Phys. Rev. Lett. 107, 133603 (2011)
How do you amplify a single photon? By making it act like many photons. Amir Feizpour and colleagues have now shown how this might be possible using so-called weak measurements.
Boosting a conventional signal to improve the ratio of signal to noise is a crucial element of any computation or communication system. In photonic systems, this is often achieved using a material with nonlinear optical properties. But at the single-photon level, these effects are tiny. Feizpour et al. now propose that 'weakly' probing a photon in the nonlinear medium with a second optical beam can amplify the effect.
Weak measurements can interrogate a quantum state without disturbing it. It requires a process of post-selection in which only photons with a specific property are retained. The authors show that the improvement in the signal-to-noise ratio using their technique outweighs the loss of photons during post-selection. This idea could have a role in the development of optical quantum logic gates.
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Gevaux, D. A stronger single photon. Nature Phys 7, 833 (2011). https://doi.org/10.1038/nphys2144
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DOI: https://doi.org/10.1038/nphys2144