Achieving Ultimate Noise Tolerance in Quantum Communication

Quantum communication is the most advanced cryptographic method to distribute secret keys securely through public channels, but actual performance is still limited, due to noise. This study explores the ultimate noise tolerance of quantum communication by considering a method based on spectral, temporal, and spatial mode filtering of single photons with high efficiency. The authors also show that by actively filtering photons to a nearly single mode, quantum communication can occur in environments that are noisier by three orders of magnitude than what traditional methods tolerate. This approach could bring quantum communication under realistic conditions a step closer to reality.