arXiv subjects

Charles W. Lewandowski

Publications and source records attributed to Charles W. Lewandowski.

5 recordsLinked to original sources

arXiv2024

Cross-correlation image analysis for real-time particle tracking

Accurately measuring the translations of objects between images is essential in many fields, including biology, medicine, chemistry, and physics. One important application is tracking one or more particles by measuring their apparent displacements in a series of images. Popular methods, such as the center-of-mass, often require idealized scenarios to reach the shot-noise limit of particle tracking and are, therefore, not generally applicable to multiple image types. More general methods, like maximum likelihood estimation, reliably approach the shot-noise limit, but are too computationally intense for use in real-time applications. These limitations are significant, as real-time, shot-noise-limited particle tracking is of paramount importance for feedback control systems. To fill this gap, we introduce a new cross-correlation-based algorithm that approaches shot-noise-limited displacement detection and a GPU-based implementation for real-time image analysis of a single particle.

physics.optics↗

arXiv2020

Active Optical Table Tilt Stabilization

We show that a simple modification to an optical table with pneumatic vibration isolation can be used to actively reduce the long term drift in the tilt of the table by nearly a factor of 1000. Without active stabilization, we measure a root-mean-square (RMS) tilt variation of \SI{270}{\upmu rad} over three days. The active stabilization can be used to limit the tilt to \SI{0.35}{\upmu rad} RMS over the same time period. This technique can be used to minimize drift in tilt-sensitive experiments.

physics.ins-det↗

arXiv2020

High sensitivity accelerometry with a feedback-cooled magnetically levitated microsphere

We show that a magnetically levitated microsphere in high vacuum can be used as an accelerometer by comparing its response to that of a commercially available geophone. This system shows great promise for ultrahigh acceleration sensitivities without the need for large masses or cryogenics. With feedback cooling, the transient decay time is reduced and the center-of-mass motion is cooled to \SI{9}{K} or less. Remarkably, the levitated particle accelerometer has a sensitivity down to \SI{3.6e-8}{\mathit{g}/\sqrt{Hz}} and gives measurements similar to those of the commercial geophone at frequencies up to \SI{14}{Hz} despite a test mass that is four billion times smaller. With no free parameters in the calibration, the responses of the accelerometers match within \num{3}\% at \SI{5}{Hz}. The system reaches this sensitivity due to a relatively large particle mass of \SI{0.25}{\upmu g}, a low center of mass oscillation frequency of \SI{1.75}{Hz}, and a novel image analysis method that can measure the displacement with an uncertainty of \SI{1.6}{nm} in a single image.

physics.app-ph↗

arXiv2018

Cooling the Motion of a Silica Microsphere in a Magneto-Gravitational Trap in Ultra-High Vacuum

Levitated optomechanical systems, and particularly particles trapped in vacuum, provide unique platforms for studying the mechanical behavior of objects well-isolated from their environment. Ultimately, such systems may enable the study of fundamental questions in quantum mechanics, gravity, and other weak forces. While the optical trapping of nanoparticles has emerged as the prototypical levitated optomechanical system, it is not without problems due to the heating from the high optical intensity required, particularly when combined with a high vacuum environment. Here we investigate a magneto-gravitational trap in ultra-high vacuum. In contrast to optical trapping, we create an entirely passive trap for diamagnetic particles by utilizing the magnetic field generated by permanent magnets and the gravitational interaction. We demonstrate cooling the center of mass motion of a trapped silica microsphere from ambient temperature to an effective temperature near or below one milliKelvin in two degrees of freedom by optical feedback damping.

quant-ph↗

arXiv2016

Cooling the Motion of Diamond Nanocrystals in a Magneto-Gravitational Trap in High Vacuum

Levitated diamond nanocrystals with nitrogen-vacancy (NV) centres in high vacuum have been proposed as a unique system for experiments in fundamental quantum mechanics, including the generation of large quantum superposition states and tests of quantum gravity. This system promises extreme isolation from its environment while providing quantum control and sensing through the NV centre spin. While optical trapping has been the most explored method of levitation, recent results indicate that excessive optical heating of the nanodiamonds under vacuum may make the method impractical with currently available materials. Here, we study an alternative magneto-gravitational trap for diamagnetic particles, such as diamond nanocrystals, with stable levitation from atmospheric pressure to high vacuum. Magnetic field gradients from permanent magnets confine the particle in two dimensions, while confinement in the third dimension is gravitational. We demonstrate that feedback cooling of the centre-of-mass motion of a trapped nanodiamond cluster results in cooling of one degree of freedom to less than 1 K.

quant-ph↗