(ORDO NEWS) — Usually, in order to measure an object, we must interact with it in some way. Whether it’s a push or shove, an echo of sound waves or a stream of light, it’s almost impossible to look without touching.
In the world of quantum physics, there are some exceptions to this rule. .
Researchers at Aalto University in Finland propose a way to “see” a microwave pulse without absorbing and re-emitting any light waves.
This is an example of a special measurement without interaction, when something is observed without shaking the intermediary particle.
The fundamental concept of “seeing without touching” is not new.
Physicists have shown that it is possible to use the wavelike nature of light to explore spaces without causing it to behave like particles, by separating neatly aligned waves of light into different paths and then comparing their travels.
Instead of lasers and mirrors , the team used microwaves and semiconductors, which was a separate achievement. The setup used a so-called transmon device to detect the electromagnetic wave sent into the chamber.
Although these devices are relatively large by quantum standards, they mimic the quantum behavior of individual particles at multiple levels using a superconducting circuit.
“An interaction-free measurement is a fundamental quantum effect in which the presence of a light-sensitive object is detected without irreversibly absorbing photons,” the researchers write in their published paper.
“Here we propose the concept of coherent detection without interaction and demonstrate it experimentally using a three-level superconducting transmon circuit.”
The team relied on the quantum coherence created by their special system – the ability to have objects in two different states at the same time, like a Schrödinger’s cat – to make the complex installation a success.
“We had to adapt the concept to the various experimental tools available for superconducting devices. es,” says quantum physicist Gheorghe Sorin Paraoanu of Aalto University in Finland.
“Because of this, we also had to drastically change the standard protocol without interaction: we added another layer of quantumness. by using a higher energy level of the transmon. We then used the quantum coherence of the resulting three-level system as a resource.”
The experiments conducted by the team have been saved. with theoretical models supporting the results. This is an example of what scientists call quantum advantage, the ability of quantum devices to go beyond what is possible with classical devices.
In the delicate landscape of quantum physics, touching things is akin to destroying them. Nothing breaks a neat wave of probability like the crunch of reality. In cases where detection requires a softer touch, alternative sensing methods such as this one may come in handy.
Areas where this protocol can be applied include quantum computing, optical imaging, noise detection, and cryptographic key distribution. In each case, the efficiency of the systems involved will be greatly improved.
“In quantum computing, our method can be applied to diagnose the states of microwave photons in certain memory elements,” says Paraoanu. “This can be seen as a highly efficient way to extract information without disrupting the quantum processor.”
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