IQN (NewsDesk): IBM researchers have connected two 120 qubit Nighthawk R1 quantum processors using four superconducting cables, in a demonstration that could support larger modular quantum computers built from multiple chips.
The links, called L-couplers, span about 80 centimetres and transferred quantum states with an average fidelity of 99 percent, with the best link reaching 99.29 percent. According to a preprint posted on arXiv, the connections also supported entangling operations between qubits on separate processors. The researchers say this is the first demonstration of a multi channel quantum interconnect between large superconducting processors.
Full operations between the two chips, which combine two state transfers with three local two qubit gates, averaged 94.75 percent fidelity, below the roughly 99.5 percent typical on a single chip. The team says improving qubit coherence could push state transfer fidelity to between 99.68 and 99.77 percent, and noted that qubit stability, magnetic shielding and manufacturing all need further work before the approach can scale. The experiment connects only two modules so far.
