Nanoparticles as ultraclean mechanical oscillators
A central thrust of my work at UCL is the development of nanoparticles levitated in optical tweezers and Paul traps — isolated from their environment by the absence of any mechanical contact. Key achievements include the first simultaneous cavity cooling of all six degrees of freedom (translational and rotational) of a single nanoparticle (Nature Physics, 2023).
I demonstrated directional force sensing via cross-correlations between translational modes, realising a 'force compass' for detecting stochastic signals from specific directions (Physical Review Research, 2024). More recently, strong Coulomb coupling between two co-levitated nanospheres and the emergence of dark modes in their joint motion (Optica, 2024; PRL, 2025), and high-purity two-dimensional quantum states (Nature Communications, 2025). Engineering contributions include robust 3D feedback cooling schemes, imaging-based detection, and systematic comparisons of feedback cooling methods.
Micro-oscillating mirrors in Fabry–Pérot cavities
In collaboration with groups in Trento and Florence, I contributed to the design, fabrication, and characterisation of silicon and silicon nitride micro-oscillating mirrors with simultaneously low optical and mechanical losses — the prerequisite for quantum-noise-limited cavity optomechanics.
Building on this platform, I demonstrated ponderomotive squeezing via parametric modulation of the optical spring (PRL, 2014; PRL, 2016), quantum non-demolition measurement of optical field fluctuations (PRA, 2018), and novel heterodyne signal-processing techniques for quantum displacement sensing (PRL, 2018). These experiments pushed optomechanical systems toward the standard quantum limit and established practical routes to continuous-variable entanglement between macroscopic modes.
Beyond the standard model with mechanical sensors
The extreme sensitivity of levitated oscillators makes them ideal probes of physics beyond the standard model. I have used Paul-trap nanoparticles to set competitive bounds on spontaneous wave-function collapse models (CSL and Diósi–Penrose), exploiting mechanical quality factors approaching 10¹² (Physical Review Research, 2020).
I have also contributed to probing deformed canonical commutators predicted by quantum gravity (Nature Communications, 2015), and to a perspective on using levitated sensors for directional dark matter searches, including the potential of quantum superpositions of mesoscopic particles for rare-event detection (AVS Quantum Science, 2024).
Current and future directions
Current work focuses on generating genuine quantum entanglement between pairs of levitated nanoparticles via Coulomb coupling and coherent scattering, preparing non-classical motional states for tests of macroscopic quantum mechanics, and developing directional sensing protocols for ultralight dark matter searches.
The platform of levitated nano-oscillators — now controllable across all six degrees of freedom and in multi-particle configurations — provides a uniquely versatile testbed at the intersection of quantum information, precision metrology, and fundamental physics.
