  An analysis of quantum measurement is presented that relies on an
information-theoretic description of quantum entanglement. In a consistent
quantum information theory of entanglement, entropies (uncertainties)
conditional on measurement outcomes can be negative, implying that measurement
can be described via unitary, entropy-conserving, interactions, while still
producing randomness in a measurement device. In such a framework, quantum
measurement is not accompanied by a wave-function collapse, or a quantum jump.
The theory is applied to the measurement of incompatible variables, giving rise
to a stronger entropic uncertainty relation than heretofore known. It is also
applied to standard quantum measurement situations such as the Stern-Gerlach
and double-slit experiments to illustrate how randomness, inherent in the
conventional quantum probabilities, arises in a unitary framework. Finally, the
present view clarifies the relationship between classical and quantum concepts.
