Quantum's weirdness opens new doors for electron microscopes used in high-resolution imaging.
These microscopes are being studied in the laboratory of University of Oregon Physicist Ben McMorran. It improves microscopes with two new developments they have made. Both developments were conceived using the fundamental principles of quantum mechanics.
Duality in Physics
An electron can act as a wave and a particle at the same time. This is one of many examples of weird, quantum-level quirks where subatomic particles often pretend to violate the laws of classical physics.
One study finds a way to examine an object under a microscope without touching it, preventing the inspection from damaging fragile specimens.
Second, it devises a way to make two measurements on a sample at once, through a way of examining how particles in that object potentially interact across distances.
Both of the studies are reported in two papers published in Physical Review Letters.
“It's often difficult to observe something without affecting it, especially when looking at details. This is actually no stranger to physicists. Heisenberg Uncertainty Principle tells. Quantum physics seems to provide a way for us to look at samples further without distorting them.”
Electron microscopes are used to take close-up images of proteins and cells, as well as non-biological samples such as new types of materials.
Instead of the light used in more traditional microscopes, electron microscopes focus a beam of electrons on a sample. When the beam interacts with the sample, some of its properties change. A detector measures the changes in the beam and then it is converted into a high resolution image.
However, this powerful electron beam can damage fragile structures in the sample. Over time, it can distort the details scientists are trying to study.
As a workaround, McMorran's team used a thought experiment published in the early 1990s that proposed a way to detect a sensitive bomb without touching it and risking detonating it.
The trick relies on an instrument called a diffraction grating, a thin membrane with microscopic slits inside. When the electron beam hits the diffraction grating, it splits in two.
With the correct alignment of these beamsplitting diffraction gratings, "the electron goes in and splits into two paths, but then recombines, so it only goes to one of the two possible outputs," said Amy Turner, a graduate student at McMorran's.
"The idea is that when you drop a sample, the electron's interaction with itself is interrupted."
A New Era in Electron Microscopes
In this setup, the electrons do not hit the sample as they do in a conventional electron microscope. Instead, the way the electron beam recombines gives information about the sample in scope.
In another study, McMorran's team used a similar diffraction grating pattern to measure a sample in two places simultaneously. They split a beam of electrons so that a small gold particle passed on either side and measured the tiny bits of energy the electrons transferred to the particle on either side.
This approach can reveal delicate atomic-level nuances about a sample and understand how particles interact in a sample.
Lawrence Berkeley National Laboratory"The special thing about it is that you can look at the two separate parts and then put them together to see if it's a collective oscillation or unrelated," said Cameron Johnson, a postdoctoral researcher in the .
He did his PhD in McMorran's lab and led the work. “We can go beyond the limits of the energy resolutions of the microscope and probe interactions that are normally inaccessible.”
While the two studies take different types of measurements, they use the same basic setup known as interferometry.
What is Interferometry and Let's Get to Know It?
Interferometry is a technique that uses the interference of superimposed waves to extract information. Interferometry typically uses electromagnetic waves and is an important research technique in the fields of astronomy, fiber optics, engineering metrology, optical metrology, oceanography, seismology, spectroscopy (and its applications in chemistry), quantum mechanics, nuclear and particle physics, and plasma physics. It is used in remote sensing, biomolecular interactions, surface profiling, microfluidics, mechanical stress/strain measurement, velocity measurement, optometry and hologram making methods.
"This is the first electron interferometer of its kind," Turner said. Said. "People have used diffraction gratings before, but this is a functional, flexible version that can be adjusted for different experiments."
McMorran said that with the right materials and instructions, the setup can be added to many existing electron microscopes. His team has already caught the attention of researchers in other labs who want to use the interferometer in their own microscopes.
“An electron microscope allows us to look at things at the atomic scale, but many things are difficult to see, such as biological materials that are both highly invisible to electrons and easily damaged,” McMorran added.
"But here we have shown that we can use the quantum wave properties of electrons to overcome these problems and gain insight into the fundamental nature of how these electron waves interact with electromagnetic fields such as light."