Quantum Communication and the SETI Frontier: Coherent Qubits, 100-km Apertures, and Directed Interstellar Signals

To the point

Latham Boyle argues that the next SETI leap could be interstellar quantum communication with photon qubits that remain coherent, but it would require wavelengths shorter than 26.5 cm to beat the cosmic microwave background and telescope baselines around 100 kilometers, making detection possible only with extremely high angular resolution and potentially aided by Astronomically Long Baseline Interferometry and quantum repeaters.