Researchers suggest a new way to generate a light source from entangled photons

Entanglement is a strange phenomenon in quantum physics where two particles are intrinsically linked to each other, regardless of the distance between them. When one is measured, the other measurement is instantly data. Researchers from Purdue University have proposed a new, unconventional approach to generating a special light source made up of entangled photons. On September 6, 2022, they published their findings in Physical examination research.

The team proposed a method to generate entangled photons at extreme ultraviolet (XUV) wavelengths where no such source currently exists. Their work provides a roadmap for how to generate these entangled photons and use them to track electron dynamics in molecules and materials on incredibly short timescales of attoseconds.

“The entangled photons in our work are guaranteed to arrive at a given location within a very short time 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 ultrafast events. An important application is in attosecond metrology to push the limits of measurement of shortest time scale phenomena. be used in quantum imaging and spectroscopy, where entangled photons have been shown to improve the ability to obtain information, but now at XUV wavelengths and even X-rays.”

The authors of the publication, titled “Attosecond Entangled Photons from the Two-Photon Decay of Metastable Atoms: A Source for Attosecond Experiments and Beyond”, are all from the Physics and Astronomy Department of Purdue University and work with the Purdue Quantum Science and Engineering Institute. (PQSEI). They are Dr. Yimeng Wang, a recent graduate of Purdue University; Siddhant Pandey, Ph.D. candidate in the field of ultrafast experimental spectroscopy; Dr. Chris H. Greene, Albert Overhauser Emeritus Professor of Physics and Astronomy; and Dr Shivaram.

“Purdue’s Department of Physics and Astronomy has a strong program in Atomic, Molecular, and Optical (AMO) Physics, which brings together experts in various subfields of AMO,” says Shivaram. “Chris Greene’s expert knowledge of theoretical atomic physics combined with Niranjan’s experience in the relatively young field of experimental attosecond science led to this collaborative project. While many universities have AMO programs, the program Purdue’s AMO is particularly diverse in that it has experts in several subfields of OMA Sciences.”

Each researcher has played an important role in this ongoing research. Greene initially suggested the idea of ​​using photons emitted from 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 made estimates of the entangled photon emission/absorption rates and worked out the details of the experimental schemes. proposed attoseconds.

The publication marks the beginning of this research for Shivaram and Greene. In this publication, the authors propose the idea and elaborate the theoretical aspects of the experiment. Shivaram and Greene plan to continue collaborating on additional experimental and theoretical ideas. Shivaram’s lab, the Ultrafast Quantum Dynamics Group, is currently building a device to experimentally demonstrate some of these ideas. According to Shivaram, the hope is that other researchers in attosecond science 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 timescale of entangled photons to zeptoseconds, 10^-21 seconds.

“Typically, experiments on attosecond timescales are performed using attosecond laser pulses as ‘strobes’ to ‘image’ electrons. Current limits for these pulses are around 40 attoseconds. Our idea proposed use of entangled photons could reduce this to attoseconds or zeptoseconds,” says Shivaram.

In order to understand timing, one must understand that electrons play a fundamental role in determining the behavior of atoms, molecules, and solid materials. The time scale of electron movement is usually 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). According to Shivaram, it is essential to better understand the dynamics of electrons and to follow their movement on these ultrashort timescales.

“The goal of the field of superfast science is to create such ‘films’ of electrons, and then to use light to control the behavior of those electrons to create chemical reactions, to create materials with novel properties, to fabricate devices at the molecular level, etc.” he says. “This is about light-matter interaction at its most basic level, and the possibilities for discovery are many. A single zeptosecond equals 10^-21 seconds. A thousand zeptoseconds is an attosecond. Researchers are only beginning to explore zeptosecond phenomena, although they are experimentally out of reach due to the lack of zeptosecond laser pulses. Our unique approach of using entangled photons instead of photons in laser pulses could allow us to reach the zeptosecond regime. This will require considerable experimental effort and is likely possible on a five-year timescale.”