An Introduction to Quantum Computing
An Introduction to Quantum Computing ____________________________________________________________________________________
_______________________________________________________________________________________________ SCTE Technical Committee : Dave Hodges and Dr Anthony Basham. © 2026 Society for Broadband Professionals. All rights reserved Page 3 The labels "spin-up" and "spin-down", which appear to belong to a binary classification, are by no means merely two mutually exclusive classical tags that can only act as static counters. However, during the unmodified, unrecorded early phase before the irreversible process of measurement-induced wavefunction collapse occurs, an electron can be arranged in a quantum superposition that incorporates both basis states. This state corresponds to both spin types, combining to produce a complex number that represents both possibilities simultaneously. This quantum property allows electrons to exist in physical states defined by distinct probability amplitudes and the precise relative phase Electron Spin Beyond the familiar basic properties such as electric charge, kinetic energy, and potential energy, electrons possess an intrinsic, purely quantum-mechanical trait called "spin.". This strictly microscopic phenomenon is exclusive to quantum mechanics, and there is no accurate, direct, and intuitively perceptible counterpart for it in classical physics. When a measurement is conducted on the electron's intrinsic spin the physical record will only produce two mutually exclusive outcomes, which are referred to as spin-up and spin-down. This intrinsic property of the electron's angular momentum is bound to a related electromagnetic moment, which exhibits net dipole-like behaviour under the action of an external magnetic field. Therefore, we can synthesise precisely tuned external electromagnetic radiation to control the spin state and complete the measurement. The two distinguishable spin states of an electron, conventionally labelled spin-up and spin-down along a selected measurement axis, can serve as the computational basis states of a spin qubit. Appropriate electromagnetic control and measurement techniques allow quantum information to be prepared, manipulated and read out. Figure 1. Discrete energy levels and resonant transitions. Electrons are restricted to specific quantum energy levels within an atom. They can only move between these levels by the atom interaction in a way that allows a change in the quantum state by absorbing or emitting a photon whose energy exactly equals the difference between the two levels. This quantised behaviour produces the characteristic spectral lines of each element and forms one of the fundamental principles of quantum mechanics. The resonance phenomenon can be used to understand abstract quantum systems. A resonance system has a natural frequency and will produce a stronger response to an external input that matches this frequency. Quantum systems follow rules like those of harmonic oscillators: they have strictly defined energy level differences, which correspond to precise transition frequencies. This analogy is not completely rigorous, as the fundamental physical laws that underpin the two types of resonance differ. Even so, the similarity between the two still effectively explains why precisely controlled microwave or light energy can selectively excite a quantum system from one energy level to another.
Made with FlippingBook - Online magazine maker