On Monday, IBM announced that it has produced the two quantum systems that its roadmap planned to release in 2023. One is based on a chip named Condor, which is the largest transmon-based quantum processor released to date, with a capacity of 1121 qubits. The second is based on a mix of three Heron chips, each containing 133 qubits. Smaller chips like Heron and its successor Flamingo will play a crucial role in IBM’s quantum roadmap – which also received a significant update today.
Qubits and Logical Qubits
Every aspect of working with qubits suffers from errors. Adjusting their initial state, maintaining that state, performing operations, and reading the state can all introduce errors that prevent quantum algorithms from producing useful results. Therefore, the main focus for every company producing quantum devices has been to reduce these errors, and significant progress has been made in this regard.
There is some evidence that this progress has brought us to the point where some simple quantum algorithms can now be executed on existing devices. This potential is likely to expand to include more algorithms thanks to improvements we can expect over the next few years.
Qubits and Gates
Jambita stated that the company is following two approaches to prepare its devices. One aspect of that is developing the ability to manufacture high-quality qubits in large numbers continuously. He noted that Condor with over 1000 qubits is proof that the company is in good shape in this regard. “It has 50 percent smaller qubits,” Jambita told Ars. “The yield is very high – we achieved nearly 100 percent yield.”
The second aspect that IBM has worked on is reducing the errors that occur when performing operations on individual qubits or pairs of qubits. These operations, known as gates, can be susceptible to the same errors. Changing the state of a qubit can produce weak signals that can spill over to neighboring qubits, a phenomenon known as crosstalk. Heron, the smaller of the new processors, represents a four-year effort to improve gate performance. “It’s a beautiful device,” said Jambita. “It’s five times better than previous devices, and the errors are much lower, and crosstalk can’t be measured in a real way.”
Many of the improvements rely on introducing tunable couplers to the qubits, a change from the fixed-frequency devices the company previously used. This has increased the speed of all gate operations, with some seeing a tenfold increase. The less time you spend doing anything with the qubit, the less chance there is for errors to occur.
Many of these improvements have been tested on several iterations of the Eagle chip that was first introduced in 2021. The company’s new roadmap will see the release of an improved 133-qubit Heron chip next year that will enable 5000 gate operations. This will be followed by several iterations of a 156-qubit Flamingo processor next year that will bring gate operations up to 15000 by 2028.
These chips will also be linked in larger processors like Crossbill and Kookaburra, which also appear in IBM’s roadmap (for example, seven Flamingo devices could be linked to create a processor with a similar number of qubits as the current Condor). The focus here will be on testing different ways to connect qubits, whether within chips or between them.
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