Quantum-enhanced sensing of a mechanical oscillator

Understand

The use of special quantum states to achieve sensitivities below the limits established by classically behaving states has enjoyed immense success since its inception.

• In bosonic interferometers, squeezed states, number states and cat states have been implemented on various platforms and have demonstrated improved measurement precision over interferometers based on coherent states.
• Another metrologically useful state is an equal superposition of two eigenstates with maximally different energies; this state ideally reaches the full interferometric sensitivity allowed by quantum mechanics.
• By leveraging improvements to our apparatus made primarily to reach higher operation fidelities in quantum information processing, we extend a technique to create number states up to $n=100$ and to generate superpositions of a harmonic oscillator ground state and a number state of the form $\textstyle{\frac{1}{\sqrt{2}}}(\lvert 0\rangle+\lvert n\rangle)$ with $n$ up to 18 in the motion of a single trapped ion.