How are quantum circuits similar to classical computers?

How are quantum circuits similar to classical computers?

Quantum circuits are the most straightforward analogue of classical computers: wires connect gates which manipulate qubits. The transformation made by the gates is always reversible: this is a remarkable departure from classical computers. The circuit description uses simple diagrams to represent connections.

What kind of routine is a quantum circuit?

A quantum circuit is a computational routine consisting of coherent quantum operations on quantum data, such as qubits, and concurrent real-time classical computation. It is an ordered sequence of quantum gates, measurements and resets, all of which may be conditioned on and use data from the real-time classical computation.

How is a quantum circuit similar to a Turing machine?

Yao [ 218] showed that a quantum circuit model is equivalent to a quantum Turing machine in the sense that they can simulate each other in polynomial time. The relationship between programs and Turing machines is well understood; see for example [ 41, 127 ].

How are the parameters of a quantum circuit parameterized?

Here, the parameters of the state are parameterized using the quantity θ θ. Once prepared, the quantum state is then manipulated using quantum gates and measured. All of the operations within the quantum block consist of quantum circuits.

How does the composition of a quantum circuit work?

We compose components by connecting the output of one to the input of another; we also compose operations when the results of an operation are used as input to another. The composition does not affect the quantum states.

How is the evolution of a quantum circuit governed?

It is a continuous-time model of quantum computation in which the evolution of the quantum register is governed by a Hamiltonian that varies slowly. The state of the system is prepared at the beginning in the ground state of the initial Hamiltonian.

How is computation performed in a quantum circuit?

The quantum circuit is a quantum computation model where computation is performed through a quantum gate sequence. Quantum gates are reversible, such as the inverter (NOT) gate, the output of which can be undone, and thus the input data can be obtained from the output data. Quantum gates are used for the updating of qubits to obtain a better

How are quantum gates used in a circuit?

In all descriptions of quantum circuits in addition to gates, we see quantum wires that move qubits and allow us to compose more complex circuits from simpler ones that, in turn, are composed of quantum gates.

What are the properties of a quantum wire?

Electronic properties of quantum wires and quantum dots For a quantum wire the electron is confined in two directions and can move freely only in the remaining direction. They are electronic quasi-one-dimensional systems and their density of states is concentrated in a few peaks (Figure 9.4).

How is the density of States in a quantum wire?

For quantum dots the movement is confined in the three directions of space and the electron energy can only have discrete values. The density of states is zero outside these energies ( Figure 9.4 ). Quantum dots are quasi-zero-dimensional electronic systems.

How does a SWCNT behave like a quantum wire?

Transport studies reveal that SWCNTs behave like quantum wires, in which electrical conduction occurs via well-separated, discrete electron states that are quantum-mechanically coherent over long distances (Tans et al., 1997 ).