IonQ vs. Quantinuum: Which Quantum Computing Accuracy-Leading Stock Looks Like the Better Buy?

When it comes to quantum computing, one of the biggest hurdles companies face is that today's systems remain very error-prone. This stems from the fact that quantum computing technology replaces fixed computing bits, which can only be 0 or 1, with qubits.

Qubits have two unique properties that give them super-fast processing speeds but also make them sensitive to external interference, leading to calculation errors. The first is that they are in a superposition state, meaning they can be 0 or 1 simultaneously until measured.

The second is that they are entangled. This allows qubits to share information instantly, accelerating complex calculations, but it also means a single error can quickly compound and corrupt the entire system.

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Companies are pursuing several technological approaches to build lightning-fast, fault-tolerant quantum systems. The technology that has shown the best accuracy thus far is the trapped-ion approach. The technique starts with the use of actual atoms, which by nature are identical and thus less fragile than artificial qubits. The atoms are then ionized (one electron is removed), placed in a trap, and held in place using lasers and other methods.

Two companies at the forefront of this method are IonQ (NYSE: IONQ) and Quantinuum (NASDAQ: QNT), which have demonstrated among the highest accuracy with their systems. IonQ has achieved 99.99% 2-qubit gate fidelity, while Quantinuum has recorded 99.9975% 1-qubit gate fidelity and 99.92% 2-qubit gate fidelity. And while those numbers sound extremely accurate, the average computer chip in your phone or computer has an error rate of far less than 1 in a quadrillion, so the technology still has a long way to go to get to where it needs to be.

Both IonQ and Quantinuum use trapped-ion technology but are taking slightly different approaches. Let's take a deeper look at both and decide which quantum computing stock is the better buy.

IonQ

IonQ's 99.99% 2-qubit gate fidelity makes it the leader in 2-qubit gate accuracy. This was a huge milestone, as 99.99% 2-qubit gate fidelity is generally the benchmark at which companies can start pursuing error-correcting techniques beyond hardware solutions.

The company's accuracy achievement can largely be attributed to its acquisition of Oxford Ionics and its proprietary Electronic Qubit Control (EQC) technology. This allowed IonQ to go from just holding its trapped ions in place with lasers to also using microwave antennas built directly on its chips. This improved stability and allowed it to shrink the size of its systems, which will become important down the road as it looks to commercialize them.

IonQ's accuracy leadership is not the only reason to like the stock, though. The company is trying to control the entire quantum ecosystem and has made acquisitions in quantum sensing, networking, and satellite transmission. It is also in the process of acquiring quantum foundry SkyWater Technology to vertically integrate its operations. This will also allow it to quickly test prototype chips and help it scale more quickly when it is ready to commercialize its systems.

Quantinuum

While Quantinuum slightly trails IonQ in 2-qubit fidelity, the company has eschewed embedding microwave antennas directly into its chips to hold the trapped ions in place, arguing that microwave gates are too slow compared to laser-based gates and that speeding them up would use too much power. The one big downside to using the trapped-ion method is that it is slower than other quantum computing techniques, so it makes sense that the company wouldn't want to further slow it down.

Beyond its strong accuracy, Quantinuum is also known for its robust software stack. This includes Guppy, an open-source quantum computing language that performs error correction in the code, and TKET, a quantum software development kit that acts as a universal translator. Its Nexus cloud-based operating system then ties everything together in an easy-to-use package.

The verdict

Quantum computing is still in its infancy, and which technologies and companies emerge as winners is still very much in the air. I like the trapped-ion approach given its accuracy lead, but there is no guarantee it will ultimately win out.

Both IonQ and Quantinuum have similar $20 billion market caps, and if I could only choose one, it would be IonQ, given its accuracy lead and vertical integration. That said, I think investors can take small speculative positions in both stocks and keep them tucked away for the future.

Geoffrey Seiler has no position in any of the stocks mentioned. The Motley Fool has positions in and recommends IonQ and SkyWater Technology. The Motley Fool has a disclosure policy.