Quantum Computing Systems and Architecture

- Overview

Quantum computers use the physical properties of quantum physics to manipulate subatomic particles to perform computation. 

The basic unit of information in quantum computing is the quantum bit, or qubit, which is similar to a traditional binary bit. However, qubits can be in multiple states at once, including 0 or 1, or any part of both states, through superposition. 

Quantum computing systems and architecture is the study of how to construct quantum computers from fundamental hardware building blocks (qubit devices and their associated classical control hardware) and layers of abstraction above the raw hardware. 

Designing a quantum computer requires viewing the system as a whole, such that tradeoffs and compatibility between component choices must be addressed. A holistic picture is equally important for comparing different quantum computing technologies, such as ion traps or superconducting circuits.

- Quantum Computing Systems

Quantum computer systems are engineering marvels that use quantum theory principles to store and process information. They are made up of thousands of intricate components, including qubits, which are the building blocks of quantum computers. 

Qubits are similar to bits in classical computers, but they are subatomic particles like electrons or photons of light, so they operate using subatomic logic. 

Quantum computers also require demanding operating conditions and classical computers to run. Quantum firmware and software are just as important and complex as the hardware, and programmers can use Python code to run quantum algorithms.

Qubits can be made from a variety of materials, including trapped ions, photons, artificial or real atoms, or quasiparticles, depending on the architecture of the quantum system. For example, some quantum systems require extremely cold temperatures to function properly.

Qubits are used to store and process quantum information, and can also be used as photon emitters. When energy is added to a qubit, it becomes excited and emits energy in the form of a photon when it de-excites. 

Quantum computing also involves entanglement, which is a special connection between two pairs of quantum elements where the state of one element impacts the others, even at a distance. Entangling qubits can exponentially increase the number of represented states, allowing for the exploration of a large number of possibilities simultaneously. 

Quantum computing technology stacks also include specialized quantum hardware, such as superconductors and superfluids, and purpose-built firmware that compiles quantum algorithms to run on a specific quantum computer. 

- Layered Architecture of Quantum Computer

An architecture decomposes complex system behaviours into a manageable set of operations. A layered architecture does this through layers of abstraction where each embodies a critical set of related functions.

Five layered architecture of quantum computer consisting of Application, Logical, Error Correction, Virtualization, and Physical layer and interface between each layer.