Decoy state quantum key distribution with two-way classical post-processing

Decoy states have recently been proposed as a useful method for substantially improving the performance of quantum key distribution protocols when a coherent state source is used. Previously, data post-processing schemes based on one-way classical communications were considered for use with decoy states. In this paper, we develop two data post-processing schemes for the decoy-state method using two-way classical communications. Our numerical simulation (using parameters from a specific QKD experiment as an example) results show that our scheme is able to extend the maximal secure distance from 142km (using only one-way classical communications with decoy states) to 181km. The second scheme is able to achieve a 10% greater key generation rate in the whole regime of distances

An Octave-Range, Watt-Level, Fully-Integrated CMOS Switching Power Mixer Array for Linearization and Back-Off-Efficiency Improvement

The power mixer array is presented as a novel power generation approach for non-constant envelope signals. It comprises several power mixer units that are dynamically turned on and off to improve the linearity and back-off efficiency. At the circuit level, the power mixer unit can operate as a switching amplifier to achieve high peak power efficiency. Additional circuit level linearization and back-off efficiency improvement techniques are also proposed. To demonstrate the feasibility of this idea, a fully-integrated octave-range CMOS power mixer array is implemented in a 130 nm CMOS process. It is operational between 1.2 GHz and 2.4 GHz and can generate an output power of +31.3 dBm into an external 50 Ω load with a PAE of 42% and a gain compression of only 0.4 dB at 1.8 GHz. It achieves a PAE of 25%, at an average output power of +26.4 dBm, and an EVM of 4.6% with a non-constant-envelope 16 QAM signal. It can also produce arbitrary signal levels down to -70 dBm of output power with the 16 QAM-modulated signal without any RF gain control circuit