Cryomagneters

Cryomagneters are instruments that measure magnetic fields at cryogenic temperatures, typically below 4 K. The technique exploits the principle that magnetic field gradients can influence quantum two‑level systems such as superconducting flux qubits, nitrogen‑vacancy centers in diamond, or other cryogenic electromagnetic sensors. By detecting the precession or energy shift of these systems, cryomagneters provide high‑resolution mapping of magnetic flux even in environments where conventional magnetometers would suffer from noise or thermal drift.

The earliest cryomagneters were developed alongside superconducting quantum interference devices (SQUIDs) in the 1960s, using low‑temperature SQUIDs to probe weak magnetic anomalies in superconductors. In the 1990s, laser‑cooled atom clouds and nitrogen‑vacancy centers were adapted for sub‑Kelvin operation, leading to portable cryogenic magnetometers with sensitivity down to femtotesla levels. Recent advances focus on integrating cryomagneters with quantum sensors in cryogenic quantum computers to monitor magnetic flux noise that limits qubit coherence.

Applications span fundamental physics, where cryomagneters are used to search for axion‑like particles and study superfluid helium rotations, to technology, where they help calibrate cryogenic magnetic shielding for space telescopes and quantum processors. Because they operate at low temperatures, cryomagneters often require cryostats, superconducting coils, or dilution refrigerators to maintain their operational environment, but they offer unmatched sensitivity for detecting minute magnetic phenomena in cryogenic laboratories.