Measurement of quantum fields in curved spacetimes
Chris Fewster (University of York)
Abstract: A standard account of the measurement chain in quantum mechanics involves a probe (itself a quantum system) coupled temporarily to the system of interest. Once the coupling is removed, the probe is measured and the results are interpreted as the measurement of a system observable. Measurement schemes of this type have been studied extensively in Quantum Measurement Theory, but they are rarely discussed in the context of quantum fields and still less on curved spacetimes.
In this talk I will describe how measurement schemes may be formulated for quantum fields on curved spacetime within the general setting of algebraic QFT. In particular, I will show how measurements of probe observables correspond to measurements of "induced" local system observables and describe the role of state update rules. The framework is local and fully covariant, allowing the consistent description of measurements made in spacelike separated regions. Furthermore, specific models can be given in which the framework may be exemplified by concrete calculations. I will also explain how this framework can shed light on an old problem due to Sorkin concerning "impossible measurements" in which measurement apparently conflicts with causality. Finally, I will discuss new results indicating that the system observables that can be induced by measurement schemes form a large subspace of the algebra of all local observables.
The talk is based on work with Rainer Verch [Leipzig], (Comm. Math. Phys. 378, 851–889(2020), arXiv:1810.06512; see also arXiv:1904.06944 for a summary), with Henning Bostelmann and Maximilian Ruep [York] ( Phys. Rev. D 103 (2021) 025017; arXiv:2003.04660) and work in progress with Ian Jubb [Dublin] and Maximilian Ruep.
mathematical physics
Audience: researchers in the discipline
( video )
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| Organizers: | Margherita Disertori*, Wojciech Dybalski*, Ian Jauslin, Hal Tasaki* |
| *contact for this listing |