A pure state in quantum mechanics refers to a state of a quantum system that can be described by a single wave function. This means that the exact energy and position of the system can be known with certainty.
A mixed state, also known as a statistical mixture, is a combination of two or more pure states. In contrast to a pure state, a mixed state is characterized by a probability distribution of possible states and does not have well-defined energy or position.
No, a pure state cannot change into a mixed state. According to the principles of quantum mechanics, a pure state will always remain a pure state and a mixed state will always remain a mixed state.
In quantum mechanics, pure states are represented by a state vector, also known as a ket, which is an element of a complex vector space. Mixed states are represented by density matrices, which are mathematical objects that describe the probabilities of different pure states in a mixed state.
A pure state can be exemplified by a single photon, which has a well-defined energy and position. A mixed state can be seen in the state of a radioactive atom, which can decay into two different states with a certain probability, making it a mixture of two pure states.