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Information Loss
William G. Unruh, Robert M. Wald
The complete gravitational collapse of a body in general relativity will result in the formation of a black hole. Although the black hole is classically stable, quantum particle cr…
On Evolution Laws Taking Pure States to Mixed States in Quantum Field Theory
William G. Unruh, Robert M. Wald
It has been argued that any evolution law taking pure states to mixed states in quantum field theory necessarily gives rise to violations of either causality or energy-momentum con…
Varieties of Quantum Measurement
W. G. Unruh
Quantum measurement theory has fallen under the resticting influence of the attempt to explain the fundamental axioms of quantum theory in terms of the theory itself. This has not…
Maintaining coherence in Quantum Computers
W. G. Unruh
The effect of the inevitable coupling to external degrees of freedom of a quantum computer are examined. It is found that for quantum calculations (in which the maintenance of cohe…
The Reality and Measurement of the Wavefunction
W. G. Unruh
Using a simple version of the model for the quantum measurement of a two level system, the contention of Aharonov, Anandan, and Vaidman that one must in certain circumstances give…