# Quantum random number generation for 1.25 GHz quantum key distribution systems

# Quantum random number generation for 1.25 GHz quantum key distribution systems.

###### Abstract

Security proofs of quantum key distribution (QKD) systems usually assume that the users have access to source of perfect randomness. State-of-the-art QKD systems run at frequencies in the GHz range, requiring a sustained GHz rate of generation and acquisition of quantum random numbers. In this paper we demonstrate such a high speed random number generator. The entropy source is based on amplified spontaneous emission from an erbium-doped fibre, which is directly acquired using a standard small form-factor pluggable (SFP) module. The module connects to the Field Programmable Gate Array (FPGA) of a QKD system. A real-time randomness extractor is implemented in the FPGA and achieves a sustained rate of 1.25 Gbps of provably random bits.

## I Introduction

Proposed in 1984, quantum key distribution (QKD) is a cryptographic technique that allows two spatially separated users, called Alice and Bob, to exchange secret key via a potentially insecure quantum channel. A key advantage of QKD is that it offers provably secure cryptographic keys, while classical key distribution schemes can only offer computational security. Nowadays, owning to the significant progress made in photonics technology, QKD experiments are able to distribute large secret keys at high repetition rates Liu2010; Wang2012; Walenta2014; Patel2014. Among the many developments required for a fast QKD system, is the development of a fast and practical random number generator where the randomness is derived from quantum processes Kanter2009; Li2010a; Li2011a; Wahl2011; Symul2011; Zhang2012; Nguimdo2012; Xu2012; Lozach2013; Abellan2014. However, the integration of these fast quantum random number generators (QRNGs) with fast QKD systems has remained elusive, mainly due to the technical challenges in acquiring high data rates and certifying that the generated numbers are truly random. Moreover, the development of random number generator based on physical source of randomness is useful for the classical cryptography protocols too. All the recent social events have demonstrated that cryptography protocols using a pseudo-random number generators is not at all secure Markowsky2014.

In this paper, we demonstrate how a fast quantum random number generator can be easily created and integrated into a communication system. In our device, random numbers are generated by a source of amplified spontaneous emission (ASE) and acquired by a field-programmable gate array (FPGA) using a standard small form-factor pluggable (SFP) module. This allows us to generate true random numbers at a rate of