text: One form of this quantity is equal to the negative trace of the product of the density matrix with its natural log.
full_question: One form of this quantity is equal to the negative trace of the product of the density matrix with its natural log. A different form of this quantity used in information theory is the expected value of the information obtainable from a message. This quantity's differential is multiplied with temperature in the fundamental thermodynamic relation since this quantity is conjugate to temperature. This quantity, which has a variety named for Shannon, is defined as Boltzmann's constant times the natural log of the number of microstates. In an isolated system this value never decreases according to the second law of thermodynamics. For 10 points, name this measure of disorder in a system.
first_sentence: One form of this quantity is equal to the negative trace of the product of the density matrix with its natural log.
raw_answer: entropy