Provided are a device and a method performed by the device to correct an error in a quantum communication system. The method is characterized by comprising: transmitting a random access (RA) preamble to another device; receiving a random access response (RAR) from the other device as a response to the RA preamble; performing a radio resource control (RRC) connection procedure with the other device; and transmitting data to the other device, wherein the data is encoded on the basis of key information, the error is measured on the basis of a test pulse, and the key information is distributed to the device and the other device on the basis of the error being corrected using an improved Faraday rotator mirror of the device.