One of the most intriguing aspects of quantum mechanics is the impossibility of measuring at the same time observables corresponding to noncommuting operators, because of quantum uncertainty. This impossibility can be partially relaxed when considering joint or sequential weak value evaluation. Indeed, weak value measurements have been a real breakthrough in the quantum measurement framework that is of the utmost interest from both a fundamental and an applicative point of view. In this Letter, we show how we realized for the first time a sequential weak value evaluation of two incompatible observables using a genuine single-photon experiment. These (sometimes anomalous) sequential weak values revealed the single-operator weak values, as well as the local correlation between them.
Weak value measurements have recently given rise to a great amount of interest in both the possibility of measurement amplification and the chance for further quantum mechanics foundations investigation. In particular, a question emerged about weak values being proof of the incompatibility between quantum mechanics and noncontextual hidden variables theories (NCHVTs). A test to provide a conclusive answer to this question was given by Pusey [Phys. Rev. Lett. 113, 200401 (2014)], where a theorem was derived showing the NCHVT incompatibility with the observation of anomalous weak values under specific conditions. In this Letter we realize this proposal, clearly pointing out the connection between weak values and the contextual nature of quantum mechanics.
Here we present a reconstruction of the Positive Operator-Value Measurement of a photon-number-resolving detector comprised of three 50:50 beamsplitters in a tree configuration, terminated with four single-photon avalanche detectors. The four detectors' outputs are processed by an electronic board that discriminates detected photon number states from 0 to 4 and implements a "smart counting" routine to compensate for dead time issues at high count rates. c 2018 Optical Society of America OCIS codes: 270.0270, 270.5570, 270.5585.Photon-number-resolving (PNR) detectors [1, 2], i.e. photodetectors that can resolve the number of photons that are impinging on them, have achieved a critical role in a wide variety of research fields, ranging from quantum mechanics foundations experiments [3] to quantum metrology [4,5], imaging [6,7] and information [8,9]. As a consequence, a precise quantum characterization of these devices has become crucial [3][4][5][6][7][8][9][10][11]. In a quantum mechanical framework, a full operational description of a PNR device is its positive operator-valued measure (POVM), i.e. the set of operators Ξ n describing a physical process that leads to a particular measurement outcome n. A measurement of the elements of a detector's POVM can be quite non-trivial, because one has to carefully choose the best-suited technique for a tomographic reconstruction of the POVM of the device under test, depending on its particular properties [12][13][14][15][16][17][18].There exist different types of PNR detectors, e.g. photo-multiplier tubes [19,20] [28][29][30][31][32][33][34][35][36][37][38]. Some of those detector families hold a significant promise for future applications, even if their use at present is very difficult because of a large experimental overhead associated with their operation. On the other hand, even though traditional single-photon avalanche detectors (SPADs) are only capable to discriminate between zero and one (or more) detected photons, photon number resolution can be obtained by multiplexing those detectors spatially [39,40] or temporally [41][42][43][44]. At present, this solution is by far the easiest and cheapest way to achieve a photon number resolving capability, even though at a cost of sacrificing linearity due to detector saturation [45]. Here we present the POVM reconstruction of a multiplexed PNR detector (at 1550 nm) composed of four Indium/Gallium arsenide (InGaAs) SPADs connected to a beam-splitter (BS) tree made with three 50:50 fiber BSs. The output of the InGaAs SPADs is processed with a field-programmable gate array (FPGA) board, giving as output the detected photon number (up to 4 detected photons per pulse).Because this detector is not phase-sensitive, its POVM is diagonal in the Fock states basis:where the Ξ nm = m| Ξ n |m elements give the detector tree probability of counting n = 0, ..., 4 photons with m impinging photons per pulse. To reconstruct Ξ nm , we test the response of our device to a set of J coherent states. The response of our PNR detector to the j-th...
Previous studies tested the efficacy of sertraline in Binge Eating Disorder (BED) over a period of 6 weeks. The present open study assesses the efficacy of sertraline over a period of 24 weeks in obese persons with binge eating behaviour (with or without the full criteria for BED) confirmed by high scores on the Binge Eating Scale (BES). Thirty-two obese outpatients (14 with BED and 18 without full criteria for BED), without co-occurring psychiatric comorbidities, were treated with sertraline (dose range 100-200 mg/d). Subjects were assessed at baseline and at 8, 12 and 24 weeks of treatment for number of binges, weight and psychopathology. After 8 weeks of treatment a significant improvement in the BES score and a significant weight loss emerged. These results were maintained over 24 weeks. A moderate drop out rate was detected, but no significant association with the severity of side effects was found. Further studies are needed to confirm the usefulness of sertraline in the treatment of patients with BED and also in binge eaters with a less severe eating psychopathology.
Single-photon sources represent a key enabling technology in quantum optics, and single color centers in diamond are a promising platform to serve this purpose, due to their high quantum efficiency and photostability at room temperature. The widely studied nitrogen-vacancy (NV) centers are characterized by several limitations, thus other defects have recently been considered, with a specific focus of centers emitting in the near-infra red (NIR). In the present work, we report on the coupling of native NIR-emitting centers in high-quality single-crystal diamond with solid immersion lens (SIL) structures fabricated by focused ion beam (FIB) lithography. The reported improvements in terms of light collection efficiency make the proposed system an ideal platform for the development of single-photon emitters with appealing photophysical and spectral properties
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