Uncovering Quantum Correlations with Time-Multiplexed Click Detection

Sperling, Jan; Bohmann, Martin; Vogel, W.; Harder, Georg; Brecht, Benjamin; Ansari, Vahid; Silberhorn, Christine

doi:10.1103/physrevlett.115.023601

Cited by 75 publications

(105 citation statements)

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“…Experimentally, intense and spectrally tunable x-ray light sources such as the Linac Coherent Light Source facility at SLAC and ORION provide a valuable diagnostics tool for studying WDM [7][8][9][10][11][12]. These intense light sources can be used to probe a WDM sample and provide information on its underlying structure, charge states and opacity.…”

Section: Introductionmentioning

confidence: 99%

Radiative and atomic properties of C and CH plasmas in the warm-dense-matter regime

et al. 2018

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A theoretical model based on the method of super transition arrays (STA) is used to compute the emissivities, opacities and average ionization states of carbon (C) and polystyrene (CH) plasmas in the warm-dense matter regime in which the coupling constant varies between 0.02 to 2.0. The accuracy of results of STA calculations is assessed by benchmarking against the available experimental data and results obtained using other theoretical methods, assuming that a state of local thermodynamic equilibrium exists in the plasma. In the case of a carbon plasma, the STA method yields spectral features that are in reasonably-good agreement with Dirac-Fock and Hartree-Fock-Slater theories; in the case of CH, we find that STA-derived opacities are very similar to those derived using quantum-molecular-dynamics density-functional theory and Hartree-Fock method down to plasma temperature of about 20 eV. Our calculations also compare favorably with available experimental measurements of Gamboa et al [High Energy Density Phys. 11, 75 (2014)] of the plasma temperature and average ionization state behind a blast wave in a pure carbon foam. Although the STA-computed average-ionization charge state in the rarefaction region appears to be lower than the experimental data, it is within the experimental uncertainty and the discrepancy is nevertheless consistent with results reported using an atomic kinetic model. In addition, we further predict the temperature dependence of average ionization states of CH plasma in the same temperature range as for the carbon plasma.

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Section: Introductionmentioning

confidence: 99%

Radiative and atomic properties of C and CH plasmas in the warm-dense-matter regime

et al. 2018

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“…For example, varieties of nonclassicality criteria can be constructed based on second and higher order moments of the electromagnetic field [55,56]. Such criteria identify nonclassical fields directly from the measured statistics in a loss tolerant way without complicated analysis techniques and have been utilized with low order correlation functions [57,58]. Having access to higher order correlation functions gives a more complete description of the underlying photon number statistics and increases the possibilities in characterizing quantum states.…”

Section: Correlation Functionsmentioning

confidence: 99%

Single-Mode Parametric-Down-Conversion States with 50 Photons as a Source for Mesoscopic Quantum Optics

Harder¹,

Bartley²,

Lita³

et al. 2016

Phys. Rev. Lett.

188

143

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We generate pulsed, two mode squeezed states in a single spatio-temporal mode with mean photon numbers up to 20. We directly measure photon-number-correlations between the two modes with transition edge sensors up to 80 photons per mode. This corresponds roughly to a statedimensionality of 6400. We achieve detection efficiencies of 64% in the technologically crucial telecom regime and demonstrate the high quality of our measurements by heralded nonclassical distributions up to 50 photons per pulse and calculated correlation functions up to 40 th order.PACS numbers: 42.65. Lm, 42.50.Ar, 42.50.Dv, 42.50.Xa, 42.65.Wi Introduction. -The quest to study quantum effects for macroscopic system sizes is driven by one of the most fundamental issues of quantum physics, as exemplified by Schrödinger's cat states [1], and has initiated much research work over the last decades [2][3][4][5]. However, the nature of quantum decoherence renders the observation of nonclassical features in large systems increasingly difficult. Optical states are a good candidate to observe nonclassical features and to harness large systems for new quantum applications [6], since they only suffer from loss as decoherence mechanism and current development of low-loss equipment enables a new generation of experiment. Crucial for both applications and fundamental questions, in the optical domain, is the ability to generate large photonic states in well-defined optical modes [7] as well as detecting them with sufficient efficiency. Starting with the landmark experiment by , the statistical properties of photons have been used in a broad range of contexts to observe and exploit non-classical effects. Two-mode squeezed states with large photon numbers can be considered macroscopic [9] as they exhibit a large Fisher information [10]. Using the process of parametric down-conversion (PDC), bright squeezed states with billions of photons have been demonstrated [11][12][13][14][15][16][17]. However, the multi-mode nature of this approach frequently impairs the direct comparison between theoretical predictions and experimental observations and limits the applications of these states. In particular, further processing with non-Gaussian measurements projects multimode states into mixed states, thereby diminishing significantly the quantum character. Contrariwise, the combination of photon number measurements with genuine single-or two-mode squeezed vacuum states has been shown to overcome Gaussian no-go theorems [18], to enable continuous variable entanglement distillation [19,20] and to allow for the preparation of cat states [21,22]. Recent development in transition edge sensors (TES) [23] and nanowire detectors [24] offers the possibility to perform photon number measurements with single photon resolution and very high efficiency.Tight filtering [25] or mode selection [26] could be used to reduce the number of modes, at a cost of reducing the size of the systems and achievable purity due to unavoidable losses [27]. In the single photon regime pulsed PDC sou...

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“…Such negativities are commonly accepted as nonclassicality signatures of the quantum state [6], and can always be detected using nonclassicality criteria [22][23][24], or can be directly observed via an appropriate smoothing of the P -function [25][26][27]. However, in the bipartite case, such a nonclassicality interpretation (P -nonclassicality) is a source of debate.…”

mentioning

confidence: 99%

Quantum Correlations in Nonlocal Boson Sampling

2017

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Determination of the quantum nature of correlations between two spatially separated systems plays a crucial role in quantum information science. Of particular interest is the questions of if and how these correlations enable quantum information protocols to be more powerful. Here, we report on a distributed quantum computation protocol in which the input and output quantum states are considered to be classically correlated in quantum informatics. Nevertheless, we show that the correlations between the outcomes of the measurements on the output state cannot be efficiently simulated using classical algorithms. Crucially, at the same time, local measurement outcomes can be efficiently simulated on classical computers. We show that the only known classicality criterion violated by the input and output states in our protocol is the one used in quantum optics, namely, phase-space nonclassicality. As a result, we argue that the global phase-space nonclassicality inherent within the output state of our protocol represents true quantum correlations.Introduction.-Correlations play an undeniable role in our understanding of the physical world. In our macroscopic classical description of commonplace phenomena, classical physics and classical information theory are in perfect agreement in characterization and quantification of correlated events. At a microscopic level, where quantum theory is our best candidate for explaining phenomena, however, the situation is different. Our informational inspections of a quantum world, i.e., quantum information theory, is based on our intuition from classical information theory and classical probability theory, mostly the notion of quantum entropy [1, 2]. However, a discrepancy emerges when physical constraints are taken into account to distinguish between quantum physics and classical physics, hence splitting quantum information approach to correlations from that of quantum optics.In quantum optics it is common to study nonclassical features of bosonic systems in a quantum analogue of the classical phase space [3]. While in a classical statistical theory in phase-space the state of the system is represented by a probability distribution, the quantum phase-space distributions can have negative regions, and hence, fail to be legitimate probability distributions [4]. The negativities are thus considered as nonclassicality signatures. Within multipartite quantum states, the phase-space nonclassicality is tempted to be interpreted as quantum correlations, due to the fact that in a classical description of the joint system no such effects are present [5,6].The sharpest contrast between the definition of quantum correlations in quantum information science and that of quantum optics has been demonstrated very recently by Ferraro and Paris [7]. They showed that the two definitions from quantum information and quantum optics are maximally inequivalent, meaning that every quantum state which is classically correlated with respect to the quantum information definition of quantum correlations is nece...

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Uncovering Quantum Correlations with Time-Multiplexed Click Detection

Cited by 75 publications

References 38 publications

Radiative and atomic properties of C and CH plasmas in the warm-dense-matter regime

Radiative and atomic properties of C and CH plasmas in the warm-dense-matter regime

Single-Mode Parametric-Down-Conversion States with 50 Photons as a Source for Mesoscopic Quantum Optics

Quantum Correlations in Nonlocal Boson Sampling

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