Playing the quantum harp: Multipartite squeezing and entanglement of harmonic oscillators

The frequency comb of an optical resonator is a naturally large set of exquisitely well defined quantum systems, such as in the broadband mode-locked lasers which have redefined time/frequency metrology and ultraprecise measurements in recent years. High coherence can therefore be expected in the quantum version of the frequency comb, in which nonlinear interactions couple different cavity modes, as can be modeled by different forms of graph states. We show that is possible to thereby generate states of interest to quantum metrology and computing, such as multipartite entangled cluster and Greenberger-Horne-Zeilinger states

Bright tripartite entanglement in triply concurrent parametric oscillation

We show that a novel optical parametric oscillator, based on concurrent $\chi^{(2)}$ nonlinearities, can produce, above threshold, bright output beams of macroscopic intensities which exhibit strong tripartite continuous-variable entanglement. We also show that there are {\em two} ways that the system can exhibit a new three-mode form of the Einstein-Podolsky-Rosen paradox, and calculate the extra-cavity fluctuation spectra that may be measured to verify our predictions.Comment: title change, expanded intro and discussion of experimental aspects, 1 new figure. Conclusions unaltere

Generation and characterization of microwave quantum states

Quantum mechanics is the branch of physics that describes the properties and behavior of systems on the atomic and subatomic level. Over the past decades there has also been considerable progress in engineering larger-scale quantum systems. In this day and age, quantum information and quantum technology are rapidly developing areas of research where quantum effects are harnessed to improve sensitivity in measurements, encrypt secure communications, and enhance the performance of information processing and computing. Specific types of quantum states are needed for these purposes, and they can be challenging to generate in practice. This thesis describes methods to generate and characterize microwave states that could be useful for quantum computing protocols based on quantum states of light

Fiber coupled EPR-state generation using a single temporally multiplexed squeezed light source

A prerequisite for universal quantum computation and other large-scale quantum information processors is the careful preparation of quantum states in massive numbers or of massive dimension. For continuous variable approaches to quantum information processing (QIP), squeezed states are the natural quantum resources, but most demonstrations have been based on a limited number of squeezed states due to the experimental complexity in up-scaling. The number of physical resources can however be significantly reduced by employing the technique of temporal multiplexing. Here, we demonstrate an application to continuous variable QIP of temporal multiplexing in fiber: Using just a single source of squeezed states in combination with active optical switching and a 200 m fiber delay line, we generate fiber-coupled Einstein-Podolsky-Rosen entangled quantum states. Our demonstration is a critical enabler for the construction of an in-fiber, all-purpose quantum information processor based on a single or few squeezed state quantum resources

Experimental methods for measurement and analysis of quantum fluctuations and correlations in bright comb-like pulses

Within this thesis, an optical resonator is used to characterise the quantum state of a fs pulse squeezed in an optical fibre. The resonator separates the carrier pulse from the quantum state. The influences of the laser and the resonator's properties on this separation are investigated. Furthermore, the occurring Brillouin scattering on thermally excited vibrational modes of the fibre is examined. With the addition of a pulse shaper, the setup is enabled to experimentally access and measure complex correlation within the squeezed fs pulse.In dieser Arbeit wird ein optischer Resonator verwendet, um den Quantenzustand eines in einer Glasfaser gequetschten fs-Pulses umfassend zu charakterisieren. Der Resonator trennt den Trägerpuls vom Quantenzustand. Die Einflüsse der Eigenschaften von Resonator und Laser hierauf werden umfassend analysiert. Weiterhin wird der Einfluss von Brilloin-Streuung an thermisch angeregten Schwingungsmoden der Faser beobachtet. Durch Nutzung eines Pulsformers wird der Aufbau erweitert, um auch komplexe Korrelationen innerhalb des gequetschten fs-Pulses experimentell untersuchen zu können

Remote and Local Entanglement of Ions using Photons and Phonons

The scaling of controlled quantum systems to large numbers of degrees of freedom is one of the long term goals of experimental quantum information science. Trapped-ion systems are one of the most promising platforms for building a quantum information processor with enough complexity to enable novel computational power, but face serious challenges in scaling up to the necessary numbers of qubits. In this thesis, I present both technical and operational advancements in the control of trapped-ion systems and their juxtaposition with photonic modes used for quantum networking. After reviewing the basic physics behind ion trapping, I then describe in detail a new method of implementing Raman transitions in atomic systems using optical frequency combs. Several dierent experimental setups along with simple theoretical models are reviewed and the system is shown to be capable of full control of the qubit-oscillator system. Two-ion entangling operations using optical frequency combs are demonstrated along with an extension of the operation designed to suppress certain experimental errors. I then give an overview of how spatially separated ions can be entangled using a photonic interconnect. Experimental results show that pulsed excitation of trapped ions provide an excellent single photon source that can be used as a heralded entangling gate between macroscopically separated systems. This heralded entangling gate is used to show a violation of a Bell inequality while keeping the detection loophole closed and can be used a source private random numbers. Finally, the coherent Coulomb force-based gates are combined with the probabilistic photon-based gates in a proof of concept experiment that shows the feasibility of a distributed ion-photon network