Quantum computing may still largely be in the theoretical domain, but the money that it’s attracting is very real.

Riverlane, a specialist in quantum error correction technology, has raised $75 million to continue expanding its R&D and operations to build its operations amid a surge of interest from quantum computing customers — technologists hard at work building what could be the next great leap in computing power, if only they can tame those fail rates.

Riverlane believes it holds the answer to that problem: The startup is building technology that fits on chips used in quantum computing systems and can track, predict and fix the errors generated by quantum bits (known as qubits).

“Even five years ago, I would have said that only one of these qubit types is going to work,” said Steve Brierley, Riverlane’s founder and CEO, in an interview in his Cambridge office. “But actually, what we’ve seen is they’ve all progressed [along a] Moore’s Law rate. It seems to me that the pieces are in place to get to the first generation of error-corrected quantum computers. And this will be really significant because it will be the first time that a quantum computer goes beyond the capability of any supercomputer.”

Sources close to the company told TechCrunch that with this round, Cambridge, England-based Riverlane’s valuation is now above $400 million.

And for a company that is working on breaking completely new ground in a cutting-edge field, it’s achieved another kind of first with this fundraise: It’s the first quantum computing startup in Europe to raise a Series C.

In itself, this is a signal that — while quantum computing specialists are still working to scale their models — the industry is moving into more mature, growth funding on the heels of confidence and commitment that they will.

A trio of investors that describe themselves as focused on sustainability are coming in as first-time backers of the startup with this round. Planet First Partners is leading the Series C, with participation from ETF Partners and Singapore’s EDBI. Previous backers Cambridge Innovation Capital (CIC), Amadeus Capital Partners, the UK’s National Security Strategic Investment Fund (NSSIF), and Altair also invested.

Quantum computing efforts are somewhat based on a leap of faith, as much of the concept has been proven only on smaller-scale efforts. Founded by Brierley while he was still a research fellow at Cambridge, where he had been researching how to solve the problem of error rates, Riverlane is very much part of that continuum.