One embodiment provides a system for facilitating distribution of quantum keys. During operation, the system receives, from a requester, a first request for a key, wherein the first request indicates a requested length for the key and identifying information of the requester. The system determines whether a subset pool of a general pool of keys is allocated to the requester based on the identifying information of the requester, wherein the keys in the general pool are generated by a quantum engine. In response to determining that a subset pool is not allocated to the requester, the system allocates a subset pool to the requester. The system obtains from the allocated subset pool a key with a length matching the requested length, and the system returns the obtained key to the requester.