Quantum metrology including state preparation and readout times

Abstract

There is growing belief that the next decade will see the emergence of sensing devices based on the laws of quantum physics that outperform some of our current sensing devices. For example, in frequency estimation, using a probe prepared in an entangled state can, in principle, lead to a precision gain compared to a probe prepared in a separable state. Even in the presence of some forms of decoherence, it has been shown that the precision gain can increase with the number of probe particles $N$. Usually, however, the entangled and separable state preparation and readout times are assumed to be negligible. We find that a probe in a maximally entangled (GHZ) state can give an advantage over a separable state only if the entangled state preparation and readout times are lower than a certain threshold. When the probe system suffers dephasing, this threshold is much lower (and more difficult to attain) than it is for an isolated probe. Further, we find that in realistic situations the maximally entangled probe gives a precision advantage only up to some finite number of probe particles $N_{\text{cutoff}}$ that is lower for a dephasing probe than it is for an isolated probe.

arXiv comment7 pages and 2 figures. Figures are hyperlinked to animated versions [at https://www.youtube.com/playlist?list=PLU3tE4L9O6R7HW0aGuiPribDNIa7qbF1f]. Close to published version

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• Precision Limits in Quantum Metrology with Open Quantum Systems
• Robust quantum sensing in strongly interacting systems with many-body scars
• Strong quantum metrological limit from many-body physics
• Efficient detection of inhomogeneous magnetic fields from a single spin with Dicke states
• Universal shot-noise limit for quantum metrology with local Hamiltonians
• Entanglement-enhanced sensing using a chain of qubits with always-on nearest-neighbor interactions
• Quantum metrology based on symmetry-protected adiabatic transformation: Imperfection, finite time duration, and dephasing
• Single Spin Detection with Entangled States
• Optimal limits of continuously monitored thermometers and their Hamiltonian structure