Joint quantum measurements with minimum uncertainty

Understand

Quantum physics constrains the accuracy of joint measurements of incompatible observables.

• Here we test tight measurement-uncertainty relations using single photons.
• We implement two independent, idealized uncertainty-estimation methods, the 3-state method and the weak-measurement method, and adapt them to realistic experimental conditions.
• Exceptional quantum state fidelities of up to 0.99998(6) allow us to verge upon the fundamental limits of measurement uncertainty.