Month: February 2017

We often have internal speakers giving talks at the Atomic, Molecular Optical and Positron Physics (AMOPP) group about their cutting-edge research. Last wednesday (15th February 2017) Professor Sugato Bose presented some of his latest results and calculations based on experiments being performed by  Professor Peter Barker’s group on macroscopic quantum behaviour.

The talk had the broad interest of the department as you can see from the fully-occupied lecture hall above,  and Professor Sugato agreed to provide a copy of his slides, which you can download here, so you may too get an insight into this topic.

 

Abstract:

Probing macroscopic quantum superpositions and the quantum nature of gravity through levitated objects

Prof. Sougato Bose, Dept of Physics & Astronomy University College London

We will discuss theoretical proposals of how quantum superpositions of distinct centre of mass states of a nano-crystal may be created and probed purely by measuring a spin embedded in the object. The idea is to use a levitated diamond with an NV centre spin. Next we will also describe how to reach conditions whereby two such masses interacting purely through gravitational interaction can become entangled. Witnessing such an entanglement experimentally is equivalent to establishing the quantum nature of the gravitational field. Time permitting, we will discuss how the violation of macro-realism can be verified for a levitated nano-object in a loop-hole free manner simply by coarse grained position measurements.

Last Wednesday (February 8th 2016) we were lucky enough to have Charles W. Clark from the Joint Quantum Institute at NIST as an invited speaker to give a talk about “Twisting the neutron wavefunction”. The talk focused on the importance of fundamental wave theory and how the wave-particle duality of neutrons studied with interferometers (particularly on a Mach-Zehnder configuration) can provide great insight about basic optical principles being applied to matter waves, such as the addition of angular momentum to neutron wavefunctions.

The abstract for his talk can be found below, and he kindly agreed to provide a copy of his presentation slides which you can download here.

We will be updating our blog with subsequent talks from visiting speakers that may visit UCL, so stay tuned!

Abstract:

Twisting the neutron wavefunction

Charles W. Clark, Joint Quantum Institute, University of Maryland , USA

Wave motions in nature were known to the ancients, and their mathematical expression in physics today is essentially the same as that first provided by d’Alembert and Euler in the mid-18th century. Yet it was only in the early 1990s that physicists managed to control a basic property of light waves: their capability of swirling around their own axis of propagation. During the past decade such techniques of control have also been developed for quantum particles: atoms, electrons and neutrons. I will present a simple description of these phenomena, emphasizing the most basic aspects of wave and quantum particle motion. Neutron interferometry offers a poignant perspective on wave- particle duality: at the time one neutron is detected, the next neutron has not yet even been born. Here, indeed, each neutron “then only interferes with itself.” Yet, using macroscopically-machined objects, we are able to twist neutron deBroglie waves with sub-nanometer wavelengths.