Researchers suggest novel way to generate a light source made from entangled photons


In the bizarre phenomenon known as entanglement, two particles are always attached to one another, regardless of how far apart they are. As soon as one is measured, the other measurement follows naturally. To create a unique light source consisting of entangled photons, Purdue University researchers have suggested a creative, unorthodox method. They released their research on September 6, 2022, in Physical Review Research.

In the absence of an existing source, the team suggested a technique to produce entangled photons at extreme ultraviolet (XUV) wavelengths. In order to observe the behavior of electrons in molecules and materials on the exceedingly brief timeframes of attoseconds, it is necessary to produce these entangled photons. Their work provides a roadmap for doing this.

According to Dr. Niranjan Shivaram, an assistant professor of physics and astronomy, "the entangled photons in our work are guaranteed to reach at a specific site within a very short length of attoseconds, as long as they travel the same distance." This source of entangled photons can also be used in quantum imaging and spectroscopy, where entangled photons have been shown to enhance the ability to gain information, but now at XUV and even X-ray wavelengths. One important application is in attosecond metrology to push the limits of measurement of the shortest time scale phenomena.

The Purdue University Department of Physics and Astronomy's Attosecond Entangled Photons from Two-Photon Decay of Metastable Atoms: A Source for Attosecond Experiments and Beyond has produced the article. The authors also collaborate with the Purdue Quantum Science and Engineering Institute (PQSEI). They are Dr. Shivaram, Dr. Chris H. Greene, Albert Overhauser Distinguished Professor of Physics and Astronomy, Siddhant Pandey, a Ph.D. candidate in the field of experimental ultrafast spectroscopy, and Dr. Yimeng Wang, a recent graduate of Purdue University.

The atomic, molecular, and optical (AMO) physics program at Purdue University, according to Shivaram, "brings together experts in several subfields of AMO." While many Universities have AMO programs, Purdue's AMO program is uniquely diverse in that it has experts in multiple subfields of AMO science. Chris Greene's expert knowledge of theoretical atomic physics and Niranjan's background in the relatively new field of experimental attosecond science led to this collaborative project.

inuing study. The concept of employing helium atom photons as a source of entangled photons was first put forth by Greene, while Shivaram added applicability to attosecond physics and offered experimental plans. As Pandey and Shivaram estimated entangled photon emission/absorption rates and worked out the specifics of the suggested attosecond experimental techniques, Wang and Greene created the theoretical foundation to calculate entangled photon emission from helium atoms.

For Shivaram and Greene, the publication represents the start of their investigation. The concept is put forth and the theoretical underpinnings of the experiment are worked out by the writers in this publication. Greene and Shivaram intend to keep working together on theoretical and experimental projects. The Ultrafast Quantum Dynamics Group, Shivaram's lab, is constructing a device to experimentally test some of these hypotheses. Shivaram expresses optimism that more attosecond science experts will start pursuing these concepts. The significance of this work could be further increased by a coordinated effort by other research organizations. They eventually want to reduce entangled photons' timescale to the zeptosecond, or 10–21 seconds.

Current limits on these pulses are around 40 attoseconds, but Shivaram's proposed idea of using entangled photons could reduce this to a few attoseconds or zeptoseconds. "Typically, experiments on attosecond timescales are performed using attosecond laser pulses as'strobes' to 'image' the electrons," he says.

Understanding the fundamental function electrons play in determining the behavior of atoms, molecules, and solid materials is necessary to comprehend the timing. Electrons commonly move in timescales of femtoseconds and attoseconds (one billionth of a billionth of a second, or 10-18 seconds), which are measured in billionths of a second. Shivaram asserts that it is crucial to get knowledge of the dynamics of electrons and follow their movement on these extremely brief durations.

The aim of ultrafast research is to create such "pictures" of electrons, which can subsequently be used to engineer chemical reactions, create materials with unique properties, create molecular-scale electronics, and other processes. Researchers are only now starting to explore zeptosecond phenomena, albeit it is experimentally out of reach due to lack of zeptosecond laser pulses.

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