IBM intends Starling to be able to perform computational tasks beyond the capability of classical computers. Starling will have 200 logical qubits, which will be constructed using the company’s chips. It should be able to perform 100 million logical operations consecutively with accuracy; existing quantum computers can do so for only a few thousand.
The system will demonstrate error correction at a much larger scale than anything done before, claims Gambetta. Previous error correction demonstrations, such as those done by Google and Amazon, involve a single logical qubit, built from a single chip. Gambetta calls them “gadget experiments,” saying “They’re small-scale.”
Still, it’s unclear whether Starling will be able to solve practical problems. Some experts think that you need a billion error-corrected logical operations to execute any useful algorithm. Starling represents “an interesting stepping-stone regime,” says Wolfgang Pfaff, a physicist at the University of Illinois Urbana-Champaign. “But it’s unlikely that this will generate economic value.” (Pfaff, who studies quantum computing hardware, has received research funding from IBM but is not involved with Starling.)
The timeline for Starling looks feasible, according to Pfaff. The design is “based in experimental and engineering reality,” he says. “They’ve come up with something that looks pretty compelling.” But building a quantum computer is hard, and it’s possible that IBM will encounter delays due to unforeseen technical complications. “This is the first time someone’s doing this,” he says of making a large-scale error-corrected quantum computer.
IBM’s road map involves first building smaller machines before Starling. This year, it plans to demonstrate that error-corrected information can be stored robustly in a chip called Loon. Next year the company will build Kookaburra, a module that can both store information and perform computations. By the end of 2027, it plans to connect two Kookaburra-type modules together into a larger quantum computer, Cockatoo. After demonstrating that successfully, the next step is to scale up and connect around 100 modules to create Starling.
This strategy, says Pfaff, reflects the industry’s recent embrace of “modularity” when scaling up quantum computers—networking multiple modules together to create a larger quantum computer rather than laying out qubits on a single chip, as researchers did in earlier designs.
IBM is also looking beyond 2029. After Starling, it plans to build another, Blue Jay. (“I like birds,” says Gambetta.) Blue Jay will contain 2000 logical qubits and is expected to be capable of a billion logical operations.