This PDF file contains the front matter associated with SPIE Proceedings Volume 11195, including the Title Page, Copyright information, Table of Contents, Author and Conference Committee lists.

One of the most famous cats in modern physics must be the Schroedinger’s Cat, in which he hypothesized that his cat cannot be determined alive or death until we look into his box. By which the paradox of his half-live cat had been puzzling the quantum physicists over three-quarter of a century since Schrödinger disclosed it in a Copenhagen forum in1935. Since the disclosure, the paradox has been debating by Einstein, Bohr, Schroedinger himself and many others renowned physicists, until now. We have found the cause of the paradox and we will show in this article, of which the hypothesis of Schroedinger’s Cat is not a paradox after all. It was the timeless radioactive particle he introduced into the box, since timeless and temporal spaces are mutually exclusive. We will show that the whole Schrödinger’s quantum world is timeless (i.e., t = 0) and his fundamental principle of superposition is timeless, since his quantum mechanics was built within an empty subspace. We will also stress that Schrödinger equation is mathematics and it is primarily designed to calculate particle’s quantum dynamics using particle-wave duality. Similar to the set of Maxwell equations; the solution has to satisfy the boundary condition of our universe; dimensionality, temporal and causality (i.e., t > 0) condition.

Raman fiber lasers are known for a various types of generation regimes based on their stochasticity properties. Usually, Raman fiber lasers generate in so-called turbulent generation regime characterized by almost stochastic temporal dynamics and wide generation spectrum. However, under specific conditions, one can achieve a so-called laminar generation regimes with largely suppressed temporal intensity fluctuations and narrow generation spectrum consisting of highly correlated longitudinal modes. From other side, by an introducing a concept of PT-symmetry, one can achieve generation regimes different by their parity-time-symmetry properties. In coupled Raman fiber lasers PT-symmetry could be introduced as well. In this manuscript we consider an interplay between PT-symmetric generation properties and temporal properties of the generation. We show that various turbulent and laminar generation regimes could have different PT-symmetric properties.

Quantum communication, i.e., the ability to transport a quantum state from one place to another, represents a crucial task for many quantum applications, i.e. quantum cryptography, quantum secret sharing and quantum networks. However current systems present main limitations in terms of low information rates, short propagation distances and low compatibility with today classical optical infrastructure. These restrictions bound the development of this field and its practical applications. High-dimensional quantum communication can help in overcoming these challenges enhancing the information rate and the system error tolerance. We here report our recent results on high-dimensional fiber based quantum communication, both with multicore and multimode fibers, in which we prove the capability of preparing, manipulating, transmitting and measuring advanced quantum states with excellent fidelities. Our results pave the way towards high-dimensional quantum communication in an optical fiber infrastructure.

Light propagation in disordered media is a fundamental and important problem in optics and photonics. In particular, engineering light-matter interaction in disordered cold atomic ensembles is one of the central topics in modern quantum and atomic optics. The collective response of dense atomic gases under light excitation, which crucially depends on the spatial distribution of atoms and the geometry of the ensemble, has important impacts on quantum technologies like quantum sensors, atomic clocks and quantum information storage. Here we analyze near-resonant light transmission in two-dimensional dense ultracold atomic ensembles with short-range positional correlations. Based on the coupled-dipole simulations under different atom number densities and correlation lengths, we show that the collective effects are strongly influenced by those positional correlations, manifested as significant shifts and broadening or narrowing of transmission resonance lines. We also analyze the eigenstate distribution of different atomic ensembles. This work may provide profound implications on collective and cooperative effects in cold atomic ensembles as well as the study of mesoscopic physics concerning light transport in strongly scattering disorder media.

We introduce our recent photonic quantum information processing experiments using the high-speed electro-optic modulator (EOM) based on a lithium niobate waveguides. First, we demonstrated the frequency shifter for single photons by using an optical single sideband (OSSB) modulator, which is based on the nested configuration of four phase modulators (PMs). By properly setting the RF modulation signal and the bias voltage to each PM, we can suppress unwanted sidebands to realize a frequency shifter that can tune the frequency of single photons with accuracy of an RF synthesizer. Using the OSSB modulator, we eliminated the frequency distinguishability between two single photons whose frequencies were different by 25 GHz, and as a result observed a Hong-Ou- Mandel interference with a visibility exceeding 90%. We also proposed and demonstrated a two-qubit controlled logic gate for time-bin qubits using a two-input, two-output optical switch. The switch enables us to individually perform different functions for two temporal bases as a time-dependent beam splitter, so that we can realize controlled-phase (C-Phase) gate for a time-bin qubit. We showed that the states of two separable single photons were entangled as a result of the C-Phase gate operation. We performed the quantum state tomography to obtain density matrices of the output states from the C-Phase gate for some specific input states, and confirmed that the averaged state fidelity to the pure states was 85%. These results indicate that the EOMs will be a useful tool for realizing advanced photonic quantum communication systems.

We report an experimental realization of nonlinear frequency conversion (NFC) and manipulation of vector beams (VBs) that can be used to expand the available frequency band. The main idea of our scheme is introduction of a Sagnac loop to solve the polarization dependence problem of NFC in nonlinear crystals. The experimental results agree well with those of our theoretical model.

Characteristics of vector beams in mid-infrared waveband are analyzed numerically in an As₂Se₃ photonic crystal fiber (PCF) with small central hollow core (SCHH), including the mode fields, confinement loss, effective refractive index and chromatic dispersion. In the PCFs with the SCHH diameter d₀ of 0-1.5 μm, the confinement losses of the four vector beams (HE₁₁, TM₀₁, TE₀₁, and HE₂₁) are smaller than 1.0 dB/m for the wavelengths up to ~5 μm. For the SCHH diameter d₀ of 0.5-1.5 μm, the field enhancement of the HE₁₁ mode occurs in the SCHHs in the central area for the wavelengths ≤ 5 μm. This happens because the evanescent light penetrates into the SCHH. With d₀ increasing, the effective refractive index separations (δ_neff) between the HE₁₁ mode and high-order modes (TM₀₁, TE₀₁, and HE₂₁) decreases, while the δ_neff among the high-order modes increases. At the wavelength of 5 μm, the δ_neff of HE₁₁-TE₀₁, TE₀₁- HE₂₁, and HE₂₁-TM₀₁ is 0.03098, 0.03960, and 0.06867, respectively, when d₀ is 1.5 μm. The second ZDWs of TE₀₁, HE₂₁ and TM₀₁ mode are blueshifted with the increase of d₀, but they are longer than 5 μm. The negative dispersion regions of the high-order modes (TE₀₁, HE₂₁, and TM₀₁) are much wider than the HE₁₁ modes. With the increase of d₀, the HE₁₁ mode dispersion curves have no obvious change, while the high-order modes (TE₀₁, HE₂₁, and TM₀₁) dispersion curves become steep at the longer wavelength, the TM₀₁ mode changes most obviously, and the depression appears. To demonstrate the application of the PCF, super-continuum generation pumped by the four vector modes are simulated and analyzed. Our simulated results will be useful for the optical applications in mid-infrared waveband, such as the generation of cylindrical vector mode and orbital angular momentum (OAM) and the particle manipulation by optical fields.

In this work, we propose and demonstrate the frequency-bin entangled two-photon state via cascaded second harmonic generation and spontaneous parametric down conversion (SHG-SPDC) processes in a single piece of PPLN waveguide. Our scheme is based on all fiber-pigtailed components at 1.5 μm telecom band. Two frequency-bins at 1531.34 nm and 1548.91 nm with bandwidth of 1.04 nm are prepared to be entangled. The frequency entanglement property of our generated two-photon states is measured by spatial two-photon quantum beating. A two-photon beating curve with a visibility of 87.92±0.47% is obtained, showing a good property of frequency-bin entanglement.

Presented for the first time is our research into reduction of energy consumption of miniaturised Rb atomic clocks based on coherent population trapping (CPT) effect at lowered microwave modulation frequency. We studied properties of a CPT-based atomic frequency standard pumped with multi-frequency radiation from sidebands of a single-frequency semiconductor laser whose injection current was modulated at subharmonics (1/2–1/6) of the frequency of Rb hyperfine ground state splitting. Pumping by third-order sidebands is the optimum when the atomic clock stability drops only slightly (by 11%), whereas energy consumption of the microwave components is reduced by a factor of 1.5.

In this paper, mathematical model and simulations displaying the phenomenon of modal instability (MI) in 1050 nm pumped heavily doped Thulium (Tm³⁺) fiber amplifier is presented. Pulse splitting effect through MI with variation in chirp parameter and non-linear fiber length was modeled and simulated. The pulses considered were sech, Gaussian, and super-Gaussian type. Model was computationally solved on MatLab and the results were verified by incorporating similar conditions and parameters on OptiSystem 16 simulation platform. Results concludes the optimum non linear length (L_NL) and the chirp parameter (C = 12) which has to be taken so as to obtain continues time domain pulse train as well as linearly spaced frequency combs. The repetition rate of 500 MHz for 4 ps pulse at 1460 nm with peak sub-pulse energy of 8 nJ was obtained and has been reported to the first time (under MI mechanism) to the authors' knowledge. Optimum TDFA length was concluded as 375 m at which MI phenomenon was triggered.