Absorption spectroscopy at the ultimate quantum limit from single-photon states. (2nd February 2017)

• Record Type: Journal Article
• Authors: Whittaker, R; Erven, C; Neville, A; Berry, M; O'Brien, J L; Cable, H; Matthews, J C F
• Is Part Of: New journal of physics. Volume 19:Number 2(2017:Feb.)
• Publication Date: 2017-02-02
• Subjects: quantum metrology -- absorption spectroscopy -- sub-Poissonian photon statistics -- ultimate quantum limit; Physics -- Periodicals; Physics; Periodicals; 530.05
• DOI: 10.1088/1367-2630/aa5512
• Languages: English
• ISSNs: 1367-2630

Abstract

Abstract: Absorption 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.