Experimental System and Manipulation Techniques

Yuma Nakamura

Nicholas A. Peters, Joseph B. Altepeter, Evan R. Jeffrey +2 more

We present the theoretical basis for and experimental verification of arbitrary single-qubit state generation, using the polarization of photons generated via spontaneous parametric downconversion. Our precision measurement and state reconstruction system has the capability to distinguish over 3 million states, all of which can be reproducibly generated using our state creation apparatus. In order to complete the triumvirate of single qubit control, there must be a way to not only manipulate single qubits after creation and before measurement, but a way to characterize the manipulations themselves. We present a general representation of arbitrary processes, and experimental techniques for generating a variety of single qubit manipulations, including unitary, decohering, and (partially) polarizing operations.

Bodhaditya Santra, Herwig Ott

Ultracold quantum gases offer unique possibilities to study interacting many-body quantum systems. Probing and manipulating such systems with ever increasing degree of control requires novel experimental techniques. Scanning electron microscopy is a high resolution technique which can be used for in situ imaging, single site addressing in optical lattices and precision density engineering. Here, we review recent advances and achievements obtained with this technique and discuss future perspectives.

Suranjana Sengupta

Sebastian Will

Jean‐François Morizur

We present in this thesis a study of the spatial properties of light at the quantum level. More specifically, we focus on techniques to manipulate the quantum fluctuations of different degrees of freedom in a beam's transverse plane, and on the quantum protocols we can implement using these specific fluctuations. We begin by providing an experimental characterization of different methods to manipulate the quantum fluctuations of multiple transverse profiles, or modes, in one beam. While manipulating the quantum fluctuations of a mode, a process known as squeezing, for a single mode beam can be performed very efficiently using a conventional optical parametric oscillator, we present implementations of different, less conventional techniques able to generate a beam carrying multiple squeezed modes. Conventionally, the squeezed modes we can generate using these techniques are fixed by the optical design. We present a new optical system, called a Unitary Programmable Mode Converter (UPMC), able to reshape these modes at will. We show theoretically that such a UPMC can in principle perform any desired reshaping of the modes. We present the performances of an experimental implementation of the UPMC, both in a classical and quantum context. We find that the UPMC performs as predicted, and we present a method to optimize the UPMC settings taking into account experimental restrictions. The UPMC, combined with a technique to build a beam carrying multiple squeezed modes, allows us to generate a beam with squeezing in any desired set of spatial modes. In order to detect these fluctuations, we built a multipixel homodyne detection, a detection system able to record simultaneously the quantum fluctuations in all these modes. We provide in this thesis our solutions to overcome the electronic challenges associated with such a device, and present an experimental characterization of the performances of our multipixel homodyne detection. Finally, we combine these experimental characterizations to discuss how these techniques help us implement different quantum protocols involving multiple spatial modes, more specifically quantum enhanced detections and cluster states quantum computation.