Quantum Properties of Multimode Light Successfully Measured Despite Significant Losses

On July 2, 2026, a collaborative team of researchers from the Max Planck Institute for the Science of Light and various international institutions successfully demonstrated a method to measure quantum properties of multimode light, even under extreme losses. Their findings, published in Nature Communications, could significantly advance scalable quantum technologies.

Understanding Quantum Properties of Light

Quantum properties of light are notoriously fragile. Researchers often struggle to measure these properties, as even minor losses during transmission can render them undetectable. This challenge has previously limited practical applications of quantum light outside controlled environments. The recent work by the international team has unveiled a new method to measure multiple quantum channels simultaneously, revealing their entanglement despite significant light loss.

In quantum optics, noise can distort the information transmitted by light, much like interference in radio or television signals. This noise manifests as fluctuations in the electromagnetic field and is present even in perfect laser light, known as shot noise. Researchers aim to reduce this noise through a process called squeezing, which has become essential in various quantum technologies, such as LIGO, which detected gravitational waves.

Innovative Approach: Multimode Optical Parametric Amplifier

To tackle the issue of light loss, the team led by Prof. Maria Chekhova utilized a multimode optical parametric amplifier (MOPA). This device amplifies the signal without introducing additional noise, enabling the measurement of quantum properties even when over 99.7% of the light is lost before detection. Mahmoud Kalash, a Ph.D. student at Friedrich-Alexander-Universität Erlangen-Nürnberg, noted, "Amplifying a quantum state before detection is like properly packaging fragile glass before shipping it." This analogy highlights the importance of preserving quantum features during the measurement process.

After amplification, the researchers separated the light into individual modes using a spatial light modulator (SLM). While this method allows for individual access to each mode, it also introduces significant losses, further complicating the measurement process. However, the prior amplification of the quantum state ensured that the quantum properties remained intact, enabling successful measurements.

Results and Implications for Quantum Technologies

The research team achieved squeezing levels of up to 7.9 decibels, indicating noise levels one-sixth that of a perfect laser. Remarkably, they monitored eight modes simultaneously, all exhibiting significant squeezing and high purity. The results also demonstrated quantum entanglement among groups of modes, showcasing the potential for high-dimensional quantum information processing.

According to Marcello Passos, a research group leader at the Centro Brasileiro de Pesquisas Físicas, "The method presented in this work opens up new possibilities for high-dimensional quantum information processing, particularly in quantum computing with complex networks, where many modes can process information simultaneously." This advancement paves the way for enhanced applications in quantum computing and other quantum technologies.