A superconducting quantum interferometer is a device that senses magnetic fields billions of times weaker than the needle of an ordinary compass. Inside it, there is a narrow bridge where superconductivity briefly breaks. This bridge works like a turnstile for magnetic flux: by counting how many 'quanta' pass through, the device measures the field.
But the trouble is that the bridge is made from two pieces of superconductor fused under a microscope. The seam is uneven: wider in some places, narrower in others, with microscopic holes here and there. As a result, each device behaves differently, and mass production is hard to achieve.
This approach produced devices with record-low noise — 40 femtotesla per square root of hertz. That's like hearing a clock ticking in the next room while a jackhammer is going off right next to you, and still catching every tick.
Now, instead of a lottery with unpredictable quality, you can stamp out equally sensitive sensors. And that's a path to cheap, reliable SQUIDs for hospitals, geological exploration, and quantum computers.
SQUIDs are so sensitive they can pick up the magnetic field generated by an electrical impulse in a human nerve — without any contact with the body.
In the movie 'Interstellar,' the characters use quantum sensors to search for gravitational anomalies — ultrasensitive SQUIDs could be their real-life prototype.