Experimental demonstration of continuous variable purification of squeezed states

We report on the first experimental demonstration of purification of nonclassical continuous variable states. The protocol uses two copies of phase-diffused states overlapped on a beam splitter and provides Gaussified, less mixed states with the degree of squeezing improved. The protocol uses only linear optical devices such as beam splitters and homodyne detection, thereby proving these optical elements can be used for successful purification of this type of state decoherence which occurs in optical transmission channels

Preparing the bound instance of quantum entanglement

Among the possibly most intriguing aspects of quantum entanglement is that it comes in "free" and "bound" instances. Bound entangled states require entangled states in preparation but, once realized, no free entanglement and therefore no pure maximally entangled pairs can be regained. Their existence hence certifies an intrinsic irreversibility of entanglement in nature and suggests a connection with thermodynamics. In this work, we present a first experimental unconditional preparation and detection of a bound entangled state of light. We consider continuous-variable entanglement, use convex optimization to identify regimes rendering its bound character well certifiable, and realize an experiment that continuously produced a distributed bound entangled state with an extraordinary and unprecedented significance of more than ten standard deviations away from both separability and distillability. Our results show that the approach chosen allows for the efficient and precise preparation of multimode entangled states of light with various applications in quantum information, quantum state engineering and high precision metrology.Comment: The final version accounts for a recent comment in Nature Physics [24] clarifying that a previous claim of having generated bound entanglement [23] was not supported by the authors' data. We also extended our introduction and discussion and also added reference

Photon number discrimination without a photon counter and its application to reconstructing non-Gaussian states

The non-linearity of a conditional photon-counting measurement can be used to `de-Gaussify' a Gaussian state of light. Here we present and experimentally demonstrate a technique for photon number resolution using only homodyne detection. We then apply this technique to inform a conditional measurement; unambiguously reconstructing the statistics of the non-Gaussian one and two photon subtracted squeezed vacuum states. Although our photon number measurement relies on ensemble averages and cannot be used to prepare non-Gaussian states of light, its high efficiency, photon number resolving capabilities, and compatibility with the telecommunications band make it suitable for quantum information tasks relying on the outcomes of mean values.Comment: 4 pages, 3 figures. Theory section expanded in response to referee comment

Direct Sampling of Negative Quasiprobabilities of a Squeezed State

Although squeezed states are nonclassical states, so far, their nonclassicality could not be demonstrated by negative quasiprobabilities. In this work we derive pattern functions for the direct experimental determination of so-called nonclassicality quasiprobabilities. The negativities of these quantities turn out to be necessary and sufficient for the nonclassicality of an arbitrary quantum state and are therefore suitable for a direct and general test of nonclassicality. We apply the method to a squeezed vacuum state of light that was generated by parametric down-conversion in a second-order nonlinear crystal.Comment: 4 pages, 4 figures, supplementary material adde

Entangled Qubits in a non-Gaussian Quantum State

We experimentally generate and tomographically characterize a mixed, genuinely non-Gaussian bipartite continuous-variable entangled state. By testing entanglement in 2$\times$2-dimensional two-qubit subspaces, entangled qubits are localized within the density matrix, which, firstly, proves the distillability of the state and, secondly, is useful to estimate the efficiency and test the applicability of distillation protocols. In our example, the entangled qubits are arranged in the density matrix in an asymmetric way, i.e. entanglement is found between diverse qubits composed of different photon number states, although the entangled state is symmetric under exchanging the modes

Body Mass Index and VO2max Relationship of FKUI Fitness Challenge 2012 Participants in Gelora Bung Karno Jakarta

Introduction: In determining fatness the most common technique is measuring body mass index (BMI). Scientific evidence showed that risk of premature illness and death is greater for those who are overweight but also increased in individuals who are underweight. BMI is useful to screen general population although it fails to differentiate fat from lean body mass or determine where the most of the fat is located. Maximum oxygen consumption determined by VO2max is maximal amount of oxygen that human body can utilize per minute of physical activity. VO2max shows cardiorespiratory endurance as aerobic fitness parameter. Higher oxygen consumption shows more efficient cardiorespiratory system. VO2max is affected by genetics, training, gender, age, and body composition. Fitness Challenge is a serial fitness tests held annually by Sports Medicine Program Faculty of Medicine Universitas Indonesia including BMI and cardiorespiratory endurance examination. In the year 2012 it was held in Gelora Bung Karno (GBK) Jakarta, where most Jakarta citizens spent their weekend relaxing and/or exercising. In this study we would like to describe the results of body composition examination and cardiorespiratory endurance test from that event and analyze the relationship between them. Methods: All 59 participants of the competition were taken height, weight, and VO2max measurement. Body mass index was calculated by the formula of weight in kg/(height in meter)2. VO2max was measured by field test which was Bleep test. Correlation was counted using Spearman’s rho. Results: Participants are 23 women and 36 men age 15-48 years old with mean age 32.86 ± 12.85 years old. Mean VO2max is 27.94 ± 6.91 and mean BMI is 23.36 ± 3.41. There is a significant negative correlation between VO2max and BMI which is -0.408 (p=0.01). Discussion: The finding is consistent with previous study in Israel where correlation coefficients between BMI, waist circumference, and VO2max were statistically significant. This study gave general description on how components of fitness interact, which are BMI as metabolic fitness parameter and VO2max as aerobic fitness parameter. Higher VO2max can be achieved by having lower BMI. Since this study is a cross sectional study based on field tests in a competition setting and taken in a small population of visitors in GBK Jakarta, the relationship cannot be taken as general Indonesian population. But the point that body composition is one of the factors affecting VO2max, is shown. Thus people might improve their aerobic fitness by reducing their BMI to the normal value

Squeezed-field injection for gravitational wave interferometers

In a recent table-top experiment, we demonstrated the compatibility of three advanced interferometer techniques for gravitational wave detection, namely power-recycling, detuned signal recycling and squeezed-field injection. The interferometer's signal-to-noise ratio was improved by up to 2.8 dB beyond the coherent state's shot-noise. This value was mainly limited by optical losses on the squeezed field. We present a detailed analysis of the optical losses in our experiment and provide an estimation of the possible nonclassical performance of a future squeezed-field enhanced GEO 600 detector