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Quantum electron microscopy

 

The laws of quantum mechanics make it possible to detect the presence or absence of an object without disturbing it in any way. Such experiments are called “interaction-free measurements” [1]. They exploit the wave-like properties of quantum particles: only parts of a particle’s wave function ever encounter the object. This happens in such a way that there are noticeable changes in the particle’s overall behavior even though the probability of an interaction between particle and object remains small. The method was experimentally verified using single photons as particles [2].

Proposal for interaction-free measurement

Two coupled electron traps represent a possible realization of interaction-free measurements with electrons. Illustration taken from [3].

The goal of this project is the realization of an interaction-free measurement with electrons instead of photons. This is a first step towards the development of a quantum electron microscope that makes use of interaction-free measurements. In the future, this device could make it possible to analyze samples with the high resolution of an electron microscope but with significantly less radiation damage [3]. A promising application is the imaging of biological samples, which are often destroyed by radiation damage in regular electron microscopes.

We examine different proposals for the setup of an interaction-free measurement with electrons. The main technical challenge is the design of a coherent beam splitter for electron waves. Additionally, we examine the effect of semitransparent samples in interaction-free measurements to find out whether it is possible to distinguish gray values in an interaction-free way.

This project is part of an international collaboration, which is funded by the Gordon and Betty Moore foundation.

 

[1] Elitzur, A. C., Vaidman, L. Quantum mechanical interaction-free measurements. Foundations of Physics 23, 987–997 (1993)

[2] Kwiat, P., Weinfurter, H., Herzog, T., Zeilinger, A., Kasevich, M. A. Interaction-free measurement. Physical Review Letters 74, 4763–4766 (1995)

[3] Putnam, W. P., Yanik, M. F. Noninvasive electron microscopy with interaction-free quantum measurements. Phys. Rev. A 80, 040902(R) (2009).