Abstract
Continuous-variable (CV) quantum key distribution (QKD) employs the quadratures of a bosonic mode to establish a secret key between two remote parties, and this is usually achieved via a Gaussian modulation of coherent states. The resulting secret key rate depends not only on the loss and noise in the communication channel, but also on a series of data processing steps that are needed for transforming shared correlations into a final string of secret bits. Here we consider a Gaussian-modulated coherent-state protocol with homodyne detection in the general setting of composable finite-size security. After simulating the process of quantum communication, the output classical data is post-processed via procedures of parameter estimation, error correction, and privacy amplification. In particular, we analyze the high signal-to-noise regime which requires the use of high-rate (non-binary) low-density parity check codes. We implement all these steps in a Python-based library that allows one to investigate and optimize the protocol parameters to be used in practical experimental implementations of short-range CV-QKD.
Highlights
In quantum key distribution (QKD), two authenticated parties (Alice and Bob) aim at establishing a secret key over a potentially insecure quantum channel [1]
The latter approach is adopted and is certainly valid under conditions of channel stability. Concatenating their local pECnbks error-corrected strings, Alice and Bob construct two long binary sequences S S, each having n := pECnbksnp bits. Each of these sequences will be compressed to a final secret key of r := pECnbksnRbits, where Ris determined by the composable key rate
We are interested in short-range high-rate implementations of CV-QKD, over distances of around 5 km in standard optical fiber
Summary
In quantum key distribution (QKD), two authenticated parties (Alice and Bob) aim at establishing a secret key over a potentially insecure quantum channel [1]. At the beginning of the 2000s, a more modern family of protocols emerged, in which information is encoded in the position and momentum quadratures of a bosonic mode [6,7] These continuous-variable (CV) QKD protocols are practical and cost effective, being already compatible with the current telecommunication technology [1,8]. We consider the basic CV-QKD protocol based on Gaussian modulation of coherent states and homodyne detection. Starting from a simulation of the quantum communication in typical noisy conditions, we process the generated data into a finite-size secret key which is composably secure against collective Gaussian attacks. Our procedure for data processing is based on the composable secret key rate developed in Sec. III of Ref.
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