Performing optimal phase measurements with a universal quantum processor

The use of qubits to perform phase or frequency measurements of classical fields arises naturally in a variety of sensing applications including operating atomic clocks and calibrating quantum processors. In such scenarios, it has long been known that the generation of entanglement within ensembles of qubits can provide a metrological advantage over what is achievable with the same number of unentangled qubits. However, demonstrations saturating the lowest achievable bound on measurement errors in practical sensing tasks which require the dynamic range of detectable shifts to be finite and independent of the number of probed qubits, have remained elusive. Here, we demonstrate a quantum metrological advantage using Quantinuum's latest universal quantum processor, Helios-1, to perform phase measurements which are designed to saturate the above practical sensing bound.