Active stabilization of a fiber-optic two-photon interferometer using continuous optical length control

Abstract

The practical realization of long-distance entanglement-based quantum communication systems strongly rely on the observation of highly stable quantum interference between correlated single photons. This task must accompany active stabilization of the optical path lengths within the single-photon coherence length. Here, we provide two-step interferometer stabilization methods employing continuous optical length control and experimentally demonstrate two-photon quantum interference using an actively stabilized 6-km-long fiber-optic Hong-Ou-Mandel interferometer. The two-step active control techniques are applied for measuring highly stable two-photon interference fringes by scanning the optical path-length difference. The obtained two-photon interference visibilities with and without accidental subtraction are found to be approximately 90.7% and 65.4%, respectively.

Highly Coherent Frequency-Entangled Photons Based on Parametric Instability in Active Fiber Ring Cavity

“…This large bandwidth makes more than one subpeaks account for the coincidence detection. The HOM visibility can be further improved by optimizing the splitting ratio of OC, the polarization dependence of the optical devices, and most importantly, the path difference fluctuations due to temperature variations and wind vibrations in the laboratory [41]. On the other side, spatial quantum beating is observed when the wavelengths of the two OTFs are adjusted to be the centers of Stokes and anti-Stokes sidebands, respectively.…”

“…Importantly, the fiber-based MZI is running at room temperature without any stabilization techniques. Namely, there is not stable phase difference due to the influence of environment, and the induced path fluctuation would seriously deteriorate the two-photon interference visibility [41]. The photons in the two channels are detected by two identical InGaAs SPDs under Geiger-mode within a high speed nearinfrared single photon detection module (Auréa Technology), then the coincidence counts are registered.…”

“…The coherence statistics of the two sidebands are depicted in Figs.3(b) and 3(c). The positive central peak at zero frequency shift arises from the narrow lines in the single-shot spectra, whereas fluctuations at larger frequency shift denote cooperative (positive value) and competitive (negative value) interactions of the individual cavity modes[41]. Both autocorrelation analysis for the Stokes and anti-Stokes regions show quasi-periodicity along the frequency shift, indicating strong correlation among the single-shot spectra.…”

Long-range distribution of high-quality time-bin entangled photons for quantum communication

“…To resolve the phase drift issue, we introduced an auxiliary CW laser (Nortel networks, LC155CDC-20), shown in Fig. 2a, to actively stabilize the interferometer with a feedback system [32,33]. In the following, we explain how to stabilize the Michelson interferometer; the unbalanced Mazh-Zehnder interferometers (UMZIs) for qubit analysis, as shown in Fig.…”

Implementation of quantum synchronization over a 20-km fiber distance based on frequency-correlated photon pairs and HOM interference

“…Therefore, efforts to reduce the fiber path drift within the coherence length of the photon pairs become a challenge. The typical methods include applying narrowband spectral filter to increase the two-photon coherence time 9 or employing a) Electronic mail: dongruifang@ntsc.ac.cn continuous optical length control based on an auxiliary reference light 10 . However, the narrowband filter will not only induce loss but also degrade the spectral correlation between the photon pairs, which is key to various quantum information applications.…”