Following a recent suggestion  that interaction-free measurements are possible with electrons, we have analyzed the possibilities to use this concept for imaging of biological specimen with reduced damage. We have also made preliminary designs for an atomic resolution interaction-free electron microscope, or “quantum electron microscope” , for one example see figure 1.
The idea of interaction-free measurements follows Elitzur and Vaidman , who proposed that an opaque object may be observed by detecting a photon that did not interact with that object. This concept uses a Mach-Zehnder interferometer in which one branch of the particle wave passes through the specimen (“specimen beam”) while the other part follows another path (“reference beam”). For a substantial reduction of the interaction, the amplitude of the wave passing through the specimen must be small and the interaction must be repeated many times. To implement this concept in an electron microscope would require a number of unique components not found in conventional transmission electron microscopes. These components include a coherent electron beam-splitter or two-state-coupler, and a resonator structure to allow each electron to interrogate the specimen multiple times. A two-state-coupler has the function of moving the electron wave slowly between the reference beam and the specimen beam, as in a Rabi-oscillation. We have come up with four different choices for this: a thin crystal, a grating mirror, a standing light wave and an electro-dynamical pseudopotential.
Figures 2 shows a typical example of the theoretical output of a measurement, where for each pixel there is signal in the reference beam, the specimen beam and the inelastic channel, possibly detected in an energy loss measurement. Figure 3 shows the advantage of interaction free measurement in the detection of the presence of a dark pixel as compared to dark field microscopy. In the analysis of the image contrast that interaction-free microscopy can create, our tentative conclusion is that transparent specimen can be detected, but different transparencies cannot be distinguished . Other modes of operation of a microscope with multiple interactions with the specimen, however, may enable this.
This research is funded by the Gordon and Betty Moore Foundation.
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To cite this abstract:Pieter Kruit, Karl Berggren, Peter Hommelhoff, Mark Kasevich; The concept of quantum electron microscopy.. The 16th European Microscopy Congress, Lyon, France. https://emc-proceedings.com/abstract/the-concept-of-quantum-electron-microscopy/. Accessed: December 1, 2022
EMC Abstracts - https://emc-proceedings.com/abstract/the-concept-of-quantum-electron-microscopy/