Why in News? 

• For the first time, quantum messages have been successfully transmitted over 254 km in Germany, using existing commercial telecommunication infrastructure. 

About the Recent Development 

• The communication was enabled through optical fiber cables, without the need for cryogenic cooling. 
• It used a coherence-based twin-field quantum key distribution, which facilitates the distribution of secure information over long distances. 
• This demonstration indicates that advanced quantum communication protocols, which exploit the coherence of light, can be made to work over existing telecom infrastructure.