- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Photon bunching and N-photon interference in thermal light
摘要： We investigate the contribution of four-photon bunching term in fourth-order double-slit interference intensity correlation based on two different detection schemes with a pseudo-thermal light source. It is clearly demonstrated that the resolution of intensity correlation is significantly enhanced by using of double-slit in both fourth-order and third-order intensity correlation. Meanwhile, the visibility of fourth-order correlation can be dramatically improved in contrast to the third-order due to the four-photon bunching term by contributing in the visibility of fourth-order correlation. The position and full width at half maximum of interference peaks of fourth-order intensity correlation are same as third-order. We also use two different scanning approaches to change the resolution and visibility of interference intensity correlation. In the first detection scheme, we scan three reference detectors along the same orientation and speed. In second detection scheme we scan two of three reference detectors in the same orientation, and speed of one reference detector is twice that of the other, and simultaneously moving the other two reference detectors with opposite orientation but identical speed. Those investigations can also be promoted to high order intensity correlation of thermal light.
关键词： Correlation,Photon bunching,Photon interference,Fourier optics
更新于2025-09-23 15:23:52
-
Single photon interference between bidirectionally extracted photons originating from semiconductor quantum dots
摘要： We report the experimental demonstration of the single-photon interference of bidirectionally extracted photons from epitaxially grown semiconductor quantum dots. The quantum dots were directly connected to single-mode optical fibers. Single-photon nature between transmission and reflection directions was confirmed through detection of antibunching in second-order photon correlation measurements. A Mach–Zehnder interferometer that was naturally formed by introducing the two outputs into a 2 x 2-fiber coupler was used to perform first-order photon correlation measurements.
关键词： single photon interference,single-mode optical fibers,Mach–Zehnder interferometer,semiconductor quantum dots
更新于2025-09-23 15:21:01
-
[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Time-Energy Entangled Photon Pairs from Doppler-Broadened Atomic Ensemble Via Collective Two-Photon Coherence
摘要： We experimentally demonstrate two-photon interference between a time-energy entangled photon pair generated from Doppler-broadened cascade-type 87Rb atoms using an unbalanced Michelson interferometer. In our system, the CW-mode time-energy entangled photon-pair sources are generated via the SFWM process and the collective two-photon coherence effect of a Doppler-broadened cascade-type atomic ensemble. The coherence time of the two-photon state from the Doppler-broadened atomic ensemble is more than 100 times longer than that of the single-photon state. We investigate two-photon interference (TPI) by means of highly time-resolved coincidence detection and determine the two-photon coherence length of a photon pair from the Doppler-broadened atomic ensemble. We observed fourth-order interference with visibility as high as 97% with the time-energy entangled CW-mode photon pairs from the atomic ensemble for the first time.
关键词： Doppler-Broadened Atomic Ensemble,Quantum Optics,Time-Energy Entangled Photon Pairs,Collective Two-Photon Coherence,Two-Photon Interference
更新于2025-09-12 10:27:22
-
[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Photon Correlations in PT-Symmetric Waveguide Systems
摘要： Parity-Time (PT)-symmetric systems have been intensely studied since their first description by Bender & Boettcher in 1998 [1]. Especially in photonics, numerous PT-symmetric effects and systems were investigated [2]. However, all of these experiments used classical light or single photons. Here, we present the first observation of two-photon interference in a lossy directional coupler and its associated Hong-Ou-Mandel (HOM) dip. In optics, PT symmetric potentials can be realized by enforcing a symmetric real part of the refractive index and an antisymmetric imaginary part (gain/loss) [3]. Notably, the transition to the quantum-optical regime precludes one from deploying gain [4], thus, we make use of entirely passive systems: By choosing an appropriate loss distribution, the behaviour of the system can be separated into a global loss factor and the desired non-Hermitian dynamics [5]. In this vein, the object of our following considerations is a passive PT-symmetric coupler in which two waveguides interact over a distance z, see Fig. 1 A. Rapid microscopic undulations of the waveguide trajectory serve to introduce effectively constant Markovian losses, resulting in the desired complex index distribution (B). Fig. 1. (A) In a pair of coupled waveguides, rapid undulations introduce bending losses and the (B) effective complex index distribution. (C) Dependence of the two-photon coincidence on the propagation length in the coupler. In contrast to the Hermitian case, PT-symmetry systematically displaces the dip minimum towards shorter propagation lengths, as indicated by the vertical dashed red line. In the experiment (D), corresponding coincidence data were obtained for Hermitian and PT-symmetric couplers. We achieved a dip with a visibility of 87±2 % and the minimum at 3 cm in the Hermitian case, and in the PT case 90±4 % at a position of 2.75 cm. We theoretically describe light propagation in the lossy directional coupler by a quantum master equation in Lindblad form. Our rigorous approach provides information on the full quantum state of the system. It is based on a Lie algebra treatment that provides us with an eigen-decomposition of the density matrix. The analytical solution holds for the unbroken PT-symmetry case, i.e. for losses that do not exceed twice the coupling. The resulting coincidence function for a |1,1> input state is plotted in Fig. 1 C: In the Hermitian case, the HOM dip occurs at exactly half the coupling length. In contrast, the interference minimum occurs after a shorter propagation length in the PT-symmetric system, as the vertical dashed line indicates. For the experiment, a set of lossy directional couplers of identical couplings with different propagation lengths was implemented to sample light at different z positions. A corresponding set of conventional Hermitian couplers served as baseline reference. Our measurements were executed with pairs of indistinguishable photons obtained by type-I spontaneous parametric down conversion, the coincidences at the sample output were recorded by avalanche photo detectors. In conclusion, our theoretical and experimental findings indicate that the asymmetric loss distribution in the PT-symmetric case can systematically accelerate the quantum interference dynamics in comparison to the Hermitian case.
关键词： PT-symmetric systems,two-photon interference,quantum optics,non-Hermitian dynamics,Hong-Ou-Mandel dip
更新于2025-09-12 10:27:22
-
Twin-field quantum key distribution with large misalignment error
摘要： Based on the novel idea of twin-field quantum key distribution [TF-QKD; Lucamarini et al., Nature (London) 557, 400 (2018)], we present a protocol named the "sending or not sending TF-QKD" protocol, which can tolerate large misalignment error. A revolutionary theoretical breakthrough in quantum communication, TF-QKD changes the channel-loss dependence of the key rate from linear to square root of channel transmittance. However, it demands the challenging technology of long-distance single-photon interference, and also, as stated in the original paper, the security proof was not finalized there due to the possible effects of the later announced phase information. Here we show by a concrete eavesdropping scheme that the later phase announcement does have important effects and the traditional formulas of the decoy-state method do not apply to the original protocol. We then present our "sending or not sending" protocol. Our protocol does not take postselection for the bits in Z-basis (signal pulses), and hence the traditional decoy-state method directly applies and automatically resolves the issue of security proof. Most importantly, our protocol presents a negligibly small error rate in Z-basis because it does not request any single-photon interference in this basis. Thus our protocol greatly improves the tolerable threshold of misalignment error in single-photon interference from the original a few percent to more than 45%. As shown numerically, our protocol exceeds a secure distance of 700, 600, 500, or 300 km even though the single-photon interference misalignment error rate is as large as 15%, 25%, 35%, or 45%.
关键词： misalignment error,single-photon interference,quantum key distribution,twin-field,decoy-state method
更新于2025-09-04 15:30:14