Abstract
We present an experimental demonstration of the feasibility of the first 20 + Mb/s Gaussian modulated coherent state continuous variable quantum key distribution system with a locally generated local oscillator at the receiver (LLO-CVQKD). To increase the signal repetition rate, and hence the potential secure key rate, we equip our system with high-performance, wideband devices and design the components to support high repetition rate operation. We have successfully trialed the signal repetition rate as high as 500 MHz. To reduce the system complexity and correct for any phase shift during transmission, reference pulses are interleaved with quantum signals at Alice. Customized monitoring software has been developed, allowing all parameters to be controlled in real-time without any physical setup modification. We introduce a system-level noise model analysis at high bandwidth and propose a new ‘combined-optimization’ technique to optimize system parameters simultaneously to high precision. We use the measured excess noise, to predict that the system is capable of realizing a record 26.9 Mb/s key generation in the asymptotic regime over a 15 km signal mode fibre. We further demonstrate the potential for an even faster implementation.
Highlights
We present an experimental demonstration of the feasibility of the first 20 + Mb/s Gaussian modulated coherent state continuous variable quantum key distribution system with a locally generated local oscillator at the receiver (LLO-continuous variable Quantum key distribution (QKD) (CVQKD))
CVQKD systems have the benefits of compatibility with commercial off-the-shelf (COTS) telecom components and exhibit high detection efficiency, enabling low-cost[10] and possibly higher secret key rates over access and metro Dense Wavelength Division Multiplexing (DWDM) network d istances[11,12,13]
Several obstacles have been identified in practical CVQKD systems, especially those associated with a co-transmitted local oscillator (LO) between Alice and Bob
Summary
We present an experimental demonstration of the feasibility of the first 20 + Mb/s Gaussian modulated coherent state continuous variable quantum key distribution system with a locally generated local oscillator at the receiver (LLO-CVQKD). To achieve a high-efficiency quadrature detection at Bob, the necessary LO intensity required is typically eight orders of magnitude higher than that of the quantum signal Such a large power disparity requires a dedicated separation technique to mitigate the photon scatter contamination from LO to quantum signals[21,22]. Since the previous sequential-LLO CVQKD demonstrations have been run at low repetition rates and the sequentially generated quantum signal and reference signal pulses have relatively large time intervals, several approaches with increased system complexity have been deployed to minimize the phase drift noise induced from the large pulse intervals[23,26,28]. In our system, the high repetition rate leads to very short pulse intervals, resulting in low phase drift noise, enabling us to achieve better performance with a lower complexity configuration
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