Modelling a Particle Detector in Field Theory

Abstract

Particle detector models allow to give an operational definition to the particle content of a given quantum state of a field theory. The commonly adopted Unruh-DeWitt type of detector is known to undergo temporary transitions to excited states even when at rest and in the Minkowski vacuum. We argue that real detectors do not feature this property, as the configuration "detector in its ground state + vacuum of the field" is generally a stable bound state of the underlying fundamental theory (e.g. the ground state-hydrogen atom in a suitable QED with electrons and protons) in the non-accelerated case. As a concrete example, we study a local relativistic field theory where a stable particle can capture a light quantum and form a quasi-stable state. As expected, to such a stable particle correspond energy eigenstates of the full theory, as is shown explicitly by using a dressed particle formalism at first order in perturbation theory. We derive an effective model of detector (at rest) where the stable particle and the quasi-stable configurations correspond to the two internal levels, "ground" and "excited", of the detector.

13 pages, references added, final version

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Cited by in corpus (13)

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• Coherences of accelerated detectors and the local character of the Unruh effect
• Entanglement between smeared field operators in the Klein-Gordon vacuum
• Relativistic Unruh-DeWitt detectors with quantized center of mass
• Quantized mass-energy effects in an Unruh-DeWitt detector
• Acceleration Radiation from Derivative-Coupled Atoms Falling in Modified Gravity Black Holes
• New views on the low-energy side of gravity
• Short-time quantum detection: probing quantum fluctuations
• Renormalized entropy of entanglement in relativistic field theory
• General quantum measurements in relativistic quantum field theory
• Time-dependent accelerated Unruh-DeWitt detector without event horizon