Quantum computing investing is an incredibly speculative space, but if you pick the right company, you could be rewarded with incredible results. On the flip side, if you pick the wrong stock, the investment could go to zero.
There are also two types of companies in this realm: Pure-plays and legacy big tech. Legacy big tech includes companies like Alphabet and IBM that are getting into the quantum computing race, and have businesses to fall back on if their quantum computing endeavors don't pan out. These are much safer investments, but don't have near the upside potential as investing in pure-plays like IonQ (IONQ 0.21%) or Rigetti Computing (RGTI 2.78%).
Both of these are popular pure-play quantum computing stock picks, but does one offer a more compelling investing case than the other? Let's find out.

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The two are taking fundamentally different paths
Rigetti Computing and IonQ are taking two different approaches to quantum computing.
Rigetti Computing is using superconducting quantum computing, which is the approach that many companies are taking, including most of the legacy tech businesses. This technique cools a particle down to absolute zero, then uses its quantum mechanics for calculations. Cooling a particle down to absolute zero isn't cheap, so this gives IonQ an advantage.
IonQ uses a trapped ion approach, which can be done at room temperature. Furthermore, IonQ's trapped ion approach is far more accurate, and IonQ holds world records in one-qubit and two-qubit gate fidelity tests, which measure how accurate a quantum computer is. IonQ's two-qubit gate fidelity sits at 99.97%, while Rigetti's system has a 99.5% two-qubit gate fidelity. While IonQ's advantage may not sound like much, that extra 0.47% is incredibly difficult to come by and shows the inherent accuracy advantage of the trapped ion approach.
However, IonQ's accuracy advantage isn't without its drawbacks. Superconducting quantum computing has far better processing speeds. So, the question of which technology will become commercially relevant boils down to what the market wants.
For a quantum computer to be commercially viable, it must be accurate. This makes IonQ seem like the better buy. However, if Rigetti can reach an accuracy level that's on par with IonQ -- say, a year or two later -- IonQ may not have established a strong enough foothold to hold off a competitor with superior processing speed.
It's impossible to predict the winner of this outcome years before it happens. Both Rigetti and IonQ point toward 2030 as being a turning point in quantum computing relevance, and predicting that far out is a fool's errand. As a result, there may be a better option than picking just Rigetti or IonQ.
Picking both stocks increases the odds of success
Instead of picking one or the other, I'd advise that investors purchase both. That way, if one succeeds while the other flops, the entire investment isn't worthless. Furthermore, the winner of the quantum computing race is likely to provide massive returns, and one gigantic winner can outweigh a lot of losers. This balanced approach decreases the risk in investing in an emerging trend like quantum computing.
Another way to invest in both companies while also grabbing some others in the quantum computing realm is by purchasing a quantum computing ETF. This investment basket is filled with stocks that are investing in the quantum computing realm, including legacy tech players. While the upside for this investment isn't as great, it doesn't have nearly the downside, because some large companies won't go belly-up if they fail to deliver a successful quantum computing solution.
While I like IonQ's chances a bit more, I can't ignore Rigetti Computing or some of its other peers. That's why I think taking a balanced approach to this industry is a smart idea, and that approach has a much better chance of getting investors positive returns compared to just picking a single pure-play.