Cyclic order superpositions enable quantum information transmission through completely depolarizing channels

Noise fundamentally limits quantum communication capacity, completely preventing information transmission in fully depolarizing environments. While indefinite causal order theoretically circumvents this limitation, experimentally realizing multi-channel configurations for genuine quantum transmission remains challenging. Here we show the activation of quantum communication through completely depolarizing channels using a programmable silicon photonic chip. By implementing a superposition of cyclic orders across four completely depolarizing channels, we achieve an output state fidelity of 0.712 ± 0.013, which strictly exceeds the classical threshold of 2/3. This mechanism provides a powerful tool for overcoming extreme noise, offering broad potential for building robust quantum networks in highly decoherent environments. Noise severely limits quantum communication, particularly in completely depolarizing channels where information transmission is impossible. Here, the authors use a programmable silicon photonic chip to show quantum information transmission through multiple concatenated depolarizing channels by implementing a superposition of cyclic orders, achieving fidelities above the classical qubit threshold in a strongly noisy regime.