Driven by Curiosity: Igor Pikovski Awarded $514,230 NSF CAREER Award to Enable Experimental Searches for Quantum Gravity at Low Energies
The theoretical physicist is on a quest to develop novel experimental approaches for resolving quantum theory with Einstein’s theory of general relativity
Stevens Institute of Technology’s Igor Pikovski loves a mystery. But not just any mystery: specifically, the mysteries of the bizarre and unexplained phenomena of matter and energy that occur at the smallest possible scale in existence which hold the truths of the very nature of the universe itself.
“I'm fascinated by the strange phenomena and the very basic questions that we don't fully understand that usually offer puzzling answers,” he said. “My study is focused on unraveling some of these mysteries — about time, about what nature is made of, about what exists in the world and may be beyond, and what new theories may even be beyond quantum theory.”
An assistant professor in the Department of Physics, Pikovski was recently awarded a $514,230 CAREER Award from the National Science Foundation (NSF) to help solve a more than 100-year-old mystery: how to resolve two seemingly unresolvable theories of the nature of the universe — Einstein’s theory of general relativity and quantum theory.
A theory of classical physics, Einstein’s theory of general relativity, which describes gravity as a product of curved space and time, governs the physical dynamics of life on the macroscopic scale — those fundamental principles by which everything on Earth and throughout the cosmos behaves.
Quantum theory, on the other hand, describes the behaviors of the smallest building blocks of nature at a quantum (atomic and subatomic) scale. Invisible to the naked eye, these building blocks of matter behave in unusual ways that are wildly different from what we experience in everyday life.
While both theories have been proven experimentally, no single intellectual framework has been found that describes both these macroscopic and microscopic phenomena according to the same principles simultaneously.
“The problem is that these two pillars, these fundamental principles, they don't work together,” explained Pikovski. “Why exactly don’t they work together? Every physicist has their favorite theory, but the honest answer is, we really don't know why. The math works a little bit at some level, and then at some point, it doesn't work anymore.”
Titled “Towards Low-Energy Tests of Quantum Gravity with AMO Systems,” Pikovski’s five-year research project will leverage advances in quantum technology and quantum information science and apply them to the specific problem of how to search for signatures (characteristics) of gravity at a quantum scale. Science has yet to establish a quantum theory of gravity or to identify a proven method for searching for it.
Pikovski will design and develop new gravity detection methods that will enable primarily tabletop laboratory experiments to indirectly detect signs of quantum gravity, helping to guide the way toward determining the fundamental nature of gravity, and, ultimately, to resolving quantum theory with general relativity. Discovering experimental methods for detecting quantum gravity signatures would be a gamechanger for the natural sciences and for humanity’s understanding of nature itself.
Pikovski is quick to note that his research goal is not to develop a new universal theory for these phenomena himself. Rather, his goal is to approach the problem from a new perspective in order to pave the way to make developing such a theory possible.
In other words, Pikovski is not on a search for quantum gravity: He’s on a search for how to search for quantum gravity.
“I don't do the experiments: I try to shine light on new, interesting directions — where one could use new quantum technologies in order to do such experiments. I do pure theory, but the goal is to find what experiments we could do to reveal the quantum nature of gravity.”
This curiosity-driven approach fits at the core of Pikovski’s general approach to science — and is emblematic of the eclectic experiences that led Pikovski to a career in theoretical quantum research.
A random encounter
Pikovski earned his physics diploma (equivalent to a master’s of science degree in the U.S.) in 2009 from the Free University in his hometown of Berlin. Fluent in four languages, he took maximum advantage of the university’s exchange fellowships program as a student, starting with a year at Uppsala University in Sweden.
“That's where, I think for the first time, I understood quantum mechanics and got excited about it,” he said. “The more I studied it, the more I was fascinated by its strangeness.”
A year later, Pikovski set off for the United States to work on a master’s thesis project at the University of California, Santa Barbara (UCSB). A random connection made there would ultimately set the stage for the rest of his career.
“I wanted to study gravity when I was in Santa Barbara. It always fascinated me,” Pikovski explained. There, he was fortuitously introduced to a professor from the Netherlands who suggested that they run experiments to test the quantum nature of gravity.
“I’d never heard of something like that. I thought it was impossible. You heard all these arguments why you can’t — that gravity is too weak; that you need these accelerators that are as big as the universe,” Pikovski joked. “But it turned out that was naïve — that you could be clever and come up with certain things to test it.”
“It really hooked me,” he added. “That has been my field ever since.”
After a year at UCSB, Pikovski followed his new mentor back to the Netherlands where he spent a year as a visiting student at Leiden University. These early international experiences, he said, “really set my path.”
In the fall of 2009, Pikovski moved to the University of Vienna in Austria to pursue a Ph.D. in quantum physics, where he focused on theoretical physics, quantum optics, quantum information and gravity. Working within a subgroup focused on quantum theory with physicist Caslav Brukner, Pikovski was part of the larger fundamental quantum research group through which Anton Zeilinger would later win the Nobel Prize for Physics in 2022. During this time, Pikovski was also awarded a research fellowship with the Vienna Center for Quantum Science and Technology.
After earning his doctorate in 2014, Pikovski was awarded two consecutive independent research fellowships that would allow him to pursue any line of inquiry of his choosing.
The first was a three-year ITAMP postdoctoral fellowship at the Institute for Theoretical Atomic, Molecular and Optical Physics, an NSF-funded institute hosted by the Harvard-Smithsonian Center for Astrophysics.
At the same time, Pikovski served as a member of the scientific advisory group for the Breakthrough Starshot Initiative, a $100-million research and engineering program launched by then-Chair of Harvard’s Department of Astronomy Avi Loeb and famed theoretical physicist Stephen Hawking to develop proof-of-concept sunlight-powered nano-spacecraft capable of interstellar flight to the Alpha Centauri star system.
Then in 2017, Pikovski was awarded the prestigious Branco Weiss Society in Science fellowship, administered by the Swiss Federal Institute of Technology Zurich. With the freedom to conduct research on any topic at any institution anywhere in the world through this five-year grant, Pikovski chose to remain at the Harvard-Smithsonian Center for Astrophysics, later transferring the fellowship to Stevens.
“For that project, I studied the interface between quantum technology development and fundamental physics related to gravity — questions like, as you develop quantum technologies, what type of novel aspects of gravity can you test, and what kind of new opportunities arise?” he explained. “This NSF CAREER award is, in many ways, building on that.”
An assistant professor at Stevens since 2018, Pikovski has published more than 30 scientific articles on quantum physics in publications including Nature Physics, Nature Communications and the American Physical Society’s Physical Review. He is also an associate research fellow with Harvard University and holds an affiliated professorship with Stockholm University in Sweden. His research group is located at both Stevens and Stockholm University.
Seeking answers, seeking questions
For decades, most fundamental quantum research has been developed through high-energy experiments, such as those conducted by the European Organization for Nuclear Research (generally known by its French acronym CERN) of smashing particle beams together at ultra-high speeds via the world’s largest and most powerful particle accelerator.
But Pikovski’s low-energy, quantum information science methods take a different approach.
“Let's go back to the roots — to the basic notions of quantum theory, and focus on tabletop experiments, with single atoms or particles or lasers, to test some of the very basic phenomena of these theories, especially as they intertwine. You don't need high energies or to create new phenomena or to study how particles interact. Instead of smashing particles, you control them.”
A major challenge to developing a complete theory of quantum gravity has been how little experimental evidence exists that could help guide theoretical developments since quantum theory and Einstein’s theory of general relativity are relevant at seemingly distant scales: the very large and the very small. Pikovski seeks to tackle this problem by developing experimental methods that employ advanced quantum optical (light photon-based) systems and modern quantum information concepts to test the interplay of gravity and quantum theory in ways that historically have never been possible before.
In fact, thanks to major technological and theoretical advances in quantum physics made in just the last 20 years, said Pikovski, right now is the perfect moment for exploring such decades-old questions in ways researchers could never have dreamed of previously.
“It's always exciting to ask very fundamental questions, but we need to have the tools and the ways to think about it to be able to approach them,” he said. “We're really at the stage now where it's become realistic to ask these questions. I think we are at the nexus where new experiments are possible, where new theory ideas are possible.”
Because the force of gravity is so weak, it is difficult to detect through direct experiments. So Pikovski’s aim is to find new ways to detect quantum gravity by observing its presence indirectly.
What exactly are those ways of observing quantum gravity’s presence indirectly? What signatures of quantum gravity can be extracted for testing? What kinds of experiments would make these characteristics observable, and where and under what circumstances should one even look?
Those are just some of the many questions Pikovski seeks to answer through this research. Some surprising new directions have been outlined in recent works, both from Pikovski’s group and other colleagues in the field, he said, that show that experiments with massive or precise quantum systems can be influenced by gravity, and could even show signatures of quantum gravity. But much remains to be investigated.
The process, he said, is one of creative exploration — of defining that which is not yet well-defined in order to determine what it is about the quantum nature of gravity that can — or cannot — be tested. Before starting to put the puzzle together, he must first find at least some of its pieces. Where quantum gravity is concerned, Pikovski is not simply searching for the right answers: He is searching for the right questions.
Physics in practice, physics as poetry
In 2022, Pikovski was awarded a $400,000 grant from the U.S. Department of Energy to advance quantum sensing technologies to improve the encoding, detection, transmission and shielding of quantum information in such systems as quantum magnetometers and atomic clocks.
Exploring the practical side of quantum physics, he said, goes “hand in hand” with his studies of the fundamental nature of quantum phenomena. While basic quantum research is interested in developing experiments to answer fundamental questions of the nature of the universe, quantum technology development is interested in leveraging those explorations for a specific purpose. The two approaches — practical application and pure research — hold a symbiotic relationship, with each able to advance and improve upon the other.
In this way, Pikovski views quantum technology development as a crucial and socially beneficial side effect of fundamental quantum research.
Harnessing the unusual phenomena of the quantum level discovered through pure research has already led to revolutionary advances in quantum computing, quantum cryptography and quantum communications in just the last two decades alone. Smartphones, MRI scanners, solar cells and GPS systems all take advantage of quantum research discovery, and future possible applications include weather and climate change forecasting, drug development, improved electric vehicle batteries and traffic management.
Even more than the practical applications, however, Pikovski’s personal pursuit of the quantum mysteries of the universe is driven, above all, by curiosity. To him, the most important reason to explore such fundamental questions as the nature of quantum gravity is for the sake of itself.
“I don't want to even sugarcoat it. The honest answer is that it's truly blue-sky research,” he said. “In many ways, it's a bit like art. It's deeply inspiring to try and understand the world around us. And the world is so much more fascinating and bizarre than I think we can imagine.”
This striving to understand nature and the universe, according to Pikovski, “makes us human” and connects humanity both to each other and to generations of curious people attempting to understand themselves.
“Every century, humanity has a view of what nature is like, and we think we understand everything. A long time ago, it was mechanistic, so there was Newton's laws, and everything was gears and so forth. Then suddenly there was electromagnetism, where electricity and magnetism came together. And now came space-time into the picture and quantum theory, so it just gets more and more bizarre,” Pikovski said. “We're still at the very starting point. I would be extremely fascinated to know what will be our picture in 500 years from now. Probably something completely different.”