Person: DURAK, Kadir
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Kadir
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DURAK
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ArticlePublication Metadata only Cryptographic security concerns on timestamp sharing via a public channel in quantum-key-distribution systems(American Physical Society, 2022-07) Pahalı, Melis; Durak, Kadir; Tefek, U.; Electrical & Electronics Engineering; DURAK, Kadir; Pahalı, MelisQuantum-key-distribution protocols are known to be vulnerable against a side channel attack that exploits the time difference in detectors' responses used to obtain key bits. The recommended solution against this timing side channel attack is to use a large time bin width instead of high-resolution timing information. A common notion is that using a large bin width reduces the resolution of detectors' responses, hence supposedly minimizes the information leakage to an eavesdropper. We challenge this conventional wisdom and demonstrate that increasing the bin width does not monotonically reduce the mutual information between the key bits and the eavesdropper's observation of detectors' responses. Instead of randomly increasing the bin width, it should be carefully chosen because the mutual information fluctuates with respect to the bin width. We also examine the effect of full width half maximums (FWHMs) of the detectors' responses on the mutual information and show that decreasing the FWHM increases the mutual information. Lastly, the start time of binning is also shown to be important in the binning process and the mutual information fluctuates periodically with respect to it.ArticlePublication Metadata only Effect of photon statistics on vacuum fluctuations based QRNG(IOP Publishing, 2021-06) Dandaşi, Abdulrahman; Özel, Helin; Hasekioglu, O.; Durak, Kadir; Electrical & Electronics Engineering; DURAK, Kadir; Dandaşi, Abdulrahman; Özel, HelinThe speed of quantum random number generators (QRNGs) is a major concern for practical applications. In this work, we introduce scattering as a method to enhance the randomness characteristics of the entropy source. This method allows optical bit extraction with a faster sampling rate without compromising the randomness quality compared to the coherent source based balanced homodyne detection. Scattering is a probabilistic phenomenon which increases the chaotic behaviour of coherent sources. It broadens the distribution of photon statistics and makes it super-Poissonian. We show that a signal with super-Poissonian distribution has better randomness compared to a Poissonian one, indicated by their autocorrelation characteristics and the randomness test results. The use of scattering mechanisms as an entropy source eases the miniaturization of QRNGs, it also makes them compatible and adaptable to existing technologies.ArticlePublication Metadata only Attack to quantum cryptosystems through RF fingerprints from photon detectors(IEEE, 2022-03) Durak, Kadir; Jam, Naser Chamani; Karamzadeh, S.; Electrical & Electronics Engineering; DURAK, Kadir; Jam, Naser ChamaniThe well-known RF penetration method is implemented on the quantum cryptosystems. In this study, RF radiations from the single photon detectors in a quantum key distribution system are intercepted. It was found that the data contents of a quantum transmission system can be detected from the vicinity of the receiving parties by exploiting the radiations of avalanche effect of single photon detectors. We showed that any Geiger-mode avalanche photodetector acts like a downconverter that converts the optical-wavelength photons to radio-wavelength photons. In our experiment, the fingerprints of the avalanche radiations from commercial single photon detectors were fed to a trained deep learning neural network, and the bit content of quantum transmission was cloned with >99% accuracy up to a distance of 2 meters from the detectors. We also speculate on the enhancement of the key cloning accuracy and range of the eavesdropping.Conference paperPublication Metadata only Single photon detection with silicon-based avalanche photodiode(SPIE, 2023) Yerli, Burcu; Eraydın, Can; Cinkaya, H.; Durak, Kadir; Electrical & Electronics Engineering; DURAK, Kadir; Yerli, Burcu; Eraydın, CanThanks to the significant advances in quantum technologies, the use of single photon detectors (SPDs) is becoming increasingly common. As a result of the excellent photodetection performance of these detectors, they have been utilized in a wide range of fields such as quantum cryptography, astronomy, spectroscopy, and medical applications. There is no doubt that improvements in the performance of these detectors will open new paths to their multidisciplinary applications. Over the years, several different types of SPDs have been developed, such as photomultiplier tubes based on vacuum tubes, avalanche photodiodes (APDs) based on semiconductors, or nanowires based on superconducting technology. Any of these technologies, which are also commercially offered by many companies, has been used according to their advantages and disadvantages for intended applications by making a trade-off. At that point, SPDs based on Silicon APD technology have many advantages including low voltage operation, high reliability, simple electronic requirements, and high detection efficiency. In this study, the TO-8 SAP500 series Silicon APD provided by Laser Component was preferred, and the driving circuit was designed for visible-range sensing applications. The quenching and thermoelectric cooling circuit designs were presented, and the performance of the detector was analyzed according to some important parameters. Our motivation is to investigate the CubeSat compatibility of the detector for space applications.ArticlePublication Metadata only Noise-tolerant object detection and ranging using quantum correlations(IOP Publishing, 2022-10) Kuniyil, Hashir Puthiyapurayil; Özel, Helin; Yılmaz, H.; Durak, Kadir; Electrical & Electronics Engineering; DURAK, Kadir; Kuniyil, Hashir Puthiyapurayil; Özel, HelinImaging, detection and ranging of objects in the presence of significant background noise is a fundamental challenge in optical sensing. Overcoming the limitations imposed in conventional methods, quantum light sources show higher resistance against noise in a time-correlation-based quantum illumination. Here, we introduce the advantage of using not only time correlations but also polarization correlations in photon pairs in the detection of an object that is embedded in a noisy background. In this direction, a time- and polarization-correlated photon pair source using the spontaneous parametric down-conversion process is exploited. We found that the joint measurement of correlated pairs allows distinguishing the signal from the noise photons and that leads to an improved signal-to-noise ratio. Our comparative study revealed that using polarization correlations in addition to time correlations provides improved noise rejection. Furthermore, we show that polarization correlation allows undoing the detector limitation where high background often leads to detector saturation.Conference paperPublication Metadata only Effect of phase and spatial distinguishability of photon pairs on the entanglement fidelity(SPIE, 2021) Kuniyil, Hashir Puthiyapurayil; Durak, Kadir; Electrical & Electronics Engineering; DURAK, Kadir; Kuniyil, Hashir PuthiyapurayilPolarization entanglement based cryptography uses the photon pairs generated in a spontaneous parametric down-conversion process and guarantees the security through the violation of Bell's inequality. Certain experimental parameters affects the entanglement fidelity and leads to a possible information leakage. The optical path difference of photons born at different crystals contributes to reduced fidelity, due to the extra birefringence of the nonlinear crystal. Although previous studies suggested methods to erase the distinguishability of photons by introducing compensation crystals, the phase difference, which is due to the lateral ray distribution is not studied. We used two commercially available collection optics; an aspheric and an achromatic lens. With these collection optics, the effect of collection optics on the entanglement fidelity is studied. We developed a simulation of such a system and found that aspheric collection optics is more suitable to achieve high fidelity.ArticlePublication Metadata only Development of an aerial interface for extraction of the electrodynamic fingerprints of the single-photon detectors(Wiley, 2021-12) Karamzadeh, S.; Durak, Kadir; Jam, Naser Chamani; Rafiei, V.; Awad, B.; Electrical & Electronics Engineering; DURAK, Kadir; Jam, Naser ChamaniIn this study, a novel structure of semi array of antipodal Vivaldi antenna is designed to extract the RF radiations from the single-photon detectors in a quantum key distribution system. The proposed antenna covers a frequency range from 2 to 12 GHz with an average gain of 12.5 dBi which has improved by a lens structure. In the first step, the design proceeding of the antenna has been discussed, and then, some of the unique futures of the proposed antenna which promoted it to use in quantum attack systems, such as linear momentum, a good Envelope Correlation Coefficient, and Gaussian pulse response, are discussed.ArticlePublication Open Access Optimization of collection optics for maximum fidelity in entangled photon sources(TÜBİTAK, 2020) Durak, Kadir; Electrical & Electronics Engineering; DURAK, KadirIn this report, decoherence sources for entangled photons created by spontaneous parametric down-conversion phenomenon are studied. The phase and spatial distinguishability of photon pairs from orthogonal crystals reduce the maximum achievable entanglement fidelity. Carefully chosen compensation crystals are used to erase the phase and spatial traces of down-conversion origins. Emission angle of photon pairs also leads to optical path difference and results in phase distinguishability. A realistic scenario is numerically modelled, where the photon pairs with nonzero emission angle gather a phase difference. These pairs can still be collected and manipulated for practical use but the collection optics adds upon the phase difference. Two commercially available optics for collection; aspheric and achromatic lenses are compared. The numerical simulation results are compared with the experimental results to validate the built model for predicting the maximum achievable entanglement fidelity. The results indicate that the fidelity can be accurately estimated with the presented model by inserting the experimental parameters to it. The study is expected to be very useful for preparation and optimization of entangled photon pair sources in critical phase-matching configuration.ArticlePublication Open Access Quantum signatures in a quadratic optomechanical heat engine with an atom in a tapered trap(Optica Publishing Group, 2022-12) Izadyari, M.; Öncü, Mehmet; Durak, Kadir; Müstecaplioğlu, Ö. E.; Electrical & Electronics Engineering; DURAK, Kadir; Öncü, MehmetWe investigate how quantum signatures can emerge in a single atom heat engine consisting of an atom confined in a tapered trap and subjected to hot and cold thermal reservoirs. A similar system was realized experimentally in Science 352, 325 (2016). We model such a system using a quadratic optomechanical model and identify an effective Otto cycle in the system’s dynamics. We compare the engine’s performance in quantum and classical regimes by evaluating the power dissipated. We find that lowering the temperature is insufficient to make the single atom engine in Science 352, 325 (2016) a genuine quantum-enhanced heat engine. We show that it is necessary to make the trap more asymmetric and confined to ensure that quantum correlations cause an enhancement in the power output.ArticlePublication Metadata only Tracking capacitance of liquid crystal devices to improve polarization rotation accuracy(Optical Society of America, 2017-08-21) Chandrasekara, R.; Durak, Kadir; Ling, A.; Electrical & Electronics Engineering; DURAK, KadirWe report a capacitance tracking method for achieving arbitrary polarization rotation from nematic liquid crystals. By locking to the unique capacitance associated with the molecular orientation, any polarization rotation can be achieved with improved accuracy over a wide temperature range. A modified relaxation oscillator circuit that can simultaneously determine the capacitance and drive the rotator is presented.