Revolutionary discovery in the conversion of carbon capture to ethylene production

New way to generate an entangled photon-based light source

Entanglement is a strange phenomenon in quantum physics in which two particles are intrinsically connected to each other, regardless of the distance between them. When one is measured, the other measure is instantaneously given. Purdue University researchers have proposed a novel and unconventional approach to generate a special light source composed of entangled photons. On September 6, 2022, they published their findings in Physical Review Research.

The team proposed a method for generating entangled photons at extreme ultraviolet (XUV) wavelengths where no such source currently exists. Their work provides a road map on how to generate these entangled photons and use them to track the dynamics of electrons in molecules and materials over incredibly short time scales of attoseconds.

“The entangled photons in our work are guaranteed to arrive at a certain place within a very short duration of attoseconds, as long as they travel the same distance,” says Dr. Niranjan Shivaram, assistant professor of physics and astronomy. “This correlation in their time of arrival makes them very useful for measuring ultra-fast events. An important application is in attosecond metrology to push the limits of measuring phenomena on a shorter time scale. This source of entangled photons can also be used in quantum imaging and spectroscopy, where entangled photons have been shown to improve the ability to obtain information, but now at XUV and even X-ray wavelengths.

The authors of the publication, titled “Attosecond entangled photons from two-photon decay of metastable atomis: A source for attosecond experiments and beyond”, are all from Purdue University’s Department of Physics and Astronomy and work with the Purdue Quantum Science and Engineering Institute ( PQSEI). I’m Dr. Yimeng Wang, a recent graduate of Purdue University; Siddhant Pandey, PhD student in the field of experimental ultrafast spectroscopy; Dr. Chris H. Greene, Albert Overhauser’s distinguished professor of physics and astronomy; and Dr. Shivaram.

“The Purdue Department of Physics and Astronomy has a strong atomic, molecular and optical (AMO) physics program, which brings together experts in various subfields of the AMO,” says Shivaram. “Chris Greene’s expert knowledge of theoretical atomic physics, combined with Niranjan’s background in the relatively young field of experimental attosecond science, led to this collaborative project. While many universities have AMO programs, Purdue’s AMO program is extraordinarily diverse as it has experts in multiple subfields of AMO science. “

Each researcher has played a significant role in this ongoing research. Greene initially suggested the idea of ​​using photons emitted by helium atoms as a source of entangled photons and Shivaram suggested applications to attosecond science and proposed experimental schemes. Wang and Greene then developed the theoretical framework for calculating the entangled photon emission from helium atoms, while Pandey and Shivaram estimated the emission / absorption rates of entangled photons and worked out the details of the proposed attosecond experimental schemes.

The publication marks the beginning of this quest for Shivaram and Greene. In this publication, the authors propose the idea and elaborate the theoretical aspects of the experiment. Shivaram and Greene intend to continue collaborating on experimental and further theoretical ideas. Shivaram’s lab, the Ultrafast Quantum Dynamics Group, is currently building an apparatus to experimentally demonstrate some of these ideas. According to Shivaram, the hope is that other attosecond science researchers will start working on these ideas. A concerted effort by many research groups could further increase the impact of this work. Eventually, they hope to reduce the time scale of the entangled photons to the zeptosecond, 10-21 seconds.

“Typically, attosecond time scale experiments are performed using attosecond laser pulses as ‘strobes’ to ‘imagine’ electrons. The current limits on these pulses are approximately 40 attoseconds. Our proposed idea of ​​using entangled photons could reduce this to a few attoseconds or zeptoseconds, ”says Shivaram.

To understand the times, it is necessary to understand that electrons play a fundamental role in determining the behavior of atoms, molecules and solid materials. The time scale of electron motion is typically in the femtosecond (one millionth of a billionth of a second – 10-15 seconds) and attosecond (one billionth of a billionth of a second, or 10-18 seconds) scale. According to Shivaram, it is essential to acquire information on the dynamics of electrons and to follow their movement on these ultra-short time scales.

“The goal of the ultrafast field of science is to make such electron ‘films’ and then use light to control the behavior of these electrons to design chemical reactions, create materials with new properties, make devices on a molecular scale, etc. ” he says. “This is the light-matter interaction at its most basic level and the possibilities for discovery are many. A single zeptosecond is 10-21 seconds. A thousand zeptoseconds are an attosecond. Researchers are only now beginning to explore the zeptosecond phenomenon, although it is experimentally out of range due to the lack of zeptosecond laser pulses. Our unique approach to using entangled photons instead of photons in laser pulses could enable us to achieve the zeptosecond regime. This will require considerable experimental effort and is likely to be possible within five years. “


  1. Yimeng Wang, Siddhant Pandey, Chris H. Greene, Niranjan Shivaram. Attosecond entangled photons from the decay of two photons of metastable atoms: a source for attosecond experiments and beyond. Physical Review Research, 2022; 4 (3) DOI: 10.1103 / PhysRevResearch.4.L032038
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