Automated detection of orbital angular momentum (OAM) can tremendously contribute to quantum optical experiments. We develop convolutional neural networks to identify and classify noisy images of Laguerre–Gaussian (LG) modes collected from two different experimental set ups. We investigate the classification performance measures of the predictive classification models for experimental conditions. The results demonstrate accuracy and specificity above 90% in classifying 16 LG modes for both experimental set ups. However, the F-score, sensitivity, and precision of the classification range from 57% to 92%, depending on the number of imperfections in the images obtained from the experiments. This research could enhance the application of OAM light in telecommunications, sensing, and high-resolution imaging systems.
While several approaches have been proposed to optimize the geometrical dimensions of multilayer photonic nanostructures with a given material composition, very few works have considered simultaneously optimizing the material composition and dimensions of such nanostructures. Here, we develop a hybrid optimization algorithm as a method to design optimal multilayer photonic structures. Leveraging recent progress in metaheuristic optimization, we develop an optimization method consisting of a Monte Carlo simulation, a continuous adaptive genetic algorithm, and a pattern search algorithm. We first perform a Monte Carlo simulation over the entire design space. Structures are ranked according to the chosen fitness function. We find that this method yields viable material compositions. The material compositions of the best structures are used to parameterize the genetic algorithm in the next stage. A number of genetic algorithm populations are generated, one for each material composition, to optimize the thicknesses. These populations are run in parallel for a number of generations, evaluating the structures of each generation and using the characteristics of those that best satisfy the fitness function to improve other structures. The resulting populations converge towards the optimum of their solution space typically after a few thousand generations. The genetic algorithm used is continuous because parameters are treated as real numbers rather than bit strings as in classical genetic algorithms, and adaptive because the algorithm uses characteristics of the population pool to guide optimization. Finally, we apply a pattern search local optimization algorithm to the best result from each population to find the exact optimum.
In the lore of quantum metrology, one often hears (or reads) the following no-go theorem: If you put a vacuum into one input port of a balanced Mach-Zehnder interferometer, then no matter what you put into the other input port, and no matter what your detection scheme, the sensitivity can never be better than the shot-noise limit (SNL). Often the proof of this theorem is cited to be in C. Caves, Phys. Rev. D 23, 1693 (1981), but upon further inspection, no such claim is made there. Quantum-Fisher-information-based arguments suggestive of this no-go theorem appear elsewhere in the literature, but are not stated in their full generality. Here we thoroughly explore this no-go theorem and give a rigorous statement: the no-go theorem holds whenever the unknown phase shift is split between both of the arms of the interferometer, but remarkably does not hold when only one arm has the unknown phase shift. In the latter scenario, we provide an explicit measurement strategy that beats the SNL. We also point out that these two scenarios are physically different and correspond to different types of sensing applications.
We present optimized aperiodic structures for use as broadband, broad-angle thermal emitters which are capable of drastically increasing the efficiency of tungsten lightbulbs. These aperiodic multilayer structures designed with alternating layers of tungsten and air or tungsten and silicon carbide on top of a tungsten substrate exhibit broadband emittance peaked around the center of the visible wavelength range. We investigate the properties of these structures for use as lightbulb filaments, and compare their performance with conventional lightbulbs. We find that these structures greatly enhance the emittance over the visible wavelength range, while also increasing the overall efficiency of the bulb.
The implementation of polarization-based quantum communication is limited by signal loss and decoherence caused by the birefringence of a single-mode fiber. We investigate the Knill dynamical decoupling scheme, implemented using half-wave plates, to minimize decoherence and show that a fidelity greater than 99% can be achieved in absence of rotation error and fidelity greater than 96% can be achieved in presence of rotation error. Such a scheme can be used to preserve any quantum state with high fidelity and has potential application for constructing all optical quantum delay line, quantum memory, and quantum repeater.
Bulk thermal emittance sources possess incoherent, isotropic, and broadband radiation spectra that vary from
material to material. However, these radiation spectra can be drastically altered by modifying the geometry of
the structures. In particular, several approaches have been proposed to achieve narrowband, highly directional
thermal emittance based on photonic crystals, gratings, textured metal surfaces, metamaterials, and shock waves
propagating through a crystal. Here we present optimized aperiodic structures for use as narrowband, highly
directional thermal infrared emitters for both TE and TM polarizations. One-dimensional layered structures
without texturing are preferable to more complex two- and three-dimensional structures because of the relative
ease and low cost of fabrication. These aperiodic multilayer structures designed with alternating layers of silicon
and silica on top of a semi-infinite tungsten substrate exhibit extremely high emittance peaked around the
wavelength at which the structures are optimized. Structures were designed by a genetic optimization algorithm
coupled to a transfer matrix code which computed thermal emittance. First, we investigate the properties of the
genetic-algorithm optimized aperiodic structures and compare them to a previously proposed resonant cavity
design. Second, we investigate a structure optimized to operate at the Wien wavelength corresponding to a
near-maximum operating temperature for the materials used in the aperiodic structure. Finally, we present a
structure that exhibits nearly monochromatic and highly directional emittance for both TE and TM polarizations
at the frequency of one of the molecular resonances of carbon monoxide (CO); hence, the design is suitable for
a detector of CO via absorption spectroscopy.
We explore an approach to enhance the efficiency of solar cells using photonic nanostructures for solar ther-mophotovoltaics. Our focus is on designing photonic nanostructures that can provide broadband absorption in a narrow angular range for solar thermophotovoltaic systems which do not employ sunlight concentration. We consider structures consisting of an aperiodic multilayer stack of alternating layers of silicon and silica on top of a thick tungsten layer. The layer thicknesses are optimized to maximize the angular selectivity in the absorp-tivity for both TE and TM polarizations. Using such an approach, we design structures with highly directional absorptivity for both polarizations.
Optical coherent states can be interpreted as d-dimensional quantum systems, or qudits of even superposition of pseudo-number states. Cross-Kerr nonlinear interaction can generate the maximal entanglements of pseudo- phase and pseudo-number states from two opticl coherent states. Extended network of these entangled coherent states is a qudit cluster state and can be used as qudit communication network for d-dimensional teleportation or multi-user quantum cryptographic network.
We develop an improvement to the weak laser pulse BB84 scheme for quantum key distribution, which utilizes
entanglement to increase the security of the scheme and enhance its resilience to the photon-number-splitting attack.
This protocol relies on the non-commutation of phase and number to detect an eavesdropper performing quantum nondemolition
measurement on photon number. The potential advantages and disadvantages of this scheme are compared to
the coherent decoy state protocol.
Mach-Zehnder interferometry based on mixing the coherent and the squeezed vacuum states of light has Heisenberg limited capabilities for phase estimation. This is also, because the quantum Cramer-Rao bound on sensitivity of phase estimation with the above interferometric scheme reaches the Heisenberg limit when the inputs are mixed in hear equal proportions. We show that a detection strategy based on the measurement of parity of photon number in one of the output modes of the interferometer saturates the quantum Cramer-Rao bound of the interferometric scheme, and therefore- as a consequence- hits the Heisenberg limit when the inputs are mixed in equal intensities.
We present a model for quantum Mie scattering in one dimension, and show that quantum states of light, such as
Fock states, exhibit the same transmission functions as coherent states for an ordinary intensity measurement. If
a number-resolving measurement is carried out instead, we observe narrower transmission functions than for the
classical case. We discuss applications of this effect for high-precision length measurements in interferometry.
Quantum entanglement has the potential to revolutionize the entire field of interferometric sensing by providing
many orders of magnitude improvement in interferometer sensitivity. The quantum-entangled particle interferometer
approach is very general and applies to many types of interferometers. In particular, without nonlocal
entanglement, a generic classical interferometer has a statistical-sampling shot-noise limited sensitivity that scales
like 1/√N
N, where N is the number of particles passing through the interferometer per unit time. However, if
carefully prepared quantum correlations are engineered between the particles, then the interferometer sensitivity
improves by a factor of √N
to scale like 1/N, which is the limit imposed by the Heisenberg Uncertainty Principle.
For optical interferometers operating at milliwatts of optical power, this quantum sensitivity boost corresponds
to an eight-order-of-magnitude improvement of signal to noise. This effect can translate into a tremendous science
pay-off for space missions. For example, one application of this new effect is to fiber optical gyroscopes
for deep-space inertial guidance and tests of General Relativity (Gravity Probe B). Another application is to
ground and orbiting optical interferometers for gravity wave detection, Laser Interferometer Gravity Observatory
(LIGO) and the European Laser Interferometer Space Antenna (LISA), respectively. Other applications are to
Satellite-to-Satellite laser Interferometry (SSI) proposed for the next generation Gravity Recovery And Climate
Experiment (GRACE II).
Information science is entering into a new era in which certain subtleties of quantum mechanics enables large enhancements in computational efficiency and communication security. Naturally, precise control of quantum systems required for the implementation of quantum information processing protocols implies potential breakthoughs in other sciences and technologies. We discuss recent developments in quantum control in optical systems and their applications in metrology and imaging.
Quantum entanglement has the potential to revolutionize the entire field of interferometric sensing by providing many orders of magnitude improvement in interferometer sensitivity. The quantum entangled particle interferometer approach is very general and applies to many types of interferometers. In particular, without nonlocal entanglement, a generic classical interferometer has a statistical-sampling shot-noise limited sensitivity that scales like 1/√N, where N is the number of particles passing through the interferometer per unit time. However, if carefully prepared quantum correlations are engineered between the particles, then the interferometer sensitivity improves by a factor of √N to scale like 1/N, which is the limit imposed by the Heisenberg Uncertainty Principle. For optical interferometers operating at milliwatts of optical power, this quantum sensitivity boost corresponds to an eight-order-of-magnitude improvement of signal to noise. This effect can translate into a tremendous science pay-off for NASA-JPL missions. For example, one application of this new effect is to fiber optical gyroscopes for deep-space inertial guidance and tests of General Relativity (Gravity Probe B). Another application is to ground and orbiting optical interferometers for gravity wave detection, Laser Interferometer Gravity Observatory (LIGO) and the European Laser Interferometer Space Antenna (LISA), respectively. Other applications are to Satellite-to-Satellite laser Interferometry (SSI) proposed for the next generation Gravity Recovery And Climate Experiment (GRACE II).
We show how to beat the `fundamental' noise limits in optical lithography using entangled quantum states. In this talk we will give the theoretical background to optical lithography and its quantum formulation. A proof-in-principle experimental demonstration is described.
The technique of projective measurements in linear optics can provide apparent, efficient nonlinear interaction between photons, which is technically problematic otherwise. We present an application of such a technique to prepare large photon-number path entanglement. Large photon-number path entanglement is an important resource for Heisenberg-limited optical interferometry, where the sensitivity of phase measurements can be improved beyond the usual shot-noise limit. A similar technique can also be applied to signal the presence of a single photon without destroying it. We further show how to build a quantum repeater for long-distance quantum communication.
We consider the use of Electron-Nuclear Double Resonance (ENDOR) techniques in quantum computing. ENDOR resolution as a possible limiting factor is discussed. It is found that ENDOR and double-ENDOR techniques have sufficient resolution for quantum computing applications.
Recent theoretical and experimental demonstrations have shown that blue-detuned laser light, propagating in the annular core-cladding region of a hollow-glass fiber, produces a repulsive, evanescent light-wave potential in the hollow, that can be used to guide near-resonant atoms down the fiber. In this work, I show that slight modifications to the hollow-fiber geometry can be used to turn this atom guide into an atom-bottle trap. The trap can be open and shut by varying the aperture angle at which light couples into the fiber, allowing the atoms to be easily loaded. This trap has an advantage over other optical atom traps in that the atoms move coherently in a field-free region with only brief specular reflections at the step-like potential walls.
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