arXiv subjects

Joseph W. Britton

Publications and source records attributed to Joseph W. Britton.

15 recordsLinked to original sources

arXiv2026

BIFROST: A First-Principles Model of Polarization Mode Dispersion in Optical Fiber

We present BIFROST, a first-principles model of polarization mode dispersion (PMD) in optical fibers. Unlike conventional models, BIFROST employs physically motivated representations of the PMD properties of fibers, allowing users to computationally investigate real-world fibers in ways that are connected to physical parameters such as environmental temperature and external stresses. Our model, implemented in an open-source Python module, incorporates birefringence from core geometry, material properties, environmental stress, and fiber spinning. We validate our model by examining commercial fiber specifications, fiber-paddle measurements, and published PMD statistics for deployed fiber links, and we showcase BIFROST's predictive power by considering wavelength-division-multiplexed PMD compensation schemes for polarization-encoded quantum networks. BIFROST's physical grounding enables investigations into such questions as the sensitivity of fiber sensors, the evaluation of PMD mitigation strategies in quantum networks, and many more applications across fiber technologies.

physics.optics↗

arXiv2025

Spectrally-pure optical serrodyne modulation for continuously-tunable laser offset locking

The comb-like spectrum added to laser light by an electro-optic modulator (EOM) finds use in a wide range of applications, including coherent optical communication, atomic spectroscopy, and laser frequency and phase stabilization. In some cases a sideband-free optical frequency shift is preferred, such as in laser offset locking using an optical cavity, single-photon frequency shifting, and laser range finding. Approaches to obtaining an optical frequency offset (OFO) involve trade-offs between shift range, conversion gain, and suppression of spurious sidebands. Here we demonstrate an OFO of continuous-wave 871 nm laser light by serrodyne modulation using a fiber EOM and radio-frequency (RF) tones from a commercial RF system on a chip (RFSoC) to achieve shifts of 40 to 800 MHz with > 15 dB suppression of spurious sidebands and < 1.5 dB conversion loss. We also observe a smoothly varying conversion gain. The utility of this tool is demonstrated by continuously shifting the offset of a cavity-locked laser from 50 to 1600 MHz, a capability useful in spectroscopy of unknown optical transitions.

quant-ph↗

arXiv2025

Errors in PDH offset locking due to spurious spectral features

The Pound-Drever-Hall (PDH) technique is widely used to stabilize the frequency of lasers. Here we report on a routinely underestimated source of error in PDH offset-locking: a shift in the lock point due to the unintended interaction between residual optical sidebands and higher-order spatial modes in misaligned Fabry-Perot cavities. Significant frequency deviations-up to 50% of the cavity linewidth-can arise when the optical offset is obtained from a sinusoidally driven EOM. We measure this deviation experimentally, find agreement with a simple model, and show how a spectrally-pure frequency offset can reduce the deviation by an order of magnitude. Our findings draw attention to a systematic effect of importance to precision optical spectroscopy, optical clocks, and quantum information science.

physics.optics↗

arXiv2025

A practical guide to feedback control for Pound-Drever-Hall laser linewidth narrowing

The Pound-Drever-Hall (PDH) technique for laser linewidth narrowing is widely used by AMO experimentalists. However, achieving a high-performance PDH locking requires substantial engineering experience, which is scattered across literature and often lacks a cohesive control-theory perspective. Excellent pedagogical papers exist on the theory of the PDH error signal but they rarely cover feedback control. General-purpose control theory literature seldom discuss PDH laser locking specifically. Although excellent PDH review articles provide thorough knowledge and practice on both aspects but they are not reader-friendly. We extend prior works by addressing component choice and loop tuning using modern tools like a vector network analyzer. We organize multifaceted engineering considerations systematically, grounded in feedback control principles. Our target reader is researchers setting up a PDH laser lock for the first time; we eschew advanced topics like minimizing residual amplitude modulation (RAM). Our guidance is illustrated by step-by-step optimization of the lock for a 1650 nm ECDL.

quant-ph↗

arXiv2025

Coupling a Fabry-Pérot Cavity to a Single-Mode Optical Fiber Using a Metalens

Efficient coupling of light from an optical cavity to a single-mode fiber is required in a range of quantum technologies. In this work we consider the coupling of a high-finesse macroscopic Fabry-Pérot (FP) cavity to a single-mode fiber using a metalens. We perform sensitivity analysis with respect to longitudinal and transverse misalignment errors. We then detail a fiber-coupled cavity at 1650 nm using a monolithic cryo-compatible assembly incorporating a metalens.

physics.optics↗

arXiv2025

Can TCOs Transform Cavity-QED?

Transparent conductive oxides (TCO) enable confinement of charge-sensitive ions and Rydberg atoms proximal to dielectric structures including waveguides and photon detectors. However, optical loss precludes the use of TCOs within high-finesse optical micro-resonators. Here we characterize a ZnO-based TCO that markedly reduces optical absorption. At 1650\text{ nm} we observe a 22,000 finesse in a Fabry-Pérot optical cavity coated with a 30\text{ nm} ZnO layer. This is a 5000 times reduction relative to indium tin oxide (ITO) at this wavelength. The same ZnO film exhibits 0.01\text{ \ensuremathΩ\ensuremath{\cdot}cm} surface resistivity at DC. We anticipate a step change in cavity-QED systems incorporating ultra-low loss TCOs like ZnO.

quant-ph↗

arXiv2019

A stroboscopic approach to trapped-ion quantum information processing with squeezed phonons

In trapped-ion quantum information processing, interactions between spins (qubits) are mediated by collective modes of motion of an ion crystal. While there are many different experimental strategies to design such interactions, they all face both technical and fundamental limitations to the achievable coherent interaction strength. In general, obtaining strong interactions and fast gates is an ongoing challenge. Here, we extend previous work [Phys. Rev. Lett. 112, 030501 (2019)] and present a general strategy for enhancing the interaction strengths in trapped-ion systems via parametric amplification of the ions' motion. Specifically, we propose a stroboscopic protocol using alternating applications of parametric amplification and spin-motion coupling. In comparison with the previous work, we show that the current protocol can lead to larger enhancements in the coherent interaction that increase exponentially with the gate time.

quant-ph↗

arXiv2016

Perpendicular laser cooling with a rotating wall potential in a Penning trap

We investigate the impact of a rotating wall potential on perpendicular laser cooling in a Penning ion trap. By including energy exchange with the rotating wall, we extend previous Doppler laser cooling theory and show that low perpendicular temperatures are more readily achieved with a rotating wall than without. Detailed numerical studies determine optimal operating parameters for producing low temperature, stable 2-dimensional crystals, important for quantum information processing experiments employing Penning traps.

quant-ph↗

arXiv2016

Quantum spin dynamics and entanglement generation with hundreds of trapped ions

Quantum simulation of spin models can provide insight into complex problems that are difficult or impossible to study with classical computers. Trapped ions are an established platform for quantum simulation, but only systems with fewer than 20 ions have demonstrated quantum correlations. Here we study non-equilibrium, quantum spin dynamics arising from an engineered, homogeneous Ising interaction in a two-dimensional array of $^9$Be$^+$ ions in a Penning trap. We verify entanglement in the form of spin-squeezed states for up to 219 ions, directly observing 4.0$\pm$0.9 dB of spectroscopic enhancement. We also observe evidence of non-Gaussian, over-squeezed states in the full counting statistics. We find good agreement with ab-initio theory that includes competition between entanglement and decoherence, laying the groundwork for simulations of the transverse-field Ising model with variable-range interactions, for which numerical solutions are, in general, classically intractable.

quant-ph↗

arXiv2014

Reversing Hydride Ion Formation in Quantum Information Experiments with Be$^+$

We demonstrate photodissociation of BeH$^+$ ions within a Coulomb crystal of thousands of $^9$Be$^+$ ions confined in a Penning trap. Because BeH$^+$ ions are created via exothermic reactions between trapped, laser-cooled Be$^+$($^2\text{P}_{3/2}$) and background H$_2$ within the vacuum chamber, they represent a major contaminant species responsible for infidelities in large-scale trapped-ion quantum information experiments. The rotational-state-insensitive dissociation scheme described here makes use of 157 nm photons to produce Be$^+$ and H as products, thereby restoring Be$^+$ ions without the need for reloading. This technique facilitates longer experiment runtimes at a given background H$_2$ pressure, and may be adapted for removal of MgH$^+$ and AlH$^+$ impurities.

physics.atom-ph↗

arXiv2014

Spin Dephasing as a Probe of Mode Temperature, Motional State Distributions, and Heating Rates in a 2D Ion Crystal

We employ spin-dependent optical dipole forces to characterize the transverse center-of-mass (COM) motional mode of a two-dimensional Wigner crystal of hundreds of $^9$Be$^+$. By comparing the measured spin dephasing produced by the spin-dependent force with the predictions of a semiclassical dephasing model, we obtain absolute mode temperatures in excellent agreement with both the Doppler laser cooling limit and measurements obtained from a previously published technique (B. C. Sawyer et al. Phys. Rev. Lett. \textbf{108}, 213003 (2012)). Furthermore, the structure of the dephasing histograms allows for discrimination between initial thermal and coherent states of motion. We also apply the techniques discussed here to measure, for the first time, the ambient heating rate of the COM mode of a 2D Coulomb crystal in a Penning trap. This measurement places an upper limit on the anomalous single-ion heating rate due to electric field noise from the trap electrode surfaces of $\frac{d\bar{n}}{dt}\sim 5$ s$^{-1}$ for our trap at a frequency of 795 kHz, where $\bar{n}$ is the mean occupation of quantized COM motion in the axial harmonic well.

quant-ph↗

arXiv2013

Simulating Quantum Magnetism with Correlated Non-Neutral Ion Plasmas

By employing forces that depend on the internal electronic state (or spin) of an atomic ion, the Coulomb potential energy of a strongly coupled array of ions can be modified in a spin-dependent way to mimic effective quantum spin Hamiltonians. Both ferromagnetic and antiferromagnetic interactions can be implemented. We use simple models to explain how the effective spin interactions are engineered with trapped-ion crystals. We summarize the type of effective spin interactions that can be readily generated, and discuss an experimental implementation using single-plane ion crystals in a Penning trap.

quant-ph↗

arXiv2012

Spectroscopy and Thermometry of Drumhead Modes in a Mesoscopic Trapped-Ion Crystal using Entanglement

We demonstrate spectroscopy and thermometry of individual motional modes in a mesoscopic 2D ion array using entanglement-induced decoherence as a method of transduction. Our system is a $\sim$400 $μ$m-diameter planar crystal of several hundred $^9$Be$^+$ ions exhibiting complex drumhead modes in the confining potential of a Penning trap. Exploiting precise control over the $^9$Be$^+$ valence electron spins, we apply a homogeneous spin-dependent optical dipole force to excite arbitrary transverse modes with an effective wavelength approaching the interparticle spacing ($\sim$20 \nolinebreak$μ$m). Center-of-mass displacements below 1 nm are detected via entanglement of spin and motional degrees of freedom.

quant-ph↗

arXiv2012

Engineered 2D Ising interactions on a trapped-ion quantum simulator with hundreds of spins

The presence of long-range quantum spin correlations underlies a variety of physical phenomena in condensed matter systems, potentially including high-temperature superconductivity. However, many properties of exotic strongly correlated spin systems (e.g., spin liquids) have proved difficult to study, in part because calculations involving N-body entanglement become intractable for as few as N~30 particles. Feynman divined that a quantum simulator - a special-purpose "analog" processor built using quantum particles (qubits) - would be inherently adept at such problems. In the context of quantum magnetism, a number of experiments have demonstrated the feasibility of this approach. However, simulations of quantum magnetism allowing controlled, tunable interactions between spins localized on 2D and 3D lattices of more than a few 10's of qubits have yet to be demonstrated, owing in part to the technical challenge of realizing large-scale qubit arrays. Here we demonstrate a variable-range Ising-type spin-spin interaction J_ij on a naturally occurring 2D triangular crystal lattice of hundreds of spin-1/2 particles (9Be+ ions stored in a Penning trap), a computationally relevant scale more than an order of magnitude larger than existing experiments. We show that a spin-dependent optical dipole force can produce an antiferromagnetic interaction J_ij ~ 1/d_ij^a, where a is tunable over 0<a<3; d_ij is the distance between spin pairs. These power-laws correspond physically to infinite-range (a=0), Coulomb-like (a=1), monopole-dipole (a=2) and dipole-dipole (a=3) couplings. Experimentally, we demonstrate excellent agreement with theory for 0.05<a<1.4. This demonstration coupled with the high spin-count, excellent quantum control and low technical complexity of the Penning trap brings within reach simulation of interesting and otherwise computationally intractable problems in quantum magnetism.

quant-ph↗

arXiv2010

Corrugated Silicon Platelet Feed Horn Array for CMB Polarimetry at 150 GHz

Next generation cosmic microwave background (CMB) polarization anisotropy measurements will feature focal plane arrays with more than 600 millimeter-wave detectors. We make use of high-resolution photolithography and wafer-scale etch tools to build planar arrays of corrugated platelet feeds in silicon with highly symmetric beams, low cross-polarization and low side lobes. A compact Au-plated corrugated Si feed designed for 150 GHz operation exhibited performance equivalent to that of electroformed feeds: ~-0.2 dB insertion loss, <-20 dB return loss from 120 GHz to 170 GHz, <-25 dB side lobes and <-23 dB cross-polarization. We are currently fabricating a 50 mm diameter array with 84 horns consisting of 33 Si platelets as a prototype for the SPTpol and ACTpol telescopes. Our fabrication facilities permit arrays up to 150 mm in diameter.

astro-ph.IM↗