Experimental test of entropic noise-disturbance uncertainty relations for three-outcome qubit measurementsJune 5, 2021 10:20 am
In our latest work 1, we experimentally tested a tight information-theoretic measurement uncertainty relation, in terms of a proposed three-outcome POVM using neutron spin-1/2 qubits. Previously we reported a tight noise-disturbance uncertainty relation for projective qubit measurements 2. Meanwhile, new theoretical analysis 3 predicts that projective measurements suboptimal, with respect to the noise-disturbance trade-offs, compared to generalized (or unsharp) measurements (see here for theoretical details). We developed a new experimental technique to realize general measurements, more precisely a three-outcome positive-operator valued measure (POVM), allowing to test the suboptimal nature of projective measurements regarding noise- disturbance uncertainty realtions. In the present manuscript we provide experimental evidence that when performing such general measurements, on a qubit system (in our case a neutron spin), tighter bounds of the noise-disturbance trade-offs are observed compared to projective measurements. This advantage of POVMs over projective measurements on noise-disturbance uncertainty relations has not previously been observed experimentally (see here for details of the experiment and more results).