IBM has built the largest quantum computer yet. Dubbed Osprey, it has 433 qubits, or quantum bits, which is more than triple the size of the company’s previously record-breaking 127-qubit computer and more than eight times larger than Google’s 53-qubit computer Sycamore.
Though quantum computers hold the promise of eventually solving problems that conventional computers could never tackle, there is no consensus on the best way to make one. IBM and Google base their qubits on circuits made from superconductors that conduct electricity perfectly. Others champion devices that use unusually large atoms, charged atoms or quantum particles of light.
Building Osprey was more challenging than just making more qubits, says at IBM. Qubits can be disturbed by forces exerted on them by neighbouring qubits in a similar way to how “crossed wires” can make conventional computers malfunction. When more qubits are packed onto a chip, there are more chances for this to occur.
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Qubits within Osprey are controlled by connecting the chip to conventional electronics. Dial says he and his team designed these connections to keep the qubits in check as precisely as they could.
Since superconducting wires only superconduct at temperatures close to -273°C, Osprey must be kept inside a special fridge. Dial and his colleagues also had to make sure that the computer and all its wires didn’t raise the temperature even a little.
Researchers have high hopes for quantum computers because qubits, unlike conventional bits, can take on values of 0, 1 and, due to oddness of quantum mechanics, a combination of both simultaneously. This should allow them to perform computations that are too complex even for state-of-the-art supercomputers, such as simulating chemical reactions in subatomic detail.
In 2019, Google announced an apparent breakthrough in this direction when Sycamore solved a problem that the company claimed was impossible to complete on a conventional computer. This claim of “quantum supremacy” has been repeatedly challenged since.
Osprey has a lot more qubits than Sycamore and quantum computers become more powerful as they get bigger. In fact, a conventional computer would have to have more bits than there are atoms in the known universe to match the number of states Osprey has for storing and processing information.
“Building Osprey was an exploration of how large of a quantum chip we can really manufacture. It taught us that we really can put over 400 qubits on a chip and get that to work. That was a huge lesson in engineering,” says Dial.
“This [computer] shows that superconducting technology does scale,” says at Tufts University in Massachusetts. “But this is still what we’d call a noisy device. And noise may be the key word for quantum computers for a while.”
Physicists say quantum computers are noisy when they make errors as a result of the way qubits lose their quantumness over time. Love says that the big questions for him are whether computers like Osprey can be made to catch and correct their own errors and whether IBM could try to use it to demonstrate quantum supremacy as well.
Dial says that IBM’s team is on track to have a working quantum computer with 1121 qubits in 2023. Simultaneously, it is developing a smaller chip that will test a new way of arranging and connecting qubits with the aim of lowering noise and mitigating errors. “We are working on improving not just scale, but also quality and speed of our quantum computers,” he says.
