quantum sensing

History

The idea emerged in the late 20th century when scientists realized that quantum entanglement (a connection between particles at a distance) could be used for measurements. Important contributions were made by John Bell and Alain Aspect, who demonstrated the reality of quantum wonders.

How it works

In a quantum sensor, a particle, such as an atom, is put into a quantum state and sent to 'explore' the environment. The slightest impact changes this state, and by how the particle has changed, one determines exactly what happened.

History

The idea emerged in the late 20th century when scientists realized that quantum entanglement (a connection between particles at a distance) could be used for measurements. Important contributions were made by John Bell and Alain Aspect, who demonstrated the reality of quantum wonders.

How it works

In a quantum sensor, a particle, such as an atom, is put into a quantum state and sent to 'explore' the environment. The slightest impact changes this state, and by how the particle has changed, one determines exactly what happened.

History

The concept originated in the 1980s with the development of quantum optics and quantum information theories. John Bell in 1964 formulated Bell's theorem, showing the indispensability of quantum nonlocality. Alain Aspect in the early 1980s experimentally confirmed the violation of Bell's inequalities, paving the way for technologies based on entanglement. Since the 2000s, quantum sensors based on cold atoms and NV centers in diamond have been entering applied fields.

How it works

Quantum sensing works by creating sensitive quantum states, such as squeezed or entangled states, and then measuring their response to external fields. It uses effects like quantum superposition and entanglement to amplify the measurement signal. In atomic interferometers, phase calculation is done through the de Broglie formula (λ = h/p), linking the atom's wavelength to its momentum. The standard quantum limit and the Heisenberg limit are used to estimate the precision limit. Bell's theorem provides the basis for protocols where entanglement enhances sensitivity.

Open problems & fun facts

Preserving quantum coherence in noisy environments; Scaling systems for field conditions; Suppressing decoherence without loss of sensitivity

💡 An atomic interferometer can detect a change in gravity caused by a mosquito flying nearby, and quantum clocks based on ytterbium ions can measure time with an error of less than a second over the age of the universe.