Direct Generation and Detection of Quantum Correlated Photons with 3.2 um Wavelength Spacing

Abstract

Quantum correlated, highly non-degenerate photons can be used to synthesize disparate quantum nodes and link quantum processing over incompatible wavelengths, thereby constructing heterogeneous quantum systems for otherwise unattainable superior performance. Existing techniques for correlated photons have been concentrated in the visible and near-IR domains, with the photon pairs residing within one micron. Here, we demonstrate direct generation and detection of high-purity photon pairs at room temperature with 3.2 um wavelength spacing, one at 780 nm to match the rubidium D2 line, and the other at 3950 nm that falls in a transparent, low-scattering optical window for free space applications. The pairs are created via spontaneous parametric downconversion in a lithium niobate waveguide with specially designed geometry and periodic poling. The 780 nm photons are measured with a silicon avalanche photodiode, and the 3950 nm photons are measured with an upconversion photon detector using a similar waveguide, which attains 34% internal conversion efficiency. Quantum correlation measurement yields a high coincidence-to-accidental ratio of 54, which indicates the strong correlation with the extremely non-degenerate photon pairs. Our system bridges existing quantum technology to the challenging mid-IR regime, where unprecedented applications are expected in quantum metrology and sensing, quantum communications, medical diagnostics, and so on.

Entanglement and nonlocality between disparate solid-state quantum memories mediated by photons

“…To do this we note that the repetition period of our pump laser is 12.5 ns. Moreover, since the photon-pair generation process is spontaneous, there are no statistical correlations between subsequently emitted pairs as has been verified in [32,33]. Hence, the coincidence detection probability P 12 (0; 12.5 ns) equals the product of the probabilities for individual detections of two uncorrelated photons (i.e., photons from independent pairs emitted 12.5 ns apart): P(0; 12.5 ns) = P 1 (0)P 2 (12.5 ns).…”

Perspectives for Applications of Quantum Imaging

“…Typical nonlinear materials, such as LN and KTP, provide access to SPDC wavelengths from ultraviolet to near infrared. SPDC in bulk ppLN as well as ppLN waveguides have already been used to generate non‐degenerate wavelength combinations with the signal in the visible and the idler at 4–5 µm. However, significantly longer wavelengths cannot be achieved due to the limited transparency range of these materials.…”

Numerical Study of Reconfigurable Mid‐IR Single Photon Sources Based on Functional Ferroelectrics

“…It has been shown that despite probabilistic operation, PDC sources can produce highly pure single photons approaching on‐demand operation in multiplexed schemes . There has been a surge of interest in single photon sources from nonlinear parametric processes operated in wider spectral regions and in mid‐IR in particular . The applications for mid‐IR single photon sources primarily concern quantum sensing and metrology, stealth ranging and quantum LIDARs, quantum‐enhanced medical imaging, as well as for free‐space secure communication in the atmospheric window, in light of recent demonstration of entanglement distribution using satellite‐to‐ground downlinks …”