Early pioneering work in quantum mechanics in the 1930s first suggested the possibility of developing sensors with unprecedented precision by harnessing quantum effects. However, the technology to manipulate and control individual quantum systems at the atomic or microscopic scale took many decades to develop. By the 1980s and 1990s, advances in laser cooling and trapping of atoms allowed researchers to begin experimentally probing quantum superpositions and entanglement. This opened up new possibilities for developing quantum sensors that surpass the sensitivity of conventional devices.

In the 2000s, further progress was made in techniques like optical lattice clocks that use the ultrastable frequency of light absorbed or emitted by confined atoms to serve as incredibly precise clocks and gyroscopes. Trapped ions were also demonstrated to function as quantum logic gates, enabling potentially massive parallelism through quantum computing. These advances laid the groundwork for the first demonstrations of practical Quantum Sensors in the late 2000s and early 2010s. Since then, quantum sensing has progressed rapidly as an active area of research with many remarkable demonstrations.

Atomic Clocks and Magnetometers

One of the earliest and most established applications of quantum sensing is atomic clocks, which use the ultraprecise frequency of transitions between quantum energy levels of atoms to keep time. Ordinary atomic clocks improved timekeeping to within a second over many millions of years. However, optical lattice clocks have now surpassed this with an uncertainty of just a second over the lifespan of the universe. Their precision enables applications from global navigation to tests of fundamental physics.

Related to atomic clocks are atomic magnetometers, which function by detecting tiny shifts in atomic energy levels caused by magnetic fields. They can sense magnetic fields with a sensitivity approaching one femtotesla, enabling applications from healthcare to mineral exploration. Magnetic resonance imaging (MRI) uses a related principle to non-invasively image the inside of the human body with resolutions on the millimeter scale. Quantum magnetometers may one day allow real-time MRI or enable new applications like detecting unexploded landmines.

Quantum Photonic Sensing

Another rapidly advancing area is quantum photonic sensing, which harnesses quantum properties of light like coherence, entanglement and squeezing. Quantum light sources allow ultrasensitive measurements of phase, amplitude, frequency and polarization that beat the limits of classical optics. This finds applications in precision measurements from measuring minute stresses and strains in materials to detecting ripples in spacetime itself from gravitational waves.

Get more insights on Quantum Sensors