Designs for a quantum electron microscope

Abstract

One of the astounding consequences of quantum mechanics is that it allows the detection of a target using an incident probe, with only a low probability of interaction of the probe and the target. This 'quantum weirdness' could be applied in the field of electron microscopy to generate images of beam-sensitive specimens with substantially reduced damage to the specimen. A reduction of beam-induced damage to specimens is especially of great importance if it can enable imaging of biological specimens with atomic resolution. Following a recent suggestion that interaction-free measurements are possible with electrons, we now analyze the difficulties of actually building an atomic resolution interaction-free electron microscope, or "quantum electron microscope". A quantum 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, thus supporting high success probabilities for interaction-free detection of the specimen. Different system designs are presented here, which are based on four different choices of two-state-couplers: a thin crystal, a grating mirror, a standing light wave and an electro-dynamical pseudopotential. Challenges for the detailed electron optical design are identified as future directions for development. While it is concluded that it should be possible to build an atomic resolution quantum electron microscope, we have also identified a number of hurdles to the development of such a microscope and further theoretical investigations that will be required to enable a complete interpretation of the images produced by such a microscope.

Experimental test of decoherence theory using electron matter waves

“…Given that Δx is generally between 100 nm and 100 μm and T flight is roughly between 1 and 100 ns, this corresponds to a transverse velocity of v x T T flight º D ∼10 5 m s −1 and a decoherence factor of ∼10 7 , which is not currently feasible to observe. To observe such decoherence, the transverse velocity has to be increased by changing the experimental configuration (for example as in a quantum electron microscope [54,55]).…”

A nanofabricated, monolithic, path-separated electron interferometer

“…The interferometer could also be incorporated into a specially-designed electron-optic column for specific applications. The separation of paths on the second grating makes it feasible to place an absorbing object in the path of one of the beams, which may allow the implementation, with electrons, of Elitzur and Vaidman’s scheme for interaction-free imaging 46, 47 . In the same vein, we can also configure the gratings in order to implement multiple and repeated quantum interrogation of distinct absorbing objects 48, 49 .…”

Second-order correlations in single-particle interferometry

“…If there is no greatest common divisor gcd w , the superperiod s t is infinite and the only position, where the amplitudes have a maximum value of 1, is at 0 t = . Therefore, the determination of the contrast and spatial periodicity using equation (36) can always be applied to the correlation function at the correlation time of 0 t = .…”

“…This advance opened the door for experiments in Aharonov-Bohm physics [30][31][32] and Coulomb-induced decoherence [13,33,34]. Technical devices with interfering single particles can decrease the amount of destructive particle deposition in electron microscopy for the analysis of fragile biological specimen [35,36].…”