Beamlike photon pairs entangled by a2×2fiber (original) (raw)

Cascaded ultrabright source of polarization-entangled photons

Physical Review A, 2002

A new ultra bright pulsed source of polarization entangled photons has been realized using type-II phase matching in spontaneous parametric down conversion process in two cascaded crystals. The optical axes of the crystals are aligned in such a way that the extraordinarily (ordinarily) polarized cone from one crystal overlaps with the ordinarily (extraordinarily) polarized cone from the second crystal. This spatial overlapping removes the association between the polarization and the output angle of the photons that exist in a single type-II down conversion process. Hence, entanglement of photons originating from any point on the output cones is possible if a suitable optical delay line is used. This delay line is particularly simple and easy to implement.

Beamlike photon-pair generation for two-photon interference and polarization entanglement

Physical Review A, 2011

Beamlike photon pairs were generated by spontaneous parametric down-conversion using a type-II β-BaB 2 O 4 crystal. A pump laser generated photon pairs when it transmitted through the crystal and was reflected back into the crystal by a mirror to generate more photon pairs. The photon pairs generated when the pump laser first transmitted through the crystal (first photon pairs) were also reflected back into the crystal to overlap with the light path of the photon pairs generated in the second transmission of the pump laser through the crystal (second photon pairs). We observed interference between the first and second photon pairs modulated with a half period of the wavelength of the photon pairs, which demonstrates two-photon interference using the beamlike photon pairs. The fringe period confirms that the observed interference is not classical interference but quantum two-photon interference. Through rotating the angles of quarter-wave plates in the light paths of the photon pairs, we generated beamlike photon pairs with entangled polarization. The phase between the first and second photon pairs could be tuned by changing the position of mirrors reflecting the pump pulses and photon pairs. The fringes of coincidence counts showed that the beamlike photon pairs have polarization entanglement.

A pulsed source of polarization-entangled photon pairs

Physics Procedia, 2009

We report a Bell state preparation experiment using polarization-entangled photon pairs which are produced by spontaneous parametric down conversion of a 405 nm pulse laser beam inside two orthogonally oriented 0.1 mm beta-barium borate nonlinear crystals with Type-I phased matching. The degree and phase of all four Bell states are easily tunable. With two-photon interference visibilities in excess of 85%, we observe that the Bell parameter S for any of the four Bell states exceeds the classical limit in the Clauser-Horne-Shimony-Holt form of Bell inequality by five standard deviations.

Generation of entangled photon states by using linear optical elements

Physical Review A, 2002

We present a scheme to generate the polarization-entangled two-photon state 1 √ 2 (|H |V + |V |H), which is of much interest in the field of quantum information processing. Furthermore we demonstrate the capability of this concept in respect of a generalization to entangle N-photon states for interferometry and lithography. This scheme requires single-photon sources, linear optical elements and a multi-fold coincidence detection.

Simple experimental setup for producing polarization-entangled photons

Journal of Physics: Conference Series, 2019

Quantum entanglement is an important action in quantum mechanics. Basically, quantum entanglement of correlated photon pairs can be produced by spontaneous down-conversion process inside the two birefringence crystals. This work aims to create a pair of photons, i.e. signal and idler, that are entangled and to assay the relation between these photons by using polarization-entangled photon pairs to demonstrate quantum non-locality by comparing with the Malus’s law. From the experiments, the coincidence counts as a function of relative angle (α - β) between transmission axis of the polarizer and analyzer were obtained and the polarization entanglement curve was demonstrated. This result corresponding with polarization entanglement prediction term of ½ cos2 (α - β) which confirmed the entanglement of photons.

Phase-stable source of polarization-entangled photons in a linear double-pass configuration

Optics Express, 2013

We demonstrate a compact, robust, and highly efficient source of polarization-entangled photons, based on linear bi-directional down-conversion in a novel 'folded sandwich' configuration. Bi-directionally pumping a single periodically poled KTiOPO4 (ppKTP) crystal with a 405-nm laser diode, we generate entangled photon pairs at the non-degenerate wavelengths 784 nm (signal) and 839 nm (idler), and achieve an unprecedented detection rate of 11.8 kcps for 10.4 µW of pump power (1.1 million pairs / mW), in a 2.9-nm bandwidth, while maintaining a very high two-photon entanglement quality, with a Bell-state fidelity of 99.3 ± 0.3%.

Quantum entanglement of complex photon polarization patterns in vector beams

Physical Review A, 2014

We report the efficient creation and detection of hybrid entanglement between one photon's polarization and another photon's complex transverse polarization pattern. The polarization measurement of the first photon triggers a polarization sensitive imaging of its partner photon, the vector photon, using a single-photon sensitive camera. Thereby, we reconstruct tomographically the vector photons complex polarization patterns dependent on the type of polarization measurement performed on its partner. We visualize the varying strengths of polarization entanglement for different transverse regions and demonstrate a novel feature: each vector photon can be both entangled and not entangled in polarization with its partner photon. We give an intuitive, information theoretical explanation for our results.

A high-brightness source of polarization-entangled photons for applications in free-space

We present a simple but highly efficient source of polarization-entangled photons based on spontaneous parametric down-conversion (SPDC) in bulk periodically poled potassium titanyl phosphate crystals (PPKTP) pumped by a 405 nm laser diode. Utilizing one of the highest available nonlinear coefficients in a non-degenerate, collinear type-0 phasematching configuration, we generate polarization entanglement via the crossed-crystal scheme and detect 0.64 million photon pair events/s/mW, while maintaining an overlap fidelity with the ideal Bell state of 0.98 at a pump power of 0.025 mW.