Olivier Pfister

One-Way Quantum Computing in the Optical Frequency Comb

One-way quantum computing allows any quantum algorithm to be implemented easily using just measurements. The difficult part is creating the universal resource, a cluster state, on which the measurements are made. We propose a scalable method that uses a single, multimode optical parametric oscillator (OPO). The method is very efficient and generates a continuous-variable cluster state, universal for quantum computation, with quantum information encoded in the quadratures of the optical frequency comb of the OPO.

Parallel generation of quadripartite cluster entanglement in the optical frequency comb.

Scalability and coherence are two essential requirements for the experimental implementation of quantum information and quantum computing. Here, we report a breakthrough toward scalability: the simultaneous generation of a record 15 quadripartite entangled cluster states over 60 consecutive cavity modes (Q modes), in the optical frequency comb of a single optical parametric oscillator. The amount of observed entanglement was constant over the 60 Q modes, thereby proving the intrinsic scalability of this system. The number of observable Q modes was restricted by technical limitations, and we conservatively estimate the actual number of similar clusters to be at least 3 times larger. This result paves the way to the realization of large entangled states for scalable quantum information and quantum computing.

Experimental realization of multipartite entanglement of 60 modes of a quantum optical frequency comb.

We report the experimental realization and characterization of one 60-mode copy and of two 30-mode copies of a dual-rail quantum-wire cluster state in the quantum optical frequency comb of a bimodally pumped optical parametric oscillator. This is the largest entangled system ever created whose subsystems are all available simultaneously. The entanglement proceeds from the coherent concatenation of a multitude of Einstein, Podolsky, and Rosen pairs by a single beam splitter, a procedure which is also a building block for the realization of hypercubic-lattice cluster states for universal quantum computing.

Multipartite continuous-variable entanglement from concurrent nonlinearities

We show theoretically that concurrent interactions in a second-order nonlinear medium placed inside an optical resonator can generate multipartite entanglement between the resonator modes. We show that there is a mathematical connection between this system and van Loock and Braunsteins proposal for entangling

Experimental continuous-variable entanglement from a phase-difference-locked optical parametric oscillator

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Observation of triply coincident nonlinearities in periodically poled KTiOPO 4

continuous quantum optical variables by interfering with the outputs of

Bright tripartite entanglement in triply concurrent parametric oscillation

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Ultracompact generation of continuous-variable cluster states

degenerate optical parametric amplifiers (OPA) at a

Quantum Interference of Ultrastable Twin Optical Beams

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Polarization instabilities in a two-photon laser.

-port beam splitter. Our configuration, however, requires only one nondegenerate OPA and no interferometer. In a preliminary experimental study, we observe the concurrence of the appropriate interactions in periodically poled