Quantum Sensing
Quantum systems are so fragile to foreign influences. Quantum sensors take advantage of just that. Quantum sensors measure for magnetic and electric fields, time and frequency, and to pressure.
Here’s what we’ll go over:
- Why Quantum Sensing Matters
- The glossy intricacies of different types of Quantum Sensors
Why Quantum Sensors Matter
Quantum Sensing is not as headline grabbing as Quantum Computing. But it is also a hot area of research.
What clouds what we know? If we had a way to measure the smallest of small fluctuations in the fields that govern magnets and electricity, one could observe the neatest changes in the world around us. The effects of tiny changes in gravity can be observed, which is useful for earthquake predictions.
In addition, one could also use quantum sensing to develop ways to measure time more precisely, which could be of use in a multitude of ways.
Quantum sensors steer measurements using the principles of quantum entanglement. More precisely, often, quantum sensors examine the spins of materials.
Intricacies of Such Quantum Sensors
There are four main guidelines for a quantum sensor:
For example, electrical fields affect trapped ions; magnetic fields are more likely to affect spin-based systems.
As there are so many different types of materials used to measure metrics in quantum sensing, we’ll only discuss some of the above types today.
Atomic Vapor
A thermal vapor of atoms as a quantum sensor for magnetic fields. These atoms are held at or above room temperature, where these atoms are spin-polarized by an optical pump beam, which allow for electrons to increase in energy level. These are very sensitive. An application of atomic vapor quantum sensors is in the detection of neural activity in magnetoencephalography (long word to describe a way scientists can map brain activity using magnets). In addition, there is room for promise in high-energy physics, where one could detect anomalous dipole moments from coupling to exotic elementary particles beyond the standard model.
Trapped Ions
Electrical field noise is a source of decoherence. Therefore, one can measure an electric field by using ions, trapped in a vacuum by electric or magnetic fields. These are difficult sensors to control. But very worthwhile.
Rydberg atoms
Rydberg atoms (atoms in highly excited electronic states) are remarkable quantum sensors for electric fields for a similar reason as trapped ions. They give strong electric dipole transitions. Preparation and readout of states is possible by laser excitation and spectroscopy. Very neat!
Atomic Clocks
These are clocks that repeatedly compare the qubit’s transition to the frequency of an unstable local oscillator, hence measuring a time function.
Solid State Spins — Ensemble Sensors
An example of an ensemble sensor that measures solid state spins is nitrogen-vacancy centers. Diamonds may be worth so much, but the carbon atoms hold defects in spin structure. Expanding upon this, these defects may be optically analyzed and read out. This gives off a very accurate measure of spin.
Solid State Spins are called so because their constitute parts constitute of some sort of solid state lattice.
Superconducting Circuits
Superconducting Quantum Interference Device (SQUIDs) is one of the oldest and most sensitive type of magnetic sensor. A SQUID is very sensitive and is made of superconducting loops.
