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Quantum computing offers the promise of being the next big technological breakthrough after artificial intelligence (AI). The technology has drawn the interest of the U.S. government, which has been investing in the sector. Meanwhile, investors can buy the stocks of several public companies that are attempting to develop fault-tolerant quantum computers using a variety of different techniques.
Five of the best-known pure plays in the space are IonQ (NYSE: IONQ), Quantinuum (NASDAQ: QNT), Rigetti Computing (NASDAQ: RGTI), Infleqtion (NYSE: INFQ), and D-Wave Quantum (NASDAQ: QBTS). Let’s consider which of these quantum stocks looks like the best buy.
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IonQ and Quantinuum
All quantum computers are built around qubits, which are extremely sensitive to even the slightest external interference. As a result, their computations have high error rates. The error-reduction and error-correction problems are among the chief challenges faced by every company trying to make quantum computing practical.
The two companies at the forefront of accuracy, though, are IonQ and Quantinuum. Both companies use trapped-ion technology: Each qubit in their computers is made out of an individual charged atom (aka, an ion). This method results in qubits that are more stable than qubits created using other techniques. The result is that IonQ has achieved 99.99% 2-qubit gate fidelity (a standard metric for quantum computing accuracy), while Quantinuum sits at 99.92%.
The companies differ primarily in how they hold their qubits in place. IonQ uses a combination of lasers and microwave antennas built into its chips, while Quantinuum employs only lasers, arguing that microwave antennas slow computational speed too much.
Quantinuum is known for its comprehensive software stack, while IonQ has been developing an entire quantum ecosystem, having made acquisitions in quantum sensing, networking, and satellite transmission. It is even in the process of acquiring quantum chip foundry SkyWater Technology, a deal that will enable it to manufacture its own chips in-house and become vertically integrated.
Rigetti Computing
Rigetti is pursuing one of the more common approaches to quantum computing: superconducting qubits. These are electronic circuits that can be made in conventional semiconductor fabs. While they must be brought to temperatures near absolute zero in order to operate, which requires expensive dilution refrigerators, they are controlled by microwave pulses, and the qubits don’t need bulky lasers to hold them in place.
The big advantage is that this technique provides much faster speeds than trapped-ion and other approaches. The disadvantage is that Rigetti lags in accuracy, with 2-qubit fidelity currently around 99.1% for its new Cepheus-1-108Q system. While that may sound close to the level that IonQ has reached, in the world of computing, it is considered way behind.
Infleqtion
Infleqtion has carved out a niche in quantum sensing and precision timing tools, giving it a solid revenue base as it pursues the development of a fault-tolerant quantum system using neutral-atom technology. Similar to trapped-ion technology, it creates each qubit out of an individual atom. But because it uses atoms that are not charged, they don’t repel each other. This allows neutral-atom systems to operate with higher qubit densities.
Right now, Infleqtion’s technology sits between trapped-ion and superconductor techniques. Its technology is faster than the trapped-ion approach but much slower than superconducting qubits. Meanwhile, the 99.73% 2-gate fidelity it recorded in 2024 is much better than Rigetti’s but still meaningfully trails its trapped-ion peers.
D-Wave Quantum
D-Wave Quantum has established itself as a leader in quantum annealing, which offers a niche solution for solving optimization problems. Because the technology is more mature and less complex, the company has already started to commercialize its systems, which can be particularly useful for certain industries like finance and logistics, where finding the most efficient solutions to complex problems (or even a solution that’s close to the best) can provide a company with competitive advantages.
Meanwhile, following its acquisition of Quantum Circuits, D-Wave is looking to apply what it learned in developing quantum annealing to superconducting qubit architecture. It plans to use Fluxonium qubits, which can remain in their quantum states longer, and a dual-rail gate-model processor with built-in error detection. It believes that by combining these technologies, it can create a system with the accuracy of a trapped-ion system and the speed of superconducting qubits.
The verdict
Ultimately, for those who want to invest in this still-speculative technology, taking a basket approach could prove to be a wise course, as no one knows yet which of the many qubit technologies will reach fault tolerance and commercial viability first. However, if I could only invest in one quantum stock, it would be IonQ. It has the accuracy lead today, and I think its ecosystem and vertically integrated approach should give it an advantage.
