5 research outputs found
Experimental Demonstration of High-Rate Discrete-Modulated Continuous-Variable Quantum Key Distribution System
A high-rate continuous-variable quantum key distribution (CV-QKD) system
based on high-order discrete modulation is experimentally investigated. With
the help of the novel system scheme, effective digital signal processing
algorithms and advanced analytical security proof method, the transmission
results of 5 km, 10 km, 25 km, and 50 km are achieved for the 1 GBaud optimized
quantum signals. Correspondingly, the asymptotic secret key rate (SKR) is
288.421 Mbps, 159.395 Mbps, 50.004 Mbps and 7.579 Mbps for discrete Gaussian
(DG) 64QAM, and 326.708 Mbps, 179.348 Mbps, 50.623 Mbps and 9.212 Mbps for DG
256QAM. Under the same parameters, the achieved SKRs of DG 256QAM is almost
same to ideal Gaussian modulation. In this case, the demonstrated high-rate
discrete modulated CV-QKD system has the application potential for high speed
security communication under tens of kilometers.Comment: 5 pages, 5 figure
Sub-Mbps key-rate continuous-variable quantum key distribution with local-local-oscillator over 100 km fiber
We experimentally demonstrated a sub-Mbps key rate Gaussian-modulated
coherent-state continuous-variable quantum key distribution (CV-QKD) over 100
km transmission distance. To efficiently control the excess noise, the quantum
signal and the pilot tone are co-transmitted in fiber channel based on
wide-band frequency and polarization multiplexing methods. Furthermore, a
high-accuracy data-assisted time domain equalization algorithm is carefully
designed to compensate the phase noise and polarization variation in low
signal-to-noise ratio. The asymptotic secure key rate (SKR) of the demonstrated
CV-QKD is experimentally evaluated to be 10.36 Mbps, 2.59 Mbps, and 0.69 Mbps
over transmission distance of 50 km, 75 km, and 100 km, respectively. The
experimental demonstrated CV-QKD system significantly improves transmission
distance and SKR compared to the state-of-art GMCS CV-QKD experimental results,
and shows the potential for long-distance and high-speed secure quantum key
distribution.Comment: 4 pages, 7 figure
High-speed Gaussian modulated continuous-variable quantum key distribution with a local local oscillator based on pilot-tone-assisted phase compensation
A high-speed Gaussian modulated continuous-variable quantum key distribution
(CVQKD) with a local local oscillator (LLO) is experimentally demonstrated
based on pilot-tone-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
Performance analysis for OFDM-based multi-carrier continuous-variable quantum key distribution with arbitrary modulation protocol
Multi-carrier continuous-variable quantum key distribution (CV-QKD) is
considered to be a promising way to boost the secret key rate (SKR) over the
existing single-carrier CV-QKD scheme. However, the extra excess noise induced
in the imperfect multi-carrier quantum state preparation process of N
subcarriers will limit the performance of the system. Here, a systematic
modulation noise model is proposed for the multi-carrier CV-QKD based on the
orthogonal frequency division multiplexing (OFDM). Subsequently, the
performance of multi-carrier CV-QKD with arbitrary modulation protocol (e.g.
QPSK, 256QAM and Gaussian modulation protocol) can be quantitatively evaluated
by combining the security analysis method of the single-carrier CV-QKD. Under
practical system parameters, the simulation results show that the SKR of the
multi-carrier CV-QKD can still be significantly improved by increasing the
carrier number N even with imperfect practical modulations. Specifically, the
total SKR of multi-carrier CV-QKD can be optimized by carefully choosing N. The
proposed model provides a feasible theoretical framework for the future
multi-carrier CV-QKD experimental implementation.Comment: 15 pages, 14 figure
Polarization Attack on Continuous-Variable Quantum Key Distribution with a Local Local Oscillator
The estimation of phase noise of continuous-variable quantum key distribution protocol with a local local oscillator (LLO CVQKD), as a major process in quantifying the secret key rate, is closely relevant to the intensity of the phase reference. However, the transmission of the phase reference through the insecure quantum channel is prone to be exploited by the eavesdropper (Eve) to mount attacks. Here, we introduce a polarization attack scheme against the phase reference. Presently, in a practical LLO CVQKD system, only part of the phase reference pulses are measured to compensate for the polarization drift of the quantum signal pulses in a compensation cycle due to the limited polarization measurement rate, while the other part of the phase reference pulses are not measured. We show that Eve can control the phase noise by manipulating the polarization direction of the unmeasured phase reference to hide her attack on the quantum signal. Simulations show that Eve can obtain partial or total key rates information shared between Alice and Bob as the transmission distance increases. Improving the polarization measurement rate to 100% or monitoring the phase reference intensity in real-time is of great importance to protect the LLO CVQKD from polarization attack