Efficient Quantum Secure Direct Communication Protocol Based on Quantum Channel Compression

The article presents the concept of quantum channel compression-decrease in the amount of qubits utilized in a protocol-which is achieved by means of data source encoding. It is also a report on an efficient quantum secure direct communication (QSDC) protocol, which is used for transferring predetermined cryptographic keys (e.g., keys that are generated by the algorithm of Advanced Encryption Standard). This type of quantum secure communication combines the ideas of dense coding process and quantum channel compression. It is justified that such a protocol obtains overall transfer efficiency over unity, i.e., over 100%.