Adaptive phase estimation with squeezed thermal light

A. A. Berni, Lars Skovgaard Madsen, Mikael Østergaard Lassen, Bo Melholt Nielsen, M. G. A. Paris, Ulrik Lund Andersen

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Summary form only given. The use of quantum states of light in optical interferometry improves the precision in the estimation of a phase shift, paving the way for applications in quantum metrology, computation and cryptography. Sub-shot noise phase sensing can for example be achieved by injecting a squeezed vacuum into an interferometer . However, this approach leads to enhanced sensitivity only for small phase shifts. In this work we aim for ab initio sub-shot noise estimation of an unknown phase shift using a pre-determined squeezed probe and an adaptive measurement approach. We experimentally investigate the performances of such protocol under the realistic assumption of thermalization of the probe state. Indeed, adaptive phase estimation schemes with squeezed states and Bayesian processing of homodyne data have been shown to be asymptotically optimal in the pure case, thus approaching the quantum Cramér-Rao bound. In our protocol we take advantage of the enhanced sensitivity of homodyne detection in proximity of the optimal phase which maximizes the homodyne Fisher information. A squeezed thermal probe state (signal) undergoes an unknown phase shift. The first estimation step involves interference on a beam splitter of the signal and a local oscillator followed by homodyne detection. Homodyne data is then processed to compute a rough estimation of the phase through Bayesian inference. The rough estimation is fed back to the local oscillator in order to match the optimal relative phase with the signal. A second estimation step leads to the final estimation of the phase shift. Thermalization of the probe state prevents the attainability of the quantum Cramér-Rao bound. Nevertheless, we show that the studied adaptive scheme still saturates the classical Cramér-Rao bound, showing sub-shot noise behaviour and therefore extracting the maximum available information from homodyne data. In contrast to previous approaches, our scheme is optimized for Gaussian states.
Original languageEnglish
Title of host publicationCLEO/Europe 2013 - European Conference on Lasers and Electro-Optics
Number of pages1
Publication date2013
Publication statusPublished - 2013
Event2013 Conference on Lasers & Electro-Optics Europe & the International Quantum Electronics Conference (CLEO/Europe-IQEC) - Munich, Germany
Duration: 12 May 201316 May 2013


Conference2013 Conference on Lasers & Electro-Optics Europe & the International Quantum Electronics Conference (CLEO/Europe-IQEC)
Internet address


  • Aerospace
  • Bioengineering
  • Communication, Networking and Broadcast Technologies
  • Components, Circuits, Devices and Systems
  • Engineered Materials, Dielectrics and Plasmas
  • Engineering Profession
  • Fields, Waves and Electromagnetics
  • General Topics for Engineers
  • Nuclear Engineering
  • Photonics and Electrooptics
  • Power, Energy and Industry Applications
  • Estimation
  • Local oscillators
  • Noise
  • Optical interferometry
  • Phase estimation
  • Phase measurement
  • Probes


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