Improving source-in-the-middle continuous-variable quantum key distribution using a heralded hybrid linear amplifier

A hybrid linear amplifier is inserted at the output of the source-in-the-middle distribution protocol to overcome the shortcomings of the transmission distance.The modified protocol aims to maintain a high key rate for long-distance transmission under high noise.It has the potential to significantly broaden the application range of the continuous variable quantum key distribution protocol.The effects of amplifier parameters and noise on the modified protocol are analyzed in detail with regard to applying it to a practical system.To make the simulation more realistic,the effect of finite size on the new protocol is taken into account.It will serve as a guideline for the future use of hybrid linear amplifiers.Different parameters can be adjusted to achieve the best performance for key rates of different quantum channels.

Hybrid linear amplifier-involved detection for continuous variable quantum key distribution with thermal states

Continuous-variable quantum key distribution(CVQKD)can be integrated with thermal states for short-distance wireless quantum communications.However,its performance is usually restricted with the practical thermal noise.We propose a method to improve the security threshold of thermal-state(TS)CVQKD by employing a heralded hybrid linear amplifier(HLA)at the receiver.We find the effect of thermal noise on the HLA-involved scheme in near-and-mid infrared band or terahertz band for direct and reverse reconciliation.Numerical simulations show that the HLA-involved scheme can compensate for the detriment of thermal noise and hence increase the security threshold of TS-CVQKD.In near-and-mid infrared band,security threshold can be extended by 2.1 dB in channel loss for direct reconciliation and 1.6 dB for reverse reconciliation,whereas in terahertz band,security threshold can be slightly enhanced for the gain parameter less than 1 due to the rise in thermal noise.

All-fiber laser seeded femtosecond Yb:KGW solid state regenerative amplifier

A high efficiency compact Yb:KGW regenerative amplifier using an all-fiber laser seed source was comprehensively studied.With thermal lensing effect compensated by the cavity design,the compressed pulses with energy of 1 mJ at 1 kHz and 0.4 mJ at 10 kHz in sub-400-fs pulse duration using chirped fiber Bragg grating(CFBG)stretcher were demonstrated.A modified Frantz-Nodvik equation was developed to emulate the dynamic behavior of the regenerative amplifier.The simulation results were in good agreement with the experiment.Numerical simulations and experimental results show that the scheme can be scalable to higher energy of multi-mJ,sub-300 fs pulses.

A Low Noise L-band Dispersion-Compensating Hybrid Fiber Amplifier with 1500 nm Raman Pumping

This report presents a low noise L-band dispersion-compensating hybrid fiber amplifier with 1500-nm Raman pumping. It describes the pre-stage optimization, Raman pump selection, and possible nonlinearity problems to achieve a practical low noise L-band optical amplifier.