Parametric Down-conversion In Nonlinear Crystal Research Articles

Thick-crystal regime in photon pair sources

The workhorse technique for generating correlated pairs of photons is based on spontaneous parametric downconversion in nonlinear crystals. These photon pair sources are usually designed with relatively short crystal lengths, in the belief that this is necessary to attain good performance. We show, contrary to common practice, that concurrent high brightness and efficiency are also available to longer crystals. We present comprehensive measurement data on the pump and collection beam parameters necessary to achieve high collection efficiency (89.0%±1.7% and 81.9%±3.7% for signal and idler) together with high brightness when a single thick β-barium borate crystal (15.76 mm) is pumped with a narrow linewidth laser. Spectral analysis of the collinear, nondegenerate photons suggests that the effective interaction length within the crystal is dominated by the collection beam mode, and the use of longer crystals with increased spatial walk-off does not necessarily lead to reduced collection efficiency. This surprising result is an important consideration for optical designers who seek to develop practical photon pair sources.

Controlling the Spectrum of Spontaneous Parametric Down-Conversion in Nonlinear Crystals by External Electric Field

Abstract. We discuss the possibilities of controlling the spectrum of correlated photons generated via spontaneous parametric down-conversion by using external homogeneous electric field acting on the nonlinear crystal.

Quantum information splitting and open-destination teleportation using decomposable multipartite quantum channel Part 2: experiment

Full detail of a proposed experiment required for implementing and verifying a theoretical scheme for four-partite splitting and open-destination teleportation of an arbitrary two-qubit photonic state is discussed. In this proposed experiment the quantum channel is provided by a pair of decomposable generalized (G) Bell states, which offer the experimental advantage that they can be very easily generated in photonic experiments. Our experiment is based on generating a two-qubit photonic state by ultrafast spontaneous parametric downconversion in nonlinear crystal and relies on Bell-state measurements, which in this experiment are performed by an optical Bell-state analyzer that can unambiguously determine all four Bell states. In this proposed experiment unitary transformation required at the destination station is implemented using a quantum control NOT gate. We finally show that in our four-partite optical system the two-qubit photonic state originally prepared at a sending station can be experimentally split and subsequently regenerated at any one of the three distinct receiving stations.