Quantum sensing exploits the extreme sensitivity of quantum systems to external perturbations — the same fragility that makes quantum computing difficult makes quantum sensors extraordinarily precise. Quantum sensors use superposition, entanglement, or other quantum effects to measure physical quantities (magnetic fields, electric fields, gravity, temperature, time) with precision approaching or exceeding the fundamental limits set by quantum mechanics (the Heisenberg limit or standard quantum limit).
Key quantum sensing platforms include atomic clocks (the most precise timekeeping devices, with accuracy of 1 second per 30 billion years, enabling GPS and future quantum-enhanced navigation), nitrogen-vacancy (NV) centers in diamond (nanoscale magnetic field sensors capable of detecting single electron spins, with applications in biomedical imaging and materials characterization), atom interferometers (gravity sensors using matter-wave interference, with applications in mineral exploration, navigation, and fundamental physics), and superconducting quantum interference devices (SQUIDs, ultra-sensitive magnetometers used in medical brain imaging via MEG).
Quantum sensing is often cited as the most near-term commercially viable quantum technology, ahead of quantum computing and quantum communication. Unlike quantum computing, which requires maintaining coherence across many entangled qubits through long circuits, quantum sensing typically uses small numbers of well-controlled quantum systems and benefits from environmental sensitivity rather than fighting it. The quantum sensing market is already generating revenue in sectors including defense (inertial navigation without GPS), healthcare (brain imaging), and resource exploration (subsurface mapping). Companies like Quantum Brilliance, Q-CTRL, and ColdQuanta have quantum sensing product lines alongside their computing efforts.