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Articles 61 - 85 of 85
Full-Text Articles in Optics
Transients Of The Electromagnetically-Induced-Transparency-Enhanced Refractive Kerr Nonlinearity, John C. Howell, M. V. Pack, R. M. Camacho
Transients Of The Electromagnetically-Induced-Transparency-Enhanced Refractive Kerr Nonlinearity, John C. Howell, M. V. Pack, R. M. Camacho
Mathematics, Physics, and Computer Science Faculty Articles and Research
We report observations of the dynamics of electromagnetically induced transparency (EIT) in a Λ system when the ground states are Stark shifted. Interactions of this type exhibit large optical nonlinearities called Kerr nonlinearities, and have numerous applications. The EIT Kerr nonlinearity is relatively slow, which is a limiting factor that may make many potential applications impossible. Using rubidium atoms, we observe the dynamics of the EIT Kerr nonlinearity using a Mach-Zehnder interferometer to measure phase modulation of the EIT fields resulting from a pulsed signal beam Stark shifting the ground state energy levels. The rise times and transients agree well …
Electromagnetically Induced Transparency Line Shapes For Large Probe Fields And Optically Thick Media, M. V. Pack, R. M. Camacho, John C. Howell
Electromagnetically Induced Transparency Line Shapes For Large Probe Fields And Optically Thick Media, M. V. Pack, R. M. Camacho, John C. Howell
Mathematics, Physics, and Computer Science Faculty Articles and Research
We calculate the line shape and linewidths for electromagnetically induced transparency (EIT) in optically thick, Doppler broadened media (buffer gasses are also considered). In generalizing the definition of the EIT linewidth to optically thick media, we find two different linewidth definitions apply depending on whether the experiment is pulsed or continuous wave (cw). Using the cw definition for the EIT line shape we derive analytic expressions describing the linewidth as a function of optical depth. We also review the EIT line shapes in optically thin media and provide physical arguments for how the line shapes change as a function of …
Wide-Bandwidth, Tunable, Multiple-Pulse-Width Optical Delays Using Slow Light In Cesium Vapor, Ryan M. Camacho, Michael V. Pack, John C. Howell, Aaron Schweinsberg, Robert W. Boyd
Wide-Bandwidth, Tunable, Multiple-Pulse-Width Optical Delays Using Slow Light In Cesium Vapor, Ryan M. Camacho, Michael V. Pack, John C. Howell, Aaron Schweinsberg, Robert W. Boyd
Mathematics, Physics, and Computer Science Faculty Articles and Research
We demonstrate an all-optical delay line in hot cesium vapor that tunably delays 275 ps input pulses up to 6.8 ns and 740 input ps pulses up to 59 ns (group index of approximately 200) with little pulse distortion. The delay is made tunable with a fast reconfiguration time (hundreds of ns) by optically pumping out of the atomic ground states.
Large-Alphabet Quantum Key Distribution Using Energy-Time Entangled Bipartite States, Irfan Ali-Khan, Curtis J. Broadbent, John C. Howell
Large-Alphabet Quantum Key Distribution Using Energy-Time Entangled Bipartite States, Irfan Ali-Khan, Curtis J. Broadbent, John C. Howell
Mathematics, Physics, and Computer Science Faculty Articles and Research
We present a protocol for large-alphabet quantum key distribution (QKD) using energy-time entangled biphotons. Binned, high-resolution timing measurements are used to generate a large-alphabet key with over 10 bits of information per photon pair, albeit with large noise. QKD with 5% bit error rate is demonstrated with 4 bits of information per photon pair, where the security of the quantum channel is determined by the visibility of Franson interference fringes. The protocol is easily generalizable to even larger alphabets, and utilizes energy-time entanglement which is robust to transmission over large distances in fiber.
All-Optical Delay Of Images Using Slow Light, Ryan M. Camacho, Curtis J. Broadbent, Irfan Ali-Khan, John C. Howell
All-Optical Delay Of Images Using Slow Light, Ryan M. Camacho, Curtis J. Broadbent, Irfan Ali-Khan, John C. Howell
Mathematics, Physics, and Computer Science Faculty Articles and Research
Two-dimensional images carried by optical pulses (2 ns) are delayed by up to 10 ns in a 10 cm cesium vapor cell. By interfering the delayed images with a local oscillator, the transverse phase and amplitude profiles of the images are shown to be preserved. It is further shown that delayed images can be well preserved even at very low light levels, where each pulse contains on average less than one photon.
Slow Light With Large Fractional Delays By Spectral Hole-Burning In Rubidium Vapor, Ryan M. Camacho, Michael V. Pack, John C. Howell
Slow Light With Large Fractional Delays By Spectral Hole-Burning In Rubidium Vapor, Ryan M. Camacho, Michael V. Pack, John C. Howell
Mathematics, Physics, and Computer Science Faculty Articles and Research
We report on the experimental realization of large fractional pulse delays in a hot, Doppler-broadened rubidium vapor. A pump laser burns a deep spectral hole in the inhomogeneously broadened vapor. The delay is shown to be widely tunable by both power broadening the resonance and frequency modulating the pump laser. The simplicity of the scheme opens up the possibility for practical optical delays and buffers.
Transients Of The Electromagnetically-Induced-Transparency-Enhanced Refractive Kerr Nonlinearity: Theory, M. V. Pack, R. M. Camacho, John C. Howell
Transients Of The Electromagnetically-Induced-Transparency-Enhanced Refractive Kerr Nonlinearity: Theory, M. V. Pack, R. M. Camacho, John C. Howell
Mathematics, Physics, and Computer Science Faculty Articles and Research
We present a theory describing the transients and rise times of the refractive Kerr nonlinearity which is enhanced using electromagnetically induced transparency (EIT). We restrict our analysis to the case of a pulsed signal field with continuous-wave EIT fields, and all fields are well below saturation. These restrictions enable the reduction of an EIT Kerr, four-level, density-matrix equation to a two-level Bloch-vector equation which has a simple and physically intuitive algebraic solution. The physically intuitive picture of a two-level Bloch vector provides insights that are easily generalized to more complex and experimentally realistic models. We consider generalization to the cases …
Low-Distortion Slow Light Using Two Absorption Resonances, Ryan M. Camacho, Michael V. Pack, John C. Howell
Low-Distortion Slow Light Using Two Absorption Resonances, Ryan M. Camacho, Michael V. Pack, John C. Howell
Mathematics, Physics, and Computer Science Faculty Articles and Research
We consider group delay and broadening using two strongly absorbing and widely spaced resonances. We derive relations which show that very large pulse bandwidths coupled with large group delays and small broadening can be achieved. Unlike single resonance systems, the dispersive broadening dominates the absorptive broadening which leads to a dramatic increase in the possible group delay. We show that the double resonance systems are excellent candidates for realizing all-optical delay lines. We report on an experiment which achieved up to 50 pulse delays with 40% broadening.
Erratum: Exploring The Optimal Sensitivity Of Sum-Variance Nonseparability Critera For Spin-1/2 Systems, Irfan Ali Khan, John C. Howell
Erratum: Exploring The Optimal Sensitivity Of Sum-Variance Nonseparability Critera For Spin-1/2 Systems, Irfan Ali Khan, John C. Howell
Mathematics, Physics, and Computer Science Faculty Articles and Research
No abstract provided.
Experimental Demonstration Of High Two-Photon Time-Energy Entanglement, Irfan Ali Khan, John C. Howell
Experimental Demonstration Of High Two-Photon Time-Energy Entanglement, Irfan Ali Khan, John C. Howell
Mathematics, Physics, and Computer Science Faculty Articles and Research
We report on the experimental demonstration of high energy-time entanglement in two-photon states created in the process of spontaneous parametric down-conversion. We show that the classical variance product, which we violate by three orders of magnitude, actually represents a lower bound estimate of the number of information eigenmodes K. Explicit measurements estimate K to be greater than 100, with theoretical estimates predicting a value of as high as 1×106. These results provide incentive for the practical feasibility of large bandwidth quantum information processing, particularly in cryptography over large distances.
Pixel Entanglement: Experimental Realization Of Optically Entangled D=3 And D=6 Qudits, Malcolm N. O'Sullivan, Irfan Ali Khan, Robert W. Boyd, John C. Howell
Pixel Entanglement: Experimental Realization Of Optically Entangled D=3 And D=6 Qudits, Malcolm N. O'Sullivan, Irfan Ali Khan, Robert W. Boyd, John C. Howell
Mathematics, Physics, and Computer Science Faculty Articles and Research
We demonstrate a simple experimental method for creating entangled qudits. Using transverse-momentum and position entanglement of photons emitted in spontaneous parametric down-conversion, we show entanglement between discrete regions of space, i.e., pixels. We map each photon onto as many as six pixels, where each pixel represents one level of our qudit state. The method is easily generalizable to create even higher dimensional, entangled states. Thus, the realization of quantum information processing in arbitrarily high dimensions is possible, allowing for greatly increased information capacity.
Exploring The Optimal Sensitivity Of Sum-Variance Nonseparability Criteria For Spin-1/2 Systems, Irfan Ali Khan, John C. Howell
Exploring The Optimal Sensitivity Of Sum-Variance Nonseparability Criteria For Spin-1/2 Systems, Irfan Ali Khan, John C. Howell
Mathematics, Physics, and Computer Science Faculty Articles and Research
We report on experimental and theoretical studies on recently introduced entanglement measures which use a sum of spin-variance criteria for two spin-1∕2 particles. Three inequalities are explored which exhibit useful concatenating properties. They are each shown to have greater sensitivities than a Bell’s measurement, while each requiring fewer measurements than a Bell’s measurement to obtain. The simplest inequality, requiring just four measurements, is shown to be efficient at testing for entanglement in down-conversion sources which naturally exhibit maximally polarized noise. The most complex inequality, requiring just 12 measurements, is shown to have a sensitivity equal to that of the Peres …
Bell’S Inequalities For Particles Of Arbitrary Spin In Fixed Analyzers, Ronen Mukamel, John C. Howell
Bell’S Inequalities For Particles Of Arbitrary Spin In Fixed Analyzers, Ronen Mukamel, John C. Howell
Mathematics, Physics, and Computer Science Faculty Articles and Research
We propose a new set of observables for experiments on entangled particles of arbitrarily large spin that produce significant Clauser-Horne-Shimony-Holt inequality violations for fixed analyzer settings over a wider range of spins than was previously possible. These observables are better suited for experiments where analyzer orientations must be chosen before the spin of the entangled particles is known, such as experiments using polarization entangled downconverted photons.
Hong-Ou-Mandel Cloning: Quantum Copying Without An Ancilla, Irfan Ali Khan, John C. Howell
Hong-Ou-Mandel Cloning: Quantum Copying Without An Ancilla, Irfan Ali Khan, John C. Howell
Mathematics, Physics, and Computer Science Faculty Articles and Research
In this paper we report an experimental realization of an ancilla-free 1→2 phase-covariant quantum cloner. The cloner is realized by interfering a linearly polarized photon, which we wish to clone with a circularly polarized photon at a beam splitter. The two-photon effect can be understood in light of Hong-Ou-Mandel interference. The fidelity of the cloner was measured as 0.829±0.008 for the 0∕90 basis and 0.835±0.006 for the 45∕135 basis, which is in good agreement with the theoretical prediction of 5∕6 fidelity. The experimental scheme is straightforward and has a high cloning success rate.
Realization Of The Einstein-Podolsky-Rosen Paradox Using Momentum- And Position-Entangled Photons From Spontaneous Parametric Down Conversion, John C. Howell, Ryan S. Bennink, Sean J. Bentley, Robert W. Boyd
Realization Of The Einstein-Podolsky-Rosen Paradox Using Momentum- And Position-Entangled Photons From Spontaneous Parametric Down Conversion, John C. Howell, Ryan S. Bennink, Sean J. Bentley, Robert W. Boyd
Mathematics, Physics, and Computer Science Faculty Articles and Research
We report on a momentum-position realization of the EPR paradox using direct detection in the near and far fields of the photons emitted by collinear type-II phase-matched parametric down conversion. Using this approach we achieved a measured two-photon momentum-position variance product of 0.01ℏ2, which dramatically violates the bounds for the EPR and separability criteria.
Quantum And Classical Coincidence Imaging, Ryan S. Bennink, Sean J. Bentley, Robert W. Boyd, John C. Howell
Quantum And Classical Coincidence Imaging, Ryan S. Bennink, Sean J. Bentley, Robert W. Boyd, John C. Howell
Mathematics, Physics, and Computer Science Faculty Articles and Research
Coincidence, or ghost, imaging is a technique that uses two correlated optical fields to form an image of an object. In this work we identify aspects of coincidence imaging which can be performed with classically correlated light sources and aspects which require quantum entanglement. We find that entangled photons allow high-contrast, high-resolution imaging to be performed at any distance from the light source. We demonstrate this fact by forming ghost images in the near and far fields of an entangled photon source, noting that the product of the resolutions of these images is a factor of 3 better than that …
Experimental Quantum Cloning Of Single Photons, Antia Lamas-Linares, Christoph Simon, John C. Howell, Dik Bouwmeester
Experimental Quantum Cloning Of Single Photons, Antia Lamas-Linares, Christoph Simon, John C. Howell, Dik Bouwmeester
Mathematics, Physics, and Computer Science Faculty Articles and Research
Although perfect copying of unknown quantum systems is forbidden by the laws of quantum mechanics, approximate cloning is possible. A natural way of realizing quantum cloning of photons is by stimulated emission. In this context, the fundamental quantum limit to the quality of the clones is imposed by the unavoidable presence of spontaneous emission. In our experiment, a single input photon stimulates the emission of additional photons from a source on the basis of parametric down-conversion. This leads to the production of quantum clones with near-optimal fidelity. We also demonstrate universality of the copying procedure by showing that the same …
Experimental Violation Of A Spin-1 Bell Inequality Using Maximally Entangled Four-Photon States, John C. Howell, Antia Lamas-Linares, Dik Bouwmeester
Experimental Violation Of A Spin-1 Bell Inequality Using Maximally Entangled Four-Photon States, John C. Howell, Antia Lamas-Linares, Dik Bouwmeester
Mathematics, Physics, and Computer Science Faculty Articles and Research
We demonstrate the experimental violation of a spin-1 Bell inequality. The spin-1 inequality is based on the Clauser, Horne, Shimony, and Holt formalism. For entangled spin-1 particles, the maximum quantum-mechanical prediction is 2.55 as opposed to a maximum of 2, predicted using local hidden variables. We obtained an experimental value of 2.27±0.02 using the four-photon state generated by pulsed, type-II, stimulated parametric down-conversion. This is a violation of the spin-1 Bell inequality by more than 13 standard deviations.
Stimulated Emission Of Polarization-Entangled Photons, Antia Lamas-Linares, John C. Howell, Dik Bouwmeester
Stimulated Emission Of Polarization-Entangled Photons, Antia Lamas-Linares, John C. Howell, Dik Bouwmeester
Mathematics, Physics, and Computer Science Faculty Articles and Research
Entangled photon pairs—discrete light quanta that exhibit non-classical correlations—play a crucial role in quantum information science (for example, in demonstrations of quantum non-locality1,2,3,4,5,6,7, quantum teleportation8,9 and quantum cryptography10,11,12,31). At the macroscopic optical-field level non-classical correlations can also be important, as in the case of squeezed light13, entangled light beams14,15 and teleportation of continuous quantum variables16. Here we use stimulated parametric down-conversion to study entangled states of light that bridge the gap between discrete and macroscopic optical quantum correlations. We demonstrate experimentally the onset of laser-like action for entangled photons, through …
Optically Simulating A Quantum Associative Memory, John C. Howell, John A. Yeazell, Dan Ventura
Optically Simulating A Quantum Associative Memory, John C. Howell, John A. Yeazell, Dan Ventura
Mathematics, Physics, and Computer Science Faculty Articles and Research
This paper discusses the realization of a quantum associative memory using linear integrated optics. An associative memory produces a full pattern of bits when presented with only a partial pattern. Quantum computers have the potential to store large numbers of patterns and hence have the ability to far surpass any classical neural-network realization of an associative memory. In this work two three-qubit associative memories will be discussed using linear integrated optics. In addition, corrupted, invented and degenerate memories are discussed.
Nondestructive Single-Photon Trigger, John C. Howell, John A. Yeazell
Nondestructive Single-Photon Trigger, John C. Howell, John A. Yeazell
Mathematics, Physics, and Computer Science Faculty Articles and Research
A triggering device sensitive to a single photon is discussed. It is based on a balanced quantum nondemolition (QND) measurement proposed by Chuang and Yamamoto [Phys. Rev. Lett. 76, 4281 (1996)]. The balanced measurement measures the total photon number and obtains no which-path/mode information. Hence, the timing of the photon can be determined without destroying its wave function or entangling the probe field. This could have extensive use in the realization of long-distance quantum communications systems.
Quantum Computation Through Entangling Single Photons In Multipath Interferometers, John C. Howell, John A. Yeazell
Quantum Computation Through Entangling Single Photons In Multipath Interferometers, John C. Howell, John A. Yeazell
Mathematics, Physics, and Computer Science Faculty Articles and Research
Single-photon interferometry has been used to simulate quantum computations. Its use has been limited to studying few-bit applications due to rapid growth in physical size with numbers of bits. We propose a hybrid approach that employs n photons, each having L degrees of freedom yielding Ln basis states. The photons are entangled via a quantum nondemolition measurement. This approach introduces the essential element of quantum computing, that is, entanglement into the interferometry. Using these techniques, we demonstrate a controlled-NOT gate and a Grover's search circuit. These ideas are also applicable to the study of nonlocal correlations in many dimensions.
Entangling Macroscopic Quantum States, John C. Howell, John A. Yeazell
Entangling Macroscopic Quantum States, John C. Howell, John A. Yeazell
Mathematics, Physics, and Computer Science Faculty Articles and Research
Spatial entanglements of macroscopic quantum systems are proposed. The which-path uncertainty of a single photon passing through a beam splitter is transformed into the which-path uncertainty of two macroscopic fields via two quantum nondemolition measurements. The macroscopic fields are nonlocally correlated.
Reducing The Complexity Of Linear Optics Quantum Circuits, John C. Howell, John A. Yeazell
Reducing The Complexity Of Linear Optics Quantum Circuits, John C. Howell, John A. Yeazell
Mathematics, Physics, and Computer Science Faculty Articles and Research
Integrated optical elements can simplify the linear optics used to simulate quantum circuits. These linear optical simulations of quantum circuits have been developed primarily in terms of the free space optics associated with single-photon interferometry. For an L-bit simulation the number of required free-space optical elements is ∝2L if 50/50 beam splitters are used. The implementation (construction and alignment) of these circuits with these free-space elements is nontrivial. On the other hand, for the cases presented in this paper in which linear integrated optics (e.g., 2L×2L fiber couplers) are used, the number of optical devices does …
Linear Optics Simulations Of The Quantum Baker’S Map, John C. Howell, John A. Yeazell
Linear Optics Simulations Of The Quantum Baker’S Map, John C. Howell, John A. Yeazell
Mathematics, Physics, and Computer Science Faculty Articles and Research
The unitary evolution of linear optics can be used to model quantum computational networks. In this paper, a quantum simulation of a classically chaotic map (the baker’s map) is developed using linear optics. Two different models are presented. The first model employs only 50-50 beam splitters and phase shifters to simulate universal 2-qubit gates of a quantum computer. The second model uses the discrete Fourier transform generated by symmetric N×N fiber couplers. If single photons are used as inputs for these linear optics models, the result is a physical realization of the quantum baker’s map.