Can you perceive anything without looking at it?

 Researchers from Aalto University propose a technique for "viewing" microwave pulses without any absorption and reemission of light waves.

In order to measure anything, we often have to interact with it in some manner. Being touched—whether by a prod, a poke, an echo of sound, or a shower of light—makes it nearly hard to see.

According to a research published in Nature Communications, there are a few quantum physics-related exceptions to this generalisation.

Researchers from Finland's Aalto University propose a technique for "viewing" a microwave pulse devoid of any absorption and reemission of light waves. It serves as an example of a special measurement type called interaction-free measurement, in which there is no mediating particle to affect the thing being seen.

A component of the transmon apparatus, which generates the quantum effects needed to detect microwaves without interfering with them. — Science Alert via Aalto University

"Seeing without touching" as a fundamental concept is not new. Physics has shown that it is feasible to use the wave-like properties of light to travel through spaces without triggering its particle-like behaviour by dividing finely aligned waves of light into numerous courses and comparing their journeys.

Because the researchers employed semiconductors and microwaves rather than lasers and mirrors, it is a noteworthy feat. The system used a transmon gadget to detect an electromagnetic pulse fired into a chamber.

Despite being rather large by quantum standards, these devices employ a superconducting circuit to imitate the quantum behaviour of individual particles on several layers.

The existence of a photosensitive item may be identified without irreversible photon absorption thanks to a basic quantum phenomena called interaction-free measurement, according to the researchers' findings in a study that was just published.

Here, using a three-level superconducting transmon circuit, we introduce the idea of coherent interaction-free detection and show it experimentally.

The complex arrangement was made possible by the scientists' reliance on the quantum coherence produced by their unique system, which permits objects to exist in two states at once, like Schrödinger's cat.

Quantum physicist Gheorghe Sorin Paraoanu of Aalto University said, "We had to adapt the notion to the diverse experimental instruments available for superconducting devices," according to Science Alert.

"Due to this, we were also forced to make a significant modification to the conventional interaction-free protocol: we introduced an additional layer of quantumness by employing a higher energy level of the transmon. The resulting three-level system's quantum coherence was then utilised as a resource."

Theoretical models that validated the results of the team's studies supported the experiments. It serves as an example of the quantum advantage, the ability of quantum devices to perform better than those of classical devices.

In the brittle realm of quantum physics, touching something is the same as shattering it. A neat wave of potential can be destroyed by nothing like the crush of reality. When detection calls for a gentler touch, other sensing methods like this one could be helpful.

Among the applications for this technology are quantum computing, optical imaging, noise detection, and cryptographic key distribution. The mechanisms at work would always be substantially more efficient.

Our technique might be used in quantum computing to identify microwave-photon states in certain memory components, claims Paraoanu. This method of retrieving information without interfering with the operation of the quantum processor can be viewed as extremely effective.