arXiv subjects

R. Nicholas Lanning

Publications and source records attributed to R. Nicholas Lanning.

12 recordsLinked to original sources

arXiv2024

Two-Way Quantum Time Transfer: A Method for Daytime Space-Earth Links

High-precision remote clock synchronization is crucial for many classical and quantum network applications. Evaluating options for space-Earth links, we find that traditional solutions may not produce the desired synchronization for low Earth orbits and unnecessarily complicate quantum-networking architectures. Demonstrating an alternative, we use commercial off-the-shelf quantum-photon sources and detection equipment to synchronize two remote clocks across our freespace testbed utilizing a method called two-way quantum time transfer (QTT). We reach picosecond-scale timing precision under very lossy and noisy channel conditions representative of daytime space-Earth links and software-emulated satellite motion. This work demonstrates how QTT is potentially relevant for daytime space-Earth quantum networking and/or providing high-precision timing in GPS-denied environments.

quant-ph↗

arXiv2024

Practical Approach to Extending Baselines of Telescopes using Continuous-Variable Quantum Information

Interferometric telescopes are instrumental for the imaging of distant astronomical bodies, but optical loss heavily restricts how far telescopes in an array can be placed from one another, leading to a bottleneck in the resolution that can be achieved. An entanglement-assisted approach to this problem has been proposed by Gottesman, Jennewein, and Croke (GJC12) [Physical Review Letters, 109(7):070503, July 2011], as a possible solution to the issue of optical loss if the entangled state can be distributed across long distances by employing a quantum repeater network. In this paper, we propose an alternative entanglement-assisted scheme that interferes a two-mode squeezed vacuum state with the astronomical state and then measures the resulting state by means of homodyne detection. We use a continuous-variable approach and compute the Fisher information with respect to the mutual coherence of the astronomical source. We show that when the Fisher information is observed cumulatively at the rate at which successful measurements can be performed, our proposed scheme does not outperforms the traditional direct detection approach or the entanglement-assisted approach of GJC12.

quant-ph↗

arXiv2023

Quantum time transfer: a practical method for lossy and noisy channels

Timing requirements for long-range quantum networking are driven by the necessity of synchronizing the arrival of photons, from independent sources, for Bell-state measurements. Thus, characteristics such as repetition rate and pulse duration influence the precision required to enable quantum networking tasks such as teleportation and entanglement swapping. Some solutions have been proposed utilizing classical laser pulses, frequency combs, and biphoton sources. In this article, we explore the utility of the latter method since it is based upon quantum phenomena, which makes it naturally covert, and potentially quantum secure. Furthermore, it can utilize relatively low performance quantum-photon sources and detection equipment, but provides picosecond-level timing precision even under high loss and high noise channel conditions representative of daytime space-Earth links. Therefore, this method is relevant for daytime space-Earth quantum networking and/or providing high-precision secure timing in GPS denied environments.

quant-ph↗

arXiv2022

An Optimal Polarization-Entanglement Source: Frequency-Converted SPDC with Degeneracy, Indistinguishability, and Ultra-High Purity Configurable Over a Large Spectral Range

Modeling and simulations of entanglement-based quantum-networking protocols commonly assume perfect entangled states. Some investigations have been performed which show how imperfections cause the efficiency of the protocols to rapidly deteriorate. For polarization-entangled states created by SPDC, the fundamentals of phase matching lead to a trade-off problem for the optimal properties of the state. We present a new SPDC method which circumvents the trade-off problem and allows one to obtain degeneracy, indistinguishability, and heralded-single-photon spectral purity greater than 99% for any target SPDC wavelength in the visible and NIR spectrum. Therefore, our method can in principle generate optimal polarization-entangled states for polarization-entanglement-based quantum-networking protocols.

quant-ph↗

arXiv2021

Quantum Communication Over Atmospheric Channels: A Framework for Optimizing Wavelength and Filtering

Despite quantum networking concepts, designs, and hardware becoming increasingly mature, there is no consensus on the optimal wavelength for free-space systems. We present an in-depth analysis of a daytime free-space quantum channel as a function of wavelength and atmospheric spatial coherence (Fried coherence length). We choose decoy-state quantum key distribution bit yield as a performance metric in order to reveal the ideal wavelength choice for an actual qubit-based protocol under realistic atmospheric conditions. Our analysis represents a rigorous framework to analyze requirements for spatial, spectral, and temporal filtering. These results will help guide the development of free-space quantum communication and networking systems. In particular, our results suggest that shorter wavelengths in the optical band should be considered for free-space quantum communication systems. Our results are also interpreted in the context of atmospheric compensation by higher-order adaptive optics.

quant-ph↗

arXiv2021

Adaptive-optics-enabled quantum communication: A technique for daytime space-to-Earth links

Previous demonstrations of free-space quantum communication in daylight have been touted as significant for the development of global-scale quantum networks. Until now, no one has carefully tuned their atmospheric channel to reproduce the daytime sky radiance and slant-path turbulence conditions as they exist between space and Earth. In this article we report a quantum communication field experiment under conditions representative of daytime downlinks from space. Higher-order adaptive optics increased quantum channel efficiencies far beyond those possible with tip/tilt correction alone while spatial filtering at the diffraction limit rejected optical noise without the need for an ultra-narrow spectral filter. High signal-to-noise probabilities and low quantum-bit-error rates were demonstrated over a wide range of channel radiances and turbulence conditions associated with slant-path propagation in daytime. The benefits to satellite-based quantum key distribution are quantified and discussed.

physics.optics↗

arXiv2018

Quantized Nonlinear Gaussian-Beam Dynamics $-$ Tailoring Multimode Squeezed-Light Generation

We present a general, second quantization procedure for multi-transverse-spatial mode Gaussian beam dynamics in nonlinear interactions. Previous treatments have focused on the spectral density and angular distribution of spatial modes. Here we go a layer deeper by investigating the complex transverse-spatial mode in each angular-spatial mode. Furthermore, to implement the theory, we simulate four-wave mixing and parametric down-conversion schemes, showing how one can elucidate and tailor the underlying multi-transverse-spatial mode structure along with it's quantum properties.

quant-ph↗

arXiv2018

An analytically simple and computationally efficient Gaussian beam mode-decomposition approach to classical diffraction theory

We present a method of Gaussian-beam-mode decomposition to calculate classical diffraction of optical beams by apertures. This method offers a entirely different approach to examine the classic problem. Although our method is based on a very straightforward setup, it is surprisingly effective. We validate our method by comparing its results with those of Kirchhoff's full diffraction formula. Not only does our method have a simple and organized analytical framework, it also offers significant computational advantage.

physics.optics↗

arXiv2017

Multi-pass configuration for Improved Squeezed Vacuum Generation in Hot Rb Vapor

We study a squeezed vacuum field generated in hot Rb vapor via the polarization self-rotation effect. Our previous experiments showed that the amount of observed squeezing may be limited by the contamination of the squeezed vacuum output with higher-order spatial modes, also generated inside the cell. Here, we demonstrate that the squeezing can be improved by making the light interact several times with a less dense atomic ensemble. With optimization of some parameters we can achieve up to -2.6 dB of squeezing in the multi-pass case, which is 0.6 dB improvement compared to the single-pass experimental configuration. Our results show that other than the optical depth of the medium, the spatial mode structure and cell configuration also affect the squeezing level.

physics.atom-ph↗

arXiv2017

Gaussian Beam-Propagation Theory for Nonlinear Optics - Featuring an Exact Treatment of Orbital Angular Momentum Transfer

We present a general, Gaussian spatial mode propagation formalism for describing the generation of higher order multi-spatial-mode beams generated during nonlinear interactions. Furthermore, to implement the theory, we simulate optical angular momentum transfer interactions, and show how one can optimize the interaction to reduce the undesired modes. Past theoretical treatments of this problem have often been phenomenological, at best. Here we present an exact solution for the single-pass no-cavity regime, in which the the nonlinear interaction is not overly strong. We apply our theory to two experiments, with very good agreement, and give examples of several more configurations, easily tested in the laboratory.

physics.optics↗

arXiv2017

Why a hole is like a beam splitter--a general diffraction theory for multimode quantum states of light

Within the second-quantization framework, we develop a formalism for describing a spatially multimode optical field diffracted through a spatial mask and show that this process can be described as an effective interaction between various spatial modes. We demonstrate a method to calculate the quantum state in the diffracted optical field for any given quantum state in the incident field. Using numerical simulations, we also show that with single-mode squeezed-vacuum state input, the prediction of our theory is in qualitative agreement with our experimental data. We also give several additional examples of how the theory works, for various quantum input states, which may be easily tested in the lab; including two single-mode squeezed vacuums, single- and two-photon inputs, where we show the diffraction process produces two-mode squeezed vacuum, number-path entanglement and a Hong-Ou-Mandel-like effect--analogous to a beam splitter.

quant-ph↗

arXiv2016

Spatial Multi-Mode Structure of Atom-Generated Squeezed Light

We investigated the spatial distribution of quantum fluctuations in a squeezed vacuum field, generated via polarization self-rotation (PSR) interaction of an ensemble of Rb atoms and a strong near-resonant linearly polarized laser field. We found that the noise suppression is greatly effected by the transverse profile of a spatial mask, placed in both the squeezed field and the local oscillator, as well as its position along the focused beam near the focal point. These observations indicate the spatial multi-mode structure of the squeezed vacuum field. We have developed a theoretical model that describes the generation of higher-order Laguerre-Gauss modes as a result of PSR light-atom interaction. The prediction of this model are in a good qualitative agreement with the experimental measurements.

physics.optics↗