Quantum coherence and interaction-free measurements

Abstract

We investigate the extent to which ``interaction-free'' measurements perturb the state of quantum systems. We show that the absence of energy exchange during the measurement is not a sufficient criterion to preserve that state, as the quantum system is subject to measurement dependent decoherence. While it is possible in general to design interaction-free measurement schemes that do preserve that state, the requirement of quantum coherence preservation rapidly leads to a very low efficiency. Our results, which have a simple interpretation in terms of ``which-way'' arguments, open up the way to novel quantum non-demolition techniques.

4 pages incl. 2 PostScript figures (.eps), LaTeX using RevTeX, submitted to Phys. Rev. A (Rapid Comm.)

References in corpus (4)

• Quantum Mechanical Interaction-Free Measurements
• High-efficiency quantum interrogation measurements via the quantum Zeno effect
• "Interaction-Free" Imaging
• Resonance energy-exchange-free detection and "welcher Weg" experiment

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• Entanglement Creation Using Quantum Interrogation
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• On Interchangeability of Probe-Object Roles in Quantum-Quantum Interaction-Free Measurement
• Conditions for Nondistortion Interrogation of Quantum System