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arXiv · 1405.7198

Multi-mode Entanglement is Detrimental to Lossy Optical Quantum Metrology

P. A. Knott·T. J. Proctor·Kae Nemoto·J. A. Dunningham·W. J. Munro
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Abstract

In optical interferometry multi-mode entanglement is often assumed to be the driving force behind quantum enhanced measurements. Recent work has shown this assumption to be false: single mode quantum states perform just as well as their multi-mode entangled counterparts. We go beyond this to show that when photon losses occur - an inevitability in any realistic system - multi-mode entanglement is actually detrimental to obtaining quantum enhanced measurements. We specifically apply this idea to a superposition of coherent states, demonstrating that these states show a robustness to loss that allows them to significantly outperform their competitors in realistic systems. A practically viable measurement scheme is then presented that allows measurements close to the theoretical bound, even with loss. These results promote a new way of approaching optical quantum metrology using single-mode states that we expect to have great implications for the future.

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P. A. Knott, T. J. Proctor, Kae Nemoto, J. A. Dunningham, W. J. Munro. 2015-04-14. Multi-mode Entanglement is Detrimental to Lossy Optical Quantum Metrology. https://doi.org/10.1103/physreva.90.033846

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