Vasileios E. Lembessis

We study the quantum dynamics of cold atoms initially confined in a helical optical tube (HOT) and subsequently released into free space. This helicoidal potential, engineered via structured light fields with orbital angular momentum, imposes a twisted geometry on the atomic ensemble during confinement. We examine how this geometry shapes the initial quantum state—particularly its spatial localization and phase structure—and how these features influence the subsequent free evolution. Our analysis reveals that the overall confinement geometry supports the formation of spatially coherent, structured wavepackets, paving the way for the realization of twisted Bose–Einstein condensates and directed atom lasers. The results are of particular interest for applications in quantum technologies, such as coherent atom beam shaping, matter-wave interferometry, and guided transport of quantum matter.

Advances in lasers and atomic clock technologies have enabled delicate measurements to be made of minute relativistic effects. Here, we propose that such developments should lead to the measurement of relativistic effects involving atoms and molecules in dynamic optical traps. Specifically, we make a case for the study of time dilation in the context of atoms and molecules trapped in a rotating optical Ferris wheel. With experimentally relevant examples, we demonstrate how this would extend relativity tests down to the micron scale and would constitute a potential advance toward micron-size Mössbauer-style spectroscopy for trapped atoms and molecules.

We study the quantum dynamics of cold atoms initially confined in a Helical Optical Tube (HOT) and subsequently released into free space. This helicoidal potential, engineered via structured light fields with orbital angular momentum, imposes a twisted geometry on the atomic ensemble during confinement. We examine how this geometry shapes the initial quantum state particularly its spatial localization and phase structure and how these features influence the subsequent free evolution. Our analysis reveals that the overall confinement geometry supports the formation of spatially coherent, structured wavepackets, paving the way for the realization of twisted Bose Einstein condensates and directed atom lasers. The results are of particular interest for applications in quantum technologies, such as coherent atom beam shaping, matter-wave interferometry, and guided transport of quantum matter.

The availability of coherent sources of higher order Poincaré optical beams have opened up new opportunities for applications such as in the optical trapping of atoms and small particles, the manipulation of chirally-sensitive systems and in improved encoding schemes for broad-bandwidth communications. Here we determine the intrinsic properties of integer order m ⩾ 0 Poincaré Laguerre–Gaussian (LG) modes which have so far neither been evaluated, nor their significance highlighted. The theoretical framework we adopt here is both novel and essential because it emphasises the crucial role played by the normally ignored axial components of the twisted light fields of these modes. We show that the inclusion of the axial field components enables the intrinsic properties of the Poincaré modes, notably their angular momentum, both spin and orbital as well as their helicity and chirality, to be determined. We predict significant enhancements of the intrinsic properties of these modes when compared with those due to the zero order LG modes. In particular, we show that higher order LG Poincaré modes exhibit super-chirality and, significantly so, even in the case of the first order m = 1.

It is well established that the interaction of light with matter generally imparts mechanical forces and associated torques. Where laser light is involved, such effects can be deployed for the microscale and nanoscale manipulation of matter, giving rise to notable applications in wide areas of physics, chemistry, and the life sciences. The diversity of applications is enriched not only by the complexity of the constitution of matter, but also by the structure of the laser light itself, according to its polarisation, amplitude, and phase. This article reviews in comprehensive terms the origins of laser-based optical forces and their manifestations in a variety of current contexts and applications.

The helicities of the magnetic fields associated with non-relativistic electron vortex beams are considered for radially extended Bessel modes. Investigating the helicity density of this system lies in realizing the unique electric and magnetic properties of electron vortex beams that influence their interactions with matter. We have evaluated the vector potential components needed for the derivation of the magnetic helicity density and found that this has a non-zero distribution. This is attributed entirely to the cylindrically symmetric density flux of the electron beam, which scales with the winding number ℓ . It is also related to the magnetic moments of the electron oriented along the z-direction, giving rise to the z-component of the magnetic field. We obtain different helicity distributions for different signs of winding number ± ℓ , which confirms the chiral character of the magnetic fields associated with the electron vortex beam. The physical consequences of taking the spin current density into consideration are also examined. This allows a comparison to be made between the evaluated total current helicities, one with and one without including the spin-polarization.

We highlight what we believe to be a novel optical set-up which enables the confinement of cold atoms in a finite set of sub-wavelength bottle traps. This involves two counter-propagating vortex beams with the same winding number ℓ = ±1 and the same circular polarization (. Strong focusing generates significant longitudinal field components which become responsible for an on-axis standing wave enabling the axial confinement of far blue-detuned atoms. The off-axis radial confinement is provided by the optical potential due to the transverse components of the light. The trap characteristics are illustrated using experimentally accessible parameters and are tunable by changing the power, focusing and ellipticity of the light. Atoms trapped in such a set-up are useful for applications, including quantum simulation and quantum information processing.