Abstract
The speed at which two remote parties can exchange secret keys in continuous-variable quantum key distribution (CV-QKD) is currently limited by the computational complexity of key reconciliation. Multi-dimensional reconciliation using multi-edge low-density parity-check (LDPC) codes with low code rates and long block lengths has been shown to improve error-correction performance and extend the maximum reconciliation distance. We introduce a quasi-cyclic code construction for multi-edge codes that is highly suitable for hardware-accelerated decoding on a graphics processing unit (GPU). When combined with an 8-dimensional reconciliation scheme, our LDPC decoder achieves an information throughput of 7.16 Kbit/s on a single NVIDIA GeForce GTX 1080 GPU, at a maximum distance of 142 km with a secret key rate of 6.64 × 10−8 bits/pulse for a rate 0.02 code with block length of 106 bits. The LDPC codes presented in this work can be used to extend the previous maximum CV-QKD distance of 100 km to 142 km, while delivering up to 3.50× higher information throughput over the tight upper bound on secret key rate for a lossy channel.
Highlights
Quantum key distribution (QKD), referred to as quantum cryptography, offers unconditional security between two remote parties that employ one-time pad encryption to encrypt and decrypt messages using a symmetric secret key, even in the presence of an eavesdropper with infinite computing power and mathematical genius.[1,2,3,4] The security of QKD stems from the nocloning theorem of quantum mechanics.[5,6,7] Unlike classical cryptography, quantum cryptography allows the two remote parties, Alice and Bob, to detect the presence of an eavesdropper, Eve, while providing security against brute force, key distillation attacks that may be enabled through quantum computing.[8]
It shows that the graphics processing unit (GPU) decoder can achieve between 2.05× and 3.50× higher information throughput KG0 PU over the upper bound on secret key rate Kl0im with a 1 MHz source using QC-lowdensity parity-check (LDPC) codes with d = 8 dimensional reconciliation only
We introduced quasi-cyclic multi-edge LDPC codes to accelerate long-distance reconciliation in continuous-variable quantum key distribution (CV-QKD) by means of a GPU-based decoder implementation and multi-dimensional reconciliation schemes
Summary
Quantum key distribution (QKD), referred to as quantum cryptography, offers unconditional security between two remote parties that employ one-time pad encryption to encrypt and decrypt messages using a symmetric secret key, even in the presence of an eavesdropper with infinite computing power and mathematical genius.[1,2,3,4] The security of QKD stems from the nocloning theorem of quantum mechanics.[5,6,7] Unlike classical cryptography, quantum cryptography allows the two remote parties, Alice and Bob, to detect the presence of an eavesdropper, Eve, while providing security against brute force, key distillation attacks that may be enabled through quantum computing.[8] Today’s public key exchange schemes such as Diffie-Hellman and encryption algorithms like RSA, respectively, rely on the computational hardness of solving the discrete log problem and prime factorization.[9,10] Both of these problems, can be solved in polynomial time by applying Shor’s algorithm on a quantum computer.[11,12,13] Future threats may arise from the discovery of a new classical algorithm capable of solving such cryptography problems in polynomial time on a classical Turing machine
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