Absorption spectroscopy at the ultimate quantum limit from single-photon states

Beccie Solweling Whittaker, Chris Erven, Alex Neville, Monica Berry, Jeremy O'Brien, Hugo Cable, Jonathan Matthews

Research output: Contribution to journalArticle (Academic Journal)peer-review

76 Citations (Scopus)
355 Downloads (Pure)


bsorption spectroscopy is routinely used to characterise chemical and biological samples. For the state-of-the-art in laser absorption spectroscopy, precision is theoretically limited by shot-noise due to the fundamental Poisson-distribution of photon number in laser radiation. In practice, the shot- noise limit can only be achieved when all other sources of noise are eliminated. Here, we use wavelength-correlated and tuneable photon pairs to demonstrate how absorption spectroscopy can be performed with precision beyond the shot-noise limit and near the ultimate quantum limit by using the optimal probe for absorption measurement—single photons. We present a practically realisable scheme, which we characterise both the precision and accuracy of by measuring the response of a control feature. We demonstrate that the technique can successfully probe liquid samples and using two spectrally similar types of haemoglobin we show that obtaining a given precision in resolution requires fewer heralded single probe photons compared to using an idealised laser.
Original languageEnglish
Article number023013
Number of pages9
JournalNew Journal of Physics
Publication statusPublished - 2 Feb 2017

Structured keywords

  • Bristol Quantum Information Institute
  • QETLabs


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