Toward a downconversion source of positively spectrally correlated and decorrelated telecom photon pairs

Abstract

The frequency correlation (or decorrelation) of photon pairs is of great importance in long-range quantum communications and photonic quantum computing. We experimentally characterize a spontaneous parametric down conversion (SPDC) source, based on a β-Barium Borate (BBO) crystal cut for type-II phase matching at 1550 nm which emits photons with the positive or no spectral correlations. Our system employs a carefully designed detection method exploiting two InGaAs detectors.OCIS codes: 190.4410,300.6190,270,4180,270.5565 Many quantum information processing protocols benefit from photon pairs that are positively correlated or uncorrelated in their spectra. Optical quantum gates often require pure states, which can be created using spontaneous parametric down-conversion (SPDC) only if there are no correlations within the resulting photon pair. On the other hand, practical quantum communication using existing infrastructure suffers from noisy detectors, which limit the achievable range. This could be improved by utilizing photon pairs that are positively correlated. Spectral filtering [1-6] makes it possible to minimize correlations, but positive correlations can be achieved only by careful source design. In a typical scenario, the SPDC process naturally leads to spectral anticorrelations [7][8][9][10][11]. Positively spectrally correlated photons at 1500 nm were suggested in theory [12] but were never shown in experiment. Our particular source allows for anti-, positive-or no-spectral correlations without the need for spectral filtering.In the SPDC process, one photon of the pump converts into two daughter photons. Energy and momentum conservation relations, jointly described as phase matching, and the properties of the pumping photons, govern the characteristics of the generated photons. The probability amplitude governing a photon pair emission in a given direction and at a given frequency can be described by a product of the pump spatio-temporal amplitude and the phase matching function [6,12]. The phase matching describes the properties of the nonlinear media and specifies the allowed emissions that can take place.

Spectrally Pure States at Telecommunications Wavelengths from Periodically PoledMTiOXO4(M=Jin1, Zhao2, Deng3 et al. 2016Phys. Rev. Applied210150View full textAdd to dashboardCite

“…Such a quantum state engineering method can be realized by considering the group-velocity-matched (GVM) condition in specific crystals at certain wavelengths [4][5][6]. Previous work in the field has shown that the GVM condition can be realized in several crystals, e.g., KDP crystal at 830 nm [1,2,7], periodically poled KTP crystal (PPKTP) at 1584 nm [5,8] and BBO crystal at 1514 nm [4,9,10].…”

Spectral correlation control in down-converted photon pairs

“…Optical elements are dispersive and cause unwanted modification of the photons' temporal characteristics. The deteriorating dispersion effects can be reduced by using photon pairs that are spectrally narrow and feature appropriate spectral correlations [16][17][18].The spectra of SMF coupled photon pairs generated in SPDC process can be negatively [19,20], positively [16][17][18][21][22][23] or not correlated at all [24][25][26]. The effect of negative correlation originates from the energy conservation relation and is a consequence of pumping by a continuous wave (CW) laser.…”

Demonstration of spectral correlation control in a source of polarization-entangled photon pairs at telecom wavelength

“…The spectral part of the pump can also be approximated by a Gaussian function with the characteristic spectral width 1/(2τ pump ). The spectral wave function then reads:(1) It has already been show experimentally [18] that the EPMF of the type II BBO crystal cut for telecom wavelength facilitates spectral correlation control. Tuning capabilities arise due to the variable pulse duration τ p of the pump laser and the variable collection optics which influences the characteristic width σ of the EPMF.…”

“…We use a method similar to the one already used to reconstruct EPMF in Ref. [18]. The results are presented in Fig.…”

“…[18] produces both, any desired kind of spectral correlations and high quality polarization entanglement in the same time. This can be used for long distance quantum communication where photons sent through long single mode fibers suffer from chromatic dispersion.…”