You’re Listening To Quantum Radio

Researchers at Delft University of Technology have created a detector that enables the detection of a single photon’s worth of radio frequency energy. The chip is only 10 mm square and the team plans to use it to explore the relationship of mass and gravity to quantum theory.

The chip has immediate applications in MRI and radio astronomy. Traditionally, detecting a single photon at radio frequencies is difficult due to the significance of thermal fluctuations. At lower frequencies, cryogenic cooling can reduce the issue, but as frequency increases the fluctuations are harder to tame.

The trick requires a qubit that samples the radio frequency energy. While the radio source is at 173 MHz, the qubit is at 1 GHz, allowing a fine time resolution. Coupling of the two is via an LC circuit that uses a Josephson junction which, of course, requires very cold temperatures.

The paper is pretty math-heavy and we haven’t seen a lot of activity around homemade Josephson junctions. However, if you have access to niobium and liquid helium, this lab experiment looks like you could try it. Or watch [Sumner Davis] do roughly the same thing during a lecture at Berkeley. Keep in mind that dealing with liquid helium is much more difficult than liquid nitrogen.

It won’t help you with junctions, but you can make some relatively high-temperature superconductor material yourself. It turns out that the super cold junctions have a lot of applications in creating very precise voltage references.

7 thoughts on “You’re Listening To Quantum Radio

  1. You can detect single photons using an Avalanche Photodiode – which won’t put you into the poor house, is pretty easy to obtain, and not too hard to work with provided you’ve got your Analog ducks in a row. Try this:

    https://www.mouser.com/Optoelectronics/Optical-Detectors-and-Sensors/Photodiodes/_/N-6jjuh?P=1yzmniw&Keyword=avalanche+photodiode&FS=True

    Here are some prebuilt SPD modules ($Kaching! – build your own instead):

    https://www.pacer-usa.com/components/photon-detection-and-photon-counting/spcms/

    But of-course, that kind of photon detect/count is NOT the same as what these folks at DUT doing.

  2. This is an interesting step along the way. However, I believe the real big step will be in figuring out Quantum Entanglement, and applying that to communications. Imagine talking to Asia from North America, instantaneously, without any infrastructure. Flip the channel, and talk to the Moon, or Mars instantaneously. Imagine all of this without static, or propagation issues. Flip to another channel and communicate with Alpha Centurai instantaneously with complete disregard for the speed of light.

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