Pauli‐Y type of quantum gate is a significant name in the logic family of quantum gates, as this gate deals with complex qubits. It has many significant applications in quantum computing. In this study, the authors propose a new method of generation of Pauli‐Y gate by the proper uses of optical polarisation encoding and phase encoding jointly. This quantum gate can be implemented by dibit and tribit mechanisms instead of single qubit system, where tribit‐based system deals with the high degree of error sensitivity.
Pauli‐Y type of quantum gate is a significant name in the logic family of quantum gates, as this gate deals with complex qubits. It has many significant applications in quantum computing. In this study, the authors propose a new method of generation of Pauli‐Y gate by the proper uses of optical polarisation encoding and phase encoding jointly. This quantum gate can be implemented by dibit and tribit mechanisms instead of single qubit system, where tribit‐based system deals with the high degree of error sensitivity.
Abstract In quantum optical computing both of Pauli X, Y, Z gates and Hadamard gate are essential and important issues. Several proposals are given for addressing these issues. In this paper, the authors propose polarization encoded all-optical schemes which implement Hadamard logic, Pauli X, Pauli Y and Pauli Z gates followed by Hadamard logic gate separately. An integrated scheme is also proposed where three Pauli gates (X, Y and Z) followed by a single Hadamard gate is developed using polarization encoding mechanism. The outputs of the proposed systems follow the truth tables of the respective operations exactly. As the systems use the polarization character of light, so fully quantum optical operations with superfast speed are achieved.
Unlike classical digital computers in which a bit can represent either 1 or 0 at any time, quantum computers use a two-level system, i.e., a qubit, to implement logical operations based on quantum mechanical laws, which can represent both values at once. Owing to the superposition property of qubits, quantum computers have natural parallel processing advantages and thus have potential to exceed the computational efficiency of classical computers for particular tasks. Quantum logic gates are the generalization of classical logic gates in computational networks. It has been proved that two-qubit quantum gates together with one-qubit quantum gates are adequate for constructing networks with any possible quantum computational property. Directional couplers are the most critical elementsfor constructing the quantum gates. In recent years, photonic quantum technologies have emerged as a promising experimental platform for quantum computing. Single photons have robust noise resistance, long coherence time, high transmission speed and great compatibility with other systems. They can be easily manipulated and encoded in any of several degrees of freedom, for example, polarization, path, spatial mode or time bin. Optical waveguide technology enables the realizing of complex optical schemes comprised of many elements with desired scalability, stability and miniaturization. Femtosecond laser direct writing of waveguide has been adopted as a powerful tool for integrated quantum photonics with characteristics of rapidness, cost-effectiveness, mask-less and single-step process. In particular, it has the ability to build arbitrary three-dimensional circuits directly inside bulk materials, which is impossible to achieve with conventional lithography. In this article we review the femtosecond laser writing and quantum characterization of directional coupler and important one-qubit and two-qubit optical quantum logic gates, such as Hadamard gate, Pauli-X gate, controlled-NOT gate, and controlled-Phase gate. The qubits in these gates are usually encoded through optical paths or polarizations of photons. The key to the realization of polarization-encoded one-qubit gates is to achieve flexible wave-plate operations, which is described in detail. Controlled-NOT gate and controlled-phase gate are the most crucial two-qubit gates in the linear optics computation and sometimes they can be converted into each other by adding some one-qubit gates or special superposition states. Many different kinds of waveguide circuits have been used to implement these two-qubit gates. The outlook and challenges for the femtosecond laser writing of three-qubit gates, such as Toffoli gate and Fredkin gate, are briefly introduced.
Abstract Quantum logic gate operates on a number of qubits, where a controlled Z gate operates on two qubit data. Similarly, the square root of controlled Z (SRCZ) operates also on two qubit data. The SRCZ gate is very much advantageous in quantum computing. Different quantum gates are implemented by using the physical properties of light such as phase, polarization, intensity, and frequency. Here, the authors propose a photonic scheme for implementing quantum SRCZ logic gate using phase as well as intensity encoding. The non‐linear property of Pockels material with proper external biasing voltage is used to develop the scheme.
We propose a universal gate set for quantum computing with all-to-all connectivity and intrinsic robustness to bit-flip errors based on parity encoding. We show that logical controlled phase gate and R_{z} rotations can be implemented in parity encoding with single-qubit operations. Together with logical R_{x} rotations, implemented via nearest-neighbor controlled-NOT gates and an R_{x} rotation, these form a universal gate set. As the controlled phase gate requires only single-qubit rotations, the proposed scheme has advantages for several cornerstone quantum algorithms, e.g., the quantum Fourier transform. We present a method to switch between different encoding variants via partial on-the-fly encoding and decoding.
Quantum gates are dependable in new fields, including superconducting flux 1 ogic, q uantum-dot c ellular automata, optical quantum computing, and quantum computing. Quantum gates such as the Feynman, double Feynman, Fredkin, Peres, and Toffoli have low power dissipation. For designing these gates in the electronic era, a bottleneck problem is the speed limitations of the electron and also the power dissipation due to the optoelectronic devices. Therefore realization of the quantum gates in all-optical (A-O) domain is an important issue. Therefore, a design of A-O Fredkin gate is proposed using optical-add/drop multiplexer (OADM) and reflective semiconductor optical amplifier (RSOA). I nt his d esign, we a lso i ntroduced t he dibit-based logic and frequency encoding scheme. The developed method is simulated using MATLAB.