Quantum key distribution (QKD) promises unconditionally secure communications, however, the low bit rate of QKD cannot meet the requirements of high-speed applications. Despite the many solutions that have been proposed in recent years, they are neither efficient to generate the secret keys nor compatible with other QKD systems. This paper, based on chaotic cryptography and middleware technology, proposes an efficient and universal QKD protocol that can be directly deployed on top of any existing QKD system without modifying the underlying QKD protocol and optical platform. It initially takes the bit string generated by the QKD system as input, periodically updates the chaotic system, and efficiently outputs the bit sequences. Theoretical analysis and simulation results demonstrate that our protocol can efficiently increase the bit rate of the QKD system as well as securely generate bit sequences with perfect statistical properties. Compared with the existing methods, our protocol is more efficient and universal, it can be rapidly deployed on the QKD system to increase the bit rate when the QKD system becomes the bottleneck of its communication system.
We suggest a combined modulation quantum key distribution (QKD) system which encodes each single-photon signal with both phase modulation and polarization modulation. With the aid of dual-velocity protocol of hybrid QKD system, we construct a scheme to realize this combined modulation QKD which generates two-bit key with one signal for increasing the efficiency of QKD. We also develop a combined modulation Michelson QKD system, then solve the stability problem of the combined modulation QKD system in principle.
This letter proposes a novel modulation signaling-based quantum key distribution (QKD) protocol that employs eight phases of the optical carrier, therefore named octa-phase shift keying QKD (8PSK-QKD). The proposed QKD protocol shares two key bits simultaneously and consequently exhibits increased spectral efficiency compared to existing modulation signaling-based QKD protocols. Different performance metrics, viz., probability of sifted keys (
Psift), quantum bit error rate, probability of sifted keys of Eve, and Eve’s error probability (
Peve), are determined using a novel analytical framework for a free-space optical channel under the combined effect of atmospheric turbulence and pointing error. To inspect the potential of the system, the 8PSK-QKD system is compared with the quadrature phase shift keying-based QKD (QPSK-QKD) and subcarrier intensity modulation binary phase shift keying-based QKD (SIM/BPSK-QKD) systems. Numerical results reveal that the 8PSK-QKD system follows the criteria of an acceptable QKD system even with transmitting two key bits at a time. Additionally, the 8PSK-QKD system outperform the SIM/BPSK-QKD and QPSK-QKD by offering better
Psiftand
Peve.