MIT Technology Review: This new startup has built a record-breaking 256-qubit quantum computer. QuEra Computing, launched by physicists at Harvard and MIT, is trying a different quantum approach to tackle impossibly hard computational tasks. The QuEra machine is the latest leap in scaling up quantum computing to make it more powerful and capable of tackling practical problems. More qubits mean more information can be stored and processed, and researchers developing the technology have been racing to continually raise the bar. In 2019, Google announced that its 53-qubit machine had achieved quantum supremacy—performing a task not manageable by a convention computer—but IBM challenged the claim. The same year, IBM launched its 53-bit quantum computer. In 2020, IonQ unveiled a 32-qubit system that the company said was the “world’s most powerful quantum computer.” And just this week IBM launched its new 127-qubit quantum processor, which the press release described as a “minor miracle of design.” “The big news, from my perspective, is it works,” says Jay Gambetta, IBM’s vice-president of quantum computing. Now QuEra claims to have made a device with far more qubits than any of those rivals. The ultimate goal of quantum computing, of course, is not to play Tetris but to outperform classical computers in solving problems of practical interest. Enthusiasts reckon that when these computers become powerful enough, perhaps in a decade or two, they might bring transformative effects in fields such as medicine and finance, neuroscience and AI. Quantum machines will likely need thousands of qubits to manage such complex problems. The number of qubits, however, is not the only factor that matters. QuEra is also touting the enhanced programmability of its device, in which each qubit is a single, ultra-cold atom. These atoms are precisely arranged with a series of lasers (physicists call them optical tweezers). Positioning the qubits allows the machine to be programmed, tuned to the problem under investigation, and even reconfigured in real time during the computation process. “Different problems are going to require the atoms to be placed in different configurations,” says Alex Keesling, QuEra’s CEO and co-inventor of the technology. “One of the things that’s unique about our machine is that every time we run it, a few times a second, we can completely redefine the geometry and the connectivity of the qubits.” https://www.technologyreview.com/2021/11/17/1040243/quantum-computer-256-bit-startup/