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Brida, G., Genovese, M., & Ruo Berchera, I. (2010). Experimental realization of sub-shot-noise quantum imaging. Nat. Photon., 4(4), 227–230.
Abstract: The properties of quantum states have led to the development of new technologies, ranging from quantum information to quantum metrology. A recent field of research to emerge is quantum imaging, which aims to overcome the limits of classical imaging by making use of the spatial properties of quantum states of light . In particular, quantum correlations between twin beams represent a fundamental resource for these studies. One of the most interesting proposed schemes takes advantage of the spatial quantum correlations between parametric down-conversion light beams to realize sub-shot-noise imaging of weak absorbing objects, leading ideally to noise-free imaging. Here, we present the first experimental realization of this scheme, showing its potential to achieve a larger signal-to-noise ratio than classical imaging methods. This work represents the starting point for this quantum technology, which we anticipate will have applications when there is a requirement for low-photon-flux illumination (for example for use with biological samples).
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Buchanan, M. (2010). Body of evidence (Vol. 6).
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Buchanan, M. (2011). Nothing's impossible (Vol. 7).
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Bylander, J., Gustavsson, S., Yan, F., Yoshihara, F., Harrabi, K., Fitch, G., et al. (2011). Noise spectroscopy through dynamical decoupling with a superconducting flux qubit. Nat. Phys., 7(7), 565–570.
Abstract: Quantum coherence in natural and artificial spin systems is fundamental to applications ranging from quantum information science to magnetic-resonance imaging and identification. Several multipulse control sequences targeting generalized noise models have been developed to extend coherence by dynamically decoupling a spin system from its noisy environment. In any particular implementation, however, the efficacy of these methods is sensitive to the specific frequency distribution of the noise, suggesting that these same pulse sequences could also be used to probe the noise spectrum directly. Here we demonstrate noise spectroscopy by means of dynamical decoupling using a superconducting qubit with energy-relaxation time T1=12μs. We first demonstrate that dynamical decoupling improves the coherence time T2 in this system up to the T2=2T1 limit (pure dephasing times exceeding 100μs), and then leverage its filtering properties to probe the environmental noise over a frequency (f) range 0.2-20MHz, observing a 1/fα distribution with α<1. The characterization of environmental noise has broad utility for spin-resonance applications, enabling the design of optimized coherent-control methods, promoting device and materials engineering, and generally improving coherence.
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Capmany, J., Gasulla, I., & Sales, S. (2011). Microwave photonics: Harnessing slow light. Nat. Photon., 5(12), 731–733.
Abstract: Slow-light techniques originally conceived for buffering high-speed digital optical signals now look set to play an important role in providing broadband phase and true time delays for microwave signals.
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