Impossible Measurements on Quantum Fields

Abstract

It is shown that the attempt to extend the notion of ideal measurement to quantum field theory leads to a conflict with locality, because (for most observables) the state vector reduction associated with an ideal measurement acts to transmit information faster than light. Two examples of such information-transfer are given, first in the quantum mechanics of a pair of coupled subsystems, and then for the free scalar field in flat spacetime. It is argued that this problem leaves the Hilbert space formulation of quantum field theory with no definite measurement theory, removing whatever advantages it may have seemed to possess vis a vis the sum-over-histories approach, and reinforcing the view that a sum-over-histories framework is the most promising one for quantum gravity.

13 pages, preprint number SU-GP-92/12-4

Cited by in corpus (23)

• Causal and localizable quantum operations
• Quantum temporal logic and decoherence functionals in the histories approach to generalised quantum theory
• Shortcomings in the Understanding of Why Cosmological Perturbations Look Classical
• General Relativistic Quantum Optics: Finite-size particle detector models in curved spacetimes
• A detector-based measurement theory for quantum field theory
• Broken covariance of particle detector models in relativistic quantum information
• Impossible measurements require impossible apparatus
• Measurability of Wilson loop operators
• Tall tales from de Sitter space II: Field theory dualities
• Weakly coupled local particle detectors cannot harvest entanglement
• Anti-particle detector models in QFT
• Thermality, causality and the quantum-controlled Unruh-deWitt detector
• S-Matrix on the Moyal Plane: Locality versus Lorentz Invariance
• The First Law of Quantum Field Thermodynamics
• QED on the Groenewold Moyal Plane
• Quantum Information in Relativity: the Challenge of QFT Measurements
• Notes on nonlocal projective measurements in relativistic systems
• Superluminal local operations in quantum field theory: A ping-pong ball test
• A non-perturbative analysis of spin-boson interactions using the Weyl relations
• Uncertainties in Quantum Measurements: A Quantum Tomography
• Telefilters, telemirrors, and causality
• Thermal Fisher information for a rotating BTZ black hole
• Limits on Relativistic Quantum Measurement