Towards a measurement theory in QFT: "Impossible" quantum measurements are possible but not ideal
arXiv:2311.13644 · doi:10.22331/q-2024-02-27-1267
Abstract
Naive attempts to put together relativity and quantum measurements lead to signaling between space-like separated regions. In QFT, these are known as impossible measurements. We show that the same problem arises in non-relativistic quantum physics, where joint nonlocal measurements (i.e., between systems kept spatially separated) in general lead to signaling, while one would expect no-signaling (based for instance on the principle of no-nonphysical communication). This raises the question: Which nonlocal quantum measurements are physically possible? We review and develop further a non-relativistic quantum information approach developed independently of the impossible measurements in QFT, and show that these two have been addressing virtually the same problem. The non-relativistic solution shows that all nonlocal measurements are localizable (i.e., they can be carried out at a distance without violating no-signaling) but they (i) may require arbitrarily large entangled resources and (ii) cannot in general be ideal, i.e., are not immediately reproducible. These considerations could help guide the development of a complete theory of measurement in QFT.
arXiv comment11 pages, 6 figures. Accepted in Quantum Journal
References in corpus (17)
- Everything You Always Wanted to Know About LOCC (But Were Afraid to Ask)
- Causal and localizable quantum operations
- Simplified instantaneous non-local quantum computation with applications to position-based cryptography
- Semicausal operations are semilocalizable
- Instantaneous measurement of non-local variables
- Entanglement 25 years after Quantum Teleportation: testing joint measurements in quantum networks
- Nonlocal variables with product states eigenstates
- Impossible measurements require impossible apparatus
- Causality Constraints on Nonlocal Quantum Measurements
- Measurements of semi-local and non-maximally entangled states
- Impossible measurements revisited
- Entanglement consumption of instantaneous nonlocal quantum measurements
- Causal State Updates in Real Scalar Quantum Field Theory
- Bounds on Instantaneous Nonlocal Quantum Computation
- Optimal amount of entanglement to distinguish quantum states instantaneously
- Superluminal local operations in quantum field theory: A ping-pong ball test
- Multi-system measurements in generalized probabilistic theories and their role in information processing