Rigetti Computing Inc., a startup developing quantum computers, today said that it has closed a $79 million round of funding led by Bessemer Venture Partners.

Franklin Templeton, Alumni Ventures Group and several other institutional investors participated in the round as well. Rigetti has raised more than $190 million to date. The latest round follows a $71 million funding in March when the company reportedly suffered a significant reduction in its valuation.

Berkeley, California-based Rigetti develops a quantum chip line called Aspen that’s based an approach known as superconducting quantum computing. The technique produces qubits, the quantum equivalent of bits, from circuits that are made out of superconducting materials and kept at temperatures near absolute zero. Google LLC’s Sycamore chip implements the same approach, as do systems from IBM Corp. and number of other players.

Rigetti is pursuing what it calls a “full-stack” strategy. The startup is not only designing quantum chips, but has also set up its own fabrication facility to produce them and makes software tools to help customers write code for the hardware. Rigetti is building out a partner ecosystem in parallel, partnering with other firms to make their software available to its users.

Another element of the startup’s strategy is that it invests in practical as well as theoretical research. Its in-house research team has discovered, among other things, an operating condition that helps improve the reliability of certain quantum computing operations. 

Rigetti offers access to its chips via a cloud platform. The startup’s hardware is also available via Amazon Braket, the quantum computing service Amazon Web Services Inc. introduced last year.

The biggest chip the startup has built to date features 32 qubits, nearly double what its previous most powerful chip provided. The new $79 million funding round will enable Rigetti to keep advancing its hardware as deep-pocketed rivals such as Google also work to increase the size and sophistication of their systems. 

“This round of financing brings us one step closer to delivering quantum advantage to the market,” Riggeti Chief Executive Chad Rigetti said in a statement. “The company is dually focused on building scalable, error-corrected quantum computers and supporting high-performance access to current systems over the cloud.”

Though quantum computing is still at an early stage, investors have shown a willingness to make long-term bets on startups working to unlock practical applications of the technology. Rigetti is the latest in a series of contenders that have raised funding.

Not all the players in this segment use the superconducting quantum computing approach favored by Rigetti and Google. PsiQuantum Corp., which in April disclosed that it has raised $215 million from investors, relies on light instead. The British startup has designed a silicon chip that uses photons as qubits and hopes to make a million-qubit chip within a few years.  

Photo: Rigetti