Støttet af Lundbeck Fonden
Spatial squeezing
The simplest spatial mode that can carry orbital angular momentum (OAM) is the first order Laguerre-Gaussian (LG) mode, which produces either a left-handed or right-handed corkscrew-like phase front and a ring-like intensity profile. In this work we produce continuous variables quadrature entanglement between the two first-order LG modes and thereby demonstrating a new type of entanglement from non-degenerate optical parametric oscillators (OPOs). The entanglement is manifested in the squeezing of the rotated modes in the Hermite-Gauss (HG) basis, measured with a specially tailored local oscillator.
By changing the OPO cavity resonance frequency it is possible to generate the two first order Hermite-Gauss (HG) modes simultaneously due to their frequency degeneracy (stemming from their identical Gouy phase shifts). This means that the down-converted signal and idler photons are produced in two distinct orthogonal spatial modes (the OAM modes, LG+1 and LG-1), and thus creates quadrature entanglement between these two modes similarly to the production of entanglement between polarization.
For more details about this work please check http://xxx.lanl.gov/abs/0901.2783
Ref: M. Lassen, G. Leuchs and U.L. Andersen ArXiv: 0901.2783
Extreme optical states
The toolbox of operations that are available for the manipulation of CV states have been recently extended with conditional photon subtraction, a process which enabled the generation of highly non-classical states of light with negative Wigner functions such as the single photon state and the Schrödinger cat state (see the box for explanation). This has opened access to the realm of non-Gaussian operations and states, which are essential to CV quantum processors. Of particular high importance is the non-Gaussian Schrödinger cat state since it serves as a resource for CV quantum computing.
The aim of the present proposed project is to fully exploit the potential of photon counting measurements combined with linear optics, homodyne detection and electro-optic feedforward. We will use these tools to generate highly non-Gaussian CV states and to design schemes for implementation of various non-linear quantum operations on light modes.
Coherent state Single photon state Schödinger cat state
Gaussian and non-Gaussian states: Quantum states can be fully characterized by their Wigner function, W(x,p), which is a two dimensional quasi-probability distribution of the amplitude, x, and phase, p, of the light field. Simple light fields such as the coherent states (typically generated by a laser) are described by Gaussian and positive Wigner functions. The Wigner functions for highly non-classical states, such as the single photon state or the Schrodinger Cat state, show oscillations and negativities revealing pure quantum interference. These states are therefore referred to as non-Gaussian states and are resources for quantum information processors. |