Designing more efficient quantum circuits with Claude

Quantum computers will need carefully designed circuits to run useful algorithms on limited hardware. We gave Claude plain-language specifications for eight such circuits, drawn from chemistry, optimization, physics simulation, and number theory, along with an automated evaluator that checks and scores each design. Working largely on its own, Claude found designs that improve on the best published circuits, in some cases by an order of magnitude or more. Such improvements substantially reduce the quantum resources that useful applications require, so practical quantum computers could arrive sooner than previously anticipated.

This work was led by Andi Gu as part of Anthropic’s STEM Fellows Program, with mentorship from Alek Kemeny, a quantum physicist at Anthropic, in collaboration with Susanne Yelin (Harvard University) and Mikhail Lukin (Harvard University and QuEra Computing). Read the full paper on arXiv .

Unlike classical computers, which store information in bits whose value is either 0 or 1, quantum computers store information in qubits, which can be built from single atoms, superconducting circuits, or particles of light. These qubits make use of quantum phenomena such as superposition —which allows a quantum system to exist in a combination of states at once—in order to process information in ways that could make certain problems in fields like chemistry, materials science, and number theory tractable, even when they are too hard for traditional computers.

The quantum computers the field has built to date only have hundreds to thousands of qubits—too few to run many of the algorithms that promise practical advantages over classical computers. And these qubits are highly sensitive to environmental noise, such as heat, vibration, and even cosmic rays. A tiny disturbance can nudge a qubit’s state, and these small errors pile up until the computer gives the wrong answer.

Given that both qubits and computing time are scarce resources, researchers have been working to redesign quantum algorithms to use fewer qubits and complete computations in less time. An illustrative example is simulating FeMoco, the iron–sulfur cluster at the heart of nitrogenase, the enzyme that bacteria use to turn nitrogen from the air into ammonia. Understanding how it works could help scientists design better industrial catalysts—the substances manufacturers use to speed up chemical reactions.

In 2017, researchers estimated that a quantum computer would need about 50 trillion Toffoli gates to compute FeMoco’s ground-state energy—the energy of its most stable configuration, which chemists need in order to predict how FeMoco reacts. (Similar to ordinary computers, quantum computers work by applying a long sequence of simple operations, called gates, to their qubits. The Toffoli gate is one of the most expensive gates to run, so counting Toffoli gates is a standard way to estimate how long a computation will take.)