Abstract
Quantum key distribution (QKD) allows unconditionally secure communication based on the laws of quantum mechanics rather than assumptions about computational hardness. Optimizing the operation parameters of a given QKD implementation is indispensable in order to achieve high secure key rates. So far, there exists no model that accurately describes entanglement-based QKD with continuous-wave pump lasers. We analyze the underlying mechanisms for QKD with temporally uniform pair-creation probabilities and develop a simple but accurate model to calculate optimal tradeoffs for maximal secure key rates. In particular, we find an optimization strategy of the source brightness for given losses and detection-time resolution. All experimental parameters utilized by the model can be inferred directly in standard QKD implementations, and no additional assessment of device performance is required. Comparison with experimental data shows the validity of our model. Our results yield a tool to determine optimal operation parameters for already existing QKD systems, to plan a full QKD implementation from scratch, and to determine fundamental key rate and distance limits of given connections.
Highlights
Quantum key distribution (QKD) is a method of creating a secret and random one-time pad for two remote users usable for unconditionally secure encryption of messages [1,2]
Optimizing the operation parameters of a given QKD implementation is indispensable in order to achieve high secure key rates
That we have shown the validity of our model in different parameter scenarios, we want to use it to illustrate the limits and potential of CW-QKD
Summary
Quantum key distribution (QKD) is a method of creating a secret and random one-time pad for two remote users usable for unconditionally secure encryption of messages [1,2]. A model describing sources pumped with a pulsed laser was published in 2007 [16] and has been the state of the art ever since In such pulsed schemes, all photon pairs are found in discrete and evenly spaced time modes depending on the laser’s repetition rate. Due to the broad frequency spectra in a pulsed-pump scheme, dispersion effects in the optics have to be accounted for, especially in the nonlinear crystals where the entangled photons are created. This model of pulsed operation can be applied to CW pumped sources with limited accuracy only, as will be shown below. V we discuss our findings and present optimal parameters to maximize key rates
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