Ghostly visualization enables scientists to monitor plants without impacting them.

Scientists need to study plants for various agricultural purposes, including those used for biofuel production, in order to optimize their growth and maintain their health for maximum yield, disease resistance, pest control, and resilience to adverse weather conditions.

Researchers from the United States have successfully observed processes in living sorghum using a method that does not harm the plant. The study has been published in the journal Optica.

Typically, to study processes in a plant in detail, it is necessary to cut it, introduce special "markers" inside, or expose it to harmful levels of light radiation, which can cause stress or damage the plant's tissues. Markers and dyes allow researchers to observe details of the plant and its condition at the micro level, but they can disrupt the natural processes occurring within the plants.

The quantum ghost imaging method (Quantum Ghost Imaging, QGI) enables the capture of images at extremely low lighting levels. Moreover, it enhances image quality in wavelength ranges where traditional cameras perform poorly and cannot provide a clear picture. The method utilizes the effect of spontaneous parametric down-conversion (SPDC) to create a pair of entangled photons. One of these photons, known as the signal, is used to form the image, while the other, called the idler, is used for measurement and correlation with the signal. The photons have different wavelengths; the signal is in the infrared range, while the idler is in the visible range.

The idler passes through the plant, interacts with the water inside it, and reaches its detector, while the signal photon goes to its own detector. After correlating the information from the two detectors, researchers can draw conclusions about the object that the radiation was directed at and construct an image.

The scientists placed sorghum, cilantro, and fern plants in a light beam with an intensity of three attowatts per square centimeter. Following this, they detected specific chemicals visible in this range and visible light using infrared light.

The non-invasive method examines the sample at one wavelength of radiation while forming the image through correlated photons of another wavelength. The spectral separation eliminates the need for highly sensitive detectors in the near-infrared range, reducing the required lighting intensity. To capture the light that has passed through the plant, a single-photon detector was sufficient.

The researchers achieved quantum ghost imaging with unprecedented sensitivity and contrast. The plants involved in the experiments sustained no damage.

By using non-contact infrared imaging, researchers can gather crucial information about key processes in a living plant, directly observing photosynthesis processes and fluctuations in water content.

The application of QGI expands the capabilities of biovisualization under extremely low lighting conditions. This is significant when working with light-sensitive samples, as some plant tissues degrade under certain radiation.