(TechnologyReview) A team at the Institute of Science and Technology in Austria has used entangled microwaves to create the world’s first quantum radar. Their device, which can detect objects at a distance using only a few photons, raises the prospect of stealthy radar systems that emit little detectable electromagnetic radiation.
The researchers compared their quantum radar with conventional systems operating with similarly low numbers of photons and say it significantly outperforms them, albeit only over relatively short distances. The researchers say it could be useful for short-range low-power radar for security applications in closed and populated environments. Such a radar device relying on entangled photons at low power makes it useful for biomedical and security applications.
This technique has some important advantages over conventional radar. Ordinary radar works in a similar way but fails at low power levels that involve small numbers of microwave photons. That’s because hot objects in the environment emit microwaves of their own. In a room temperature environment, this amounts to a background of around 1,000 microwave photons at any instant, and these overwhelm the returning echo. This is why radar systems use powerful transmitters.

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