This PDF file contains the front matter associated with SPIE Proceedings Volume 8875, including the Title Page, Copyright information, Table of Contents, Introduction (if any), and Conference Committee listing.

We report on an experimental demonstration of quantum imaging where the images are stored in both space and time. Quantum images of remote objects are produced with rotating ground glass induced chaotic laser light and two sensors measuring at different space-time points. Quantum images are observed to move depending on the time delay between the sensor measurements. The experiments provide a new testbed for exploring the time and space scale fundamental physics of quantum imaging and suggest new pathways for quantum information storage and processing. The moved quantum images are in fact new images that are stored in a space-time virtual memory process. The images are stored within the same quantum imaging data sets and thus quantum imaging can produce more information per photon measured than was previously realized.

The resolutions of the optical lithography is limited by the well-known Rayleigh limit. Although the atom lithography can generate features smaller than this limit, the spacing of the pattern is still limited by the optical wavelength. Here, we proposed two atom lithography methods, both of which used the coherent Rabi oscillation to break the diffraction limit. One is in the microwave regime where the Rydberg atom is used and micrometer resolution can be achieved. The other is in the optical regime where sub-10 nanometer resolution is possible.

We derive an approximation to the intensity covariance function of two scanning pinhole detectors, facing a distant source (e.g., a star) being occluded partially by an absorptive object (e.g., a planet). We focus on using this technique to identify or image an object that is in the line-of-sight between a well-characterized source and the detectors. We derive the observed perturbation to the intensity covariance map due to the object, showing that under some reasonable approximations it is proportional to the real part of the Fourier transform of the source’s photon-flux density times the Fourier transform of the object’s intensity absorption. We highlight the key parameters impacting its visibility and discuss the requirements for estimating object-related parameters, e.g., its size, velocity or shape. We consider an application of this result to determining the orbit inclination of an exoplanet orbiting a distant star. Finally, motivated by the intrinsically weak nature of the signature, we study its signal-to-noise ratio and determine the impact of system parameters.

Quantum entanglement is a critical resource for quantum information and quantum computation. However, entanglement of a quantum system is subjected to change due to the interaction with the environment. One typical result of the interaction is the amplitude damping that usually results in the reduction of the entanglement. Here we propose a protocol to protect quantum entanglement from the amplitude damping by applying Hadamard and CNOT gates. As opposed to some recently studied methods, the scheme presented here does not require weak measurement in the reversal process, leading to a faster recovery of entanglement. We propose a possible experimental implementation based on linear optical system.

We propose a scheme to generate polarization-entangled photon pairs by spontaneous parametric downconversion in a phase-modulated, type-II, quasi-phasematched (QPM) crystal. Instead of using two distinct crystals to generate |HV⟩and |VH⟩states, the phase-modulated QPM grating allows both states to be generated simultaneously in a distributed fashion throughout the nonlinear crystal. Temporal compensation is still needed to correct for effects of birefringence in the crystal. The distributed generation of the polarization-entangled photons is compared to generation using two sequential crystals.

The resolution of optical scanning microscopes is limited by the spot size of the scanning beam. It has been proposed by Boto1 et al. and Nasr2 et al. that momentum entangled photons can be focused more tightly than classical light. Thus they should enable one to break the di ractive resolution limit. We report experiments measuring the spatial distribution of strong focussed momentum entangled photon pairs at a center wavelength of 812 nm from a spontaneous parametric down conversion source. Using a single gold stripe deposited on a glass surface as test object we observe a two-photon spot size as small as 194 nm, thereby beating the di raction limit even for conventional two-photon microscopy.

The development of a non-invasive high resolving power quantum microscope would further advance progress in research and development in biomedical and biosciences as well as the field of medical technology. Longer wavelengths, i.e visible or near-infrared, provide less invasive impact. On the other hand shorter wavelengths, i.e. UV, can provide better resolving power. That is why the development of a non-invasive high resolving power quantum microscope is critical. In this article, we propose such a microscope by using two-color entangled photon ghost imaging technology.

The inverse of magnetic resonance imaging is used to develop a simple approach to super-resolution lithography that can write arbitrary patterns with high contrast. In this approach a thin layer of material that exhibits optically detected magnetic resonance (ODMR) is used to transfer 2D spatial information that has been encoded in spin sublevel populations of the ODMR material into an optical emission pattern that can expose photoresist. To create the pattern in spin sublevels, coherent excitation is performed using either microwave or radiofrequency fields in the presence of a controllable magnetic field gradient. To better illustrate the technique, a simulation is presented based on nitrogenvacancy (NV) color centers in diamond which is a popular room temperature ODMR material. In this simulation it is shown how a simple 2D pattern can be written using predefined optical and microwave pulses. The advantage to using this comparatively simple approach to super-resolution lithography is that more emphasis can be on solving the practical implementation issues rather than just striving to demonstrate the basic physics.

In recent years, we developed two very high speed single photon photometers, Aqueye and Iqueye, as prototypes for “quantum” photometers for the Extremely Large Telescopes of the next decade. These instruments, based on single photon avalanche photodiodes and a 4-fold split-pupil concept, have been successfully used to obtain data of the highest quality on optical pulsars. Subsequently, we performed an attempt to utilize the Orbital Angular Momentum and associated Optical Vorticity to achieve high performance stellar coronagraphy. Presently, we are making a synergic effort in building Aqueye Plus, a new instrument for the 1.8 m telescope of the Asiago - Cima Ekar Observatory, which combines both functions, namely high speed simultaneous multicolor photon counting photometry and stellar coronagraphy. The innovative capability of Aqueye Plus is to take advantage of the two parallel outputs (NIM and TTL) of the four high time accuracy photon counting sensors. The NIM output preserves the best timing capability, while the TTL output drives a deformable 32-element mirror in a sort of quadrant detector to correct for defocus and tip/tilt aberrations of the stellar image on the phase mask discontinuity. This paper describes the Aqueye Plus instrument main characteristics and its foreseen performance.

The connection between the boson sampling problem in a linear optical interferometer with single photon sources and the computation of matrix permanents has recently brought a strong interest for quantum computing applications. In this work we explore the physics of N-order interference in terms of N-order correlation functions in a generic linear optical interferometer with both Fock states sources and thermal sources. We will show how also in this case the connection of such a problem with matrix permanents play a fundamental role.

We present some Quantum Tomography related results recently obtained in the Quantum Optics labs of the National Institute of Metrological Research (INRIM). Initially we describe the first experimental implementation of a new protocol for the reconstruction of a photon-number-resolving (PNR) detector’s POVM (Positive Operator-Valued Measure): such a protocol, exploiting the strong quantum correlations of an ancillary state, results more robust and efficient than its classical counterparts. The second part of the paper focuses on the quantum characterization of a transition-edge sensor (TES) based PNR detector, i.e. the experimental tomography of the POVM of a TES, with a method based on a quorum of coherent probes: we show the reconstruction of the POVM elements up to 11 detected photons and 100 incoming photons, demonstrating the linearity of such a device. Finally, we present a method for the experimental reconstruction of the modal structure of multimode optical fields exploiting a single measurement of higher-order photon number autocorrelation functions. We show our reconstructions of up to three different modes per optical state, demonstrating the excellent agreement with the theoretical predictions and the robustness of our method itself.

Decoherence, which causes degradation of entanglement and in some cases entanglement sudden death, is a critical issue faced in quantum information. Protecting entanglement from decoherence, therefore, is essential in practical realization of quantum computing and quantum communication protocols. In this paper, we demonstrate a novel method to protect entanglement from amplitude damping decoherence via weak measurement and quantum measurement reversal. It is shown that even entanglement sudden death can be circumvented.

Until recently, it was believed that long-lived quantum memories were necessary for long-distance quantum communication. However, by using error-correction codes in an efficient way—specifically, by correcting for photon loss—it is possible to transmit quantum information over long distances without quantum memories. For quantum computation, recent architectures for topological quantum computation indicate that the simplest large-scale structure could be memory-less. While a quantum memory may no longer be an essential resource for quantum networks, it could nonetheless be a key device in the development of quantum information technology. However, it is still not clear what benefits a functioning device could bring to quantum information systems, largely due to a lack of detailed models. Recently we have developed a detailed model for a quantum network based on a simple device designed to act as a building block for a full system architecture. The device is based on an optical cavity containing a negatively charged nitrogen-vacancy center in diamond. This model naturally integrates quantum communication with computation, and using this model we can assess quantitatively the costs and benefits of quantum memories. With or without quantum memories, it is necessary for us to preserve quantum information for a long period of time in either communication or computation.

Hybrid quantum systems can be formed that combine the strengths of multiple platforms while avoiding the weaknesses. Here we report on progress toward a hybrid quantum system of neutral atom spins coupled to superconducting qubits. We trap laser-cooled rubidium atoms in the evanescent field of an ultrathin optical fiber, which will be suspended a few microns above a superconducting circuit that resonates at the hyperfine frequency of the Rb atoms, allowing magnetic coupling between the atoms and superconductor. As this will be done in a dilution refrigerator environment, the technical demands on the optical fiber is severe. We have developed and optimized a tapered fiber fabrication system, achieving optical transmission in excess of 99.95% , and fibers that can sustain 400 mW of optical power in a UHV environment. We have also optimized tapered fibers that can support higher order optical modes with high transmission (> 97%), which may be useful for different optical potential geometries. We have developed an in-situ tunable high-Q superconducting microwave resonator that can be tuned to within the resonator linewidth of the 6.8 GHz frequency of the Rb hyperfine transition.

The shot noise limit is a fundamental lower limit on the sensitivity of any measurement and is de ned by nature. We propose an experiment in which we measure the di erence current from each heterodyne detector and nd that the result is a sinusoidal function of the path length di erence between the the two heterodyne systems. For certain values of the path length, we expect to overcome the shot noise limit set by the local oscillator. Here we review our experiment and report on the current experimental progress.

It has been reported that error-free quantum reading of a classical digital memory is possible when the entangled coherent state |a〉 |a〉– |– a〉|–a〉 is used as the probe state for quantum reading with binary phase shift keying format under the assumption that the channel is noiseless [quant-ph/1108.4163v2]. In this paper, the theoretical performance limits of the minimum error probability and classical capacity of quantum reading with binary phase shift keying entangled coherent state signal are investigated in the presence of channel loss.

We show how to extend the paradigm of software-de ned communication to include quantum communication systems. We introduce the decomposition of a quantum communication terminal into layers separating the concerns of the hardware, software, and middleware. We provide detailed descriptions of how each component operates and we include results of an implementation of the super-dense coding protocol. We argue that the versatility of software-de ned quantum communication test beds can be useful for exploring new regimes in communication and rapidly prototyping new systems.

This paper introduces an m-ary version of the Three-stage Quantum Cryptography protocol. The three-stage protocol was first proposed in 2006 and implemented in 2012. The m-ary version of the three-stage protocol proposed in this paper results in enhanced data transfer between a sender Alice and a receiver Bob since each pulse carries more than one bit of information. An experimental realization of the m-ary three-stage protocol is also reported in this paper. The implementation has used free-space optics as the transmission medium and passive optical components controlled through LabView. Furthermore, analytical results that address the impact of the noise factor and its trade-off with data rate are presented. This analysis includes a study of the probability of errors and channel capacity variations in terms of the noise variance factor for the m-ary three-stage protocol using two, four and eight levels. Limits within which the m-ary three-stage protocol can be used with higher performance efficiency compared to its original version counterpart are set.

The development of quantum networks requires stable quantum bits with which we can process, store and transport quantum information. A significant bottleneck in their performance is the ability to perform reliable local gates. It is well known that superconducting flux qubits have excellent processing ability while electron-spin nitrogen-vacancy centers in diamond are a natural memory and optical interface. Hybridization of these two systems thus presents the promise of an effective and efficient way to perform local gates. Here we report on the first step towards this: quantum state transfer between these systems.

Optical and paramagnetic deep defects in silicon carbide (SiC) offer a vast opportunity to realize advanced quantum device and sensors based on SiC bulk material and SiC nanostructures. Nanostructures in silicon carbide such as nanoparticle and quantum dots possess strong sub-bandgap emission due to both quantum confinement and radiative recombination in deep defects, making them ideal as bio-markers. We will highlight silicon carbide extremely rich underlying resources, ideal for the implementation of next generation nanophotonics and spintronics quantum devices and related biomedical applications. Specifically, we show here the isolation of intrinsic defects in SiC achieved by electron irradiation of the material, yielding single photon emission.

We define an Asymmetric Partially Polarizing Beam Splitter (APPBS) to be a linear optical component having different reflectivity (transmittance) coefficients, on the upper and the lower arms, for horizontally and vertically Polarized incident photons. Our CNOT model is composed by two APPBSs, one Half Wave Plate (HWP), two Polarizing Beam Splitters (PBSs), a Beam Splitter (BS) and a -phase rotator for specific wavelength. Control qubit operates with dual rail encoding while target qubit is based on polarization encoding. To perform CNOT operation in 4/27 of the cases, input and target incoming photons are injected with different wavelengths.

We experimentally demonstrate turbulence-free space-time quantum imaging. Quantum images of remote objects are produced with two sensors measuring at different space-time points under turbulent conditions. The quantum images generated move depending on the time delay between the two sensor measurements and the speed of a rotating ground glass that is part of a chaotic laser light source. For small delay times turbulence has virtually no adverse affect on the moving quantum images. The experimental setup and findings contribute to understanding the fundamentals of multi-photon quantum interference in complex media. Furthermore, the space-time memory demonstrated in our research provides important new pathways for investigating quantum imaging, quantum information storage and quantum computing. The turbulence-free space-time quantum imaging procedure greatly increases the information content of each photon measured. The moved quantum images are in fact new images that are stored in a space-time virtual memory process. The images are stored within the same quantum imaging data sets and thus quantum imaging can produce more information per photon measured than was previously realized.