gatemodel

Gatemodel, often called the quantum circuit model, is a framework for quantum computation in which information is processed by applying a sequence of quantum gates to an initial state of qubits and then measuring the output. The model treats computation as a reversible evolution of quantum states under unitary operators, with measurement translating the final state into classical results.

Computational universality is achieved with a finite set of gates that, when composed, approximate any unitary to arbitrary accuracy. Common universal gate sets include the combination of single-qubit gates (such as the Hadamard, phase, and rotation gates) with at least one entangling two-qubit gate (such as the controlled NOT). The Clifford+T gate set is a widely used example in fault-tolerant schemes.

Historically, the circuit model became the standard paradigm for quantum computation in the 1990s and 2000s, paralleling the development of quantum algorithms such as Shor's factoring and Grover's search. It is equivalent in computational power to other paradigms like adiabatic quantum computation and measurement-based quantum computation, given suitable encodings and resources.

Implementation on various hardware platforms—such as superconducting qubits, trapped ions, and photonic systems—realizes gates as calibrated control pulses or interactions. The performance is governed by gate fidelity, coherence times, and the availability of quantum error correction schemes, with fault-tolerant designs aiming to suppress errors through these corrections.

The gatemodel remains the standard framework for expressing and analyzing quantum algorithms, simulations, and communications, providing a direct link between abstract unitary operations and physical control in quantum devices.