Abstract
We report a bright and tunable source of spectrally pure heralded single photons in the telecom O-Band, based on cross-polarized four wave mixing in a commercial birefringent optical fiber. The source can achieve a purity of 85%, heralding efficiency of 30% and a coincidence-to-accidentals ratio of 108. Furthermore, through the measurements of joint spectral intensities, we find that the fiber is homogeneous over at least 45 centimeters and thus can potentially realize 4 sources that can produce identical quantum states of light. This paves the way for a cost-effective fiber-optic approach to implement multi-photon quantum optics experiments.
Highlights
Photonics has always been at the forefront of testing fundamental theories of quantum mechanics and optical implementations of various quantum information processing (QIP) protocols [1,2,3,4,5,6,7,8,9]
Since the joint spectral intensity (JSI) is a good measure to explore the output bi-photon state, we carry out a seeded measurement which stimulates the four wave mixing (FWM) process and results in difference frequency generation (DFG) [26, 42]
To this approximate joint spectral amplitude (JSA), we apply a singular value decomposition to determine the approximate number of modes present and determine an upper bound on the purity of P = 75%
Summary
Photonics has always been at the forefront of testing fundamental theories of quantum mechanics and optical implementations of various quantum information processing (QIP) protocols [1,2,3,4,5,6,7,8,9]. While photon pair generation has been earlier explored in birefringent optical fiber [36], the source was not designed for telecom wavelengths and the reported bi-photon state was marked with spectral correlations, thereby limiting the purity of the achievable single photons. The shape of the JSI characterizes spectral correlations between the signal and idler photons and is governed by the pump bandwidth σp, the length of the fiber L and the angle θsi which the phase matching function φ(ωs, ωi) makes with the signal frequency axis. In order to generate photons with high purity, the source should emit photons into a single spectral mode and have a factorable JSA This can be achieved by a careful choice of the pump spectral bandwidth and by engineering the phase matching angle θsi to be in the range of [0◦ - 90◦]. We have to trade off between the purity of the source and its brightness and chose a length of 9 cm in the fiber and pump bandwidth of 2 nm which give rise to photons with 85% purity and high brightness as will be discussed
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