Advances in quantum physics and computational complexity threaten the security of present day cryptographic systems and have driven the development of quantum key distribution (QKD). Entangled quantum key distribution (EQKD) is a secure protocol that is based on fundamental quantum mechanics and is not vulnerable to these threats. The primary figure of merit for QKD systems is ability to generate secret bits. However, to date, methods that have been developed to simulate the secret bit rate generation for EQKD systems have been limited by techniques that do not provide a complete description of the quantum state produced by the source. In this paper, we provide a complete description and comparison of the secret bit rate for continuous-wave and pulsed laser EQKD systems. In particular, we highlight the relevant Poissonian and thermal photon statistics that affect the EQKD secret bit rate and use practical system parameters and configurations to show regimes where one expects optimal performance for each case.
Deployment of Entanglement-Based QKD in Financial Infrastructure
zerothird GmbH（零第三有限公司）；University of Vienna, Faculty of Physics, Vienna Center for Quantum Science and Technology (VCQ)（维也纳大学物理学院维也纳量子科学与技术中心）；Vienna Doctoral School in Physics (VDSP)（维也纳物理学博士学院）；qtlabs GmbH（量子实验室有限公司）；Atominstitut, Technische Universität Wien（维也纳工业大学原子研究所）
Resonant spontaneous bremsstrahlung of an electron scattered by a nucleus in the field of two moderately strong pulsed laser waves is studied theoretically. The process is studied in detail within the interference kinematic region. This region is determined by scattering of particles in the same plane at predetermined angles, at that stimulated absorption and emission of photons of external pulsed waves by an electron occurs in correlated manner. The correspondence between the emission angle and the final-electron energy is established in the kinematic region where the resonant parametric inte…
Quantum random number generator (QRNG) can produce true randomness by utilizing the inherent probabilistic nature of quantum mechanics. Recently, the spontaneous-emission quantum phase noise of the laser has been widely deployed for QRNG, due to its high rate, low cost and the feasibility of chip-scale integration. Here, we perform a comprehensive experimental study of phase-noise based QRNG with two independent lasers, each of which operates in either continuous-wave (CW) or pulsed mode. We implement QRNGs by operating the two lasers in three configurations, namely CW+CW, CW+pulsed and pulsed…
We have constructed a pulsed laser system for the manipulation of cold Rb atoms. The system combines optical telecommunications components and frequency doubling to generate light at 780 nm. Using a fast, fibre-coupled intensity modulator, output from a continuous laser diode is sliced into pulses with a length between 1.3 and 6.1 ns and a repetition frequency of 5 MHz. These pulses are amplified using an erbium-doped fibre amplifier, and frequency-doubled in a periodically poled lithium niobate crystal, yielding a peak power up to 12 W. Using the resulting light at 780 nm, we demonstrate Rabi…
The dynamics of atom lasers with a continuous output coupler based on two-photon Raman transitions is investigated. With the help of the time-convolutionless projection operator technique the quantum master equations for pulsed and continuous wave (cw) atom lasers are derived. In the case of the pulsed atom laser the power of the time-convolutionless projection operator technique is demonstrated through comparison with the exact solution. It is shown that in an intermediate coupling regime where the Born-Markov approximation fails the results of this algorithm agree with the exact solution. To…
Pulsed laser attack at 1061 nm potentially compromises quantum key distribution
Russian Quantum Center（俄罗斯量子中心）；NTI Center for Quantum Communications, National University of Science and Technology MISiS（NTI量子通信中心，国立科技大学MISiS）；Prokhorov General Physics Institute of Russian Academy of Sciences（俄罗斯科学院普洛霍罗夫普通物理研究所）；Vigo Quantum Communication Center, University of Vigo（维戈大学维戈量子通信中心）；School of Telecommunication Engineering, Department of Signal Theory and Communications, University of Vigo（维戈大学电信工程学院信号理论与通信系）；atlanTTic Research Center, University of Vigo（维戈大学atlanTTic研究中心）；National Research University Higher School of Economics（国立高等经济大学）；College of Computer Science and Technology, National University of Defense Technology（国防科技大学计算机科学与技术学院）；Institute of Automation and Electrometry of Siberian Branch of RAS（俄罗斯科学院西伯利亚分院自动化与电磁学研究所）
The coherent dark resonance between the hyperfine levels F=1, m=0 and F=2, m=0 of the rubidium ground state has been observed experimentally with the light of a pulsed mode-locked diode laser operating at the D1 transition frequency. The resonance occurs whenever the pulse repetition frequency matches an integer fraction of the rubidium 87 ground state hyperfine splitting of 6.8 GHz. Spectra have been taken by varying the pulse repetition frequency. Using cells with argon as a buffer gas a linewidth as narrow as 149 Hz was obtained. The rubidium ground state decoherence cross section 1.1*10^(-…
Robustness of fiber-optic attenuators to 1061-nm sub-nanosecond pulsed laser radiation in quantum key distribution systems
Russian Quantum Center（俄罗斯量子中心）；NTI Center for Quantum Communications, National University of Science and Technology MISiS（国家科学技术大学MISiS NTI量子通信中心）；Prokhorov General Physics Institute of Russian Academy of Sciences（俄罗斯科学院普尔科沃普通物理研究所）；National Research Nuclear University MEPhI（国立核研究大学莫斯科工程物理学院）；Ulyanovsk State University（乌里扬诺夫斯克国立大学）；College of Computer Science and Technology, National University of Defense Technology（国防科技大学计算机科学与技术学院）；Vigo Quantum Communication Center, University of Vigo（维戈大学维戈量子通信中心）；School of Telecommunication Engineering（电信工程学院）
We study the output properties of a pulsed atom laser consisting of an interacting Bose-Einstein condensate (BEC) in a magnetic trap and an additional rf field transferring atoms to an untrapped Zeeman sublevel. For weak output coupling we calculate the dynamics of the decaying condensate population, of its chemical potential and the velocity of the output atoms analytically.
We theoretically study a pulsed stimulated two-photon Raman outcoupler for an atom laser using a full three-dimensional description. A finite-temperature trapped Bose-condensed atomic gas is treated self-consistently by the Hartree-Fock-Bogoliubov equations. The model is closely related to a recent experiment on optical outcoupling [E.W. Hagley et al., Science 283, 1706 (1999)]. We analyze the momentum distribution of the output atoms and show how the output beam may be used as a probe of the quantum state for the trapped atomic gas and how it could be engineered and controlled in a nonlinear …
Theoretical and experimental study of the correlation between pulsed light repetition frequency and electric field measurement
Chongqing University of Post and Telecommunications（重庆邮电大学）；State Key Laboratory of Quantum Optics Technologies and Devices, Shanxi University（山西大学量子光学技术与器件国家重点实验室）
Photoinduced biological processes occur via one photon absorption in natural light, which is weak, CW and incoherent, but are often studied in the laboratory using pulsed coherent light. Here we compare the response of a molecule to these two very different sources within a quantized radiation field picture. The latter is shown to induce coherent time evolution in the molecule, whereas the former does not. As a result, the coherent time dependence observed in the laboratory experiments will not be relevant to the natural biological process. Emphasis is placed on resolving confusions regarding …
We report a study on light force on a beam of neutral two-level atoms superimposed upon a few-cycle pulsed Gaussian laser field under both resonant and off-resonant condition. The phenomena of focusing, defocusing and steering of the neutral atoms in the laser field is analysed by solving the optical Bloch equation beyond the rotating wave approximation and the force equation self-consistently .We find that two-level atoms in an atomic beam could be focused and defocused for large, positively and negatively detuned interaction even in the regime of extreme nonlinear optics. The so-called optic…
Laser-cleaning of the electrodes in a planar micro-fabricated ion trap has been attempted using ns pulses from a tripled Nd:YAG laser at 355nm. The effect of the laser pulses at several energy density levels has been tested by measuring the heating rate of a single 40Ca+ trapped ion as a function of its secular frequency. A reduction of the electric-field noise spectral density by ~50% has been observed and a change in the frequency dependence also noticed. This is the first reported experiment where the "anomalous heating" phenomenon has been reduced by removing the source as opposed to reduc…
