Seminarium Optyczne

Under ideal conditions, quantum metrology promises a precision gainover classical techniques scaling quadratically with the number ofprobe particles. At the same time, no-go results have shown thatgeneric, uncorrelated noise limits the quantum advantage to a constantfactor. In frequency estimation scenarios, however, there areexceptions to this rule and, in particular, it has been found thattransversal dephasing does allow for a scaling quantum advantage. Yet,it has remained unclear whether such exemptions can be exploited inpractical scenarios. Here, we argue that the transversal-noise modelapplies to the setting of recent magnetometry experiments, and showthat a scaling advantage can be maintained with one-axis-twistedspin-squeezed states and Ramsey-interferometry-like measurements. Thisis achieved by exploiting the geometry of the setup that, as wedemonstrate, has a strong influence on the achievable quantumenhancement for experimentally feasible parameter settings. When, inaddition to the dominant transversal noise, other sources ofdecoherence are present, the quantum advantage is asymptoticallybounded by a constant, but this constant may be significantly improvedby exploring the geometry.