What is Q-day and why should investors be getting ready for it?

By Graeme Coles-Andrew
3rd December 2025

Related topics: Alphabet [NASDAQ:GOOGL], Saxo Markets, The technology sector, International Business Machines [NYSE:IBM]

What is Q-day and why should investors be getting ready for it?

For years, the notion of “Q-day” — the moment when a quantum computer becomes powerful enough to crack widely used encryption — has belonged more to the realm of speculative fiction than imminent geopolitical risk.

Now, as advances in quantum hardware accelerate and governments race to fund post-quantum defences, the once-remote scenario is being pencilled into timelines rather than dismissed outright. Some analysts, particularly in the more excitable corners of the cybersecurity world, caution that Q-day could feasibly arrive as early as 2026.

Others insist that is far too soon. Yet the direction of travel is unmistakable: quantum capability is growing faster than many expected, and the global digital infrastructure remains perilously dependent on cryptographic systems designed for a pre-quantum age.

A 2026 Q-day featured as one of Saxo’s outrageous predictions in its annual pre-Christmas review of unlikely – but fascinating – outcomes for next year. It is also discussed in our upcoming podcast with fund manager WisdomTree. Saxo rightly forecasts that Q-day has the potential to be highly disruptive to financial markets and the banking sector were it to arrive early.

Should you be worried about Q-day?

To be clear, a fully functioning cryptographically destructive quantum computer, capable of running Shor’s algorithm on the scale needed to break RSA, ECC and other public-key standards, does not yet exist. The engineering hurdles remain formidable: qubits are unstable, error correction is computationally expensive and today’s machines are still experimental prototypes.

But the pace of improvement has surprised even seasoned observers. IBM NYSE:IBM, Google NASDAQ:GOOGL and a collection of well-funded start-ups are scaling qubit counts while simultaneously reducing error rates. More importantly, governments, notably America, China and the EU, are now treating quantum supremacy as a strategic priority. History suggests that when national-security budgets meet rapid technological progress, breakthroughs have a habit of arriving earlier than expected.

Whether 2026 is a realistic Q-day or merely a useful prod for policymakers depends largely on one’s tolerance for risk. Cryptographers tend to be conservative: they argue that because encrypted data harvested today can be stored and decrypted later, the mere possibility of quantum decryption within a decade is enough to warrant urgent migration to post-quantum standards. Financial institutions, healthcare systems and governments hold data with “long life” sensitivity, information that remains valuable for decades. A quantum breakthrough in 2032 would still compromise data stolen in 2024. The timeline, in other words, is already uncomfortably tight.

Yet The Armchair Trader’s sober view is that Q-day in 2026 is unlikely, but no longer inconceivable. Quantum computing may not be ready to break the world’s cryptography in two years, but it is certainly close enough to demand serious contingency planning. And markets, always alert to shifts in technological power, are beginning to reflect this.

Is there an opportunity here for the small investor?

One area of opportunity for retail investors lies in post-quantum cybersecurity. Firms developing lattice-based encryption, quantum-safe key distribution and hybrid cryptographic systems are attracting attention. Some are publicly listed; others are tucked inside larger defence and software groups. The transition to post-quantum standards is shaping up to be a multi-year, multi-billion-dollar overhaul, akin to the cybersecurity build-out of the early 2010s.

Retail investors can access this theme through specialist cybersecurity ETFs or through selective exposure to companies explicitly working on quantum-resistant protocols.

A second opportunity sits in the quantum-hardware supply chain itself. While pure-play quantum-computing start-ups tend to be private, several enabling technologies are accessible in public markets: cryogenics manufacturers, advanced materials specialists, semiconductor fabrication tools and precision measurement firms. These companies benefit regardless of which quantum contender eventually triumphs; they sell the picks and shovels of the quantum gold rush.

Still, investors should temper enthusiasm with caution. Quantum computing is a field littered with ambitious timelines and delayed milestones. The path to Q-day will be uneven, uncertain and occasionally overhyped. But that does not diminish its significance. Whether it comes in 2026 or later, the moment when quantum machines render today’s cryptography obsolete will reshape digital security, economic power and geopolitics. Prudent investors (and prudent governments)would do well to prepare before the countdown ends.

Make sure you sign up for our podcast to catch our upcoming episode on quantum computing with WisdomTree’s Elvira Kuramshina.