Google's verifiable quantum circuit compilation competition

While quantum computing holds the key to solving some of our most complex scientific challenges, current hardware is still limited by qubit counts and gate errors. Quantum error correction can overcome those errors, but it adds substantial overhead to every qubit and gate an algorithm uses. That makes circuit size one of the biggest factors in when a quantum algorithm becomes practical: every qubit and gate we remove lowers the bar that hardware must clear. To bring real-world quantum applications within reach sooner, it is critical to first compress the circuits that power them.

To help bridge this gap, the Google Quantum AI team is launching a competition on Kaggle challenging you to use AI to build smaller, more efficient quantum circuits. The competition is powered by kickmix, our new open source C++20 and Python library in Qualtran for efficiently building and testing large quantum circuits. Our companion paper, Leveraging verifiable structure in quantum circuits to find more efficient compilations with agentic AI, describes the approach in detail.

In the past, optimizing quantum algorithms meant domain experts meticulously tuning circuits by hand and publishing incremental wins one paper at a time. Today, agentic AI can search for more efficient circuits automatically, but such results can only be trusted when candidate circuits can be efficiently verified for correctness. For arbitrary quantum circuits, classical verification is intractable because quantum gates create superpositions over exponentially many classical bitstrings. Fortunately, many of the most expensive subroutines in fault-tolerant algorithms can be built within a structured subclass of circuits, called “kickmix” circuits, which we introduced in our earlier work. Built from reversible classical logic, diagonal phase gates, and measurement-based uncomputation, kickmix circuits map each input bitstring to a single output bitstring and phase without creating new superpositions. A classical computer can therefore run randomized fuzz testing on bitstring inputs in linear time to establish the circuit’s approximate correctness on full quantum states with high confidence.

Randomized fuzz testing does not prove exact equivalence, but most quantum algorithms can tolerate a small, bounded error. In fact, using approximations can cut gate and qubit counts significantly. Finding such approximations by hand is tedious, making it a great task for AI agents. With kickmix in Qualtran, agents can build large circuits quickly and fuzz test them at 60 billion gates per second on a single CPU core.

The competition features three benchmarks, each targeting a major kickmix bottleneck in a useful quantum algorithm in order to call attention to the broad utility of this verification paradigm. For each benchmark, we provide a reference baseline circuit and a standalone verifier, both open source under the Apache 2.0 license. Your goal is to submit a circuit that passes the verifier while minimizing a cost score based on its qubit and gate counts: