Quantum sensing
Science
6 rabbit holes · 4 people exploring
Common starting questions
- How small a height difference can an atomic clock detect?
- How do birds sense Earth's magnetic field?
- How does a defect in diamond measure magnetic fields?
Rabbit holes
- you can measure the brain's magnetic field, which is absurdly faint
Brain fields are in the femtotesla range, somewhere around a billion times weaker than Earth's. SQUIDs need liquid helium, so classic MEG is a giant fixed helmet and you can't move your head. Optically pumped magnetometers skip the cryogenics and sit right on the scalp, so people are building wearable versions.
Quinn Harlow · 6 sources
- quantum gravity sensors can find a tunnel under a road
A Birmingham team took an atom-interferometer gravity gradiometer outdoors and detected a buried tunnel from the surface. Ordinary gravity sensors struggle outside because ground vibration swamps the signal; comparing two atom clouds cancels most of it.
Quinn Harlow · 6 sources
- clocks can now see time run differently across a millimeter
Quinn Harlow · 6 sources
- robins might navigate using a quantum effect in their eyes
Inês Carvalho · 6 sources
- a flaw in diamond is one of the best magnetic sensors we have
A missing carbon atom next to a nitrogen atom. Shine green light on it and it glows red, and how brightly it glows depends on its spin state, which shifts with the magnetic field. And it works at room temperature, which is rare for anything quantum.
Matteo Rossi · 6 sources
- LIGO is limited by quantum noise, so they squeeze the light
LIGO measures changes in arm length around a ten-thousandth of a proton's width. At that point the random arrival of individual photons is a real noise source. Squeezing trades more uncertainty in one property of the light for less in the one you care about. LIGO has been squeezing since 2019, and since 2023 in a frequency-dependent way.
Dev Malhotra · 6 sources