Field Implementation of Higher Dimensional Time-bin Encoded Quantum Key Distribution Within IISc Campus

This paper discusses the field deployment of higher-dimensional time-bin encoded quantum key distribution (HD-QKD) within IISc campus using the IISc campus-wide fiber backbone. The QKD link is set-up between ECE and DESE departments with a total loss of 9 dB. The quantum channel and a parallel bidirectional classical channel are employed for secure key exchange and clock synchronization / transmitter-receiver coordination respectively. The HD-QKD implementation demonstrates four times increase in the secret key rate while maintaining tolerable quantum bit error rate using higher-dimensional encoding compared to conventional qubit-based schemes. The QKD system establishes good operational stability in the real-world scenario tested over a duration of at least one hour. This study lays the groundwork for real-world quantum communication solutions.