Quantum metrology promises to provide a breakthrough in the measurement precision, with potential high impact in all the field of science, from biology and medicine to fundamental physics research. However, aside from few remarkable exceptions [1], its applicability in realistic scenario remains quite challenging, because of the fragility of quantum states to noise and losses.
For example, probing and imaging delicate systems using small number of photons with true and significant sensitivity improvement (without post selection or a-posteriori loss compensation) would be extraordinarily important. Here, we present the latest achievements in this field.
In 2017 we reported the realization of the first wide-field sub-shot-noise microscope [2]. It is based on spatially multi-mode non-classical photon number correlations detected by and high quantum efficiency CCD camera. The microscope delivers real-time images of 8000 pixels at full resolution, for (500µm)2 field-of-view, with noise reduced at 80% of the shot noise level in each pixel. However, there is a clear trade-off between the resolution and the sensitivity, due to the fact that pixels smaller than the characteristic size of the spatial modes do not intercept all the correlated photons between pairs of conjugated modes, representing a major loss contribution.
With the aim of improving the performance of this techniques, in [3] we have studied in deep detail the problem of absorption estimation towards the ultimate quantum limit, taking into account the effect of the unavoidable losses. On one side, we have shown that two mode squeezed vacuum can reach that limit in case of ideal detection efficiency by a trivial estimation strategy. On the other side, we have shown that in case of non-unitary quantum efficiency η, an optimized estimator proposed in [4] allows improving the sensitivity of a factor (1+η)/2 with respect to the simple one used in [2]. Therefore, we are now able to shift the resolution-sensitivity trade-off of the sub-shot-noise wide-filed microscope, doubling the sensitivity at the same resolution. We will also discuss some preliminary results of sub-shot-noise microscopy and quantum enhanced ghost microscopy of biological samples.
[1] J. Aasi, et al., Nat. Phot. 7, 613–619 (2013).
[2] N. Samantaray , I. Ruo-Berchera, A. Meda, M. Genovese, Light: Science & Applications 6, e17005 (2017).
[3] E. Losero, et al., Sci Rep. 8(1), 7431 (2018).
[4] P. A Moreau,. et al., Sci. Rep. 7, 6256 (2017).
Quantum sensors and quantum metrology , Quantum optics and non-classical light sources
