Session T02: Optomechanics and Foundations

Live

The permanent electric dipole moment of an optically-levitated $\sim2.4$ $\mu m$ radius silica microsphere can be driven into rotation by a constant magnitude, rotating electric field. Due to the microsphere's birefringence, some amount of the linearly polarized incident light is coupled into the perpendicular polarization as the microsphere rotates. In the frame of the rotating electric field, the microsphere's dipole moment undergoes libration about the instantaneous direction of the electric field. The power modulation of cross-polarized light transmitted through the microsphere is extracted and processed digitally to obtain the angular speed of the libration. We demonstrate cooling of the libration by applying a phase modulation to the electric field which is proportional to the instantaneous angular speed of the libration. This technique further improves the control over the microsphere's rotational degrees of freedom.   

Live

We recently reported time resolved IR pump-probe studies on strongly-coupled vibration-cavity polaritons for tungsten hexacarbonyl in hexane in a Fabry-P\'{e}rot cavity [1]. While much of the response is due to reservoir or uncoupled excited state absorption as well as polariton contraction, a component of the observed signals is due to polariton state evolution. We subsequently used low concentration samples, which reduce the Rabi splitting between the polaritons, to highlight the polariton contraction and demonstrate saturable absorption not only in pump probe measurements but also in single pulse studies.[2] We further investigated this system with two-dimensional infrared (2D IR) spectroscopy which provides evidence of hybrid light-matter polariton evolution and clear indications of direct excitation of dark states.[3] We have further expanded the investigation of vibrational dynamics for strongly coupled vibration-cavity polaritons to another solute, nitroprusside in methanol We explore salient features of the transient response, especially at short delay times, which show aspects of the response that are due to polaritons and are distinguished from uncoupled higher order excitations. [1] A. D. Dunkelberger, et al., Nat. Comm. 7, 13504 (2016). [2] ACS Photonics 6. 2719 (2019). [3] B. Xiang, R. F. Ribeiro, A. D. Dunkelberger, J. Wang, Y. Li, B.S. Simpkins, J.C. Owrutsky, J. Yuen-Zhou, W. Xiong, PNAS 115, 4845-4850 (2018).   

Live

A basic understanding of the transition from a quantum to a classical state is a fundamental key aspect in quantum physics and described by the theory of decoherence. With the rise of novel techniques and instruments in quantum electronics, the question of decoherence introduced by the Coulomb force between charged particles and an environment becomes highly relevant. Unfortunately, this kind of decoherence mechanism is not well understood yet, several competing theoretical approaches exist. Here, we clarify the current uncertain situation in the literature by performing an experimental decoherence analysis with free electrons in a superposition state aloof a semiconducting and metallic surface in a biprism electron interferometer. The decoherence was determined through a contrast loss at different beam path separations, surface distances and conductibilities. We compared four theoretical models to our data and could rule out three of them. Good agreement was achieved with a theory based on macroscopic quantum electrodynamics. The results will allow the specific calculation and minimization of decoherence channels mediated by the Coulomb force, enabling the design of novel quantum instruments in communication, metrology or microscopy.   

Live

Single-particle two-path interference has been the dominant scenario employed for analyzing and testing quantum wave-particle duality. It can be regarded as a process of regenerating the quantum object (e.g., a photon, an electron, an atom, etc.) with a two-center source. A natural question arises: will this regeneration process affect the wave and particle natures of the quantum object? To address this question, we analyze the duality property of a photon in relation to the properties of its actual two-point source, i.e., a pair of non-locally entangled two-level atoms. Surprisingly, the photon's duality is found to be solely controlled by the state coherence of the atomic source through an exact Pythagorean relation, $V^2+D^2=\mu^2_S$, where $V$ and $D$ are the single photon's interference visibility and which-way distinguishability respectively and $\mu_S$ is the source state purity. Our analysis opens a new perspective of investigating and understanding quantum duality.   

On Demand

Electron-spin systems are investigated using a quantum-open-systems description. Applications of interest include trapped atomic systems in optical lattices, semiconductor quantum dots, and vacancy defect centers in solids. Time-domain and frequency-domain formulations are self-consistently developed. The general non-perturbative and non-Markovian formulations can provide a fundamental framework for systematic investigations of corrections to the standard Born and Markov approximations. Attention is given to decoherence and relaxation processes, as well as spectral-line broadening phenomena, that are induced as a result of interactions with photons, phonons, nuclear spins, and external electric and magnetic fields. These dissipative phenomena can be described either as coherent interactions or as environmental interactions. The environmental interactions are incorporated by means of the general expressions derived for the time-domain and frequency-domain Liouville-space self-energy operators, for which the tetradic-matrix elements are explicitly evaluated in the diagonal-resolvent, lowest-order, and Markov (short-memory time) approximations.   

Casimir force between two small balls

In this paper, the Casimir force between two spheres is studied.   

Not Participating

A number of early 20th century formulas must be slightly corrected because since about 1960, all matter has been found to exhibit rotation, vibration as well as linear motion then not known. Einstein derived the total energy at slow speeds to be $E= mc^2 + 1/2mv^2.$ However, adding rotation and vibration factors is now needed .$E= mc^2 + 1/2mv^2 + 1/2I(\omega)^2 +1/2kx^2$ His Photoelectric Effect equation must also include these factors. $ hf= (1/2mv^2 + 1/2I(\omega)^2 + 1/2kx^2)max + \phi.$ In complete and partial transfer of energy in Bremsstrahlung the resulting total photon energy must now be $hf= 1/2mv^2 + 1/2I(\omega)^2 + 1/2kx^2$ for complete braking achievement of the charged particle. Also, in pair production and annihiliation total energy calculations must include rotation and vibration kinetic factors. Many other early physics formulas may possibly need the rotation and vibration factors added also. Mass equation of state may be $E=mc^2 + 1/2mv^2 + 1/2I(\omega)^2 + 1/2kx^2 + kQ_1Q_2/r + Gm_1m_2/r.$