arXiv subjects

Muddassar Rashid

Publications and source records attributed to Muddassar Rashid.

13 recordsLinked to original sources

arXiv2026

A Levitated Random Telegraph Noise Spectrometer

Random Telegraph Noise is a ubiquitous process manifesting across technology and the natural world. It is characterized by random jumps between two distinct states with Poissonian waiting times, and is the origin of 1/f noise. Understanding and characterizing this noise is critical for the reliable operation of micro-, nano- and quantum-technologies. In this work we probe random telegraph noise using a levitated microparticle sensor whose dynamics are driven almost entirely by this non-white source of noise. We observe a startling resonant behaviour, characterized by a thousand-fold increase in the underdamped sensor's position fluctuations, enabling us to measure the spectral properties of the noise over six decades of timescale. This work not only provides a unique way to probe random telegraph noise, but also demonstrates a platform for studying non-equilibrium stochastic dynamics in the presence of realistic non-white noise, with applications from biology to social behaviour.

physics.ins-det↗

arXiv2025

Extreme-temperature single-particle heat engine

There are many exotic thermodynamic processes that are hard to study in nature. Here, we synthesize a structured environment to explore the extremes of thermodynamics. We present an engine running at extreme temperatures of above ten Mega-Kelvin. Our underdamped engine is realised by electrically levitating and controlling a charged microparticle in vacuum. Giant fluctuations are observed in the engine's heat exchange with the environment, while its efficiency shows stochastic events where more work is performed by the engine than heat consumed. Moreover, the non-uniformity of the synthetic environment leads to the particle experiencing position dependent diffusion, a critical phenomenon in microscale biological processes. We theoretically account for the effects of multiplicative noise and find excellent agreement with the observed behavior.

cond-mat.stat-mech↗

arXiv2025

Neuromorphic detection and cooling of microparticles in arrays

Micro-objects levitated in a vacuum are an exciting platform for precision sensing due to their low dissipation motion and the potential for control at the quantum level. Arrays of such sensors would offer increased sensitivity, directionality, and in the quantum regime the potential to exploit correlation and entanglement. We use neuromorphic detection via a single event based camera to record the motion of an array of levitated microspheres. We present a scalable method for arbitrary multiparticle tracking and control by implementing real-time feedback to {simultaneously cool the motion of three uncoupled microscale objects

physics.ins-det↗

arXiv2024

Massive quantum systems as interfaces of quantum mechanics and gravity

The traditional view from particle physics is that quantum gravity effects should only become detectable at extremely high energies and small length scales. Due to the significant technological challenges involved, there has been limited progress in identifying experimentally detectable effects that can be accessed in the foreseeable future. However, in recent decades, the size and mass of quantum systems that can be controlled in the laboratory have reached unprecedented scales, enabled by advances in ground-state cooling and quantum-control techniques. Preparations of massive systems in quantum states pave the way for the explorations of a low-energy regime in which gravity can be both sourced and probed by quantum systems. Such approaches constitute an increasingly viable alternative to accelerator-based, laser-interferometric, torsion-balance, and cosmological tests of gravity. In this review, we provide an overview of proposals where massive quantum systems act as interfaces between quantum mechanics and gravity. We discuss conceptual difficulties in the theoretical description of quantum systems in the presence of gravity, review tools for modeling massive quantum systems in the laboratory, and provide an overview of the current state-of-the-art experimental landscape. Proposals covered in this review include, among others, precision tests of gravity, tests of gravitationally-induced wavefunction collapse and decoherence, as well as gravitymediated entanglement. We conclude the review with an outlook and summary of the key questions raised.

quant-ph↗

arXiv2022

Event-Based Imaging of Levitated Microparticles

Event-based imaging is a neurmorphic detection technique whereby an array of pixels detects a positive or negative change in light intensity at each pixel, and is hence particularly well suited to detecting motion. As compared to standard camera technology, an event-based camera reduces redundancy by not detecting regions of the image where there is no motion, allowing increased frame-rates without compromising on field-of-view. Here, we apply event-based imaging to detect the motion of a microparticle levitated under vacuum conditions, which greatly facilitates the study of nanothermodynamics and enables the independent detection and control of arrays of many particles.

physics.ins-det↗

arXiv2019

Static force characterization with Fano anti-resonance in levitated optomechanics

We demonstrate a classical analogy to the Fano anti-resonance in levitated optomechanics by applying a DC electric field. Specifically, we experimentally tune the Fano parameter by applying a DC voltage from 0~kV to 10~kV on a nearby charged needle tip. We find consistent results across negative and positive needle voltages, with the Fano line-shape feature able to exist at both higher and lower frequencies than the fundamental oscillator frequency. We can use the Fano parameter to characterize our system to be sensitive to static interactions which are ever-present. Currently, we can distinguish a static Coulomb force of $2.7 \pm 0.5 \times 10^{-15}$~N with the Fano parameter, which is measured with one second of integration time. Furthermore, we are able to extract the charge to mass ratio of the trapped nanoparticle.

quant-ph↗

arXiv2018

Detection of anisotropic particles in levitated optomechanics

We discuss the detection of an anisotropic particle trapped by an elliptically polarized focused Gaussian laser beam. We obtain the full rotational and translational dynamics, as well as, the measured photo-current in a general-dyne detection. As an example, we discuss a toy model of homodyne detection, which captures the main features typically found in experimental setups.

quant-ph↗

arXiv2018

Precession Motion in Levitated Optomechanics

We investigate experimentally the dynamics of a non-spherical levitated nanoparticle in vacuum. In addition to translation and rotation motion, we observe the light torque-induced precession and nutation of the trapped particle. We provide a theoretical model, which we numerically simulate and from which we derive approximate expressions for the motional frequencies. Both, the simulation and approximate expressions, we find in good agreement with experiments. We measure a torque of $1.9 \pm 0.5 \times 10^{-23}$ Nm at $1 \times 10^{-1}$ mbar, with an estimated torque sensitivity of $3.6 \pm 1.1 \times 10^{-31}$ Nm/$\sqrt{\text{Hz}}$ at $1 \times 10^{-7}$ mbar.

quant-ph↗

arXiv2018

Dynamical model selection near the quantum-classical boundary

We discuss a general method of model selection from experimentally recorded time-trace data. This method can be used to distinguish between quantum and classical dynamical models. It can be used in post-selection as well as for real-time analysis, and offers an alternative to statistical tests based on state-reconstruction methods. We examine the conditions that optimize quantum hypothesis testing, maximizing one's ability to discriminate between classical and quantum models. We set upper limits on the temperature and lower limits on the measurement efficiencies required to explore these differences, using a novel experiment in levitated optomechanical systems as an example.

quant-ph↗

arXiv2017

Wigner Function Reconstruction in Levitated Optomechanics

We demonstrate the reconstruction of the Wigner function from marginal distributions of the motion of a single trapped particle using homodyne detection. We show that it is possible to generate quantum states of levitated optomechanical systems even under the effect of continuous measurement by the trapping laser light. We describe the opto-mechanical coupling for the case of the particle trapped by a free-space focused laser beam, explicitly for the case without an optical cavity. We use the scheme to reconstruct the Wigner function of experimental data in perfect agreement with the expected Gaussian distribution of a thermal state of motion. This opens a route for quantum state preparation in levitated optomechanics.

quant-ph↗

arXiv2017

Force sensing with an optically levitated charged nanoparticle

Levitated optomechanics is showing potential for precise force measurements. Here, we report a case study, to show experimentally the capacity of such a force sensor. Using an electric field as a tool to detect a Coulomb force applied onto a levitated nanosphere. We experimentally observe the spatial displacement of up to 6.6 nm of the levitated nanosphere by imposing a DC field. We further apply an AC field and demonstrate resonant enhancement of force sensing when a driving frequency, $ω_{AC}$, and the frequency of the levitated mechanical oscillator, $ω_0$, converge. We directly measure a force of $3.0 \pm 1.5 \times 10^{-20}$ N with 10 second integration time, at a centre of mass temperature of 3 K and at a pressure of $1.6 \times 10^{-5}$ mbar.

quant-ph↗

arXiv2017

Parametric Feedback Cooling of Levitated Optomechanics in a Parabolic Mirror Trap

We demonstrate a simple and robust geometry for optical trapping in vacuum of a single nanoparticle based on a parabolic mirror and the optical gradient force, and we demonstrate rapid parametric feedback cooling of all three motional degrees of freedom from room temperature to a few mK. A single laser at 1550nm, and a single photodiode, are used for trapping, position detection, and cooling for all three dimensions. Particles with diameters from 26nm to 160nm are trapped without feedback to 10$^{-5}$mbar and with feedback engaged the pressure is reduced to 10$^{-6}$mbar. Modifications to the harmonic motion in the presence of noise and feedback are studied, and an experimental mechanical quality factor $>4\times 10^7$ is estimated.

quant-ph↗

arXiv2016

Experimental Realisation of a Thermal Squeezed State of Levitated Optomechanics

We experimentally squeeze the thermal motional state of an optically levitated nanosphere, by fast switching between two trapping frequencies. The measured phase space distribution of our particle shows the typical shape of a squeezed thermal state, from which we infer up to 2.7dB of squeezing along one motional direction. The experiment features a large number of thermal excitations, therefore remaining in the classical regime. Nevertheless, we argue that the manipulation scheme described here could be used to achieve squeezing below the zero-point level, if preceded by ground state cooling of the levitated mechanical oscillator. Additionally, a higher degree of squeezing could in principle be achieved by repeating the frequency-switching protocol multiple times.

quant-ph↗