Properties of system using spatial multi-mode squeezer

P. Galatola, Luigi A. Lugiato, M. G. Porreca +2 more

Nicolai B. Grosse

This thesis presents the first experimental demonstration of two-dimensional spatial squeezing. A dual squeezer was used to produce two beams of temporally squeezed light. Specially designed wave-plates were required to generate the necessary spatially orthogonal modes. These modes were mixed on an optical cavity to form a multi-mode superposition that converted the original temporal correlations into the desired spatial correlations. We used this light to improve the sensitivity of a two-dimensional beam displacement measurement to below the quantum noise limit. Our setup was also configured to generate a one-dimensional spatially squeezed state of light that did not require either of the two input modes to suffer substantial loss. This was the first experimental demonstration of a proper spatial squeezing measurement.

Nguyen Ba An, Vo Tinh

Ian R. Petersen

This paper provides a new result on the realizability of a single mode linear quantum system as a cascade of a dynamic squeezer and two static squeezers. The result can be combined with existing results to provide a simpler method of realizing linear quantum systems. This is useful in problems of coherent quantum control in which the controller of a quantum system is also a quantum system.

S. Z. Sayed Hassen

Will McCutcheon

Methods to decompose nonlinear optical transformation vary from setting to setting, leading to apparent differences in the treatments used to model photon pair sources, compared to those used to model degenerate down-conversion processes. The Bloch-Messiah reduction of Gaussian processes to single-mode squeezers and passive (linear) unitaries appears juxtaposed against the practicalities of the Schmidt-decomposition for photon pair sources into two-mode squeezers and passive unitaries. Here, we present a general framework which unifies these forms as well as elucidating more general structure in multimode Gaussian transformations. The decomposition is achieved by introducing additional constraints into the Bloch-Messiah reduction used to diagonalise Gaussian processes, these constraints motivated by physical constraints following from the inequivalence of different physical degrees of freedom in a system, ie. the temporal-spectral degrees of freedom vs different spatial modes in a transformation. The result is the emergence of the two-mode squeezing picture from the reduction, as well as the potential to generalise these constraints to accommodate spectral imperfections in a source generating 3-mode continuous variable GHZ-like states. Furthermore, we consider the practical scenario in which a transformation aims to generate a multiphoton entangled state, whereby spatial modes provide desirable degrees of freedom, whilst undesired spectral mode structure contributes noise, and show that this spectral impurity can be efficiently modeled by finding an optimal low dimensional bases for its simulation.