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:
“I’m as pure as the driven slush.”
—Tallulah Bankhead (1903–1968)
“I’ll wager that it was impossible after we got mixed together to tell an anti from a suffragist by her clothes. There might have been a difference, though, in the expression of the faces and the shape of the heads.”
—Susan B. Anthony (1820–1906)
“How many ages hence
Shall this our lofty scene be acted over
In states unborn and accents yet unknown!”
—William Shakespeare (1564–1616)