Researchers have proposed a novel method for creating high-energy ‘quantum light,’ which might be used to probe new features of matter at the atomic scale.
Researchers from the University of Cambridge, together with colleagues from the US, Israel, and Austria, have proposed a theory for a new state of light with controllable quantum properties across a broad frequency range, including X-ray frequencies.
Their findings have been published in Nature Physics.
Classical physics can be used to describe the world we see around us, but when we look at things on an atomic scale, the strange world of quantum physics takes over.
If you observe a basketball with your naked eye, you will see that it acts in accordance with the rules of classical physics. But the basketball’s basic atoms operate in a way that is consistent with quantum physics.
“Light is no exception,” says lead author Dr. Andrea Pizzi, “from sunlight to radio waves, it can mostly be described using classical physics.
“But at the micro and nanoscale so-called quantum fluctuations start playing a role and classical physics cannot account for them.”
In order to create a theory that predicts a new method of controlling the quantum nature of light, Pizzi collaborated with Ido Kaminer’s team at the Technion-Israel Institute of Technology, as well as with colleagues at MIT and the University of Vienna. Pizzi is currently based at Harvard University.
“Quantum fluctuations make quantum light harder to study, but also more interesting: if correctly engineered, quantum fluctuations can be a resource,” adds Pizzi. “Controlling the state of quantum light could enable new techniques in microscopy and quantum computation.”
Strong lasers are one of the most common ways to make light. When a powerful enough laser is directed onto a group of emitters, it may pull some of the emitters’ electrons away, energizing them.
The additional energy that these electrons acquired is eventually released as light when some of them reunite with the emitters from which they were originally removed. This process changes light with a low frequency into radiation with a high frequency.
According to Pizzi, “the assumption has been that all these emitters are independent from one another, resulting in output light in which quantum fluctuations are pretty featureless.”
They “wanted to study a system where the emitters are not independent, but correlated: the state of one particle tells you something about the state of another. In this case, the output light starts behaving very differently, and its quantum fluctuations become highly structured, and potentially more useful.”
The researchers utilized a mix of theoretical study and computer simulations to solve this sort of challenge, known as a many body problem, in which the output light from a set of correlated emitters could be represented using quantum physics.
The theory, which was developed at the Technion by Pizzi and Alexey Gorlach, illustrates that correlated emitters and a powerful laser may create programmable quantum light. The technique produces high-energy output light and may be used to modify the X-rays’ quantum-optical structure.
After months of work, they finally succeeded in simplifying the equations to the point where they could express the relationship between the output light and the input correlations in a single compact equation,” according to Pizzi.
“Looking forward, we would like to collaborate with experimentalists to provide a validation of our predictions. On the theory side of things, our work suggests many-body systems as a resource for generating quantum light, a concept that we want to investigate more broadly, beyond the setup considered in this work.”
Source: 10.1038/s41567-022-01910-7
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