Quantum revolution has made it possible to sense the world in a different way. The aim is to use the unique properties of quantum mechanics to take measurements or produce images which are otherwise considered impossible.
Majority of the work is done with the help of photons. However most of the work in quantum revolution involving quantum computing, cryptography has been done with the help of visible or near-visible light.
However, Shabir Barzanjeh and his team from the Institute of Science and Technology, Austria used entangled microwaves for creating the first quantum radar in the world. It can detect far-away objects with the help of few photons thus demonstrating the stealth radars which can function without emitting detectable electromagnetic radiation. The paper can be found here.
A pair of entangled microwave photons are created with the help of a superconducting device known as Josephson parametric converter. The first photon also defined as the signal photon is beamed toward a specific object and then the reflection is captured. In the meantime, the second photon which is also called the idler photon is stored. On the arrival of the reflection, a signature is created by interfering with the idler photon which tells the distance traversed by the signal photon. A normal radar works in the similar manner, however, fails when the power levels involve lesser numbers of microwave photons. Reason being hot objects emit their own microwaves.
In-room temperature, at any instant, 1000 microwave photons are present which overwhelm the reflecting echo. So powerful transmitters are used by radar systems. This is solved in the entangled photon system. The signal and idler photons help in filtering out the effects of other photons. So it is simple to detect the signal photon upon reflection. Reflection hurts quantum entanglement since it is a fragile property, but the correlation between idler and signal photons help in distinguishing themselves from the noise.
Researchers said that a room temperature object at a distance of 1 meter was detected with the help of entangled fields using the Josephson parametric converter at millikelvin temperatures. This setup outperforms the normal radar system as it operates with lesser number of photons. But this is only for short distances.
This experiment shows the application of microwave-based entanglement and quantum radar. A potential demonstration of quantum illumination is also shown. This technique can be used in biomedical applications since it is a non-invasive scanning technique such as human tissue imaging. For a closed environment, there is the obvious application as a stealthy radar that is difficult for adversaries to detect over background noise
Journal Reference: arxiv