Anomalous Weak Values and the Violation of a Multiple-measurement Leggett-Garg Inequality

Quantum mechanics presents peculiar properties that, on the one hand, have been the subject of several theoretical and experimental studies about its very foundations and, on the other hand, provide tools for developing new technologies, the so-called quantum technologies. The nonclassicality pointed out by Leggett-Garg inequalities has represented, with Bell inequalities, one of the most investigated subject. In this letter we study the connection of Leggett-Garg inequalities with a new emerging field of quantum measurement, the weak values. In particular, we perform an experimental study of the four-time correlators Legget-Garg test, by exploiting single and sequential weak measurements performed on heralded single photons. We show violation of a four-parameters Leggett-Garg inequality in different experimental conditions, demonstrating an interesting connection between Leggett-Garg inequality violation and anomalous weak values

Enhanced single-photon time-of-flight 3D ranging

We developed a system for acquiring 3D depth-resolved maps by measuring the Time-of-Flight (TOF) of single photons. It is based on a CMOS 32 × 32 array of Single-Photon Avalanche Diodes (SPADs) and 350 ps resolution Time-to-Digital Converters (TDCs) into each pixel, able to provide photon-counting or photon-timing frames every 10 μs. We show how such a system can be used to scan large scenes in just hundreds of milliseconds. Moreover, we show how to exploit TDC unwarping and refolding for improving signal-to-noise ratio and extending the full-scale depth range. Additionally, we merged 2D and 3D information in a single image, for easing object recognition and tracking

High linearity SPAD and TDC array for TCSPC and 3D ranging applications

An array of 32x32 Single-Photon Avalanche-Diodes (SPADs) and Time-to-Digital Converters (TDCs) has been fabricated in a 0.35 mu m automotive-certified CMOS technology. The overall dimension of the chip is 9x9 mm(2). Each pixel is able to detect photons in the 300 nm - 900 nm wavelength range with a fill-factor of 3.14% and either to count them or to time stamp their arrival time. In photon-counting mode an in-pixel 6-bit counter provides photon-number-resolved intensity movies at 100 kfps, whereas in photon-timing mode the 10-bit in-pixel TDC provides time-resolved maps (Time-Correlated Single-Photon Counting measurements) or 3D depth-resolved (through direct time-of-flight technique) images and movies, with 312 ps resolution. The photodetector is a 30 mu m diameter SPAD with low Dark Count Rate (120 cps at room temperature, 3% hot-pixels) and 55% peak Photon Detection Efficiency (PDE) at 450 nm. The TDC has a 6-bit counter and a 4-bit fine interpolator, based on a Delay Locked Loop (DLL) line, which makes the TDC insensitive to process, voltage, and temperature drifts. The implemented sliding-scale technique improves linearity, giving 2% LSB DNL and 10% LSB INL. The single-shot precision is 260 ps rms, comprising SPAD, TDC and driving board jitter. Both optical and electrical crosstalk among SPADs and TDCs are negligible. 2D fast movies and 3D reconstructions with centimeter resolution are reported

Gated SPAD Arrays for Single-Photon Time-Resolved Imaging and Spectroscopy

In this paper, we present the architecture and the experimental characterization of an improved version of a previously developed 32 × 32 Single Photon Avalanche Diodes (SPADs) and Time to Digital Converters (TDCs) array, and two new arrays (with 8 × 8 and 128 × 1 pixels) with the additional capability of actively gating the detectors with sub-nanosecond rise time. The arrays include high performance SPADs (0.04 cps/μm2, 50% peak PDE) and provide down to 410 ps Full-Width at Half-Maximum (FWHM) single shot precision and excellent linearity. We developed a camera to exploit these imagers in time-resolved, single-photon applications

Photon-efficient imaging with a single-photon camera

Reconstructing a scene’s 3D structure and reflectivity accurately with an active imaging system operating in low-light-level conditions has wide-ranging applications, spanning biological imaging to remote sensing. Here we propose and experimentally demonstrate a depth and reflectivity imaging system with a single-photon camera that generates high-quality images from ∼1 detected signal photon per pixel. Previous achievements of similar photon efficiency have been with conventional raster-scanning data collection using single-pixel photon counters capable of ∼10-ps time tagging. In contrast, our camera’s detector array requires highly parallelized time-to-digital conversions with photon time-tagging accuracy limited to ∼ns. Thus, we develop an array-specific algorithm that converts coarsely time-binned photon detections to highly accurate scene depth and reflectivity by exploiting both the transverse smoothness and longitudinal sparsity of natural scenes. By overcoming the coarse time resolution of the array, our framework uniquely achieves high photon efficiency in a relatively short acquisition time.National Science Foundation (U.S.) (1161413)National Science Foundation (U.S.) (1422034)Lincoln LaboratorySamsung (Firm

Investigating the Effects of the Interaction Intensity in a Weak Measurement

Measurements are crucial in quantum mechanics, for fundamental research as well as for applicative fields like quantum metrology, quantum-enhanced measurements and other quantum technologies. In the recent years, weak-interaction-based protocols like Weak Measurements and Protective Measurements have been experimentally realized, showing peculiar features leading to surprising advantages in several different applications. In this work we analyze the validity range for such measurement protocols, that is, how the interaction strength affects the weak value extraction, by measuring different polarization weak values on heralded single photons. We show that, even in the weak interaction regime, the coupling intensity limits the range of weak values achievable, setting a threshold on the signal amplification effect exploited in many weak measurement based experiments

Determining the Quantum Expectation Value by Measuring a Single Photon

Quantum mechanics, one of the keystones of modern physics, exhibits several peculiar properties, differentiating it from classical mechanics. One of the most intriguing is that variables might not have definite values. A complete quantum description provides only probabilities for obtaining various eigenvalues of a quantum variable. These and corresponding probabilities specify the expectation value of a physical observable, which is known to be a statistical property of an ensemble of quantum systems. In contrast to this paradigm, we demonstrate a unique method allowing to measure the expectation value of a physical variable on a single particle, namely, the polarisation of a single protected photon. This is the first realisation of quantum protective measurements.Comment: Nature Physics, in press (this version corresponds to the one initially submitted to Nature Physics

DISTANCE MEASURING DEVICE AND DISTANCE MEASURING METHOD

A distance measuring device includes a light emission portion for emitting light; a light receiving portion for receiving measurement light that is emitted by the light emission portion and reflected by a measurement object, the light receiving portion comprising a plurality of pixels, each pixel having at least one light receiving portion and outputting a light reception signal that depends on the measurement light incident on the pixel; a discrimination portion for discriminating whether the pixel receives measurement light; a pixel output control portion for selectively outputting the light reception signal of each pixel individually, depending on the determination result of the discrimination portion; and an evaluation portion for receiving the light reception signals output by the pixel output control portion and outputting a distance signal that is indicative of a distance between the measuring device and the measurement object based on these light reception signals

DISTANCE MEASURING DEVICE

A distance measuring device includes a light emission portion configured to emit light; a light receiving portion configured to receive measurement light that is emitted by the light emission portion and reflected by the measurement object, the light receiving portion comprising a plurality of pixels configured to output light reception signals that depend on the received measurement light; a plurality of determination portions configured to receive the light reception signals and to determine characteristic values from the received light reception signals, and an evaluation portion that is connected to the plurality of determination portions, the evaluation portion being configured to calculate a distance from the characteristic values determined by the determination portions. Each of the plurality of determination portions is configured to receive the light reception signals only from a plurality of non-adjacent pixels