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CMOS Circuits
Published in Michael Olorunfunmi Kolawole, Electronics, 2020
As the degree of integration increases, more components are integrated on a chip and more wires are necessary to interconnect them. As a result, more power would be consumed on on-chip interconnections, which could impair the performance of the chip. Efforts are being made by innovative technology to lower power consumption, reduce latency, and improve performance on-chip network. Some examples of this innovative technology include “quantum logic gate” in silicon [15], the use of silicon photonics—the application of photonic systems with silicon as the optical medium [14], graphene [16], and CNTs [13]. A quantum logic gate (or simply quantum gate) is a basic quantum circuit operating on a small number of qubits. Traditionally, bits are either 1 or 0, while in a quantum gate; qubits can be both numbers at the same time. Quantum logic gates are reversible, unlike many classical (traditional) logic gates. (More is said about quantum gates and electronics in Chapter 9.)
Quantum Computation
Published in Leslie Hogben, Richard Brualdi, Anne Greenbaum, Roy Mathias, Handbook of Linear Algebra, 2006
Quantum computers share many common features of the classical computers. In a classical computer, information is encoded in binary states (for example, 0 denotes the low voltage state and 1 denotes the high voltage state), and processed by various logic gates. In a quantum computer, information is represented by the states of the microscopic quantum systems, called qubits, and manipulated by various quantum gates. A qubit could be a two-level atom in the excited/ground states, a photon with horizontal/vertical polarizations, or a spin-12 particle with up/down spins. The state of a qubit can be controlled via physical devices such as laser and microwave. The distinctions between quantum and classical computers originate from the special characteristic of quantum mechanics. In contrast to a classical system, a quantum system can exist in different states at the same time, an interesting phenomenon called superposition. Superposition enables quantum computers to process data in parallel. That is why a quantum computer can solve certain problems faster than a classical computer. But, when we measure a quantum system, it randomly collapses to one of the basis states. This indeterministic nature makes the design of efficient quantum algorithms highly nontrivial. Another distinctive feature of the quantum computer is that the operations performed by quantum gates must be unitary. This is the natural consequence of the unobserved quantum systems evolving according to the Schrödinger equation.
Photonics: A Dream of Modern Technology
Published in Tarun Kumar Gangopadhyay, Pathik Kumbhakar, Mrinal Kanti Mandal, Photonics and Fiber Optics, 2019
Sourangshu Mukhopadhyay, Shuvra Dey, Subhendu Saha
In quantum computation, quantum gate is an elementary quantum circuit acting on a small number of qubits. Quantum logic gates are reversible. These quantum logic gates are represented by unitary matrices, for example an n-qubit quantum gate can be described by a 2n × 2n unitary matrix. There are several quantum logic gates, such as Hadamard gate, Pauli-X, Y, Z gates, CNOT gate, Toffoli gate, Fredkin gate [15], etc.
Multiple-Controlled Toffoli and Multiple-Controlled Fredkin Reversible Logic Gates-Based Reversible Synchronous Counter Design
Published in IETE Journal of Research, 2023
S. K. Binu Siva Singh, K. V. Karthikeyan
Quantum gates are the building blocks of quantum circuits, and they manipulate the state of qubits. In classical computing, logic gates such as AND, OR, and NOT gates are used to manipulate the state of bits. In quantum computing, there are a few universal gates that can be utilized to construct quantum circuits. One of these is the Toffoli gate, a three-qubit gate that functions similarly to a conventional AND gate. Another three-qubit gate is the Fredkin gate, also known as the controlled-SWAP gate, which swaps the second and third qubits if the first qubit is in the state.
Expressing multiagent coalition structure problems for optimisation by quantum annealing
Published in Enterprise Information Systems, 2019
One way of performing quantum computing is by using quantum gates that transform the probability amplitude of qubits, in such a way that when they are observed, their wave function collapses into a state that represents the desired solution with high probability. However, an alternative way of doing quantum computing is adiabatic computation, where the system reaches a desired ground state, and this is equivalent to solving an optimisation problem where the solution is found when an objective function reaches its minimum value.