We demonstrate a 64-pixel free-space-coupled array of superconducting nanowire single photon dete... more We demonstrate a 64-pixel free-space-coupled array of superconducting nanowire single photon detectors optimized for high detection efficiency in the near-infrared range. An integrated, readily scalable, multiplexed readout scheme is employed to reduce the number of readout lines to 16. The cryogenic, optical, and electronic packaging to read out the array, as well as characterization measurements are discussed.
We demonstrate high-efficiency superconducting nanowire single-photon detectors (SNSPDs) fabricat... more We demonstrate high-efficiency superconducting nanowire single-photon detectors (SNSPDs) fabricated from MoSi thin-films. We measure a maximum system detection efficiency (SDE) of 87 ± 0.5 % at 1542 nm at a temperature of 0.7 K, with a jitter of 76 ps, maximum count rate approaching 10 MHz, and polarization dependence as low as 3.4 ± 0.7 % The SDE curves show saturation of the internal efficiency similar to WSi-based SNSPDs at temperatures as high as 2.3 K. We show that at similar cryogenic temperatures, MoSi SNSPDs achieve efficiencies comparable to WSi-based SNSPDs with nearly a factor of two reduction in jitter.
We describe a kinetic model of recombination of non-equilibrium quasiparticles generated by singl... more We describe a kinetic model of recombination of non-equilibrium quasiparticles generated by single photon absorption in superconducting current-carrying nanowires. The model is developed to interpret two-photon detection experiments in which a single photon does not possess sufficient energy for breaking superconductivity at a fixed low bias current. We show that quasiparticle selfrecombination in relaxing hotspots dominates diffusion expansion effects and explains the observed strong bias current, wavelength and temperature dependencies of hotspot relaxation in tungsten silicide superconducting nanowire single-photon detectors.
ABSTRACT We measure a saturation of the internal quantum efficiency of superconducting nanowire s... more ABSTRACT We measure a saturation of the internal quantum efficiency of superconducting nanowire single-photon detectors based on a Mo0.75Ge0.25 alloy with peak system detection efficiency of 30%.
We present the characteristics of superconducting nanowire single photon detectors (SNSPDs) fabri... more We present the characteristics of superconducting nanowire single photon detectors (SNSPDs) fabricated from amorphous Mo 0.75 Ge 0.25 thin-films. Fabricated devices show a saturation of the internal detection efficiency at temperatures below 1 K, with system dark count rates below 500 counts per second. Operation in a Gifford-McMahon (GM) cryocooler at 2.5 K is possible with system detection efficiencies (SDE) exceeding 20% for SNSPDs which have not been optimized for high detection efficiency.
Improvements in temporal resolution of single photon detectors enable increased data rates and tr... more Improvements in temporal resolution of single photon detectors enable increased data rates and transmission distances for both classical and quantum optical communication systems, higher spatial resolution in laser ranging, and observation of shorter-lived fluorophores in biomedical imaging. In recent years, superconducting nanowire single-photon detectors (SNSPDs) have emerged as the most efficient, time-resolving single-photon counting detectors available in the near infrared, but understanding of the fundamental limits of timing resolution in these devices has been limited due to a lack investigations into the time scales involved in the detection process. We introduce an experimental technique to probe the detection latency in SNSPDs and show that the key to achieving low timing jitter is the use of materials with low latency. By using a specialised niobium nitride (NbN) SNSPD we demonstrate that the system temporal resolution can be as good as 2.6±0.2 ps for visible wavelengths and 4.3±0.2 ps at 1550 nm.
Superconducting transition-edge sensors (TES) are sensitive microcalorimeters used as photon dete... more Superconducting transition-edge sensors (TES) are sensitive microcalorimeters used as photon detectors with unparalleled energy resolution. They have found applications from measuring astronomical spectra through to determining the quantum property of photon-number,n=â †â , for energies from 0.6-2.33 eV. However, achieving optimal energy resolution requires considerable data acquisition-on the order of 1 GB/min-followed by post-processing, preventing real-time access to energy information. We report a custom hardware processor to process TES pulses while new detection events are still being registered, allowing the photon-number to be measured in real time. We resolve photonnumber up to n=16-achieving up to partsper-billion discrimination for low photonnumbers on the fly-providing transformational capacity for TES applications from astronomy to quantum technology.
ABSTRACT Since the first reported detection of a single photon using a superconducting nanowire i... more ABSTRACT Since the first reported detection of a single photon using a superconducting nanowire in 2001, rapid progress has been made in the development and application of superconducting nanowire single photon detectors (SNSPD or SSPD). I will briefly describe use of these detectors in new applications, progress in detector developments, and describe areas of research and their potential impact.
Rochester Conference on Coherence and Quantum Optics (CQO-11), 2019
We present a fiber-coupled single-photon detector with 98% system detection efficiencies at 1550 ... more We present a fiber-coupled single-photon detector with 98% system detection efficiencies at 1550 nm. We characterize beam divergence within the optical stack and the electronic compensations required for large-active-area detectors.
We developed superconducting nanowire single-photon detectors based on tungsten silicide, which s... more We developed superconducting nanowire single-photon detectors based on tungsten silicide, which show saturated internal detection efficiency up to a wavelength of 10 μm. These detectors are promising for applications in the mid-infrared requiring sub-nanosecond timing, ultra-high gain stability, low dark counts, and high efficiency, such as chemical sensing, LIDAR, dark matter searches, and exoplanet spectroscopy.
We experimentally studied the dynamics of optically excited hotspots in current-carrying WSi supe... more We experimentally studied the dynamics of optically excited hotspots in current-carrying WSi superconducting nanowires as a function of bias current, bath temperature and excitation wavelength. We observed that the hotspot relaxation time depends on bias current, temperature, and wavelength. We explained this effect with a model based on quasi-particle recombination, which provides insight into the quasiparticle dynamics of superconductors. I. INTRODUCTION When a photon is absorbed in a superconductor, it creates a non-equilibrium region referred to as a hotspot 1. The optical excitation of hotspots underpins the operation of most superconducting single photon detectors, such as microwave kinetic inductance detectors (MKIDs) 2, 3 , superconducting tunnel junctions (STJs) 4 , and superconducting nanowire single-photon detectors (SNSPDs) 5, 6. The microscopic description of hotspot dynamics is a complicated, long-standing problem in non-equilibrium superconductivity 1. If hotspot dynamics were better understood and controlled, many of the current limitations of these detectors could be overcome, potentially enabling disruptive technological advances. Here we report a combined experimental and theoretical study of hotspots excited by single photons in a current-carrying WSi superconducting nanowire. We measured the hotspot relaxation dynamics in the nanowires as a function of bias current, bath temperature, and excitation wavelength. We observed that: (1) hotspot relaxation depends on the current carried by the nanowires; and (2) the current dependence of the relaxation time changes with bath temperature and excitation wavelength. The agreement between theory and experiment 2 Copyright 2015. All rights reserved. provides insight into the quasiparticle dynamics of superconductors and the photodetection mechanism of superconducting single-photon detectors. Hotspot formation is initiated when one photon is absorbed in a thin superconducting film, creating a non-equilibrium distribution of quasiparticles (QPs). The excited QPs down-convert from higher-energy states by exchanging energy with the electron and phonon systems. During the decay, further Cooper pairs are broken, increasing the number of QPs 1, 7. Previously, the relaxation of optically excited superconductors was studied with optical and THz pump-probe techniques 8-10. These techniques offer sub-ps time resolution, but are not sensitive enough to study the evolution of a single hotspot, and are difficult to perform below ~ 5 K. In this work, we used a different technique that combines the single-hotspot sensitivity of electrical readout with the high time resolution of ultrafast optical pump-probe spectroscopy 11, 12. II. ONE-AND TWO-PHOTON DETECTION REGIMES If an SNSPD produces a response pulse (or click) when a single photon creates a single hotspot, the detector operates in the single-photon detection regime, as shown in Figure 1 a. When the bias current is lowered to a point that a click can be efficiently triggered only if two photons generate two overlapping hotspots 5, 11, 13 , the SNSPD operates in the two-photon detection regime, as shown in Figure 1 b. The current ranges in which the detector operates in single-or two-photon detection regimes depend on operating temperature and excitation wavelength. Figure 1. a. Representation of the single-photon detection regime. The current-biased superconducting nanowire produces a response pulse when a single photon creates a single hotspot (in red). b. Representation of the two-photon detection regime. The nanowire, biased at a lower current, produces a response pulse when two photons generate two overlapping hotspots.
We present a loophole-free violation of local realism using entangled photon pairs. We ensure tha... more We present a loophole-free violation of local realism using entangled photon pairs. We ensure that all relevant events in our Bell test are spacelike separated by placing the parties far enough apart and by using fast random number generators and high-speed polarization measurements. A high-quality polarization-entangled source of photons, combined with high-efficiency, low-noise, single-photon detectors, allows us to make measurements without requiring any fair-sampling assumptions. Using a hypothesis test, we compute p values as small as 5.9×10^{-9} for our Bell violation while maintaining the spacelike separation of our events. We estimate the degree to which a local realistic system could predict our measurement choices. Accounting for this predictability, our smallest adjusted p value is 2.3×10^{-7}. We therefore reject the hypothesis that local realism governs our experiment.
Bulletin of the American Physical Society, Mar 19, 2013
We report progress toward the experimental realization of information-efficient quantum imaging, ... more We report progress toward the experimental realization of information-efficient quantum imaging, here at two bits per photon. A heralded single-photon source ($ g^{2}(0)< 0.08$) is used as the input to a 4x4 multiport interferometer, compactly implemented using both polarization and spatial degrees of freedom. The interferometer can be used to read out all 4 Hadamard phase codes with a single photon. We investigate the use of cavity-enhanced spontaneous parametric downconversion for the coherent source of heralded photons. ...
For photon-counting applications at ultraviolet wavelengths, there are currently no detectors tha... more For photon-counting applications at ultraviolet wavelengths, there are currently no detectors that combine high efficiency (> 50%), sub-nanosecond timing resolution, and sub-Hz dark count rates. Superconducting nanowire single-photon detectors (SNSPDs) have seen success over the past decade for photon-counting applications in the near-infrared, but little work has been done to optimize SNSPDs for wavelengths below 400 nm. Here, we describe the design, fabrication, and characterization of UV SNSPDs operating at wavelengths between 250 and 370 nm. The detectors have active areas up to 56 µm in diameter, 70-80% efficiency, timing resolution down to 60 ps FWHM, blindness to visible and infrared photons, and dark count rates of ∼ 0.25 counts/hr for a 56 µm diameter pixel. By using the amorphous superconductor MoSi, these UV SNSPDs are also able to operate at temperatures up to 4.2 K. These performance metrics make UV SNSPDs ideal for applications in trapped-ion quantum information processing, lidar studies of the upper atmosphere, UV fluorescent-lifetime imaging microscopy, and photon-starved UV astronomy.
Till J. Weinhold1, Devin H. Smith1, Geoff Gillett1, Marcelo P. de Almeida1, Cyril Branciard2, Ale... more Till J. Weinhold1, Devin H. Smith1, Geoff Gillett1, Marcelo P. de Almeida1, Cyril Branciard2, Alessandro Fedrizzi1, Adriana Lita3, Brice Calkins3, Thomas Gerrits3, Sae Woo Nam3, Andrew G. White1 1Centre for Engineered Quantum Systems and Centre for Quantum Computation and Communication Technology (Australian Research Council), School of Mathematics and Physics, University of Queensland, 4072 Brisbane, QLD, Australia 2School of Mathematics and Physics, University of Queensland, 4072 Brisbane, QLD, Australia 3National Institute of Standards and ...
Local realism is the worldview in which physical properties of objects exist independently of mea... more Local realism is the worldview in which physical properties of objects exist independently of measurement and where physical influences cannot travel faster than the speed of light. Bell's theorem states that this worldview is incompatible with the predictions of quantum mechanics, as is expressed in Bell's inequalities. Previous experiments convincingly supported the quantum predictions. Yet, every experiment requires assumptions that provide loopholes for a local realist explanation. Here, we report a Bell test that closes the most significant of these loopholes simultaneously. Using a well-optimized source of entangled photons, rapid setting generation, and highly efficient superconducting detectors, we observe a violation of a Bell inequality with high statistical significance. The purely statistical probability of our results to occur under local realism does not exceed 3.74×10^{-31}, corresponding to an 11.5 standard deviation effect.
There is significant interest in the structure of metal thin films due to their wide application ... more There is significant interest in the structure of metal thin films due to their wide application as critical components in electronic, magnetic and optical devices. The functionality of these devices is determined by the films physical structure that includes surface morphology and in the case of polycrystalline films, grains size distribution and crystallographic orientation. Many processing schemes have been developed to control film microstructure and surface roughness in practice, however, they usually have limited application related to specific material systems or growth conditions. A comprehensive model for structure development that incorporate deposition conditions and substrate material properties is still lacking. This thesis goal is to further the present understanding on polycrystalline film structure development with an emphasis on the correlation between surface morphology and underlying microstructure evolution. The growth of polycrystalline thin films at different d...
We demonstrate a 64-pixel free-space-coupled array of superconducting nanowire single photon dete... more We demonstrate a 64-pixel free-space-coupled array of superconducting nanowire single photon detectors optimized for high detection efficiency in the near-infrared range. An integrated, readily scalable, multiplexed readout scheme is employed to reduce the number of readout lines to 16. The cryogenic, optical, and electronic packaging to read out the array, as well as characterization measurements are discussed.
We demonstrate high-efficiency superconducting nanowire single-photon detectors (SNSPDs) fabricat... more We demonstrate high-efficiency superconducting nanowire single-photon detectors (SNSPDs) fabricated from MoSi thin-films. We measure a maximum system detection efficiency (SDE) of 87 ± 0.5 % at 1542 nm at a temperature of 0.7 K, with a jitter of 76 ps, maximum count rate approaching 10 MHz, and polarization dependence as low as 3.4 ± 0.7 % The SDE curves show saturation of the internal efficiency similar to WSi-based SNSPDs at temperatures as high as 2.3 K. We show that at similar cryogenic temperatures, MoSi SNSPDs achieve efficiencies comparable to WSi-based SNSPDs with nearly a factor of two reduction in jitter.
We describe a kinetic model of recombination of non-equilibrium quasiparticles generated by singl... more We describe a kinetic model of recombination of non-equilibrium quasiparticles generated by single photon absorption in superconducting current-carrying nanowires. The model is developed to interpret two-photon detection experiments in which a single photon does not possess sufficient energy for breaking superconductivity at a fixed low bias current. We show that quasiparticle selfrecombination in relaxing hotspots dominates diffusion expansion effects and explains the observed strong bias current, wavelength and temperature dependencies of hotspot relaxation in tungsten silicide superconducting nanowire single-photon detectors.
ABSTRACT We measure a saturation of the internal quantum efficiency of superconducting nanowire s... more ABSTRACT We measure a saturation of the internal quantum efficiency of superconducting nanowire single-photon detectors based on a Mo0.75Ge0.25 alloy with peak system detection efficiency of 30%.
We present the characteristics of superconducting nanowire single photon detectors (SNSPDs) fabri... more We present the characteristics of superconducting nanowire single photon detectors (SNSPDs) fabricated from amorphous Mo 0.75 Ge 0.25 thin-films. Fabricated devices show a saturation of the internal detection efficiency at temperatures below 1 K, with system dark count rates below 500 counts per second. Operation in a Gifford-McMahon (GM) cryocooler at 2.5 K is possible with system detection efficiencies (SDE) exceeding 20% for SNSPDs which have not been optimized for high detection efficiency.
Improvements in temporal resolution of single photon detectors enable increased data rates and tr... more Improvements in temporal resolution of single photon detectors enable increased data rates and transmission distances for both classical and quantum optical communication systems, higher spatial resolution in laser ranging, and observation of shorter-lived fluorophores in biomedical imaging. In recent years, superconducting nanowire single-photon detectors (SNSPDs) have emerged as the most efficient, time-resolving single-photon counting detectors available in the near infrared, but understanding of the fundamental limits of timing resolution in these devices has been limited due to a lack investigations into the time scales involved in the detection process. We introduce an experimental technique to probe the detection latency in SNSPDs and show that the key to achieving low timing jitter is the use of materials with low latency. By using a specialised niobium nitride (NbN) SNSPD we demonstrate that the system temporal resolution can be as good as 2.6±0.2 ps for visible wavelengths and 4.3±0.2 ps at 1550 nm.
Superconducting transition-edge sensors (TES) are sensitive microcalorimeters used as photon dete... more Superconducting transition-edge sensors (TES) are sensitive microcalorimeters used as photon detectors with unparalleled energy resolution. They have found applications from measuring astronomical spectra through to determining the quantum property of photon-number,n=â †â , for energies from 0.6-2.33 eV. However, achieving optimal energy resolution requires considerable data acquisition-on the order of 1 GB/min-followed by post-processing, preventing real-time access to energy information. We report a custom hardware processor to process TES pulses while new detection events are still being registered, allowing the photon-number to be measured in real time. We resolve photonnumber up to n=16-achieving up to partsper-billion discrimination for low photonnumbers on the fly-providing transformational capacity for TES applications from astronomy to quantum technology.
ABSTRACT Since the first reported detection of a single photon using a superconducting nanowire i... more ABSTRACT Since the first reported detection of a single photon using a superconducting nanowire in 2001, rapid progress has been made in the development and application of superconducting nanowire single photon detectors (SNSPD or SSPD). I will briefly describe use of these detectors in new applications, progress in detector developments, and describe areas of research and their potential impact.
Rochester Conference on Coherence and Quantum Optics (CQO-11), 2019
We present a fiber-coupled single-photon detector with 98% system detection efficiencies at 1550 ... more We present a fiber-coupled single-photon detector with 98% system detection efficiencies at 1550 nm. We characterize beam divergence within the optical stack and the electronic compensations required for large-active-area detectors.
We developed superconducting nanowire single-photon detectors based on tungsten silicide, which s... more We developed superconducting nanowire single-photon detectors based on tungsten silicide, which show saturated internal detection efficiency up to a wavelength of 10 μm. These detectors are promising for applications in the mid-infrared requiring sub-nanosecond timing, ultra-high gain stability, low dark counts, and high efficiency, such as chemical sensing, LIDAR, dark matter searches, and exoplanet spectroscopy.
We experimentally studied the dynamics of optically excited hotspots in current-carrying WSi supe... more We experimentally studied the dynamics of optically excited hotspots in current-carrying WSi superconducting nanowires as a function of bias current, bath temperature and excitation wavelength. We observed that the hotspot relaxation time depends on bias current, temperature, and wavelength. We explained this effect with a model based on quasi-particle recombination, which provides insight into the quasiparticle dynamics of superconductors. I. INTRODUCTION When a photon is absorbed in a superconductor, it creates a non-equilibrium region referred to as a hotspot 1. The optical excitation of hotspots underpins the operation of most superconducting single photon detectors, such as microwave kinetic inductance detectors (MKIDs) 2, 3 , superconducting tunnel junctions (STJs) 4 , and superconducting nanowire single-photon detectors (SNSPDs) 5, 6. The microscopic description of hotspot dynamics is a complicated, long-standing problem in non-equilibrium superconductivity 1. If hotspot dynamics were better understood and controlled, many of the current limitations of these detectors could be overcome, potentially enabling disruptive technological advances. Here we report a combined experimental and theoretical study of hotspots excited by single photons in a current-carrying WSi superconducting nanowire. We measured the hotspot relaxation dynamics in the nanowires as a function of bias current, bath temperature, and excitation wavelength. We observed that: (1) hotspot relaxation depends on the current carried by the nanowires; and (2) the current dependence of the relaxation time changes with bath temperature and excitation wavelength. The agreement between theory and experiment 2 Copyright 2015. All rights reserved. provides insight into the quasiparticle dynamics of superconductors and the photodetection mechanism of superconducting single-photon detectors. Hotspot formation is initiated when one photon is absorbed in a thin superconducting film, creating a non-equilibrium distribution of quasiparticles (QPs). The excited QPs down-convert from higher-energy states by exchanging energy with the electron and phonon systems. During the decay, further Cooper pairs are broken, increasing the number of QPs 1, 7. Previously, the relaxation of optically excited superconductors was studied with optical and THz pump-probe techniques 8-10. These techniques offer sub-ps time resolution, but are not sensitive enough to study the evolution of a single hotspot, and are difficult to perform below ~ 5 K. In this work, we used a different technique that combines the single-hotspot sensitivity of electrical readout with the high time resolution of ultrafast optical pump-probe spectroscopy 11, 12. II. ONE-AND TWO-PHOTON DETECTION REGIMES If an SNSPD produces a response pulse (or click) when a single photon creates a single hotspot, the detector operates in the single-photon detection regime, as shown in Figure 1 a. When the bias current is lowered to a point that a click can be efficiently triggered only if two photons generate two overlapping hotspots 5, 11, 13 , the SNSPD operates in the two-photon detection regime, as shown in Figure 1 b. The current ranges in which the detector operates in single-or two-photon detection regimes depend on operating temperature and excitation wavelength. Figure 1. a. Representation of the single-photon detection regime. The current-biased superconducting nanowire produces a response pulse when a single photon creates a single hotspot (in red). b. Representation of the two-photon detection regime. The nanowire, biased at a lower current, produces a response pulse when two photons generate two overlapping hotspots.
We present a loophole-free violation of local realism using entangled photon pairs. We ensure tha... more We present a loophole-free violation of local realism using entangled photon pairs. We ensure that all relevant events in our Bell test are spacelike separated by placing the parties far enough apart and by using fast random number generators and high-speed polarization measurements. A high-quality polarization-entangled source of photons, combined with high-efficiency, low-noise, single-photon detectors, allows us to make measurements without requiring any fair-sampling assumptions. Using a hypothesis test, we compute p values as small as 5.9×10^{-9} for our Bell violation while maintaining the spacelike separation of our events. We estimate the degree to which a local realistic system could predict our measurement choices. Accounting for this predictability, our smallest adjusted p value is 2.3×10^{-7}. We therefore reject the hypothesis that local realism governs our experiment.
Bulletin of the American Physical Society, Mar 19, 2013
We report progress toward the experimental realization of information-efficient quantum imaging, ... more We report progress toward the experimental realization of information-efficient quantum imaging, here at two bits per photon. A heralded single-photon source ($ g^{2}(0)< 0.08$) is used as the input to a 4x4 multiport interferometer, compactly implemented using both polarization and spatial degrees of freedom. The interferometer can be used to read out all 4 Hadamard phase codes with a single photon. We investigate the use of cavity-enhanced spontaneous parametric downconversion for the coherent source of heralded photons. ...
For photon-counting applications at ultraviolet wavelengths, there are currently no detectors tha... more For photon-counting applications at ultraviolet wavelengths, there are currently no detectors that combine high efficiency (> 50%), sub-nanosecond timing resolution, and sub-Hz dark count rates. Superconducting nanowire single-photon detectors (SNSPDs) have seen success over the past decade for photon-counting applications in the near-infrared, but little work has been done to optimize SNSPDs for wavelengths below 400 nm. Here, we describe the design, fabrication, and characterization of UV SNSPDs operating at wavelengths between 250 and 370 nm. The detectors have active areas up to 56 µm in diameter, 70-80% efficiency, timing resolution down to 60 ps FWHM, blindness to visible and infrared photons, and dark count rates of ∼ 0.25 counts/hr for a 56 µm diameter pixel. By using the amorphous superconductor MoSi, these UV SNSPDs are also able to operate at temperatures up to 4.2 K. These performance metrics make UV SNSPDs ideal for applications in trapped-ion quantum information processing, lidar studies of the upper atmosphere, UV fluorescent-lifetime imaging microscopy, and photon-starved UV astronomy.
Till J. Weinhold1, Devin H. Smith1, Geoff Gillett1, Marcelo P. de Almeida1, Cyril Branciard2, Ale... more Till J. Weinhold1, Devin H. Smith1, Geoff Gillett1, Marcelo P. de Almeida1, Cyril Branciard2, Alessandro Fedrizzi1, Adriana Lita3, Brice Calkins3, Thomas Gerrits3, Sae Woo Nam3, Andrew G. White1 1Centre for Engineered Quantum Systems and Centre for Quantum Computation and Communication Technology (Australian Research Council), School of Mathematics and Physics, University of Queensland, 4072 Brisbane, QLD, Australia 2School of Mathematics and Physics, University of Queensland, 4072 Brisbane, QLD, Australia 3National Institute of Standards and ...
Local realism is the worldview in which physical properties of objects exist independently of mea... more Local realism is the worldview in which physical properties of objects exist independently of measurement and where physical influences cannot travel faster than the speed of light. Bell's theorem states that this worldview is incompatible with the predictions of quantum mechanics, as is expressed in Bell's inequalities. Previous experiments convincingly supported the quantum predictions. Yet, every experiment requires assumptions that provide loopholes for a local realist explanation. Here, we report a Bell test that closes the most significant of these loopholes simultaneously. Using a well-optimized source of entangled photons, rapid setting generation, and highly efficient superconducting detectors, we observe a violation of a Bell inequality with high statistical significance. The purely statistical probability of our results to occur under local realism does not exceed 3.74×10^{-31}, corresponding to an 11.5 standard deviation effect.
There is significant interest in the structure of metal thin films due to their wide application ... more There is significant interest in the structure of metal thin films due to their wide application as critical components in electronic, magnetic and optical devices. The functionality of these devices is determined by the films physical structure that includes surface morphology and in the case of polycrystalline films, grains size distribution and crystallographic orientation. Many processing schemes have been developed to control film microstructure and surface roughness in practice, however, they usually have limited application related to specific material systems or growth conditions. A comprehensive model for structure development that incorporate deposition conditions and substrate material properties is still lacking. This thesis goal is to further the present understanding on polycrystalline film structure development with an emphasis on the correlation between surface morphology and underlying microstructure evolution. The growth of polycrystalline thin films at different d...
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Papers by Adriana Lita