Pure and Mixed States
In quantum mechanics, a quantum system is represented by a state vector (or ket) . A quantum system with a state vector is called a pure state. However, it is also possible for a system to be in a statistical ensemble of different state vectors: For example, there may be a 50% probability that the state vector is and a 50% chance that the state vector is . This system would be in a mixed state. The density matrix is especially useful for mixed states, because any state, pure or mixed, can be characterized by a single density matrix.
A mixed state is different from a quantum superposition. In fact, a quantum superposition of pure states is another pure state, for example .
Read more about this topic: Density Matrix
Famous quotes containing the words pure, mixed and/or states:
“... that’s what living happens to be ... the physiological denial of reverence and good manners and Christianity.... At your age one’s quite old enough to know what the essence of life really is. Shamelessness, that’s all; pure shamelessness.”
—Aldous Huxley (1894–1963)
“What an antithetical mind!—tenderness, roughness—delicacy, coarseness—sentiment, sensuality—soaring and grovelling, dirt and deity—all mixed up in that one compound of inspired clay!”
—George Gordon Noel Byron (1788–1824)
“Our citizenship in the United States is our national character. Our citizenship in any particular state is only our local distinction. By the latter we are known at home, by the former to the world. Our great title is AMERICANS—our inferior one varies with the place.”
—Thomas Paine (1737–1809)