# Quantum-enhanced Metrology without Entanglement based on Optical Cavities with Feedback

### Lewis A. Clark, Adam Stokes, M. Mubashir Khan, Gangcheng Wang, Almut Beige

#### Abstract

There are a number of different strategies to measure the phase shift between two pathways of light more efficiently than suggested by the standard quantum limit. One way is to use highly entangled photons. Another way is to expose photons to a non-linear or interacting Hamiltonian. This paper emphasises that the conditional dynamics of open quantum systems provides an interesting additional tool for quantum-enhanced metrology. As a concrete example, we review a recent scheme which exploits the conditional dynamics of a laser-driven optical cavity with spontaneous photon emission inside a quantum feedback loop. Deducing information from second-order photon correlation measurements requires neither optical non-linearities nor entangled photons and should therefore be of immediate practical interest.

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#### Paper Citation

#### in Harvard Style

A. Clark L., Stokes A., Mubashir Khan M., Wang G. and Beige A. (2017). **Quantum-enhanced Metrology without Entanglement based on Optical Cavities with Feedback** . In *Proceedings of the 5th International Conference on Photonics, Optics and Laser Technology - Volume 1: PHOTOPTICS,* ISBN 978-989-758-223-3, pages 223-229. DOI: 10.5220/0006141702230229

#### in Bibtex Style

@conference{photoptics17,

author={Lewis A. Clark and Adam Stokes and M. Mubashir Khan and Gangcheng Wang and Almut Beige},

title={Quantum-enhanced Metrology without Entanglement based on Optical Cavities with Feedback},

booktitle={Proceedings of the 5th International Conference on Photonics, Optics and Laser Technology - Volume 1: PHOTOPTICS,},

year={2017},

pages={223-229},

publisher={SciTePress},

organization={INSTICC},

doi={10.5220/0006141702230229},

isbn={978-989-758-223-3},

}

#### in EndNote Style

TY - CONF

JO - Proceedings of the 5th International Conference on Photonics, Optics and Laser Technology - Volume 1: PHOTOPTICS,

TI - Quantum-enhanced Metrology without Entanglement based on Optical Cavities with Feedback

SN - 978-989-758-223-3

AU - A. Clark L.

AU - Stokes A.

AU - Mubashir Khan M.

AU - Wang G.

AU - Beige A.

PY - 2017

SP - 223

EP - 229

DO - 10.5220/0006141702230229