  When standard light sources are employed, the precision of the phase
determination is limited by the shot noise. Quantum entanglement provides means
to exceed this limit with the celebrated example of N00N states that saturate
the ultimate Heisenberg limit on precision, but at the same time are extremely
fragile to losses. In contrast, we provide experimental evidence that
appropriately engineered quantum states outperform both standard and N00N
states in the precision of phase estimation when losses are present.
