All-Optical Logic Device Using Bent Nonlinear Tapered Y-Junction Waveguide Structure

We propose an all-optical logic device made of a bent tapered Y-junction waveguide with a Kerr-type nonlinear interface. It could provide an AND gate, OR gate, and exclusive-OR (XOR) gate. We could obtain different transmission results by adjusting the bending angle. The numerical simulation results show that the device functions as AND, OR, and XOR gates.     

All-Optical Logic Device Using Bent Nonlinear Tapered Y-Junction Waveguide Structure

We propose an all-optical logic device made of a bent tapered Y-junction waveguide with a Kerr-type nonlinear interface. It could provide an AND gate, OR gate, and exclusive-OR (XOR) gate. We could obtain different transmission results by adjusting the bending angle. The numerical simulation results show that the device functions as AND, OR, and XOR gates.     

Time-varying coupling-induced logical stochastic resonance in a periodically driven coupled bistable system

Coupling-induced logical stochastic resonance(LSR) can be observed in a noise-driven coupled bistable system where the behaviors of system can be interpreted consistently as a specific logic gate in an appropriate noise level. Here constant coupling is extended to time-varying coupling, and then we investigate the effect of time-varying coupling on LSR in a periodically driven coupled bistable system. When coupling intensity oscillates periodically with the same frequency with periodic force or relatively high frequency, the system successfully yields the desired logic output. When coupling intensity oscillates irregularly with phase disturbance, large phase disturbance reduces the area of optimal parameter region of coupling intensity and response speed of logic devices. Although the system behaves as a desired logic gate when the frequency of time-periodic coupling intensity is precisely equal to that of periodic force, the desired logic gate is not robust against tiny frequency difference and phase disturbance. Therefore, periodic coupling intensity with high frequency ratio is an optimal option to obtain a reliable and robust logic operation.     

All-optical multiple-channel logic XOR gate for NRZ-DPSK signals based on nondegenerate four-wave mixing in a silicon waveguide

We report an all-optical multiple-channel exclusive OR (XOR) gate for 10?Gbits/s non-return-to-zero differential phase-shift keying (NRZ-DPSK) signals using nondegenerate four-wave mixing in a silicon waveguide. The function of the logic XOR gate is experimentally demonstrated using 40?bit DPSK sequences. Also, the eye diagram of the XOR signal is clearly observed as the incident signals are both modulated by DPSK sequences originating from 2(31)-1 pseudorandom binary sequences.     

All-optical high speed logic gates using SOA

In this paper a novel and simple structure of a high speed optical logic gate based on bulk semiconductor optical amplifier (SOA) is presented. The gain dynamic and phase response of bulk SOA using rate equations including the dynamics of carrier heating (CH) and spectral-hole burning (SHB) is investigated numerically. The operation of NOR gate is analyzed by using the presented numerical method, and a NOR gate that can operate up to 1 Tbps is designed. By using the proposed structure, high speed logic gates based on bulk SOA can be realized.     

Injection-locking laser-diode-based OC-192 optical non-return-to-zero-to-return-to-zero OR logic gate

An OC-192 optical return-to-zero- (RZ-) formatted OR logic gate is experimentally demonstrated and theoretically interpreted for the first time to our knowledge. It is implemented by using a data format converter based on an optically injection-locked Fabry-Perot laser diode (FPLD) modulated in below-threshold condition. By injecting two non-return-to-zero data streams into the FPLD-based OR gate, a peak-power-equalized RZ-formatted OR logic data stream extinction ratio of >8 dB is obtained from the FPLD with optimized rf-modulating and optical injecting powers of 24.7 and >-4 dBm, respectively. The highest data rate of up to 12.5 Gbits/s with a bit error rate (BER) of 10(-13) at a received optical power of >-16 dBm can be achieved by increasing the dc bias current of the FPLD-based RZ-formatted OR logic gate to 8 mA. The OR-gated RZ data stream exhibits a duty cycle (pulse width) of approximately 27% (27 ps) and a 0.5 dB power penalty at a BER of 10(-9) at a data rate of 9.953 Gbits/s.     

利用暗本征态的绝热演化实现非几何条件相位移动:一种实现量子计算的新方法

利用绝热演化，文章提出一种新的方法以实现量子相位门，这种相位移动既非源于动力学过程，也非源于几何操纵，它来源于暗态本身的演化，基于绝热演化的优点，这种量子逻辑门对实验参量的起伏不敏感，与几何相位门相比，这种相位门更简单，并且保真度可得到进一步提高。文章对这种相位门做一简述。     

Coupling induced logical stochastic resonance

In this work we will demonstrate the following result: when we have two coupled bistable sub-systems, each driven separately by an external logic input signal, the coupled system yields outputs that can be mapped to specific logic gate operations in a robust manner, in an optimal window of noise. So, though the individual systems receive only one logic input each, due to the interplay of coupling, nonlinearity and noise, they cooperatively respond to give a logic output that is a function of both inputs. Thus the emergent collective response of the system, due to the inherent coupling, in the presence of a noise floor, maps consistently to that of logic outputs of the two inputs, a phenomenon we term coupling induced Logical Stochastic Resonance. Lastly, we demonstrate our idea in proof of principle circuit experiments.     

基于频率调制激光驱动的囚禁离子几何相位逻辑门

为了避免激光相位的起伏对几何相位逻辑门保真度的影响, 提出一种基于囚禁离子的量子几何相位逻辑门的新方案。该机制是利用一束频率调制的行波激光场作用于两个囚禁离子上实现的。它的优点有：操作简单,仅需一步就能实现。不灵敏于激光场的相位也不需要对囚禁离子进行个别寻址。     

80 Gb/s All-optical logic AND operation using Mach-Zehnder interferometer with differential scheme

An all-optical logic AND gate is demonstrated by using a semiconductor optical amplifier (SOA) based Mach-Zehnder interferometer (MZI). The AND results are numerically analyzed by solving the rate equation of SOA. Q-factor values have been calculated. The operation of the AND logic gate is experimentally demonstrated at 80 Gb/s. Operation at higher data rates is feasible using SOAs with shorter phase recovery time.     

细菌视紫红质用于光子逻辑门的研究

本文对基于细菌视紫红质变种材料D96N的三种基本光逻辑操作进行了研究.随着入射黄光强度的增加,菌紫质对黄光的吸收呈饱和吸收特性,此时紫光的照射将会使此饱和吸收阈值增加.在黄光和紫光对样品的共同作用下,透射光强度会被调制,调制的程度取决于这两束光的相对强度以及被调制光波长.通过观测被调制的525nm检测光强度,我们模拟了几种基本的光子逻辑运算:“非”、“或”和“与”运算.     

Analysis of an optical logic gate using a symmetric coupler operating with pulse position modulation (PPM)

In this paper we propose the operation of an all-optical logical gate based in a symmetric nonlinear directional coupler (NLDC) operating with a pulse position modulation (PPM). The performance of a symmetric NLDC realizing two-input AND/OR logical functions, which can be applied in transmission and processing of signals in all-optical form in TDM systems, is examined. This integrated symmetric NLDC logical gate operates with two ultrashort soliton light pulses (2 ps), which are modulated in agreement with the technique of pulse position modulation (PPM). Initially, we evaluate the effect resulting of an increment in the PPM coding parameter offset (ε), for the temporal position of the output pulse, considering the anomalous group-velocity dispersion (GVD), nonlinear self phase modulation (SPM) and without loss propagation regime of input pulses, in the cores 1 and 2 of the NLDC. In this situation, we analyze the four possible situations for the two-input logical gate, modulating the 1 and 2 input pulses through temporal displacement and allowing a variation in the coding parameter offset. We can conclude that is possible to get AND/OR logical operations for the cores 1 or 2, without to insert PPM error, since a phase control (Δ?) exists applied in agreement with the logical level of the input pulse in the core 1. Finally we define the truth table, considering the adequate phase difference and coding parameter offset for the stable operation of the AND/OR logical gate based in the symmetric NLDC.     

Single-SOA-Based Ultrahigh-Speed All-Optical Half Subtracter with PolSK Modulated Signals

A novel ultrahigh-speed all-optical half subtracter based on four-wave mixing (FWM) in a single semiconductor optical amplifier (SOA) is proposed. This scheme only requires a single SOA and two input signals without additional light source, so it is quite simple and compact. Due to the polarization-shift-keying (PolSK) modulated signals being used in this scheme, pattern-dependent degradation can be avoided. By numerical simulation, dependence of the critical factors of the logic gate performance, e.g., the output power of logic 1 and extinction ratio (ER), on two input signals power is investigated. In addition, the effect of the gain polarization dependence of SOA is analysed.     

Unconventional Geometric Phase-Shift Gates Based on Superconducting Quantum Interference Devices Coupled to a Single-Mode Cavity

We present a scheme to realize geometric phase-shift gate for two superconducting quantum interference device (SQUID) qubits coupled to a single-mode microwave field. The geometric phase-shift gate operation is performed transitions during the gate operation. Thus, the docoherence due to energy spontaneous emission based on the levels of SQUIDs are suppressed. The gate is insensitive to the cavity decay throughout the operation since the cavity mode is displaced along a circle in the phase space, acquiring a phase conditional upon the two lower flux states of the SQUID qubits, and the cavity mode is still in the original vacuum state. Based on the SQUID qubits interacting with the cavity mode, our proposed approach may open promising prospects for quantum logic in SQUID-system.     

High speed logic gate using two-photon absorption in silicon waveguides

The switching speed of conventional silicon-based optical switching devices based on plasma dispersion effect is limited by the lifetime of free carriers which introduce either phase or absorption changes. Here we report an all-optical logic NOR gate which does not rely on free carriers but instead uses two-photon absorption. High speed operation was achieved using pump induced non-degenerate two-photon absorption inside the submicron size silicon wire waveguides. The device required low pulse energy (few pJ) for logic gate operation.     

Geometric phase for a coupled two quantum dot system

The adiabatic geometric phase is calculated in a coupled two quantum dot system, which is entangled through Förster interaction. This phase is then utilized for implementing basic quantum logic gate operation useful in quantum information processing. Such gates based on geometric phase provide fault-tolerant quantum computing.     

A Scheme for Atomic Entangled States and Quantum Gate Operations in Cavity QED

We propose a scheme for controllably entangling the ground states of five-state W-type atoms confined in a cavity and realizing swap gate and phase gate operations. In this scheme the cavity is only virtually excited and the atomic excited states are almost not occupied, so the produced entangled states and quantum logic operations are very robust against the cavity decay and atomic spontaneous emission.     

Realization of XNOR logic function with all-optical high contrast XOR and NOT gates

In this article, we propose the realization of XNOR logic function by using all-optical XOR and NOT logic gates. Initially, both XOR and NOT gates are designed, simulated and optimized for high contrast outputs. T-shaped waveguides are created on the photonic crystal platform to realize these logic gates. An extra input is used to perform the inversion operation in the NOT gate. Inputs in both the gates are applied with out of phase so as to have a destructive interference between them and produce negligible intensity for logic ‘0'. The XOR and NOT gates are simulated using Finite Difference Time Domain method which results with a high contrast ratio of 55.23?dB and 54.83?dB, respectively at a response time of 0.136?ps and 0.1256?ps. Later, both the gates are cascaded by superimposing the output branch of the waveguide of XOR gate with the input branch of the waveguide of NOT gate so that it can be resulted with compact size for XNOR logic function. The resultant structure of XNOR logic came out with the contrast ratio of 12.27?dB at a response time of 0.1588?ps. Finally, it can be concluded that the proposed structures with fair output performance can suitably be applied in the design of photonic integrated circuits for high speed computing and telecommunication systems.     

One-step implementation of a multi-target-qubit controlled phase gate with cat-state qubits in circuit QED

We propose a single-step implementation of a muti-target-qubit controlled phase gate with one catstate qubit (cqubit) simultaneously controlling n–1 target cqubits. The two logic states of a cqubit are represented by two orthogonal cat states of a single cavity mode. In this proposal, the gate is implemented with n microwave cavities coupled to a superconducting transmon qutrit. Because the qutrit remains in the ground state during the gate operation, decoherence caused due to the qutrit’s energy relaxation and dephasing is greatly suppressed. The gate implementation is quite simple because only a single-step operation is needed and neither classical pulse nor measurement is required. Numerical simulations demonstrate that high-fidelity realization of a controlled phase gate with one cqubit simultaneously controlling two target cqubits is feasible with present circuit QED technology. This proposal can be extended to a wide range of physical systems to realize the proposed gate, such as multiple microwave or optical cavities coupled to a natural or artificial three-level atom.     

Unconventional Geometric Phase-Shift Gates Based on Superconducting Quantum Interference Devices Coupled to a Single-Mode Cavity

We present a scheme to realize geometric phase-shift gate for two superconducting quantum interference device （SQUID） qubits coupled to a single-mode microwave field. The geometric phase-shift gate operation is performed in two lower flux states, and the excited state [2〉 would not participate in the procedure. The SQUIDs undergo no transitions during the gate operation. Thus, the docoherence due to energy spontaneous emission based on the levels of SQUIDs are suppressed. The gate is insensitive to the cavity decay throughout the operation since the cavity mode is displaced along a circle in the phase space, acquiring a phase conditional upon the two lower flux states of the SQUID qubits, and the cavity mode is still in the original vacuum state. Based on the SQUID qubits interacting with the cavity mode, our proposed approach may open promising prospects for quantum iogic in SQUID-system.