Experiments testing macroscopic quantum superpositions must be slow

We consider a thought experiment where the preparation of a macroscopically massive or charged particle in a quantum superposition and the associated dynamics of a distant test particle apparently allow for superluminal communication. We give a solution to the paradox which is based on the following fundamental principle: any local experiment, discriminating a coherent superposition from an incoherent statistical mixture, necessarily requires a minimum time proportional to the mass (or charge) of the system. For a charged particle, we consider two examples of such experiments, and show that they are both consistent with the previous limitation. In the first, the measurement requires to accelerate the charge, that can entangle with the emitted photons. In the second, the limitation can be ascribed to the quantum vacuum fluctuations of the electromagnetic field. On the other hand, when applied to massive particles our result provides an indirect evidence for the existence of gravitational vacuum fluctuations and for the possibility of entangling a particle with quantum gravitational radiation.Comment: 12 pages, 1 figur

Classical capacity of Gaussian thermal memory channels

The classical capacity of phase-invariant Gaussian channels has been recently determined under the assumption that such channels are memoryless. In this work we generalize this result by deriving the classical capacity of a model of quantum memory channel, in which the output states depend on the previous input states. In particular we extend the analysis of [C. Lupo, et al., PRL and PRA (2010)] from quantum limited channels to thermal attenuators and thermal amplifiers. Our result applies in many situations in which the physical communication channel is affected by nonzero memory and by thermal noise.Comment: 14 pages, 8 figure

A Tool for Aligning Event Logs and Prescriptive Process Models through Automated Planning

In Conformance Checking, alignment is the problem of detecting and repairing nonconformity between the actual execution of a business process, as recorded in an event log, and the model of the same process. Literature proposes solutions for the alignment problem that are implementations of planning algorithms built ad-hoc for the specific problem. Unfortunately, in the era of big data, these ad-hoc implementations do not scale sufficiently compared with well-established planning systems. In this paper, we tackle the above issue by presenting a tool, also available in ProM, to represent instances of the alignment problem as automated planning problems in PDDL (Planning Domain Definition Language) for which state-of-the-art planners can find a correct solution in a finite amount of time. If alignment problems are converted into planning problems, one can seamlessly update to the recent versions of the best performing automated planners, with advantages in term of versatility and customization. Furthermore, by employing several processes and event logs of different sizes, we show how our tool outperforms existing approaches of several order of magnitude and, in certain cases, carries out the task while existing approaches run out of memory

Constraining the Nordtvedt parameter with the BepiColombo Radioscience experiment

BepiColombo is a joint ESA/JAXA mission to Mercury with challenging objectives regarding geophysics, geodesy and fundamental physics. The Mercury Orbiter Radioscience Experiment (MORE) is one of the on-board experiments, including three different but linked experiments: gravimetry, rotation and relativity. The aim of the relativity experiment is the measurement of the post-Newtonian parameters. Thanks to accurate tracking between Earth and spacecraft, the results are expected to be very precise. However, the outcomes of the experiment strictly depends on our "knowledge" about solar system: ephemerides, number of bodies (planets, satellites and asteroids) and their masses. In this paper we describe a semi-analytic model used to perform a covariance analysis to quantify the effects, on the relativity experiment, due to the uncertainties of solar system bodies parameters. In particular, our attention is focused on the Nordtvedt parameter $\eta$ used to parametrize the strong equivalence principle violation. After our analysis we estimated $\sigma[\eta]\lessapprox 4.5\times 10^{-5}$ which is about 1~order of magnitude larger than the "ideal" case where masses of planets and asteroids have no errors. The current value, obtained from ground based experiments and lunar laser ranging measurements, is $\sigma[\eta]\approx 4.4\times 10^{-4}$. Therefore, we conclude that, even in presence of uncertainties on solar system parameters, the measurement of $\eta$ by MORE can improve the current precision of about 1~order of magnitude

Optimal quantum state discrimination via nested binary measurements

A method to compute the optimal success probability of discrimination of N arbitrary quantum states is presented, based on the decomposition of any N-outcome measurement into sequences of nested two-outcome ones. In this way the optimization of the measurement operators can be carried out in successive steps, optimizing first the binary measurements at the deepest nesting level and then moving on to those at higher levels. We obtain an analytical expression for the maximum success probability after the first optimization step and examine its form for the specific case of N=3,4 states of a qubit. In this case, at variance with previous proposals, we are able to provide a compact expression for the success probability of any set of states, whose numerical optimization is straightforward; the results thus obtained highlight some lesser-known features of the discrimination problem.Comment: v2: added references to previous works closely related to Sec. II; 8+3 pages; 3 figure

Pauli Tomography: complete characterization of a single qubit device

The marriage of Quantum Physics and Information Technology, originally motivated by the need for miniaturization, has recently opened the way to the realization of radically new information-processing devices, with the possibility of guaranteed secure cryptographic communications, and tremendous speedups of some complex computational tasks. Among the many problems posed by the new information technology there is the need of characterizing the new quantum devices, making a complete identification and characterization of their functioning. As we will see, quantum mechanics provides us with a powerful tool to achieve the task easily and efficiently: this tools is the so called quantum entanglement, the basis of the quantum parallelism of the future computers. We present here the first full experimental quantum characterization of a single-qubit device. The new method, we may refer to as ''quantum radiography'', uses a Pauli Quantum Tomography at the output of the device, and needs only a single entangled state at the input, which works on the test channel as all possible input states in quantum parallel. The method can be easily extended to any n-qubits device

Corneal Deposit of Ciprofloxacin after Laser Assisted Subepithelial Keratomileusis Procedure: A Case Report

Purpose. To report one case of corneal antibiotic deposition after ciprofloxacin administration in Laser Assisted Subepithelial Keratomileusis (LASEK). Methods. One case of post-LASEK treatment resulted in corneal precipitates and poor wound healing. Debris was analyzed with dark field microscopy and placed on a blood-agar plate seeded with a susceptible stain of Staphylococcus aureus (ATCC 29213). Results. The alterations resolved with discontinuation of ciprofloxacin treatment, although some residual deposits persisted subepithelially for 6 months. Analysis of precipitates revealed polydisperse crystalline needles of 183 μm average length (SD = 54 μm) and the excised precipitate demonstrated a zone of inhibition. Conclusions. Fluoroquinolone antibiotic drops have been used extensively in postsurgical treatment of refractive surgery. Corneal precipitates have been previously reported in the literature, but up to now nothing has been documented after LASEK. Polypharmacy during refractive surgery may impair epithelialisation, and clinical management should reduce toxic environment and promote ocular surface stability when performing surface ablations

Exploiting quantum parallelism of entanglement for a complete experimental quantum characterization of a single qubit device

We present the first full experimental quantum tomographic characterization of a single-qubit device achieved with a single entangled input state. The entangled input state plays the role of all possible input states in quantum parallel on the tested device. The method can be trivially extended to any n-qubits device by just replicating the whole experimental setup n times.Comment: 4 pages in revtex4 with 4 eps figure

Early heat waves over Italy and their impacts on durum wheat yields

In the last decades the Euro-Mediterranean region has experienced an increase in extreme temperature events such as heat waves. These extreme weather conditions can strongly affect arable crop growth and final yields. Here, early heat waves over Italy from 1995 to 2013 are identified and characterised and their impact on durum wheat yields is investigated. As expected, results confirm the impact of the 2003 heat wave and highlight a high percentage of concurrence of early heat waves and significant negative yield anomalies in 13 out of 39 durum wheat production areas. In south-eastern Italy (the most important area for durum wheat production), the percentage of concurrent events exceeds 80%.JRC.H.4-Monitoring Agricultural Resource

Normal form decomposition for Gaussian-to-Gaussian superoperators

In this paper we explore the set of linear maps sending the set of quantum Gaussian states into itself. These maps are in general not positive, a feature which can be exploited as a test to check whether a given quantum state belongs to the convex hull of Gaussian states (if one of the considered maps sends it into a non positive operator, the above state is certified not to belong to the set). Generalizing a result known to be valid under the assumption of complete positivity, we provide a characterization of these Gaussian-to-Gaussian (not necessarily positive) superoperators in terms of their action on the characteristic function of the inputs. For the special case of one-mode mappings we also show that any Gaussian-to-Gaussian superoperator can be expressed as a concatenation of a phase-space dilatation, followed by the action of a completely positive Gaussian channel, possibly composed with a transposition. While a similar decomposition is shown to fail in the multi-mode scenario, we prove that it still holds at least under the further hypothesis of homogeneous action on the covariance matrix