Artist's rendering of the ACHIP structure. An integrated silicon-photonics device in an electron microscope allows for efficient electron interactions with CW lighting, enabling detection of quantum photon statistics. The photon statistics of light determine whether the electron is entangled with light through a silicon-photonic channel. This image shows the exact silicon-photonic accelerator design. It also includes the exact photonic field distribution inside the accelerator. Credit: Urs Haeusler, SimplySci Animations and the AdQuanta team at the Technion.
Physics has known for many decades that light can be described simultaneously both as a wave or a particle. This amazing 'duality" of light is due in part to the quantum and classical nature of electromagnetic excitations. These are the processes that produce electromagnetic fields.
It has been called a wave in all of the experiments that have shown light interact with free electrons. TechnionIsrael Institute of Technology has recently collected the first experimental evidence that reveals the quantum nature of photon-free electron interaction. These findings, published in Science by TechnionIsrael Institute of Technology, could have important implications on future research into photons and the interaction with free electrons.
"The idea for this study was first suggested to us about two years ago, following our experimental discovery that an interaction between a free electron with light can maintain its coherence over distances up to a hundred times the optical time," Raphael Dahan and Alexey Gorlach, three of the researchers involved in the study, shared via email with Phys.org. "Around the same time, two important theoretical works were also published, both of them exploring how quantum properties of light could affect the interaction with electrons.
These two previous theoretical studies by Ofer Kfir, University of Gttingen, and Javier Garca de Abajo, his colleagues at Institut de Cincies Fotniques, predicted a new type of fundamental interactions that occurs between light, free electrons and light. This discovery revealed the quantum properties of light. Kaminer, Gorlach, Dahan and Gorlach were inspired by these important predictions. They began searching for an experimental system that would allow them to study this interaction experimentally. The researchers wanted to show that quantum statistics of light can affect the electronlight interaction.
Kaminer, Dahan, and Gorlach said that this led them to search for two components. The first device will better couple electrons and light. The second will produce quantum light at the highest intensity.
Researchers consulted members of the accelerator-on-chip (ACHIP), which seeks to combine electron acceleration using lasers with on-chip integration. This was done in order to improve the coupling efficiency. The team discovered that the coupling efficiency could be increased in hundred times as compared to the results of all previous experiments.
Kaminer, Dahan, and Gorlach stated that they first collaborated with a Stanford group (Solgaard England, Leedle and Byer and their students). They designed and provided an ACHIP structure to us for our first test. This was the first experiment to use a silicon-photonic microchip inside a transmission electron microscope. It already had amazing implications. Yuval Adiv and co. will soon publish another paper in PRX.
Kaminer and his team then began a collaboration with Peter Hommelhoff, an Erlangen Germany-based team, to improve the ACHIP community. Kaminer was able to use the most-respected ACHIP structures in the world for this complex experiment thanks to this research group.
The researchers collaborated closely with the Technion Eisenstein group to generate intense quantum light. The researchers were able to use an optical amplifier that could change the quantum photon statistics from a Poissonian (as in classical coherent) to a superPoissonian.
Dahan stated that "our study was quite a journey." We achieved our primary goal by combining all these elements and performing a challenging experiment with our ultrafast transmission electron microscope. This allowed us to demonstrate the first interaction of a free electron with light with different quantum properties.
Kaminer and his collaborators were able to reveal the quantum nature in the interaction between photons, free electrons. They changed the photon statistics continuously throughout the experiment and showed how the electron energy spectrum changed in response. The intensity of the laser seed and pump in the optical amplifier influenced the changes in the photon statistics.
Researchers focused their attention on the interaction between input light and free electrons. The electrons are the detectors of the state light in the experiments. Researchers were able to extract quantum information from light by measuring their energy.
Quantizing the electrons and the light is the only way to explain the electron measurements. This is what the theoretical papers that inspired them predicted. Kaminer stated that the agreement between our measurements and this theory was only achieved once. "From a fundamental perspective the main findings of our research are: the interaction of quantum light and a single electron, the emergence and maintenance of entanglement in this interaction, and the quantum-classical correspondent principle. This principle illustrates the effects of a quantum walk by an electron and its transition to a random walk.
The experimental evidence may also open the door to new light-related research. These include non-destructive, non-invasive imaging instruments that can capture high-resolution images.
Kaminer, Dahan, and Gorlach stated that they had shown that it was possible to use free electrons for measuring the quantum photon statistics. These measurements have many advantages that could be shown in the future. They are non-destructive and have high temporal resolution. Also, they happen in the nearfield with high spatial resolution.
Kaminer and his colleagues have shown that it is possible temporarily shape electrons by using continuous wave (CW), light. This could allow the integration of silicon-photonic chip into electron microscopes, thereby increasing the capability of electron microscopy. It is possible to, for example, introduce attosecond-time resolution into state of the-art microscopes, without affecting their spatial resolution.
Kaminer, Dahan, and Gorlach stated that they plan to continue their work in two major research directions. "The first is working towards full quantum state photography of photonic nearfields. This includes measuring the squeezing light on-chip without having to out-couple it. We are also looking at creating quantum light with coherently-shaped electrons. This is in line with the vision that we presented in our theory paper.
Continue reading The first demonstration of phase matching between an electron wave & a lightwave
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