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NONLINEAR-OPTICAL PROCESSING BY MEANS OF phase coding

OPTICS LETTERS 1991年第18期16卷 1418-1420页

作者： SADOVNIK, L SAWCHUK, AA CHEN, R JANNSON, T UNIV SO CALIF INST SIGNAL & IMAGE PROCLOS ANGELESCA 90089

A new look at nonlinear-optical processing that uses Fourier plane filtering is discussed. Traditional binary intensity-to-space recording (halftoning) is replaced by simple continuous phase coding. Some proof-of-principle experimental results demonstrate a superior 10(3):1 input dynamic range. The phase response of the photosensitive material can be measured as an addition to this proposed technique.

关键词： .transmittance nonlinear-optical phase coding Fourier plane halftone screen

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Decoy state method for quantum cryptography based on phase coding into faint laser pulses

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LASER PHYSICS LETTERS 2017年第12期14卷

作者： Kulik, S. P. Molotkov, S. N. Moscow MV Lomonosov State Univ Fac Phys Moscow Russia Acad Cryptog Russian Federat Moscow 121552 Russia Russian Acad Sci Inst Solid State Phys Chernogolovka 142432 Moscow Distr Russia Moscow MV Lomonosov State Univ Fac Computat Math & Cybernet Moscow Russia

We discuss the photon number splitting attack (PNS) in systems of quantum cryptography with phase coding. It is shown that this attack, as well as the structural equations for the PNS attack for phase encoding, differs physically from the analogous attack applied to the polarization coding. As far as we know, in practice, in all works to date processing of experimental data has been done for phase coding, but using formulas for polarization coding. This can lead to inadequate results for the length of the secret key. These calculations are important for the correct interpretation of the results, especially if it concerns the criterion of secrecy in quantum cryptography.

关键词： quantum key distribution PNS measurements phase coding decoy state

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Dual-chirp waveform generation and its TBWP improvement based on polarization modulation and phase coding

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OPTICS COMMUNICATIONS 2020年第0期463卷 125413-000页

作者： Li, Xuan Zhao, Shanghong Zhang, Kun Wang, Guodong Air Force Engn Univ Informat & Nav Coll Xian 710077 Peoples R China

A photonics approach to generate a phase-coded dual-chirp waveform with reconfigurable time duration, arbitrary large TBWP, flexible tuning frequency and bandwidth is proposed and demonstrated. In the scheme, one polarization modulator (PolM) is applied to modulate a repetitive parabolic waveform with an dual-wave-length optical signal, while another PolM is utilized to achieve phase coding with a Pseudorandom (PN) sequence. After balanced detection, a phase-coded dual-chirp signal with improved time-bandwidth product (TBWP) can be generated. The approach is verified by simulation. Basis dual-chirp waveforms with tunable central frequency of 20 to 30 GHz, tunable bandwidth of 1.25 to 5 GHz but fixed TBWP of 16 are generated. Then, 30-GHz central frequency, 2.5-GHz bandwidth phase-coded dual-chirp signals with phase shift of pi, TBWP of 240, 1008 and 2032 are obtained. The generated dual-chirp microwave waveform can be used in a radar system to improve its range-Doppler resolution.

关键词： Dual-chirp waveform Time-bandwidth product Polarization modulation phase coding

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Three-dimensional shape measurement based on color complementary phase coding method

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OPTICS AND LASERS IN ENGINEERING 2024年 180卷

作者： Fu, Lina Zhang, Zonghua Huang, Hong Li, Yanling Yang, Jingwen Ni, Yubo Gao, Nan Meng, Zhaozong Zhang, Guofeng Hebei Univ Technol Sch Mech Engn Tianjin 300401 Peoples R China Chongqing Univ Key Lab Optoelect Technol & Syst Educ Minist China Chongqing 400044 Peoples R China Univ Huddersfield EPSRC Adv Metrol Hub Huddersfield HD1 3DH England Xi An Jiao Tong Univ Sch Mech Engn Xian 710049 Shanxi Peoples R China

Fringe projection profilometry (FPP) has been widely studied and used in three dimensional (3D) shape measurement because of its non-contact and high accuracy. By analyzing the captured fringe patterns, phase data can be demodulated with regard to depth. However, measurement efficiency decreases as number of the projected patterns increases. Therefore, it is a challenge to improve the projection rate, while ensuring measurement accuracy. To overcome this challenge, this paper proposes a complementary encoding method to correct the jump error of the unwrapping phase based on color phase-encoded fringe projection. Meanwhile, number of the projected patterns is reduced by using color modulation technique to generate composite fringes. The 3D reconstruction results of the proposed method are verified by qualitative experiments. Moreover, effectiveness of its error correction is discussed by quantitative experiments.

关键词： 3D measurement Fringe projection profilometry phase coding Color fringe modulation

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A fast three-dimensional shape measurement method based on color phase coding

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OPTIK 2016年第3期127卷 1011-1015页

作者： Li, Biao Fu, Yanjun Zhang, Jiancheng Wu, Haitao Xia, Guisuo Jiang, Guangyu Nanchang Hangkong Univ Minist Educ Key Lab Nondestruct Testing Nanchang 330063 Peoples R China

Gray code plus phase-shifting method embed the codeword into intensity to reconstruct complex three-dimensional shape. Owing to surface reflectivity and noise, it is less robust for measuring the surfaces of object with low contrast. In order to solve the problem, the codeword is embedded into phase to determine fringe order for obtaining the unwrapped phase. However, measurement speed is limited. Therefore, a fast three-dimensional shape measurement method based on color phase coding is proposed. As it adopts a color sinusoidal fringe to obtain wrapped phase and an additional color phase coding fringe to determine fringe order, the method can achieve fast complex three-dimensional shape measurement with different contrast. Color crosstalk and gamma nonlinearity are compensated to improve the measurement accuracy. The experiment results confirm the effectiveness and robustness of the proposed method. (C) 2015 Elsevier GmbH. All rights reserved.

关键词： Three-dimensional shape measurement phase-shifting method phase coding Color crosstalk

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Theta phase coding in a network model of the entorhinal cortex layer II with entorhinal-hippocampal loop connections

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COGNITIVE NEURODYNAMICS 2007年第2期1卷 169-184页

作者： Igarashi, Jun Hayashi, Hatsuo Tateno, Katsumi Kyushu Inst Technol Dept Brain Sci & Engn Grad Sch Life Sci & Syst Engn Kitakyushu Fukuoka 8080196 Japan

We investigated successive firing of the stellate cells within a theta cycle, which replicates the phase coding of place information, using a network model of the entorhinal cortex layer II with loop connections. Layer II of the entorhinal cortex (ECII) sends signals to the hippocampus, and the hippocampus sends signals back to layer V of the entorhinal cortex (ECV). In addition to this major pathway, projection from ECV to ECII also exists. It is, therefore, inferred that reverberation activity readily appears if projections from ECV to ECII are potentiated. The frequency of the reverberation would be in a gamma range because it takes signals 20-30 ms to go around the entorhinal-hippocampal loop circuits. On the other hand, it has been suggested that ECII is a theta rhythm generator. If the reverberation activity appears in the entorhinal-hippocampal loop circuits, gamma oscillation would be superimposed on a theta rhythm in ECII like a gamma-theta oscillation. This is a reminiscence of the theta phase coding of place information. In this paper, first, a network model of ECII will be developed in order to reproduce a theta rhythm. Secondly, we will show that loop connections from one stellate cell to the other one are selectively potentiated by afferent signals to ECII. Frequencies of those afferent signals are different, and transmission delay of the loop connections is 20 ms. As a result, stellate cells fire successively within one cycle of the theta rhythm. This resembles gamma-theta oscillation underlying the phase coding. Our model also replicates the phase precession of stellate cell firing within a cycle of subthreshold oscillation (theta rhythm).

关键词： Network model Entorhinal cortex layer II Loop connections Stellate cell Theta rhythm phase coding Spike-timing dependent plasticity

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Inherent security of phase coding quantum key distribution systems against detector blinding attacks

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LASER PHYSICS LETTERS 2018年第9期15卷

作者： Balygin, K. A. Klimov, A. N. Bobrov, B. Kravtsov, K. S. Kulik, S. P. Molotkov, S. N. Moscow MV Lomonosov State Univ Fac Phys Moscow 119991 Russia Russian Acad Sci Prokhorov Gen Phys Inst Moscow 119991 Russia Moscow MV Lomonosov State Univ Quantum Technol Ctr Moscow 119991 Russia Acad Cryptog Russian Federat Moscow 121552 Russia Russian Acad Sci Inst Solid State Phys Chernogolovka 142432 Moscow Region Russia Moscow MV Lomonosov State Univ Fac Computat Math & Cybernet Moscow 119991 Russia

An attack exploiting single-photon avalanche diode (SPAD) blinding is one of the effective methods of 'quantum hacking' (Lydersen et al 2010 Nat. Photon. 4 686) or cracking quantum key distribution (QKD) systems. This attack was experimentally demonstrated for various QKD systems based on both phase and polarization coding. After such an attack, the eavesdropper knows the whole key, has not produced errors, and is not detected. So far this attack is the only one that was demonstrated in the explicit form on many real QKD systems. It is important that these demonstrations were actually performed in reality, i.e. not in speculations as some other attacks. Therefore, the presence of vulnerability in QKD systems based on polarization coding is an existing fact, rather than just a potential threat. It is often assumed that all systems regardless of the encoding method are vulnerable to such an attack. However, in the case of phase coding, some essential features of photocount statistics on the receiving side make a difference. In this Letter we prove that detector blinding attack, when acts on QKD systems with phase coding, leads to a distortion of the photocounts statistics so the eavesdropper may always be detected. Moreover, one does not need to change the design of the QKD system and/or its control electronics, as it is sufficient to amend only the processing of the quantum states registration results to make the system secure. At the same time, polarization coding-based systems remain vulnerable to such an attack and do not guarantee key security.

关键词： quantum cryptography detector blinding attacks phase coding

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Application of Wigner function for analysis of spectra in quantum cryptographic phase coding.

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ELEKTROTECHNIK UND INFORMATIONSTECHNIK 2007年第5期124卷 137-141页

作者： Suda, M. Austrian Res Ctr GmbH ARC Tech Gate TowerDonau City Str 1 A-1220 Vienna Austria

phase coding systems in quantum cryptography use two largely separated fiber glass Mach-Zehnder interferometers which belong to two communication partners, respectively. If both partners adjust their phase shifters accordingly, the time pulses behind the second interferometer exhibit interference effects which can be applied to the encoding - decoding procedure. In this article the energy and time spectra are analyzed by means of the Wigner function taking into account Gaussian wave packets, chromatic dispersion, absorption, phase shifters and the dimensions of the interferometric set-up.

关键词： quantum cryptography phase coding Wigner function

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Position reconstruction from an ensemble of hippocampal place cells: Contribution of theta phase coding

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JOURNAL OF NEUROPHYSIOLOGY 2000年第5期83卷 2602-2609页

作者： Jensen, O Lisman, JE Brandeis Univ Dept Biol Volen Ctr Complex Syst Waltham MA 02254 USA

Previous analysis of the firing of individual rat hippocampal place cells has shown that their firing rate increases when they enter a place field and that their phase of firing relative to the ongoing theta oscillation (7-12 Hz) varies systematically as the rat traverses the place held, a phenomenon termed the theta phase precession. To study the relative contribution of phased-coded and rate-coded information, we reconstructed the animal's position on a linear track using spikes recorded simultaneously from 38 hippocampal neurons. Two previous studies of this kind found no evidence that phase information substantially improves reconstruction accuracy. We have found that reconstruction is improved provided epochs with large, systematic errors are first excluded. With this condition, use of both phase and rate information improves the reconstruction accuracy by >43% as compared with the use of rare information alone. Furthermore, it becomes possible to predict the rat's position on a 204-cm track with very high accuracy (error of <3 cm). The best reconstructions were obtained with more than three phase divisions per theta cycle. These results strengthen the hypothesis that information in rat hippocampal place cells is encoded by the phase of theta at which cells fire.

关键词： Hippocampus Space Perception Theta Rhythm 海马空间知觉 θ节律 Theta Rhythm Rats FIRING phase coding Systematic errors Hippocampus Space Perception Fire Place Cells

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Mechanosensory-Based phase coding of Odor Identity in the Olfactory Bulb

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NEURON 2017年第5期96卷 1139-+页

作者： Iwata, Ryo Kiyonari, Hiroshi Imai, Takeshi RIKEN Lab Sensory Circuit Format Ctr Dev Biol Kobe Hyogo 6500047 Japan RIKEN Ctr Life Sci Technol Anim Resource Dev Unit Kobe Hyogo 6500047 Japan RIKEN Ctr Life Sci Technol Genet Engn Team Kobe Hyogo 6500047 Japan Japan Sci & Technol Agcy JST PRESTO Kawaguchi Saitama 3320012 Japan Kyoto Univ Grad Sch Biostudies Kyoto 6068501 Japan Kyushu Univ Grad Sch Med Sci Fukuoka 8128582 Japan

Mitral and tufted (M/T) cells in the olfactory bulb produce rich temporal patterns of activity in response to different odors. However, it remains unknown how these temporal patterns are generated and how they are utilized in olfaction. Here we show that temporal patterning effectively discriminates between the two sensory modalities detected by olfactory sensory neurons (OSNs): odor and airflow-driven mechanical signals. Sniff-induced mechanosensation generates glomerulus-specific oscillatory activity in M/T cells, whose phase was invariant across airflow speed. In contrast, odor stimulation caused phase shifts (phase coding). We also found that odor-evoked phase shifts are concentration invariant and stable across multiple sniff cycles, contrary to the labile nature of rate coding. The loss of oscillatory mechanosensation impaired the precision and stability of phase coding, demonstrating its role in olfaction. We propose that phase, not rate, coding is a robust encoding strategy of odor identity and is ensured by airflow-induced mechanosensation in OSNs.

关键词： olfaction temporal coding phase coding sniffing mechanosensation oscillations concentration invariance olfactory sensory neurons mitral/tufted cells olfactory bulb

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