Showing papers by "Jeffrey H. Shapiro published in 2010"

Ghost imaging: from quantum to classical to computational

Abstract: Ghost-imaging experiments correlate the outputs from two photodetectors: a high-spatial-resolution (scanning pinhole or CCD array) detector that measures a field that has not interacted with the object to be imaged, and a bucket (single-pixel) detector that collects a field that has interacted with the object. We give a comprehensive review of ghost imaging—within a unified Gaussian-state framework—presenting detailed analyses of its resolution, field of view, image contrast, and signal-to-noise ratio behavior. We consider three classes of illumination: thermal-state (classical), biphoton-state (quantum), and classical-state phase-sensitive light. The first two have been employed in a variety of ghost-imaging demonstrations. The third is the classical Gaussian state that produces ghost images that most closely mimic those obtained from biphoton illumination. The insights we develop lead naturally to a new, single-beam approach to ghost imaging, called computational ghost imaging, in which only the bucket detector is required. We provide quantitative results while simultaneously emphasizing the underlying physics of ghost imaging. The key to developing the latter understanding lies in the coherence behavior of a pair of Gaussian-state light beams with either phase-insensitive or phase-sensitive cross correlation.

Sub-Rayleigh imaging via N-photon detection.

Abstract: The Rayleigh diffraction bound sets the minimum separation for two point objects to be distinguishable in a conventional imaging system. We demonstrate sub-Rayleigh resolution by scanning a focused beam--in an arbitrary, object-covering pattern that is unknown to the imager--and using N-photon photodetection implemented with a single-photon avalanche detector array. Experiments show resolution improvement by a factor ∼(N-N(max))(½) beyond the Rayleigh bound, where N(max) is the maximum average detected photon number in the image, in good agreement with theory.

LADAR resolution improvement using receivers enhanced with squeezed-vacuum injection and phase-sensitive amplification

Abstract: The use of quantum resources—squeezed-vacuum injection (SVI) and noise-free phase-sensitive amplification (PSA)—at the receiver of a soft-aperture homodyne-detection LAser Detection And Ranging (LADAR) system is shown to afford significant improvement in the receiver's spatial resolution. This improvement originates from the potential for SVI to ameliorate the loss of high-spatial-frequency information about a target or target complex that is due to soft-aperture attenuation in the LADAR's entrance pupil, and the value of PSA in realizing that potential despite inefficiency in the LADAR's homodyne detection system. We show this improvement quantitatively by calculating lower error rates—in comparison with those of a standard homodyne detection system—for a one-target versus two-target hypothesis test. We also exhibit the effective signal-to-noise ratio (SNR) improvement provided by SVI and PSA in simulated imagery.

Experimental realization of phase-conjugate optical coherence tomography

Abstract: We demonstrate phase-conjugate optical coherence tomography (PC-OCT) using a classical source of phase-sensitive cross-correlated beams to achieve measurement improvements shared by quantum OCT (Q-OCT): a factor-of-2 enhancement in axial resolution and even-order dispersion cancellation. Compared with coincidence counting used in Q-OCT, PC-OCT employs standard photodetection that results in much faster data acquisitions. This work belongs to a new class of classical techniques inspired by quantum methods that have advantages once thought to be exclusively quantum mechanical.

Ghost Imaging in Reflection: Resolution, Contrast, and Signal-to-Noise Ratio

Abstract: United States. Army Research Office. Multidisciplinary University Research Initiative (Grant no. W911NF-05-1-0197)

Sub-Rayleigh Imaging via N-Photon Detection

Abstract: We demonstrate resolution enhancement beyond the Rayleigh diffraction limit using an N-photon detection strategy that is implemented with a single-photon imager. Experimental results are in good agreement with theory proposed by Giovannetti et al. [1].

Dispersion cancellation with phase-sensitive Gaussian-state light

Abstract: Franson's paradigm for nonlocal dispersion cancellation [J. D. Franson, Phys. Rev. A 45, 3126 (1992)] is studied using two kinds of jointly Gaussian-state signal and reference beams with phase-sensitive cross correlations. The first joint signal-reference state is nonclassical, with a phase-sensitive cross correlation that is at the ultimate quantum-mechanical limit. It models the outputs obtained from continuous-wave spontaneous parametric down-conversion. The second joint signal-reference state is classical--it has a proper P representation--with a phase-sensitive cross correlation that is at the limit set by classical physics. Using these states we show that a version of Franson's nonlocal dispersion cancellation configuration has essentially identical quantum and classical explanations except for the contrast obtained, which is much higher in the quantum case than it is in the classical case. This work bears on Franson's recent article [J. D. Franson, Phys. Rev. A 80, 032119 (2009)], which asserts that there is no classical explanation for all the features seen in quantum nonlocal dispersion cancellation.

Sub-Rayleigh imaging via N-photon detection

Abstract: We demonstrate resolution enhancement beyond the Rayleigh diffraction limit using an N-photon detection strategy that is implemented with a single-photon imager. Experimental results are in good agreement with theory proposed by Giovannetti et al. [1].

Optimal individual attack on BB84 quantum key distribution using single-photon two-qubit quantum logic

Abstract: We propose the use of single-photon two-qubit quantum logic to physically simulate the optimal individual attack on Bennett-Brassard 1984 quantum key distribution protocol.The experimental setup does not require a quantum memory due to the physical simulation character of the proposal.

Corrections to “The Quantum Theory of Optical Communications” [Nov/Dec 09 1547-1569]

Abstract: The author corrects errors made in the above titled paper (ibid., vol. 15, no. 6, pp. 1547-1569, Nov./Dec. 09), and withdraws the Note Added in Proof.

Dispersion cancellation with phase-sensitive Gaussian-state light

Abstract: Gaussian-state phase-sensitive light is used to explain Franson's nonlocal dispersion cancellation [Phys. Rev. A 45, 3126 (1982)]. It is shown that entanglement is only needed to achieve high contrast.

Quantum Illumination for Improved Detection, Imaging, and Communication

Abstract: Quantum illumination transmits part of an entangled state, retaining the rest for subsequent joint measurement in detection, imaging, or communication It outperforms classical-state systems of the same average transmitted energy over entanglement-breaking channels