This PDF file contains the front matter associated with SPIE Proceedings Volume 9269 including the Title Page, Copyright information, Table of Contents, Authors, and Conference Committee listing.

Entanglement distillation is an indispensable ingredient in extended quantum communication networks. Distillation protocols are necessarily non-deterministic and require non-trivial experimental techniques such as noiseless amplification. We show that noiseless amplification could be achieved by performing a post-selective filtering of measurement outcomes. We termed this protocol measurement-based noiseless linear amplification (MBNLA). We apply this protocol to entanglement that suffers transmission loss of up to the equivalent of 100km of optical fibre and show that it is capable of distilling entanglement to a level stronger than that achievable by transmitting a maximally entangled state through the same channel. We also provide a proof-of-principle demonstration of secret key extraction from an otherwise insecure regime via MBNLA. Compared to its physical counterpart, MBNLA not only is easier in term of implementation, but also allows one to achieve near optimal probability of success.

The classification of quantum symmetric-key encryption protocol is presented. According to five elements of a quantum symmetric-key encryption protocol: plaintext, ciphertext, key, encryption algorithm and decryption algorithm, there are 32 different kinds of them. Among them, 5 kinds of protocols have already been constructed and studied, and 21 kinds of them are proved to be impossible to construct, the last 6 kinds of them are not yet presented effectively. That means the research on quantum symmetric-key encryption protocol only needs to consider with 5 kinds of them nowadays.

Squeezed light is a nonclassical state of electro-magnetic field and has noise suppressed below the standard quantum limit in one quadrature component while increased in the other. One of the important applications of squeezed lights is quantum enhanced sensing such as gravitational wave detector with ultimate resolution. Another important application is continuous variables quantum teleportation which utilizes two mode squeezed lights as an essential resource for quantum entanglement. In these applications the final outcome is limited by squeezing level. So it is important to generate highly squeezed light. Over the past few decades a considerable number of the experiments have been performed to generate highly squeezed lights. One of the successful methods is utilization of a sub-threshold optical parametric oscillator (OPO) which includes a nonlinear optical crystal. In this article we will introduce current development of experimental investigation of continuous-wave highly squeezed light by utilizing the OPO and current topics about applications of squeezed light.

We present investigation of a single nitrogen-vacancy (NV) center in diamond and couplings to surrounding electron spins. Using double electron-electron resonance spectroscopy, we demonstrate magnetic resonance (MR) spectroscopy of nitrogen electron spins surrounding a single NV center in diamond. In addition, we discuss development of a MR system to investigate NV centers at high magnetic fields.

Recent years, the research of mid-infrared (mid-IR) photonics has inspired increasingly interest due to their potential applications in a wide variety of areas, including free-space communications, chemical or biological sensors, environmental monitors, thermal imaging, IR countermeasures and medical procedures. On the other hand, third harmonic generation (THG) has been demonstrated to be a versatile tool to realize high speed optical performance monitoring of in-band OSNR and residual dispersion. The mid-IR light sources based third-order frequency conversion opens an entirely new realm of nonlinear interactions. Nevertheless, rare experimental or analytical THG modeling has been published. In this work, we theoretically investigate the possible efficient phase-matched THG in a double symmetric plasmonic slot waveguide (DAPSW) based on a mid-IR light source. Nonlinear organic material DDMEBT with thirdorder susceptibility of χ⁽³⁾ = 1×10^-19 m²/V² is integrated into the top metallic slot region as the main slot core medium. Silicon (Si) is used to fill the bottom metallic slot region. Silver (Ag) is considered to be the metal medium due to its low Ohmic loss. The needed phase-matching condition (PMC) is satisfied between the zeroth mode at fundamental frequency (FF) and the first mode at third harmonic (TH) by appropriate designing the waveguide geometrical parameters. The associated parameters such as the width and height of the slot, pump-harmonic modal overlap, figureof- merit (FOM), pump power and detuning have been numerically investigated in detail. Finally, the conversion efficiency comes up to 1.69×10^-5 with pump power of 1 W and the corresponding waveguide length is 10.8 μm.

We theoretically and experimentally investigate the generation of square optical bottle, which are generated by double Airy beam induced by binary phase pattern. A regulable linear factor is introduced into phase function to modulate flexibly the size of optical bottle. Numerical simulations are performed and experimental results also show that Gaussian beam can be shaped into square optical bottle by a tunable binary cubic phase pattern. The linear factor can vary the region size of zero or low intensity of optical bottle. It is believed that the intriguing characteristic of square optical bottle can be applied in many applications such as optical tweezers, atom trapping and manipulating.

Mercury is the heaviest stable atom that could be laser cooled, and have a large nuclear charge number. So it has a distinct advantage in quantum precision measurement such as fine-structure constant α and permanent electric dipole moment. Due to its insensitivity of black body radiation, atomic mercury is a good candidate of optical clock. Here we report our recent development of laser cooling of neutral mercury atom. By cooling the mercury source to about -70°C, an ultra-high vacuum system was realized to produce ultracold mercury atoms. The commercial frequency quadrupled semiconductor laser is locked on the cooling transition (¹S₀-³P₁ transition, wavelength of 253.7 nm) by sub-Doppler frequency modulation spectroscopy. By the modification with feed-forward method, the UV laser becomes faster tunable and more stable. A folded beam configuration was used to realize the magneto-optical trap (MOT) because of the shortage of cooling laser power, and the ultracold mercury atoms were observed by fluorescence detection. All of six rich abundant isotopes have been observed, and the atom number is about 1.5×10⁶ with density of 3.5×10⁹ /cm³ for ²⁰²Hg. With optical shutter and the programmable system to control the time sequence, the temperature of ultracold atoms can be measured by time of flight method. To enhance the laser power, a 1014.8 nm fiber laser amplifier was developed, which can work at room temperature. After two stages of frequency doubling, about 75 mW of 253.7 nm UV laser were generated, and the saturated absorption spectroscopy of mercury atom was also observed. More power of UV laser could help to trap more atoms in the future. These works laid a good foundation to realize the mercury lattice clock.

In an imaging system based on a coherent source of moderate power density, images can be blurred when a biased photorefractive crystal is applied at the focal point of the imaging lens. In the frequency domain of the original images, the intensity patterns are diffracted through the photorefractive crystal with varied bias voltage. The high intensity region, which is usually the center or low frequency region of the intensity patterns, is more readily focused or defocused, resulting in blurred images in perception. Such blurred images could not be simply recovered by defocusing methods, which can only indistinguishably focus or defocus the whole intensity patterns. However, the blurred images may be deblurred to certain extent for recovery if a second photorefractive crystal with bias voltage is employed at the focal point of a tandem imaging system. The mechanism of deblurring is similar to that of blurring: the blurred images are transferred through the frequency domain again using an imaging lens, where the second biased photorefractive crystal diffracts the intensity patterns to revert the sensitive region where previously gets focused or defocused. In this work, theoretical analyses are presented in detail to explain the blurring-deblurring mechanism using two biased photorefractive crystals and compatible experimental results are obtained and illustrated. Considering the blurring and deblurring function subgroups of the experiment setup can be potentially developed into encryption and decryption units compatible with far field propagation, the technology presented herein may be promising to find applications in secure laser-based free-space communication systems.

We propose two interactive identification protocols based on a general construction of quantum public-key cryptosystem. Basic protocol contains set-up phase and authentication phase. Participants do operation with quantum computing of Boolean function in two-round transmission of authentication phase. Basic one only ensures completeness and soundness, but leaks information about private-key. We modify basic protocol with random string and random Boolean permutation. After modification, both transmitted states in two-round transmission can be proved to be ultimate mixed states. No participant or attacker will get useful information about private-key by measuring such states. Modified protocol achieves property of zero-knowledge.

Squeezed light is an important non-classical light field. In this paper, we demonstrated a designed active imaging system which use squeezed state light instead of coherent light as light source. The squeezed state light is generated by utilizing the degenerate optical parametric amplifier based on periodically poled KTiOPO₄ crystal. In order to obtain better imaging results, microlens arrays are used for homogenizing the squeezed light. We describe experiment setup and present some design result.

We present a theoretical study on the nonlinear behaviors of the electromagnetically induced transparency resonance subject to two microwave driving fields in a four-level atom system. The probe absorption spectrum is obtained by solving numerically the relevant equations of density matrix. It is shown that there are two pairs of the EIT windows in the probe absorption spectrum. The two pairs of EIT windows have symmetry with respect to the resonance frequency of the probe field, and the separation is equal to the Rabi frequency of the resonant microwave driving field. But in each pair, the splitting of two EIT windows is dominated to the strength of detuning microwave driving field.

We theoretically investigate the photon statistics in a cavity quantum electrodynamics system of a single quantum dot (QD) coupled to photonic molecule. Our previous work [Wen Zhang et.al, Phys. Rev. A 89, 043832 (2014)] has shown that QD-bimodal cavity system can generate ultrastrongly sub-Poissonian light by regulating the ratio between driving strengths of two cavity modes. Here we study two coupled single-mode nanocavities with a QD coupling to one of them as a photonic molecule system. Statistical character of photon emission is presented by evaluating the zero-delay secondorder correlation function g²(0). When both cavities with/without QD are driven, the sub-Poissonian character can be optimized by regulating the ratio between driving strengths of each cavities. We also present the dependences of other system parameters on the photon statistics. The physical mechanism of both effects is to optimize the combination of super-Poissonian and coherent light which results in sub-Poissonian light generation. As a result g²(0) can be reduced up to several orders of magnitude compared with the QD coupled one-mode-cavity system.

We study the entanglement dynamics of T-C (Tavis-Cummings) model without rotating wave approximation. By using displaced coherent state method, the influence of initial state and coupling strength to concurrence is numerically studied. Our result demonstrates that the entanglement between two atoms always keep maximum when the initial state is antisymmetric while the non-entangled initial state produce entanglement periodically due to the effect of non-rotating terms. We also show that the coupling strength between the cavity field and atoms play a critical role in the entanglement dynamics.

The interference resonant propagation and spectral properties of a superposition of two femtosecond chirped Gaussian pulses with equal pulse area and same size but opposite sign of the chirp coefficient (C) in a three-level Λ-type atomic medium is investigated by using the numerical solution, which is obtained by the finite-difference time-domain (FDTD) method and the iterative predictor–corrector (PC) method for the full Maxwell–Bloch equations. It is found that, for the double pulses with smaller area, (2π, 2π) double pulses, the pulse splitting occurs when the value of the |C| is smaller, and only the variation of pulse shape is present but the pulse splitting no longer occur when the value of the |C| increases to a certain value; New high frequency component doesn’t basically appear and the strength of the spectral component near the central frequency decreases considerably but the strength of blue shift component is not varied obviously with the value of |C| increasing. For the double pulses with larger areas, the case of pulse splitting is similar to that of (2π, 2π) pulses, but the strength of the spectral component with higher frequency increase evidently comparing with the case of (2π, 2π) double pulses. Moreover, the value of the |C| also has an obvious effect on population, different population evolutions can be achieved by adjusting the value of |C|.

Spatial characteristics of radiation generated from electron oscillations driven by circularly polarized femtosecond laser pulses have been investigated theoretically and numerically using a single electron model. It is discovered that the radiated power is approximately the same in all the directions for the driver laser pulses with low power intensities and the radiation is directed toward the direction of the laser pulses propagation with a narrower divergence and is tipped forward more and more with the increase of laser intensity. The full spatial emission characteristics can be exploited to measure the intensity of circularly polarized laser pulses in the experiment.

This work, based on third-order nonlinear coupled-mode equations, aims at analyzing the optimization in one-third harmonic generation processes with initial conditions, including the initial ratio of the incident light power, phase difference, diameter and effective length of silica microfibers. Through the application of the microfiber loop resonators to one-third harmonic generation process, we reduce the incident power threshold of seed light by tens orders, and increase the nonlinear effective interaction length by several hundreds of times. Theoretical calculation results show that the loop resonator can effectively enhance the conversion efficiency of one-third harmonic generation by 10⁴ compared with the straight microfibers.

We report a four-photon resonant nondegenerate eight-wave mixing (NEWM) in a dresses N-type six-level system. It has advantages that phase match condition is not stringent and NEWM signal is enhanced tremendously due to the multiple resonance with the atomic transition frequencies. In the prenence of a strong coupling field, the four-photon resonant NEWM spectrum exhibits Autler-Townes splitting. Compared to two-photon resonant nondegenerate four-wave mixing and three-photon resonant nondegenerate six-wave mixing in dressed atoms, four-photon resonant NEWM spectrum is more complicated and can provides information about the relaxation of higher-order atomic coherence.

We have experimentally investigated supercontinuum generated by using different pulse dynamics patterns as the pump pulses. These patterns, which include conventional mode-locked single pulse, condensed phase pulses and pulsed bunches, were all directly produced from a mode-locked erbium-doped fiber laser based on a multi-layer graphene saturable absorber. The strong third-order optical nonlinearity of graphene and all fiber cavity configuration led to the multi-pulses operation states at a low pump power. A flat supercontinuum with 20-dB width of 550 nm from 1200 nm to 1750 nm have all been obtained by seeding the amplified conventional mode-locked single pulse and condensed phase pulses into a segment of photonic crystal fiber. On the other hand, experimental results also show that the pulsed bunches was not conducive to form a flat supercontinuum.

Based on the four-wave mixing mechanism and light fanning effect, a mutually pumped phase conjugator(MPPC) model is proposed to analyze the variation of MPPC output response with time for different scattering seed value. It shows that preset grating can enhance the fan light intensity when it satisfies Bragg condition and also can shorten MPPC response time. In experiment the bird-wings MPPC is done with or without the preset grating and the variation of MPPC reflectivity with time is obtained in two cases, and simulation conclusion is in agreement with the experimental result. These results have importance for applications of MPPC on optical heterodyne detection.

In this paper, we do some research on the interior period microstructure of transparent materials induced by a femtosecond laser of 800-nm wavelength. By adopting a nonlinear propagation physical model of femtosecond laser pulses and considering the spherical aberration effect(SA), we analyze the influence of nonlinear effects such an self-focusing, GDV, MPA, plasma defocusing and interface aberration on femtosecond laser propagation in transparent materials. Meantime, in the case with nonlinear effects and interface aberration, we research the influence of fs laser power, pulse width, numerical aperture and focusing depth on period microvoid. Simultaneously, compared with simulating results in different focusing lens numerical aperture, we find that big numerical aperature and deep focusing more easily produced period voids.