Speaker
Description
A scheme for parallel, high-throughput continuous-variable QKD (CV-QKD) is presented that efficiently utilizes the optical bandwidth resource of broadband squeezed vacuum (of order $10-100$THz), using a novel method for broadband spectrally resolved parametric homodyne measurement. Large multi-bit frames of data can be encoded simultaneously onto the squeezed vacuum spectrum by shaping its spectral phase using a Fourier-domain pulse shaper. This data can later be decoded at the receiving end by measuring the spectral quadrature fluctuation across the entire spectrum on a linear array of fast detectors using the pump field as a single local oscillator for all frequency pairs in the spectrum. The speed-up of the proposed protocol compared to standard protocols is proportional to the number of detectors in the array, which ideally can reach $10^5$ (defined by the ratio of the total bandwidth to the modulation rate of a single channel), and practically can be well over 100.
Our Scheme relies on a common version of CV-QKD, where the data is encoded onto the amplitude and phase of squeezed vacuum light (or the field quadratures) and is read out by coherent homodyne detection against a local oscillator [1]. CV-QKD is considered faster than discrete variable QKD because of the technical details of homodyne detection, which allow faster measurement than photon counting. In addition it may allow use of multiple photons per detection (and transfer multiple data bits per detection correspondingly) [2]. The security of the communication relies on the inability to measure both quadratures simultaneously, indicating that a receiving party can measure only one quadrature with no information on the other. Moreover, variation of the quadrature axis (phase of the pump) between (0,π⁄2) and (π⁄4,-π⁄4) naturally defines two mutually exclusive bases, where measurement along the (π⁄4,-π⁄4) axis cannot provide any information for a state that was squeezed along the other (0,π⁄2) axis, very similar to measuring the polarization of a single photon along the wrong axis of polarization.
References
- T. Gehring, V. Handchen, J. Duhme, F. Furrer, T. Franz, C. Pacher, R. F. Werner and R. Schnabel, "Implementation of continuous-variable quantum key distribution with composable and one-sided-device-independent security against coherent attacks", Nature Communications 6, 8795 (2015).
- F. Grosshans, G. Van Assche, J. Wenger, R. Brouri, N. J. Cerf and P. Grangier, "Quantum key distribution using gaussian-modulated coherent states", Nature 421, 238 (2003)
- A. M. Weiner, " Ultrafast optical pulse shaping: A tutorial review", Opt. Commun. 284, 3669 (2011).
| Topic: | Mini-workshop: Quantum Foundations and Quantum Information |
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