A quantum computer can’t play Doom (yet), but we’re getting closer

Doom has long held a unique place in tech culture. Since its 1993 release, the first-person shooter has found itself at the center of countless hardware experiments. From running on a WiFi-enabled toothbrush to being powered by 100 pounds of moldy potatoes, enterprising coders have pushed the game to its limits. But what about running Doom on a quantum computer?

Enter Quandoom, an audacious project from GitHub user Lumorti, which takes Doom to an entirely new level by attempting to run it on quantum computing hardware.

Doom meets quantum computing

Quantum computing, while still highly experimental and in its infancy, holds immense potential for computing power. But it’s not ready for Doom—or any game, really—just yet. While Lumorti, who works as a quantum computing researcher at the Institute of Photonic Sciences (ICFO) in Barcelona, developed Quandoom, a version of Doom’s first level adapted for quantum hardware. The catch? There isn’t a quantum computer powerful enough to run the game as it stands.

Quandoom requires a whopping 72,376 qubits and 80 million quantum gates to operate. For reference, the most advanced quantum computer available today, from Atom Computing, supports just 1,225 qubits. That’s a long way from the 70,000+ qubits required for Quandoom, making this an experiment firmly planted in the theoretical realm.

That said, thanks to QASM, a quantum assembly simulator, it is possible to simulate the game on classical computers. This allows regular users to run Quandoom on a laptop—albeit at 10 to 20 frames per second and without many of the modern gaming comforts we’re used to, like music or enemies moving between rooms.

What it takes to port Doom to quantum

One look at the technical requirements for Quandoom, and it’s clear: this is not your standard port. According to Lumorti’s GitHub page, creating Quandoom was a massive coding challenge. The game was written in 8,000 lines of C++ and includes quantum subroutines for rendering the game, handling player movement, and interacting with game objects. To give a glimpse of just how complex this is, Lumorti shared some of the code’s functionality:

“For now, I’m still tidying up the engine code, but basically, I have about 8,000 lines of C++ functions allowing a number of reversible binary and arithmetic operations on quantum registers, for example ‘flipIfLessThanOrEqualTo,’ which flips all qubits in a register if the value of another register is less than some given value.”

There’s also a parallelization system at play, splitting the rendering process across multiple cores. Even though the game is only a wireframe version of Doom’s first level, it’s remarkable to consider that quantum computing’s parallelization capabilities—which allow it to process multiple possibilities simultaneously—could be harnessed for gaming one day.

Challenges and simplifications in “quantum doom”

It’s important to remember that Quandoom is far from the Doom experience that most gamers know and love. The graphics are simplified to basic wireframes, and many features of the original game have been left out or significantly altered. As Lumorti himself puts it, there’s no music or sound, enemies don’t move between rooms, and the iconic imp fireball now behaves as a hitscan instead of a projectile.

Still, the idea behind Quandoom isn’t necessarily to replicate the Doom experience but to explore what’s possible on quantum hardware. As Lumorti noted:

“Everything is done with integers. Using such functions, I then wrote a small 3D engine as well as all the game logic.”

This means that while Quandoom may not offer the same gameplay depth as the original, it showcases the potential for quantum computing in fields outside of its typical research applications, such as gaming.

A quantum future for gaming?

While we’re still a long way off from full-fledged games running on quantum hardware, projects like Quandoom show that we’re starting to think about the possibilities. For now, Doom running on a toothbrush or a conference badge is still far more practical, but the day may come when quantum gaming becomes a reality. Until then, we’ll just have to be content with QASM simulators and simplified graphics.