Four entangled photons generation using weak light and an all fiber optic scheme for multi-entangled photons generation

This paper proposes a simple scheme of four entangled photons generation using a pulse of weak light input into a Mach-Zehnder interferometer (MZI) incorporating a fiber optic ring resonator (FORR) without any optical pumping components included in the system. After a pair of entangled photon has been generated by a four-wave mixing of weak light pulse in the FORR [P.P. Yupapin, S. Suchat, Entangled photon generation using fiber optic Mach-Zehnder interferometer incorporating the nonlinear effect in a fiber ring resonator, Journal of Nanophotonics (JNP) 1 (2007) 013504], four and eight entangled photons can be performed. In application, the multi-entangled states can be formed using the appropriated coupling ratios into a fiber coupler. The effect of the entangled state walk-off along the optical fiber is discussed.     

An investigation of the entangled photon walk-off compensation generated by a fiber ring resonator

We firstly present an experimental investigation of the entangled photon states’ recovery using a fiber optic ring resonator incorporating an erbium-doped fiber amplifier (EDFA). The weak light entangled photons can be recovered in both amplitude and states after the optical pumping and polarization control parts are used in the system. A new experimental result of the investigation of thermal effects on the entangled states’ walk-off and compensations has shown that the entangled photon walk-off compensation is achieved by using a pair of polarization control devices. The relationship between thermal effects and the entangled states’ phase shift is investigated and discussed. The walk-off compensation due to temperature changes from 30 to 80 °C is achieved. This shows that the changes in phase of the entangled photons can be negligible when the compensation is employed.     

Quantum key distribution via fiber optic, fidelity and error corrections

We propose an interesting scheme on photon states generation using a fiber optic Mach Zehnder interferometer incorporating a fiber optic ring resonator without any optical pumping parts including in the system, which is available for long-distance link. In principle, the state of a quantum bit, it is known, unknown, or entangled to other systems. The desired quantum states are generated and transmitted in the link via a fiber optic. The transmission quality in terms of quantum fidelity is analyzed, where a high fidelity to the noiseless quantum channel is achieved by adding an ancillary photon after the signal photon within the correlation time of the fiber noise and by performing the quantum parity checking method. The error correction is also analyzed. For simplicity, feature and robustness against path-length mismatches among the nodes make our scheme suitable for multi-user quantum communication networks.     

Thermal dissipation effects of the entangled photon generated by four-wave mixing process in a nonlinear ring resonator

We firstly analyze the thermal dissipation effects of the entangled photons generated by a nonlinear optical ring resonator. To obtain the corresponding equation of motion of the entangled photons generated by a four-wave mixing process within the system, we propose the Markov approximation to repel the reservoir operators. The system master equation in the interaction picture for both degenerate and non-degenerate cases is analyzed and obtained. The established system can be used to characterize the optimum entangled photons in some cases where the thermal dissipation effects may be introduced noise into the system. In this work, the entangled photons can be generated into two forms, firstly, the two entangled photon states is generated, the other, the four entangled photon states can be easily obtained. Results obtained have shown that the optimum entangled photon in term of entangled photon visibility can be compensated (i.e. unchanged) under thermal dissipation effects.     

Quantum noise generated by four-wave mixing process within a fiber ring resonator

We have analyzed the dissipative effect of the entangled photons generated by a nonlinear optical ring resonator from a non-degenerate four-wave mixing (FWM) process. The system and reservoir Hamiltonian are established in the interaction picture. To eliminate the reservoir operators, the Markov approximation is used and result them in a Linblad form in the master equation. Consequently, the positive P representation can recast this equation to the Fokker-Planck equation, and then the stochastic differential equations i.e., the entangled photon state equation of motion for photons propagating in the fiber, are obtained and easy to analyze numerically. Results obtained have shown that the entangled strength measurement depends on three main factors; first the nonlinear susceptibility of the third harmonic generation, second the damping rate that represents loss of energy from the system to the reservoir, and final the diffusion of fluctuations in the reservoir into the entangled photon modes.     

Second-harmonic generation via micro ring resonators for optimum entangled photon visibility

An analysis of a new technique for quantum key distribution (QKD) using the entangled photon within a micro ring resonator is presented. The Kerr nonlinear type of light in the micro ring resonator induces the nonlinear behavior known as chaos within the device, where the superposition of the chaotic signals via a four-wave mixing type introduces the clear second-harmonic pulses. The generation of clear second-harmonic pulses is achieved by controlling the appropriate ring parameters. When the polarization control devices are applied into the system, the optimal entangle photon visibility is obtained. The condition for long-distance link is discussed, where the optimal entangled photon visibility in term of Bell's states is described.     

Nonlinearity penalties and benefits of light traveling in a fiber optic ring resonator

The nonlinearity properties of light traveling in a fiber optic ring resonator (FORR) are presented. The nonlinearity penalties suffering from Kerr effects and four-wave mixing nonlinear types including bistability, chaos and bifurcation are investigated. The advantages of the nonlinearity penalties including photon correlation, optical switching and information security using chaotic signals are also discussed. The obtained results have shown that the parameters of FORR can be changed, and thus the penalties of the nonlinear effects have shown the potential of using for some applications.     

纠缠相干态的纠缠浓缩

利用线性光学元器件对光场量子态进行操纵,可以实现远程的量子纠缠调控和量子通讯.通过分析光学分束器对相干态光场的作用,发现当初始光场态是两个两部分纠缠态的直乘时,让其中的两模通过光学分束器作用后再对其进行光子计数,另外两模将会塌缩到新的纠缠态.基于这个特点,提出了一个实现部分纠缠相干态纠缠浓缩的方案.在这个方案中,两个部分纠缠相干态被用来作为量子信道,通过光学分束器作用后对光场进行光子数探测时,如果测量到光场的两模分别处于奇光子数态和零光子数态,则光场另外的两模将塌缩到最大纠缠态,从而完成纠缠浓缩的过程.计算结果表明,对于纠缠相干态,无论其初始的纠缠是多么微弱,利用这种方法总有一定的几率可以从中提纯出最大纠缠态.     

Polarized soliton pulses generation using nonlinear micro ring resonators for multi- and long distance links

We propose a new concept of quantum soliton pulses generation using a soliton pulse in the micro ring resonators. Firstly, the chaotic soliton pulses are generated and circulated within the integrated micro ring resonators. Secondly, the specific second harmonic pulses are selected by using the appropriate ring parameters. The superposition of the second harmonic pulses within the micro ring devices introduces the randomly polarized photons within the micro ring device. The entangled photon visibility of the polarized photon is seen after passing the polarization control devices and projecting on the detectors. The optimum entangled photon visibility is obtained. The advantage of such a system is that the quantum repeater unit can be redundant for long distance quantum communication link, whereas the use of the system for multi-entangled photon sources and links is also available. The system degradation via the entangled photon states timing walk-off is also discussed.     

A novel multi-optical/quantum memory and encoding system using multi-photon generation

We propose a novel system of an optical/quantum memory generation, which can be used for multi-optical/quantum memory applications. The large bandwidth of a single pulse is generated using a soliton pulse in a Kerr-type nonlinear medium, i.e. a nonlinear waveguide. The generation of the localized temporal and spatial soliton pulses within the nano-waveguide is achieved. The free spectrum range enhancement of the generated multi-soliton signals can be formed and achieved using the nano-waveguide incorporating the Mach Zhender Interferometer (MZI). The different light path of the soliton pulses is introduced by the delayed lines of the interferometer. This improves the wavelength free spectrum range, where the different entangled photon pairs can also obtained. Furthermore, the generated photons can be filtered and stored within a system, where the storage of single or multi-photons using the proposed system can be achieved, which in turn can be used for multi-optical/quantum memory applications.     

Chaotic signal generation and cancellation using a micro ring resonator incorporating an optical add/drop multiplexer

We propose a new design of a chaotic signal generation and cancellation system using an all fiber optic scheme. A system consists of a standard diode laser, a fiber optic micro ring resonator, and an optical add/drop multiplexer. When light from the diode laser is input into the fiber ring resonator, the chaotic signal can be generated by using the selected fiber ring resonator parameters and the diode laser input power. The required signal is obtained in the transmission link via the add/drop device by a specific user at the drop port. Simulation results obtained have shown the potential of application, especially, when the practical ring radius is 10 μm with the optical input power is in the range of the communication standard diode laser, for instance, when the coupling coefficients of the add/drop device are κ₁ = 0.01 and κ₂ = 0.01–0.9. When the add port of the add/drop device is employed, such a system can also be utilized for the multi user applications.     

Thermal dissipation effects of the entangled photon generated by a nonlinear ring resonator

We firstly analyze the thermal dissipation effects of the entangled photons generated by a nonlinear optical ring resonator. To obtain the corresponding equation of motion of the entangled photons generated by a four-wave mixing process within the system, we propose the Markov approximation to repel the reservoir operators. The system master equation in the interaction picture for both degenerate and non-degenerate cases is analyzed and obtained. The established system can be used to characterize the optimum entangled photons in some cases where the thermal dissipation effects may introduce noise into the system. In this work, the entangled photons can be generated into two forms, firstly, the two entangled photon states are generated and, the other, the four entangled photon states, can be easily obtained. Results obtained have shown that the optimum entangled photon in terms of entangled photon visibility can be compensated (i.e. unchanged) under thermal dissipation effects.     

Generalized quantum key distribution via micro ring resonator for mobile telephone networks

We propose a novel system of quantum key generation via a micro ring resonator for mobile telephone network use, where the conversation messages can be secured by using a quantum code/decode (CODEC) technique incorporated in the public networks. The system consists of a set of micro ring devices incorporating a Mach-Zehnder interferometer (MZI). The entangled photon with different time slots is generated via each micro ring device, which is connected to an MZI. In each micro ring device, the time delay and the Kerr nonlinearity effect are exploited for the qubit (quantum key) generation. At present, fabrication technology has been promising in that the quantum key can be implemented within the mobile telephone hand set and networks, and it has also shown the feasibility of using as perfect security telephone networks.     

Self-calibration in a fiber optic sensing system using the walk-off compensation

We firstly present a concept of a self-calibration of the classical and quantum parameters’ measurement using a fiber optic system. The measurement of the change in phase of the optimum entangled states’ visibility is performed in terms of a walk-off length, i.e. birefringence. The applied physical parameters on the sensing fiber can be simultaneously measured and the self-calibration respecting the birefringence performed. The scheme of the entangled photons generation in fiber optic is reviewed and the walk-off on the polarization entangled states presented. The potential of self-calibration and simultaneous measurement using an interferometric sensing technique and fiber grating sensor are proposed and discussed. The walk-off on the entangled states in the thermal-controlled environment is presented and discussed.     

Error corrections of quantum key distribution of the quantum codes via optical wireless link

Quantum key generated by using a fiber optic Mach Zehnder interferometer incorporating a fiber optic ring resonator is proposed. The generated quantum key is distributed via an optical wireless link system, which is available for the free space link. The random quantum bits can be formed and used as the secret codes in quantum communication system. By adding an ancillary photon after the signal photon within the correlation time of the fiber noise and by performing quantum parity checking, the high fidelity to the noiseless quantum in free space is achieved by the technique known as the quantum error correction.     

Entangled photon states recovery and cloning via the micro ring resonators and an add/drop multiplexer

We propose a new system of the entangled photon generation and recovery using a Gaussian pulse traveling within the nonlinear micro ring resonators, whereas the cloning feasibility of the entangled photon states via an add/drop multiplexer is also proposed. Firstly, the optimum entangled photon visibility is generated by using the Gaussian pulse in the ring resonators, where the second harmonic pulses are generated by filtering the chaotic signals. Secondly, the small amount of the transmission power is coupled by the add/drop device, whereas the entangled photon states, i.e. cloning states, are regenerated by using the polarization control unit. Results obtained have shown that the recovery entangled photon states can be made and confirmed with the initial states, which means that the cloning of entangled photon states of the initial states is plausible. The amplified entangled photon for state recovery is also discussed.     

Generation of quantum‐entangled twin photons by waveguide nonlinear‐optic devices

This paper reviews the quasi‐phase‐matched (QPM) waveguide nonlinear‐optic device technologies for generation of quantum‐entangled twin photons indispensable for quantum‐information techniques. After a brief introduction to the concept of entanglement, quantum theory analysis of twin‐photon generation (TPG) is outlined to clarify the properties of twin photons. Then, methods for entangled‐photon generation are discussed. Practical design and theoretical performances of LiNbO₃ waveguide QPM TPG devices, as well as the fabrication techniques, are described. Finally, experimental demonstrations of polarization‐entangled twin‐photon generation by waveguide Type‐I and Type‐II QPM TPG devices are presented.     

光学超晶格中级联参量过程制备纠缠光子对

探索制备纠缠光子对的新途径是量子光学领域的一个研究热点.从理论上证明在准周期极化 的光学超晶格晶体中的级联参量过程能够产生纠缠光子对.分别利用脉冲和连续的532nm抽运 光在一块准周期极化的 LiTaO3晶体中同时实现非简并参量下转换（产生信号光与闲置光 ）与和频（闲置光与抽运光和频生成和频光）的级联参量过程，获得630nm的信号光与460nm 的和频光.指出信号光与和频光之间存在纠缠关联性质.该方案的优点是可产生短波长的纠缠 光子对. 关键词： 准相位匹配 级联参量过程 光量子纠缠态     

Quantum multiparameter estimation with multi-mode photon catalysis entangled squeezed state

We propose a method to generate the multi-mode entangled catalysis squeezed vacuum states (MECSVS) by embedding the cross-Kerr nonlinear medium into the Mach−Zehnder interferometer. This method realizes the exchange of quantum states between different modes based on Fredkin gate. In addition, we study the MECSVS as the probe state of multi-arm optical interferometer to realize multi-phase simultaneous estimation. The results show that the quantum Cramer−Rao bound (QCRB) of phase estimation can be improved by increasing the number of catalytic photons or decreasing the transmissivity of the optical beam splitter using for photon catalysis. In addition, we also show that even if there is photon loss, the QCRB of our photon catalysis scheme is lower than that of the ideal entangled squeezed vacuum states (ESVS), which shows that by performing the photon catalytic operation is more robust against photon loss than that without the catalytic operation. The results here can find applications in quantum metrology for multiparatmeter estimation.     

Fiber optic sensing applications using the entangled states walk-off compensations

This paper presents a new concept of the measurement of the entangled photon states timing walk-off in fiber optic systems. The relationship between the applied physical parameter on fiber optic and timing walk-off compensation can be performed. When polarized light pulse propagates into a fiber optic length, a pair of the entangled photons introduces the change in phase difference, i.e. birefringence, which can be recovered and detected. The potential of use in applications such as quantum interferometer and fiber optic remote sensing is proposed and described. The increase in measurement resolution in terms of the entangled photon walk-off length is analyzed and discussed.