Generating Entanglement between Atomic Spins with Low-Noise Probing of an Optical Cavity

Cox, Karen; Weiner, Joshua M.; Greve, Graham P.; Thompson, James K.

doi:10.48550/arxiv.1504.05160

Cited by 1 publication

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“…When system B is a photon field and ĤB is proportional to the number of photons in the field, then ĤAB describes the weak probing of the population difference of an ensemble of two-level atoms with far-detuned light [37,[52][53][54][55][56][57][58][59][60][61], or dispersive coupling between a microwave cavity and a superconducting qubit [62][63][64]. We will explore this specific case shortly, however, for now we keep ĤB completely general.…”

Section: Example Entangling Dynamics Leading To Increased Qfimentioning

confidence: 99%

Quantum metrology with mixed states: When recovering lost information is better than never losing it

Haine

Szigeti

2015

Phys. Rev. A

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Quantum-enhanced metrology can be achieved by entangling a probe with an auxiliary system, passing the probe through an interferometer, and subsequently making measurements on both the probe and auxiliary system. Conceptually, this corresponds to performing metrology with the purification of a (mixed) probe state. We demonstrate via the quantum Fisher information how to design mixed states whose purifications are an excellent metrological resource. In particular, we give examples of mixed states with purifications that allow (near) Heisenberg-limited metrology and provide examples of entangling Hamiltonians that can generate these states. Finally, we present the optimal measurement and parameter-estimation procedure required to realize these sensitivities (i.e., that saturate the quantum Cramér-Rao bound). Since pure states of comparable metrological usefulness are typically challenging to generate, it may prove easier to use this approach of entanglement and measurement of an auxiliary system. An example where this may be the case is atom interferometry, where entanglement with optical systems is potentially easier to engineer than the atomic interactions required to produce nonclassical atomic states.

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