High-speed Gaussian-modulated continuous-variable quantum key distribution with a local local oscillator based on pilot-tone-assisted phase compensation

Abstract

A high-speed Gaussian modulated continuous-variable quantum key distribution (CVQKD) with a local local oscillator (LLO) is experimentally demonstrated based on pilottone-assisted phase compensation. In the proposed scheme, the frequency-multiplexing and polarization-multiplexing techniques are used for the separate transmission and heterodyne detection between quantum signal and pilot tone, guaranteeing no crosstalk from strong pilot tone to weak quantum signal and different detection requirements of low-noise for quantum signal and high-saturation limitation for pilot tone. Moreover, compared with the conventional CVQKD based on homodyne detection, the proposed LLO-CVQKD scheme can measure X and P quadrature simultaneously using heterodyne detection without need of extra random basis selection. Besides, the phase noise, which contains the fast-drift phase noise due to the relative phase of two independent lasers and the slow-drift phase noise introduced by quantum channel disturbance, has been compensated experimentally in real time, so that a low level of excess noise with a 25km optical fiber channel is obtained for the achievable secure key rate of 7.04 Mbps in the asymptotic regime and 1.85 Mbps under the finite-size block of 10 7 .

Sub-Gbps Key Rate Four-State Continuous-Variable Quantum Key Distribution within Metropolitan Area

“…where Re denotes the IR, and it mainly depends on polarization IR and modulation ER when the quantum signal and pilot tone are in same time duration or frequency band based on time multiplexing or frequency multiplexing. In the former LLO-CVQKD schemes, the surplus pilot signals cannot be completely suppressed due to finite modulation ER and polarization IR, resulting in photon-leakage noise on the quantum signal in practical experiment [7,44]. Therefore, it is better to completely isolate the quantum signal and pilot tone in frequency or time domain for eliminating the photon-leakage noise.…”

“…ontinuous-variable quantum key distribution (CVQKD) provides a secret key shared between the sender (Alice) and the receiver (Bob) with information-theoretical security [1,2], which is very suitable for broadband metropolitan and access networks due to its inherent advantages of high key rate and good compatibility with commercial off-the-shelf components [3][4][5]. However, the reported CVQKD systems with several Mbps secret key rate (SKR) [6,7] are still not up to the requirements of high-speed one-time-pad encryption (e.g. 100 Mbps secure access requirements for home networks).…”

Strengthening practical continuous-variable quantum key distribution systems against measurement angular error

“…where E represents the electric field intensity, f s and f L are the center frequency of the quantum signal and the LO, ϕ 0 is the initial phase of the laser and ϕ channel represents the phase during quantum channel. Thus, the generated photocurrents of the first and second homodyne detectors can be expressed as I 1 and I 2 [25], respectively…”

Quantum Dense Coding Network using Multimode Squeezed States of Light

“…The encoding operation is performed by applying the displacement operator, which is distributed according to a Gaussian distribution of vanishing mean and variance, σ. In recent years, lots of developments have been made for the successful realization of classical information transmission, in CV systems [42,43], particularly with shared Gaussian entangled states between the sender and the receiver [44][45][46][47][48].…”