Light’s self-influence unlocks better quantum sensors, says UMD’s Dutt

Avik Dutt of the University of Maryland is applying principles of nonlinear optics, where light intensity alters a material’s interaction with the light itself, to build more sensitive quantum sensors. Dutt’s approach bridges physics and engineering, a combination he first cultivated as an undergraduate at the Indian Institute of Technology in Kharagpur, majoring in electronics and electrical communication engineering with a minor in physics.

“When I got the opportunity to work at UMD, I was like, this is a great choice,” Dutt says, citing the university’s strengths in both quantum science and photonics as key to his lab’s focus on the intersection of the two fields.

Light Self-Influence Drives Quantum Sensor Development

Achieving squeezing levels equivalent to 40% of the noise of darkness, a benchmark indicating substantial progress in minimizing measurement interference within quantum systems, was recently demonstrated by the team. Dutt’s work centers on manipulating light intensity to alter how a material interacts with that same light, effectively allowing light to shape its own behavior. This self-influence is key to building sensors capable of detecting incredibly faint signals, far beyond the reach of conventional devices.

Dutt’s approach to squeezing light differs from previous methods by focusing on manipulating quantum uncertainty, trading it between properties like electric field strength and phase. Rather than simply minimizing energy within a confined space, the team exploits the inherent uncertainty present in light itself, governed by principles similar to Heisenberg’s uncertainty principle.

By accurately measuring the electric field strength, they correspondingly increase uncertainty in the light’s phase, and vice versa, creating a squeezed state optimized for specific sensing applications. This manipulation occurs within resonators, tiny structures approximately 100 micrometers across, comparable in size to a human hair, where input light generates paired photons forming a beam of squeezed light. The resonators developed by Dutt’s group are not only more effective at squeezing light than previous iterations, but also smaller and designed for compatibility with mass production techniques.

This ability to scale is important for translating laboratory demonstrations into practical, deployable sensors. These devices operate across a broad range of frequencies, a feature that could be particularly valuable for quantum computing and communication, enabling faster and more efficient information transfer. “The most significant achievement of my lab right now is to have world record numbers of squeezing across a large number of modes and spanning a bandwidth of more than 10 terahertz,” Dutt says, highlighting the performance gains achieved through this design.

“We get fresh ideas from angles we would have never thought of, through interactions with my colleagues, by having students from physics, electrical engineering, mechanical engineering, materials science, sometimes computer science,” Dutt explains, emphasizing the value of collaborative, cross-disciplinary inquiry. Looking ahead, Dutt intends to further refine these resonators to enhance light-matter interactions and explore their potential as platforms for encoding information and generating entangled photons.

Entangled photons, linked through quantum mechanics, represent a powerful resource for quantum technologies. He envisions these resonators not just as sources of squeezed light, but as versatile tools for creating and manipulating a wider range of quantum states.

“Name almost any technology that is common to our surroundings, be it sensing, communications or computing, and photonics seems very well poised to play a role in them,” Dutt observes, suggesting a broad future for photonics-based quantum technologies. He adds, “These perspectives that we get—and the things that I get to learn at a faster rate than being in one area—have been very rewarding.” The team’s current work builds on earlier successes in creating synthetic dimensions within optical resonators.

Dutt’s Background Bridges Physics and Engineering

This combination wasn’t accidental; Dutt actively sought an education that would allow him to translate fundamental scientific principles into tangible technologies, a philosophy that continues to drive his research. He explains that the institute supported an environment where interdisciplinary collaboration was not just encouraged, but essential for innovation. This integrated approach followed Dutt to his doctoral studies, where he worked with Michal Lipson, first University and later University when she transitioned her lab.

Working with Lipson and Paulo Nussenzveig from the University of Sao Paulo in Brazil, he moved beyond theory and simulations and gained hands-on experience with experiments and making novel devices. Dutt’s lab at the University of Maryland now benefits from a similar collaborative spirit, attracting students from diverse backgrounds.

The benefits of this diversity extend beyond simply having more perspectives in the room, Dutt notes. The creation of artificial spaces with more than two dimensions relies on manipulating the properties of light, specifically encoding positions onto characteristics like color. This approach allows researchers to study complex physics phenomena, such as topological physics, in a controlled environment.

The team detailed their method for encoding synthetic dimensions into photonic molecules created by interacting resonators, in a June 2023 article in Nature Physics, proposing new experiments to explore these artificial spaces. Dutt’s lab is also focused on enhancing the performance of these resonators, aiming to improve light-matter interactions and reduce noise levels.

Nonlinear Optics and Topological Photonics Research

Dutt’s doctoral work with Michal Lipson at both University University solidified a long-term research trajectory, as he followed her lab when she transitioned between institutions. This mentorship was important in shaping his approach to photonics, encouraging a commitment to a specific line of inquiry that continues to define his work. He applied his practical training to translate theoretical proposals into tangible experiments, a skill honed during his time at both universities.

This convergence allows his team to explore how manipulating light can enhance quantum capabilities, specifically through the creation of squeezed states of light within compact chips. It is an enabling quantum resource for many quantum technological applications. Collaborations within the Joint Quantum Institute, with researchers like JQI Fellow Kartik Srinivasan and Mohammad Hafezi, have been instrumental in this process.

Srinivasan’s expertise with silicon nitride, the foundation of Dutt’s devices and Hafezi’s work in nonlinear optics, have provided essential support. Alessandro Restelli, a JQI research scientist, has further contributed by developing techniques to minimize electronic noise and maximize the degree of light squeezing.

Photonic Molecules Encode Multiple Synthetic Dimensions

The ability to create artificial spaces for quantum particles has expanded with the demonstration of photonic molecules capable of encoding multiple synthetic dimensions, a technique that bypasses limitations inherent in three-dimensional physics. Dutt and colleagues detailed their approach in Nature Physics in June 2023, outlining a method to generate any number of dimensions, initially demonstrating two using a system of interacting resonators.

The core of this work lies in the creation of pairs of interacting resonators, which behave analogously to hydrogen atoms forming a molecule. Unlike single resonators, these pairs can support additional states when fed multiple frequencies of light, with each frequency representing a position within a synthetic dimension.

By mapping positions in these artificial dimensions onto distinct light behaviors within the resonator pair, the team engineered interactions mirroring physics within the created space. Dutt used his practical Ph.D. training to perform experiments that made the group’s theoretical proposals a reality. To test the concept, the researchers used optical fibers as resonators, acknowledging their imperfections as a means for rapid prototyping. Despite these limitations, they successfully simulated the two-dimensional physics of a Chern insulator, a material exhibiting lossless edge current, observing telltale signs of current formation and associated topological effects.

The team’s simulations showed how future experiments, using more refined devices could generate additional topological behaviors for study. Dutt asserts that even a single resonator pair is sufficient to explore higher numbers of synthetic dimensions. The inspiration for this approach stemmed from discussions with colleagues at the University of Maryland and visiting researchers, highlighting the value of collaborative environments in pushing the boundaries of photonics.

Dutt realized that by adding a second resonator, he could encode as many synthetic dimensions as desired into the states of light, expanding the scope of possible experiments. Having established his own lab after postdoctoral research, Dutt aims to expand on past projects and explore the full potential of these synthetic dimensions. This work represents a step toward advanced quantum technologies building on Dutt’s commitment to pushing the boundaries of photonics devices.

He began applying this interdisciplinary approach through research projects in photonics while still an undergraduate, collaborating with professors on theory and simulations. This initial exposure to manipulating individual particles of light, or photons, set the stage for his later investigations into synthetic dimensions and quantum sensing. Expanding the possibilities for experimentation required a shift in Dutt’s approach to encoding synthetic dimensions. His postdoctoral work had already demonstrated the creation of two such dimensions within a single optical resonator, using opposing light propagation directions to define quantum states.

To test this concept, the team employed a pair of optical fiber resonators, components similar to those used to transmit data across the internet. While not ideal for the experiment, these fibers offered a rapid prototyping method for validating the core idea. This simulation demonstrates a pathway to study complex materials without physically creating them, offering a new tool for materials science.

The ability to reduce noise in quantum measurements is critical for developing more sensitive sensors. The team’s approach doesn’t focus on concentrating light’s energy, but rather on manipulating quantum uncertainty. By applying principles like Heisenberg’s uncertainty principle, which governs the relationship between a particle’s position and velocity, researchers can trade uncertainty in one property of light for certainty in another. This “squeezing” of light reduces background noise stemming from virtual particles, which constantly fluctuate even in a vacuum.

Dutt and his colleagues achieved a noise level equivalent to approximately 40% of that found in complete darkness, a significant reduction. This improvement is not merely about achieving lower noise levels. The team also demonstrated the long-term stability of their squeezed quantum states, overcoming a common challenge in quantum technology.

The resonators used in the experiment were each around 100 micrometers across, roughly the width of a human hair or a grain of table salt, highlighting the precision required for these measurements. The researchers also laid out how their devices produce these squeezed quantum states with long-term stability, circumventing the usually fragile nature of quantum states.

More like this

Quantum Research NewsPrinceton lab finds faster way to design quantum materials with chemistry

Quantum Research NewsQuantum geometry of materials mapped with light, researchers say

Quantum PhysicsContinuous-variable quantum computing mirrors discrete-variable systems

Quantum PhysicsBrookhaven’s quantum physics leader joins New York college faculty