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(Color online) Covariance matrix of an EPR state with 3 dB of squeezing. Plotted is the absolute value of the individual elements. The sinh(r) side peaks are characteristic for EPR entanglement.
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Parametric down-conversion (PDC) forms one of the basic building blocks for quantum optical experiments. However, the intrinsic multimode spectral-temporal structure of pulsed PDC often poses a severe hindrance for the direct implementation of the heralding of pure single-photon states or, for example, continuous-variable entanglement distillation...
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... visualized the covariance matrix of an EPR state containing 3 dB of EPR squeezing in Fig. 3, where we plotted the absolute value of the individual elements. Characteristic for EPR entanglement are the side peaks from the sinh(r) terms. In the following we are going to demonstrate the impact of filtering on the exemplary pulsed PDC state depicted in Fig. 4, which exhibits correlations in frequency and thus again plotted the ...
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Citations
... This makes it impossible to associate a photon detection event with a subtraction operation on a specific supermode and can eventually lead to mixed heralded states [16]. To comply with such a situation, a certain mode selectivity on the heralding path is generally obtained by adding an optical frequency filter before the photon-counting detector [7,16,17,18]. The filter action can be modelled as a BS: different scenarios can thus be considered based on the shape of the transmission coefficient of the filter BS. ...
... Expression (15) describes in a very simple and general form the mixed state heralded by a single-photon subtraction from the initial input stateρ in all cases where no mode-selective operation is possible on the heralding path. As anticipated, this corresponds to the extremely common experimental situation in which passive, linear, filters are employed on the heralding path [7,16,17,18]. The special case of mode selective single-photon subtraction in a given supermode ψn(ω) corresponds to γ k,n = δ k,n δ n,n in (15) and correctly leads to a pure output stateρ out = 1 ...
This work establishes a versatile theoretical framework that explicitly describes non-Gaussian states that are obtained, in an heralded fashion, by applying a single-photon subtraction to a multimode resource. The treatment focuses on the very common experimental situation in which no mode-selective operation is available. The obtained theoretical framework allows retrieving, given a multimode input state, optimal conditions for heralding as well as for non-Gaussian feature detection, thus providing a powerful toolbox for experiments' design. The application of the proposed approach to the case study of Schr\"odinger kitten preparation starting from a frequency multimode squeezed state illustrates the pertinence and impact of the derived theoretical tools.
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The frequency conversion of light has proved to be a crucial technology for communication, spectroscopy, imaging, and signal processing. In the quantum regime, it also offers great potential for realizing quantum networks incorporating disparate physical systems and quantum-enhanced information processing over a large computational space. The frequency conversion of quantum light, such as single photons, has been extensively investigated for the last two decades using all-optical frequency mixing, with the ultimate goal of realizing lossless and noiseless conversion. I demonstrate another route to this target using frequency conversion induced by cross-phase modulation in a dispersion-managed photonic crystal fiber. Owing to the deterministic and all-optical nature of the process, the lossless and low-noise spectral reshaping of a single-photon wave packet in the telecommunication band has been readily achieved with a modulation bandwidth as large as 0.4 THz. I further demonstrate that the scheme is applicable to manipulations of a nonclassical frequency correlation, wave packet interference, and entanglement between two photons. This approach presents a new coherent frequency interface for photons for quantum information processing.
