Quantum Ghost Imaging of Water Content and Plant Health with Entangled Photon Pairs
Authors:
James Werner1* ([email protected], PI), Duncan Ryan1, Kristina Meier1, Kati Seitz1, David Thompson1, Rebecca Holmes1, Demosthenes Morales1, Buck Hanson1, David Hanson2, Peter Goodwin1, Raymon Newell1, David Thompson1
Institutions:
1Los Alamos National Laboratory; 2University of New Mexico
Abstract
The near infrared (NIR) and mid-infrared (MIR) portions of the electromagnetic spectrum are sensitive to absorption features of specific molecular bonds and chemical species in a sample. For example, lignan and proteins in plants have specific absorption signatures in the NIR. However, because detectors are inefficient in the NIR and MIR, infrared spectroscopy requires high light levels to overcome detector limitations. Cameras in particular do not perform well in this spectral range, and microscopy methods such as Fourier transform infrared spectroscopy typically rely on scanning confocal arrangements with single-element detectors to spatially map chemical information.
To overcome these limitations, the team developed and exploited a new quantum ghost imaging microscope for obtaining absorption measurements in the NIR without the need of scanning or high light intensities. The team reports on the use of a novel detector—NCam—in quantum ghost imaging using non-degenerate photon pairs generated by spontaneous parametric down conversion (SPDC). NCam records single- photon arrival events with ~100 picosecond resolution, enhancing the correlation window of SPDC pairs over previous wide-field ghost imaging by 30-fold. This permits ghost imaging of living and intact plant samples at light levels lower than what the plants would experience from starlight. For photosynthesizing organisms, this low-light imaging method enables the study of plants without disturbing or eliciting responses from the plant due to the measurement itself. Following the development of quantum ghost imaging in the near IR to visualize binary test targets, the team has demonstrated imaging of water content in live sorghum plants (see figure).
Image
Quantum Ghost Imaging. Left: A near infrared image of selected binary targets (a Pac-Man ghost and the Los Alamos National Laboratory logo) and their corresponding quantum ghost images. Ghost images were acquired by probing the target at ~1450 nm with one entangled photon, with image formation performed at ~540 nm with the corresponding visible entangled photon pair. Right: A picture of a live sorghum plant in our quantum ghost imaging microscope and the corresponding ghost image. Similar to the binary targets on left, image formation is at ~540 nm, while sample is probed with ~1450 nm light. Rows of highly transmissible regions in the sorghum leaf are most likely stomata. Images acquired with an entangled photon flux orders of magnitude less than ambient starlight. [Courtesy Los Alamos National Laboratory]