Cables between quantum chips: IBM links two processors with 80-centimeter connections
IBM says it transferred quantum states between two separate processors with an average fidelity of 99%, a step toward modular quantum computers.
Symbolic image · Photo: OJB Quantum / Wikimedia Commons, CC BY 4.0 (cropped and resized)
IBM has linked two separate quantum processors with superconducting cables and transferred quantum information between them, company researchers said in a blog post on Oct. 27. The experiment used two Nighthawk R1 processors housed in a shared cooling system. The four links, called l-couplers, are aluminum coaxial cables, each 80 centimeters long.
According to IBM, quantum state transfer across the links reached an average fidelity of 99%, peaking at 99.3%. Two-qubit operations between qubits on the two different chips averaged 94.75%. The results are described in a preprint on the arXiv server that has not yet appeared in a journal. So far, only a subset of the qubits on the chips is wired to the links.
Modularity matters because the number of qubits on a single chip is limited. If several processors can work together as one machine, that opens a path to larger, fault-tolerant quantum computers. IBM said the approach can scale to its planned fault-tolerant Starling computer. In August, the company reported that it had connected two separate cryogenic modules for the first time.