Ghost Imaging Experiments Research Articles

Quantum deep generative prior with programmable quantum circuits

Exploiting the utility of near-term quantum devices is a long-standing challenge whereas hybrid quantum machine learning emerges as a promising candidate. Here we propose a quantum-enhanced deep generative algorithm based on programmable quantum circuit-induced quantum latent codes. To validate the effectiveness of the algorithm, we conduct optical ghost imaging experiments, collecting dataset under varying physical sampling rates. Leveraging a physically enhanced loss function and a pretrained neural network, the quantum algorithm exhibits superior reconstruction performance compared to conventional algorithms. We observe the learnable quantum latent space enhances the out-of-distribution generalization capability of the pretrained model. In the context of computer vision problems, numerical results indicate that quantum latent space can increase the generation diversity of the pretrained model. Furthermore, the algorithm outperforms classical counterparts, particularly in image inpainting and colorization, by a significant margin. Our study demonstrates the utility of hybrid quantum-classical algorithms in enhancing generalization capability, highlighting the potential of near-term quantum devices in large-scale generative artificial intelligence.

Emission Ghost Imaging: reconstruction with data augmentation.

Ghost Imaging enables 2D reconstruction of an object even though particles transmitted or emitted by the object of interest are detected with a single pixel detector without spatial resolution. This is possible because for the particular implementation of ghost imaging presented here, the incident beam is spatially modulated with a non-configurable attenuating mask whose orientation is varied (e.g. via transverse displacement or rotation) in the course of the ghost imaging experiment. Each orientation yields a distinct spatial pattern in the attenuated beam. In many cases, ghost imaging reconstructions can be dramatically improved by factoring the measurement matrix which consists of measured attenuated incident radiation for each of many orientations of the mask at each pixel to be reconstructed as the product of an orthonormal matrix and an upper triangular matrix provided that the number of orientations of the mask () is greater than or equal to the number of pixels () reconstructed. For the case, we present a data augmentation method that enables QR factorization of the measurement matrix. To suppress noise in the reconstruction, we determine the Moore-Penrose pseudoinverse of the measurement matrix with a truncated singular value decomposition approach. Since the resulting reconstruction is still noisy, we denoise it with the Adaptive Weights Smoothing method. In simulation experiments, our method outperforms a modification of an existing alternative orthogonalization method where rows of the measurement matrix are orthogonalized by the Gram-Schmidt method. We apply our ghost imaging methods to experimental X-ray fluorescence data acquired at Brookhaven National Laboratory.

All-digital quantum ghost imaging: tutorial

Quantum ghost imaging offers many advantages over classical imaging, including the ability to probe an object with one wavelength and record the image with another, while low photon fluxes offer the ability to probe objects with fewer photons, thereby avoiding photo-damage to light sensitive structures such as biological organisms. Progressively, ghost imaging has advanced from single-pixel scanning systems to two-dimensional (2D) digital projective masks, which offer a reduction in image reconstruction times through shorter integration times. In this tutorial, we describe the essential ingredients in an all-digital quantum ghost imaging experiment and guide the user on important considerations and choices to make, aided by practical examples of implementation. We showcase several image reconstruction algorithms using two different 2D projective mask types and discuss the utility of each. We additionally discuss a notable artifact of a specific reconstruction algorithm and projective mask combination and detail how this artifact can be used to retrieve an image signal heavily buried under artifacts. Finally, we end with a brief discussion on artificial intelligence (AI) and machine learning techniques used to reduce image reconstruction times. We believe that this tutorial will be a useful guide to those wishing to enter the field, as well as those already in the field who wish to introduce AI and machine learning to their toolbox.

Vortex Speckles with Customized Symmetry and Spatial Correlations

A family of optical speckles with propagation-invariant annular morphology are generated via a phase-only mask and free-space evolution, termed vortex speckles, for which phase design is inspired by the vortex beam's helical wave front carrying orbital angular momentum. Vortex beams' graceful symmetry (central and/or axial) can be naturally inherited into vortex speckles by adjusting the parity of the topological value $\ensuremath{\ell}$ and the consistency of the initial phase angle ${\ensuremath{\phi}}_{0}$. By sequentially imprinting such a series of phase profiles onto a spatial light modulator, the resultant stochastically fluctuating vortex speckles naturally constitute an annular pseudothermal light field, and the customized symmetry in intensity profiles leads to spatial correlations, which are exploited for Hanbury Brown and Twiss interferometry and beam-splitter-free lensless ghost imaging and diffraction experiments. Symmetric annular pseudothermal light also has diverse phase correlations, so in a proposed vortex self-interferometer, we can manipulate photon correlations (parity-induced anticorrelation) and observe intriguing correlation states (spatially varying photon correlation oscillations). This work not only presents a flexible light-source option for applications requiring ring-shaped speckle illumination, but it also paves the way for the customization of nontrivial classical correlation modes.

Circuit-Based Modular Implementation of Quantum Ghost Imaging

Efforts on enhancing the ghost imaging speed and quality are intensified when the debate around the nature of ghost imaging (quantum vs. classical) is suspended for a while. Accordingly, most of the studies these years in the field fall into the improvement regarding these two targets by utilizing the different imaging mediums. Nevertheless, back to the raging debate occurred but with different focus, to overcome the inherent difficulties in the classical imaging domain, if we are able to utilize the superiority that quantum information science offers us, the ghost imaging experiment may be implemented more practically. In this study, a quantum circuit implementation of ghost imaging experiment is proposed, where the speckle patterns and phase mask are encoded by utilizing the quantum representation of images. To do this, we formulated several quantum models, i.e. quantum accumulator, quantum multiplier, and quantum divider. We believe this study will provide a new impetus to explore the implementation of ghost imaging using quantum computing resources.

Ghost imaging with engineered quantum states by Hong–Ou–Mandel interference

Traditional ghost imaging experiments exploit position correlations between correlated states of light. These correlations occur directly in spontaneous parametric down-conversion, and in such a scenario, the two-photon state usually used for ghost imaging is symmetric. Here we perform ghost imaging using an anti-symmetric state, engineering the two-photon state symmetry by means of Hong–Ou–Mandel interference. We use both symmetric and anti-symmetric states and show that the ghost imaging setup configuration results in object-image rotations depending on the state selected. Further, the object and imaging arms employ spatial light modulators for the all-digital control of the projections, being able to dynamically change the measuring technique and the spatial properties of the states under study. Finally, we provide a detailed theory that explains the reported observations.

Sub-Rayleigh resolution ghost imaging by spatial low-pass filtering

A sub-Rayleigh resolution ghost imaging experiment is performed via post-detection spatial low-pass filtering of the instantaneous intensity. A super-resolution reconstructed image has been achieved, in which the spatial resolution can exceed the Rayleigh diffraction limit by more than a factor of two. The resolution depends on the filter threshold, and the Rayleigh limit can be exceeded for a wide choice of threshold values. The setup is simple and easy to implement, which is an advantage for practical applications.

Long-distance temporal quantum ghost imaging over optical fibers.

Since the first quantum ghost imaging (QGI) experiment in 1995, many QGI schemes have been put forward. However, the position-position or momentum-momentum correlation required in these QGI schemes cannot be distributed over optical fibers, which limits their large-scale geographical applications. In this paper, we propose and demonstrate a scheme for long-distance QGI utilizing frequency correlated photon pairs. In this scheme, the frequency correlation is transformed to the correlation between the illuminating position of one photon and the arrival time of the other photon, by which QGI can be realized in the time domain. Since frequency correlation can be preserved when the photon pairs are distributed over optical fibers, this scheme provides a way to realize long-distance QGI over large geographical scale. In the experiment, long-distance QGI over 50 km optical fibers has been demonstrated.

Ghost Imaging with High Visibility Using Classical Light Source**Supported by the National Basic Research Program of China under Grant No 2012CB921900, the National Natural Science Foundation of China under Grant Nos 11534006, 11274183 and 11374166, and the National Scientific Instrument and Equipment Development Project under Grant No 2012YQ17004.

We experimentally demonstrate a novel ghost imaging experiment utilizing a classical light source, capable of resolving objects with a high visibility. The experimental results show that our scheme can indeed realize ghost imaging with high visibility for a relatively complicated object composed of three near-ellipse-shaped holes with different dimensions. In our experiment, the largest hole is ~36 times of the smallest one in area. Each of the three holes exhibits high-visibility in excess of 80%. The high visibility and high spatial-resolution advantages of this technique could have applications in remote sensing.

Spectral ensemble ghost imaging

In the last few years, the field of ghost imaging has seen many new developments. From computational ghost imaging to 3D gh.ost imaging, this field has shown many interesting applications. But the method of obtaining an image in ghost imaging experiments still requires data to be recorded over a long duration of time due to averaging over many shots of data. We propose a method to get the intensity correlated images in one shot by averaging over different wavelength components rather than different time components. We derive the maximum number of wavelength components that can be used for a given multi-wavelength source. The applicability of this scheme is finally verified by numerical simulations.

Space-Time Quantum Imaging

We report on an experimental and theoretical investigation of quantum imaging where the images are stored in both space and time. Ghost images of remote objects are produced with either one or two beams of chaotic laser light generated by a rotating ground glass and two sensors measuring the reference field and bucket field at different space-time points. We further observe that the ghost images translate depending on the time delay between the sensor measurements. The ghost imaging experiments are performed both with and without turbulence. A discussion of the physics of the space-time imaging is presented in terms of quantum nonlocal two-photon analysis to support the experimental results. The theoretical model includes certain phase factors of the rotating ground glass. These experiments demonstrated a means to investigate the time and space aspects of ghost imaging and showed that ghost imaging contains more information per measured photon than was previously recognized where multiple ghost images are stored within the same ghost imaging data sets. This suggests new pathways to explore quantum information stored not only in multi-photon coincidence information but also in time delayed multi-photon interference. The research is applicable to making enhanced space-time quantum images and videos of moving objects where the images are stored in both space and time.

High-resolution ghost imaging experiments with cosh-Gaussian modulated incoherent sources.

We experimentally demonstrate that ghost imaging (GI) quality can be significantly improved by modulating the incoherent Gaussian sources with hyperbolic cosine functions. In our experiments, a source with desired cosh-Gaussian intensity distribution can be generated by a programmable spatial light modulator, and is used in the GI setup to obtain high quality ghost images. The influences of the hyperbolic cosine parameter on the point-spread function and the GI quality have been investigated experimentally and interpreted theoretically. Our experimental results show that the resolution of ghost images can be obviously enhanced with cosh-Gaussian modulated incoherent sources. The kind of source-shaping technique proposed in this paper is a high-efficiency method to improve the GI quality and may be very useful for the GI applications.

三种不同结构的无透镜鬼成像实验研究

To achieve stand-off sensing applications, ghost imaging experiments with pseudothermal light were performed from transmissive to reflective cases. First, ghost images of a transmissive double-slit aperture were retrieved in a setup that both the reference beam and signal beam were collected with two different regions of a single CCD. Then a CCD and a separate bucket detector were used to record the light intensity information of the reference beam and the signal beam, respectively. By calculating the intensity correlation function of the signal beam with no spatial light distribution and the spatial dependent reference beam that does not interact with the object, ghost images of a transmissive object and a reflective object were achieved. In order to design and develop prototype systems field applicable, detailed experimental investigations were performed to compare the effect of system parameters on the quality of imaging in the transmission configuration. The results show that enough high power of light source, large sample numbers, and proper exposure time and spatial frequency bandwidth can lead to ghost image with good resolution and visibility.

Real-Time Data Acquisition for Long-Distance Reflective Ghost Imaging Experiment

We present a real-time data acquisition (DAQ) system for the long-distance reflective ghost imaging experiment which has broad application prospects in remote sensing. In the experimental setup, the light from a pseudo thermal light source is separated into signal beam and reference beam. The signal beam illuminates the target, and then the reflected light is collected by a bucket detector. In the mean time, the reference beam is directly captured by an area detector. In order to obtain the target image, the experiment requires high-speed and high-precision correlated data acquisition to collect the light intensity fluctuation in the signal beam and the reference beam. Furthermore, to reduce imaging time, real-time data acquisition is also required. The DAQ system consists of a photon-multiplier tube (PMT), a charge-coupled device (CCD) camera, a DAQ module and DAQ software. The CCD camera as the area detector connects to computer via Gigabit Ethernet. The PMT and a telescope compose the bucket detector which outputs signals to the DAQ module. The DAQ module sends acquired data to computer through universal serial bus (USB). The DAQ software collects the data and reconstructs the target image. The results of electronic tests and experiments show that the DAQ system satisfies the requirements of the experiment.

EPR-based ghost imaging using a single-photon-sensitive camera

Correlated photon imaging, popularly known as ghost imaging, is a technique whereby an image is formed from light that has never interacted with the object. In ghost imaging experiments, two correlated light fields are produced. One of these fields illuminates the object, and the other field is measured by a spatially resolving detector. In the quantum regime, these correlated light fields are produced by entangled photons created by spontaneous parametric down-conversion. To date, all correlated photon ghost imaging experiments have scanned a single-pixel detector through the field of view to obtain spatial information. However, scanning leads to poor sampling efficiency, which scales inversely with the number of pixels, N, in the image. In this work, we overcome this limitation by using a time-gated camera to record the single-photon events across the full scene. We obtain high-contrast images, 90%, in either the image plane or the far field of the photon pair source, taking advantage of the Einstein–Podolsky–Rosen-like correlations in position and momentum of the photon pairs. Our images contain a large number of modes, >500, creating opportunities in low-light-level imaging and in quantum information processing.

Forming positive-negative images using conditioned partial measurements from reference arm in ghost imaging

A recent thermal ghost imaging experiment implemented in Wu's group [Chin. Phys. Lett. 279, 074216 (2012)] showed that both positive and negative images can be constructed by applying a novel algorithm. This algorithm allows us to form the images with the use of partial measurements from the reference arm (even which never passes through the object), conditioned on the object arm. In this paper, we present a simple theory that explains the experimental observation and provides an in-depth understanding of conventional ghost imaging. In particular, we theoretically show that the visibility of formed images through such an algorithm is not bounded by the standard value 1/3. In fact, it can ideally grow up to unity (with reduced imaging quality). Thus, the algorithm described here not only offers an alternative way to decode spatial correlation of thermal light, but also mimics a "bandpass filter" to remove the constant background such that the visibility or imaging contrast is improved. We further show that conditioned on one still object present in the test arm, it is possible to construct the object's image by sampling the available reference data.

Response to “The physics of ghost imaging—nonlocal interference or local intensity fluctuation correlation?”

Shih has objected to the semiclassical explanation for lensless pseudothermal ghost imaging—whose measurement configuration is shown schematically in Fig. 8 of [1]—that is reviewed by Shapiro and Boyd. In Shih’s view, the only valid explanation for lensless pseudothermal ghost imaging is nonlocal two-photon interference, i.e., a purely quantum phenomenon. Shapiro and Boyd also develop that explanation for the lensless pseudothermal ghost image, where they show it to be equivalent, in its quantitative predictions, to the speckle-correlation interpretation arising from semiclassical photodetection theory. Thus, Sect. 1 of [1] concludes: “That the semiclassical and quantum theories yield identical measurements statistics in this case means that pseudothermal ghost-imaging experiments cannot distinguish between these two interpretations, even though we know that light is intrinsically quantum mechanical.” Shih begins by observing that Shapiro and Boyd fail to compare lensless pseudothermal ghost imaging of Scarcelli et al. [2], with the lens-based pseudothermal ghost

The physics of ghost imaging

Ghost images are obtained by correlating the output of a single-pixel (bucket) photodetector--which collects light that has been transmitted through or reflected from an object--with the output from a high spatial-resolution scanning photodetector or photodetector array whose illumination has not interacted with that object. The term "ghost image" is apt because neither detector's output alone can yield an image: the bucket detector has no spatial resolution, while the high spatial-resolution detector has not viewed the object. The first ghost imaging experiment relied on the entangled signal and idler outputs from a spontaneous parametric downconverter, and hence the image was interpreted as a quantum phenomenon. Subsequent theory and experiments showed, however, that classical correlations can be used to form ghost images. For example, ghost images can be formed with pseudothermal light, for which quantum mechanics is not required to characterize its photodetection statistics. This paper presents an overview of the physics of ghost imaging. It clarifies and unites two disparate interpretations of pseudothermal ghost imaging--two-photon interference and classical intensity-fluctuation correlations--that had previously been thought to be conflicting. It also reviews recent work on ghost imaging in reflection, ghost imaging through atmospheric turbulence, computational ghost imaging, and two-color ghost imaging.

Entangled-photon compressive ghost imaging

We have experimentally demonstrated high-resolution compressive ghost imaging at the single-photon level using entangled photons produced by a spontaneous parametric down-conversion source and using single-pixel detectors. For a given mean-squared error, the number of photons needed to reconstruct a two-dimensional image is found to be much smaller than that in quantum ghost imaging experiments employing a raster scan. This procedure not only shortens the data acquisition time, but also suggests a more economical use of photons for low-light-level and quantum image formation.

Theoretical analysis of quantum ghost imaging through turbulence

Atmospheric turbulence generally affects the resolution and visibility of an image in long-distance imaging. In a recent quantum ghost imaging experiment [P. B. Dixon et al., Phys. Rev. A 83, 051803 (2011)], it was found that the effect of the turbulence can nevertheless be mitigated under certain conditions. This paper gives a detailed theoretical analysis to the setup and results reported in the experiment. Entangled photons with a finite correlation area and a turbulence model beyond the phase screen approximation are considered.