Warren Buffett Has a New Favorite Quantum Computing Stock. (Hint: It's Not D-Wave or IonQ.)

Warren Buffett has never been one to jump on the bandwagon of a hot new technology. That isn't about to change with the legendary investor preparing to step down as Berkshire Hathaway's (NYSE: BRK.A) (NYSE: BRK.B) at the end of the year.

However, Buffett has a new favorite quantum computing stock. And it's not D-Wave Quantum (NYSE: QBTS) or IonQ (NYSE: IONQ).

Image source: The Motley Fool.

Buffett's new quantum computing favorite

By using the word "new," I implied that Buffett already had a favorite quantum computing stock. That's true. Prior to the third quarter of 2025, his Berkshire Hathaway portfolio featured one (and only one) stock of a company that's investing in quantum computing. I'm referring to Amazon (NASDAQ: AMZN).

Earlier this year, Amazon Web Services (AWS) announced the development of a new quantum computing chip called Ocelot, which can significantly reduce the costs associated with quantum error correction. AWS also offers cloud-based quantum computing services via its Amazon Braket platform.

However, Berkshire is now invested in another company involved in quantum computing. In Q3, the conglomerate bought more than 17.8 million Class A shares of Alphabet (NASDAQ: GOOG) (NASDAQ: GOOGL). This stake in Alphabet is worth more than $5 billion, more than twice the size of Berkshire's position in Amazon. Voila! Buffett has a new favorite quantum computing stock.

Alphabet's Google Quantum AI ranks among the leaders in advancing quantum computing technology. In 2019, the unit achieved its first major quantum computing milestone by performing a calculation in 200 seconds that it said would have taken the most widely used algorithms running on the most powerful supercomputers around 10,000 years to complete. Four years later, Google Quantum AI demonstrated for the first time a prototype of a logical qubit and showed how quantum error correction could reduce errors in quantum computing as more qubits are added.

A lot more than quantum computing

Did Buffett (or one of Berkshire's two other investment managers, Todd Combs and Ted Weschler) initiate a new position in Alphabet because of its quantum computing efforts? Probably not.

It's much more likely that Buffett and his team liked Alphabet's rock-solid advertising business. In the third quarter of 2025, advertising on Google, YouTube, the Google Network, and other platforms generated a whopping $74.2 billion of revenue.

Eight years ago, Buffett acknowledged that he regretted not buying shares of Google earlier. He said then that he should have recognized the company's great advertising business. His longtime business partner, the late Charlie Munger, was even more direct, stating, "I feel like a horse's ass for not identifying Google earlier ... We screwed up."

Does Buffett have to understand the technology behind Google Search of Alphabet's other apps to appreciate the value of its business? Not at all. He knows that attracting billions of users creates an audience that advertisers will pay big bucks to reach.

Should you buy Alphabet stock, too?

No one should buy any stock solely because a famous investor bought it. However, I think Alphabet is a great pick for Buffett and for other investors.

The company's advertising business remains strong. Alphabet is using artificial intelligence (AI) to its advantage. In particular, the integration of generative AI functionality into Google search appears to be paying off.

AI is also serving as a huge tailwind for Google Cloud. The just-announced launch of Google Gemini 3.0, its most powerful large language model (LLM) yet, could accelerate Google Cloud's momentum.

I also like the prospects for Alphabet's Waymo business. Waymo is the leader in the autonomous ride-hailing service market and continues to expand into new cities.

And, yes, I think quantum computing could present a major opportunity for Alphabet in the future. Alphabet isn't just Buffett's favorite quantum computing stock; it's mine, too.

Keith Speights has positions in Alphabet, Amazon, and Berkshire Hathaway. The Motley Fool has positions in and recommends Alphabet, Amazon, Berkshire Hathaway, and IonQ. The Motley Fool has a disclosure policy.