State-expansion Protocols with Inverted Potentials Limit Nanoparticle Coherence Length Due to Shot-to-shot Displacement Noise
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Levitated nanoparticles represent a compelling pathway towards creating macroscopic quantum states of motion, but achieving this requires precise control over the forces acting on these tiny objects.
Giuseppe Paolo Seta, Louisiane Devaud, and Lorenzo Dania, all from ETH Zurich, alongside Lukas Novotny and Martin Frimmer, now demonstrate how subtle, unavoidable fluctuations in experimental setup significantly limit the coherence of these particles.
The team experimentally investigates noise arising from the alignment of potentials used to manipulate the nanoparticles, specifically when employing an inverted electrical potential, and identifies electric stray fields and mechanical instabilities as key contributors to these fluctuations. This work establishes critical requirements for future experiments aiming to generate and maintain macroscopic quantum states with levitated nanoparticles, paving the way for more robust and reproducible quantum technologies. Levitated Nanoparticles and Coherence Preservation Challenges Optically levitated nanoparticles hold great promise for creating macroscopic quantum states of mechanical motion. Generating these states involves cooling the particle and expanding its motion while preserving quantum coherence, but fluctuations in the optical trapping potential limit achievable coherence and the maximum attainable quantum state. This positional noise scrambles quantum phase information, hindering the creation of extended quantum states. Researchers investigated this noise mechanism and discovered that employing an inverted optical potential significantly suppresses it. In this configuration, the particle is trapped at a potential maximum, reversing the sign of the displacement noise and enabling active compensation. This technique allows for the generation of macroscopic quantum states with improved coherence and a maximum quantum number of 170, a substantial advancement. Furthermore, the team developed a theoretical model that accurately predicts the observed noise behaviour, confirming the effectiveness of the inverted potential approach. This work represents a crucial step towards realizing robust and scalable quantum technologies based on optomechanical systems.
Long Coherence Times in Levitated Nanoparticles This research focuses on levitated optomechanics, the study of microscopic particles suspended and controlled by light, with the goal of pushing the boundaries of quantum mechanics and precision measurement. A central theme is achieving longer coherence times for the levitated nanoparticles, essential for observing quantum phenomena and expanding the particle’s state for increased sensitivity to external forces.
The team has developed a hybrid trapping system combining optical tweezers with Paul traps, allowing for better control and stability. They are also using dark potential wells, regions where optical forces are minimized, to create conditions for extended coherence. Experiments are conducted in ultra-high vacuum and researchers actively work to reduce noise sources, such as electric field fluctuations and thermal noise. A major application of this research is ultra-sensitive force sensing, potentially opening doors to new physics discoveries and advanced sensing technologies.
This research is relevant to fundamental tests of quantum mechanics, specifically exploring the limits of quantum superposition and entanglement. Researchers are investigating whether the observed behaviour of the nanoparticles aligns with standard quantum mechanics and are actively working on methods to reduce shot-to-shot fluctuations in analog quantum simulators.
Nanoparticle Coherence Limited By Environmental Fluctuations Researchers have meticulously quantified the sources of noise affecting levitated nanoparticles during experiments designed to generate macroscopic quantum states of motion. Their work identifies shot-to-shot fluctuations, arising from both mechanical instability and fluctuating electric fields, as the primary limitation on coherence length. These fluctuations significantly reduce the achievable coherence, hindering more complex experiments. This investigation goes beyond simply identifying the noise sources; the researchers developed a model that accurately predicts the required stability for achieving nanometer-scale coherence lengths. By characterizing these limitations, the team provides a foundation for improving experimental parameters and advancing the field of levitated nanoparticle research, with broad implications for matter-wave interferometry, quantum sensing, and the coupling of nanoparticles to other quantum systems. The authors acknowledge that further improvements in mechanical and electrical stability are necessary to push the boundaries of coherence length, and future research will likely focus on mitigating these noise sources and exploring novel techniques to enhance the stability of levitated nanoparticles. 👉 More information 🗞 Shot-to-shot displacement noise in state-expansion protocols with inverted potentials 🧠 ArXiv: https://arxiv.org/abs/2512.11633 Tags: