fredkin_sort_network

GitHub

hardgate countText

results

Measured by total gate count — lower is better.

128 gates53 gates

sota

Claude-Opus-4.6

reward 0.960

Usage

Run the reference answer to verify your environment is set up correctly

$ harbor run -p tasks/fredkin_sort_network

Test model

$ harbor run -p tasks/fredkin_sort_network \
  -a claude-code -m claude-opus-4-6

Description

Build a reversible circuit that stably sorts four 2-bit unsigned values using as few gates as possible. The available gate set includes NOT, CNOT, Toffoli, and Fredkin gates. All scratch wires must be restored to zero, inputs must be preserved, and the circuit must produce correct output for all 256 possible inputs.