical system (in this case, two silicon qubits) then manipulate the quantum state to perform a calculation in a manner that isn’t possible on a classical computer. | |
Fidelity is a measure of how close the final quantum state of the real-life qubits is to the ideal case. If the fidelity of logic gates is too low, calculations will fail because errors will accumulate faster than they can be corrected. The threshold for fault-tolerant quantum computing is over 99 percent. | |
Three research groups demonstrated more than 99 percent fidelity for “if-then” logic gates between two silicon qubits (Nature, “Precision tomography of a three-qubit donor quantum processor in silicon”). This required precisely measuring failure rates, identifying the nature and cause of the errors, and fine-tuning the devices. |
The researchers used a technique called gate set tomography to achieve this in two of the three experiments. The technique combined the results of many separate experiments to create a detailed snapshot of the errors in each logic gate. | |
The researchers were able to make a precise determination of the error generated by different sources and fine-tune the gates to achieve error rates below 1 percent. | |
Quantum computing may be able to solve certain problems, such as predicting the behavior of new molecules, far faster than today’s computers. To do so, researchers must build qubits, engineer precise couplings between them, and scale up systems to thousands or millions of qubits. | |
Researchers expect qubits made of silicon to scale up better than the qubits used in today’s testbed quantum computers, which rely on either trapped ions or superconducting circuits. | |
Achieving high-fidelity logic gates opens the door to silicon-based testbed quantum computers. It also demonstrates the power of detailed error characterization to help users pinpoint error modes then work around or eliminate them. | |
Qubits – protected, controllable 2-state quantum systems – lie at the heart of quantum computing. Quantum computing processors are built by assembling an array of at least two (and hopefully someday thousands or millions) of qubits, with an integrated control system that can perform logic gates on each qubit and between pairs of qubits. Their performance and capability are limited by errors in the logic gates. | |
High-fidelity gates have low error rates. Once the error rate is less than a certain threshold – which scientists believe to be about 1 percent – quantum error correction can, in principle, reduce it even further. Beating this threshold in laboratory experiments is a major milestone for any qubit technology. | |
What kinds of errors are occurring is also a big deal for quantum error correction. Some errors are easier to eliminate or correct; others may be fatal. Quantum computing researchers from the Department of Energy (DOE)-funded Quantum Performance Laboratory worked with Australian experimental physicists to design a new kind of gate set tomography customized to a 3-qubit silicon qubit processor. They used it to measure the rates of 240 distinct types of possible errors on each of six logic gates. Of those possible errors, 95 percent did not occur in the experiments, and the remaining errors added up to less than 1 percent infidelity. | |
Research groups in Japan and the Netherlands reported similar results simultaneously, with the Dutch group also using the DOE-funded pyGSTi gate set tomography software to confirm their demonstration. |

News
Johns Hopkins Researchers Uncover a New Way To Kill Cancer Cells
A new study reveals that blocking ribosomal RNA production rewires cancer cell behavior and could help treat genetically unstable tumors. Researchers at the Johns Hopkins Kimmel Cancer Center and the Department of Radiation Oncology and Molecular [...]
AI matches doctors in mapping lung tumors for radiation therapy
In radiation therapy, precision can save lives. Oncologists must carefully map the size and location of a tumor before delivering high-dose radiation to destroy cancer cells while sparing healthy tissue. But this process, called [...]
Scientists Finally “See” Key Protein That Controls Inflammation
Researchers used advanced microscopy to uncover important protein structures. For the first time, two important protein structures in the human body are being visualized, thanks in part to cutting-edge technology at the University of [...]
AI tool detects 9 types of dementia from a single brain scan
Mayo Clinic researchers have developed a new artificial intelligence (AI) tool that helps clinicians identify brain activity patterns linked to nine types of dementia, including Alzheimer's disease, using a single, widely available scan—a transformative [...]
Is plastic packaging putting more than just food on your plate?
New research reveals that common food packaging and utensils can shed microscopic plastics into our food, prompting urgent calls for stricter testing and updated regulations to protect public health. Beyond microplastics: The analysis intentionally [...]
Aging Spreads Through the Bloodstream
Summary: New research reveals that aging isn’t just a local cellular process—it can spread throughout the body via the bloodstream. A redox-sensitive protein called ReHMGB1, secreted by senescent cells, was found to trigger aging features [...]
AI and nanomedicine find rare biomarkers for prostrate cancer and atherosclerosis
Imagine a stadium packed with 75,000 fans, all wearing green and white jerseys—except one person in a solid green shirt. Finding that person would be tough. That's how hard it is for scientists to [...]
Are Pesticides Breeding the Next Pandemic? Experts Warn of Fungal Superbugs
Fungicides used in agriculture have been linked to an increase in resistance to antifungal drugs in both humans and animals. Fungal infections are on the rise, and two UC Davis infectious disease experts, Dr. George Thompson [...]
Scientists Crack the 500-Million-Year-Old Code That Controls Your Immune System
A collaborative team from Penn Medicine and Penn Engineering has uncovered the mathematical principles behind a 500-million-year-old protein network that determines whether foreign materials are recognized as friend or foe. How does your body [...]
Team discovers how tiny parts of cells stay organized, new insights for blocking cancer growth
A team of international researchers led by scientists at City of Hope provides the most thorough account yet of an elusive target for cancer treatment. Published in Science Advances, the study suggests a complex signaling [...]
Nanomaterials in Ophthalmology: A Review
Eye diseases are becoming more common. In 2020, over 250 million people had mild vision problems, and 295 million experienced moderate to severe ocular conditions. In response, researchers are turning to nanotechnology and nanomaterials—tools that are transforming [...]
Natural Plant Extract Removes up to 90% of Microplastics From Water
Researchers found that natural polymers derived from okra and fenugreek are highly effective at removing microplastics from water. The same sticky substances that make okra slimy and give fenugreek its gel-like texture could help [...]
Instant coffee may damage your eyes, genetic study finds
A new genetic study shows that just one extra cup of instant coffee a day could significantly increase your risk of developing dry AMD, shedding fresh light on how our daily beverage choices may [...]
Nanoneedle patch offers painless alternative to traditional cancer biopsies
A patch containing tens of millions of microscopic nanoneedles could soon replace traditional biopsies, scientists have found. The patch offers a painless and less invasive alternative for millions of patients worldwide who undergo biopsies [...]
Small antibodies provide broad protection against SARS coronaviruses
Scientists have discovered a unique class of small antibodies that are strongly protective against a wide range of SARS coronaviruses, including SARS-CoV-1 and numerous early and recent SARS-CoV-2 variants. The unique antibodies target an [...]
Controlling This One Molecule Could Halt Alzheimer’s in Its Tracks
New research identifies the immune molecule STING as a driver of brain damage in Alzheimer’s. A new approach to Alzheimer’s disease has led to an exciting discovery that could help stop the devastating cognitive decline [...]