Ms. Karolina Sedziak Profile

Karolina Sedziak

at Nicolaus Copernicus University

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Publications (3)

Proceedings Article | 19 September 2017 Presentation

Quantum communication with spectrally correlated photons (Conference Presentation)

Piotr Kolenderski, Mikolaj Lasota, Karolina Sedziak, Andrzej Gajewski

Proceedings Volume 10409, 104090D (2017) https://doi.org/10.1117/12.2273179

KEYWORDS: Photons, Quantum communications, Quantum key distribution, Information security, Telecommunications, Colorimetry, Quantum efficiency, Single photon, Raman scattering, Internet

Read Abstract +

Single-photon sources are crucial components for the implementation of quantum communication protocols. However, photons emitted by some of the most popular types of realistic sources are spectrally broadband. Due to this drawback, the signal emitted from such sources is typically affected by the effect of temporal broadening during its propagation through telecommunication fibers which exhibit chromatic dispersion. Such problem can be observed e.g. when using sources based on the process of spontaneous parametric down-conversion (SPDC). In the case of long-distance quantum communication temporal broadening can significantly limit the efficiency of temporal filtering. It is a popular method, which is based on the reduction of the duration time of the detection window, used for decreasing the number of registered errors. In this work we analyzed the impact of the type of spectral correlation within a pair of photons produced by the SPDC source on the temporal width of those photons during their propagation in dispersive media. We found out that in some situations the width can be decreased by changing the typical negative spectral correlation into positive one or by reducing its strength. This idea can be used to increase the efficiency of the temporal filtering method. Therefore it can be applied in various implementations of quantum communication protocols. As an example of the application we subsequently analyzed the security of a quantum key distribution (QKD) scheme based on single photons. It was realized in the configuration with the source of photons located in the middle between the legitimate participants of a QKD protocol (called typically Alice and Bob). We demonstrated that when the information about the emission time of the photons produced by the SPDC source is not distributed to Alice and Bob, the maximal security distance can be considerably extended by using positively correlated photons, while in the opposite case strongly (no matter positively or negatively) correlated photons are optimal. We also found out that the results of our calculation may be very sensitive to the spectral widths of the photons produced by the SPDC source. In addition, we concluded that in realistic situation Alice and Bob would have to optimize their source over both the spectral widths of the generated photons and the type of spectral correlation in order to maximally extend the security distance. The results of our work are, in particular, important for the QKD systems utilizing commercial telecom fibers populated by strong classical signals. In those systems temporal filtering method can be used to reduce not only the dark counts registered by the detection system, but also the channel noise originating from the process of Raman scattering, which is the main factor limiting their performance.

Proceedings Article | 19 September 2017 Presentation

On photonic spectral entanglement improving quantum communication (Conference Presentation)

Piotr Kolenderski, Karolina Sedziak, Mikolaj Lasota, Andrzej Gajewski

Proceedings Volume 10409, 104090F (2017) https://doi.org/10.1117/12.2274730

KEYWORDS: Quantum communications, Single mode fibers, Standards development, Photodetectors, Dispersion, Signal detection, Interference (communication), Quantum key distribution, Telecommunications, Photon polarization

Read Abstract +

Proceedings Article | 8 June 2017 Presentation

Reducing detection noise of a photon pair in a dispersive medium by controlling its spectral entanglement (Conference Presentation)

Mikolaj Lasota, Karolina Sedziak, Piotr Kolenderski

Proceedings Volume 10230, 1023005 (2017) https://doi.org/10.1117/12.2264783

KEYWORDS: Optical fibers, Raman scattering, Quantum communications, Quantum key distribution, Information security, Single photon detectors, Telecommunications, Dispersion, Quantum efficiency, Single photon

Read Abstract +

Single-photon sources are crucial components for the implementation of quantum communication protocols. However, photons emitted by some of the most popular types of realistic sources are spectrally broadband. Due to this drawback, the signal emitted from such sources is typically affected by the effect of temporal broadening during its propagation through telecommunication fibers which exhibit chromatic dispersion. Such problem can be observed e.g. when using sources based on the process of spontaneous parametric down-conversion (SPDC). In the case of long-distance quantum communication temporal broadening can significantly limit the efficiency of temporal filtering. It is a popular method, which relies on the reduction of the duration time of the detection window, used for decreasing the number of registered errors. In this work we analyzed the impact of the type of spectral correlation within a pair of photons produced by the SPDC source on the temporal width of those photons during their propagation in dispersive media. We found out that in some situations this width can be decreased by changing the typical negative spectral correlation into positive one or by reducing its strength. This idea can be used to increase the efficiency of the temporal filtering method. Therefore, it can be applied in various implementations of quantum communication protocols. As an example of the application we subsequently analyzed the security of a quantum key distribution (QKD) scheme based on single photons. The investigation was performed for the configuration with the source of photons located in the middle between the legitimate participants of a QKD protocol (called typically Alice and Bob). We demonstrated that when the information about the emission time of the photons produced by the SPDC source is not distributed to Alice and Bob, the maximal security distance can be considerably extended by using positively correlated photons, while in the opposite case strongly (no matter positively or negatively) correlated photons are optimal. We also found out that the results of our calculation may be very sensitive to the spectral widths of the photons produced by the SPDC source. In addition, we concluded that in realistic situation Alice and Bob would have to optimize their source over both the spectral widths of the generated photons and the type of spectral correlation in order to maximally extend the security distance. The results of our work are, in particular, important for the QKD systems utilizing commercial telecom fibers populated by strong classical signals. In those systems temporal filtering method can be used to reduce not only the dark counts registered by the detection system, but also the channel noise originating from the process of Raman scattering, which is the main factor limiting their performance.

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