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We propose and demonstrate a protocol for high-fidelity indirect readout of trapped ion hyperfine qubits, where the state of a $^9\text{Be}^+$ qubit ion is mapped to a $^{25}\text{Mg}^+$ readout ion using laser-driven Raman transitions. By partitioning the $^9\text{Be}^+$ ground state hyperfine manifold into two subspaces representing the two qubit states and choosing appropriate laser parameters, the protocol can be made robust to spontaneous photon scattering errors on the Raman transitions, enabling repetition for increased readout fidelity. We demonstrate combined readout and back-action errors for the two subspaces of $1.2^{+1.1}_{-0.6} \times 10^{-4}$ and $0^{+1.9}_{-0} \times 10^{-5}$ with 68% confidence while avoiding decoherence of spectator qubits due to stray resonant light that is inherent to direct fluorescence detection., 7 + 6 pages, 3 + 1 figures

We demonstrate a simplified method for dissipative generation of an entangled state of two trapped-ion qubits. Our implementation produces its target state faster and with higher fidelity than previous demonstrations of dissipative entanglement generation and eliminates the need for auxiliary ions. The entangled singlet state is generated in $\sim$7 ms with a fidelity of 0.949(4). The dominant source of infidelity is photon scattering. We discuss this error source and strategies for its mitigation., 12 pages, 6 figures

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We present protocols for dissipative entanglement of three trapped-ion qubits and discuss a scheme that uses sympathetic cooling as the dissipation mechanism. This scheme relies on tailored destructive interference to generate any one of six entangled W states in a three-ion qubit space. Using a beryllium–magnesium ion crystal as an example system, we theoretically investigate the protocol's performance and the effects of likely error sources, including thermal secular motion of the ion crystal, calibration imperfections, and spontaneous photon scattering. We estimate that a fidelity of ~98% may be achieved in typical trapped ion experiments with ~1 ms interaction time. These protocols avoid timescale hierarchies for faster preparation of entangled states., New Journal of Physics, 23 (7), ISSN:1367-2630

For many quantum systems intended for information processing, one detects the logical state of a qubit by integrating a continuously observed quantity over time. For example, ion and atom qubits are typically measured by driving a cycling transition and counting the number of photons observed from the resulting fluorescence. Instead of recording only the total observed count in a fixed time interval, one can observe the photon arrival times and get a state detection advantage by using the temporal structure in a model such as a Hidden Markov Model. We study what further advantage may be achieved by applying pulses to adaptively transform the state during the observation. We give a three-state example where adaptively chosen transformations yield a clear advantage, and we compare performances on an ion example, where we see improvements in some regimes. We provide a software package that can be used for exploration of temporally resolved strategies with and without adaptively chosen transformations., Submitted for publication. 26 pages, 8 figures

Characterization and suppression of noise are essential for the control of harmonic oscillators in the quantum regime. We measure the noise spectrum of a quantum harmonic oscillator from low frequency to near the oscillator resonance by sensing its response to amplitude modulated periodic drives with a qubit. Using the motion of a trapped ion, we experimentally demonstrate two different implementations with combined sensitivity to noise from 500 Hz to 600 kHz. We apply our method to measure the intrinsic noise spectrum of an ion trap potential in a previously unaccessed frequency range., 6 + 10 pages, 4 + 7 figures

Orthogonal control of both degrees of freedom of a Kerr comb soliton allows high-precision atomic spectroscopy and stabilization., Microresonator-based soliton frequency combs, microcombs, have recently emerged to offer low-noise, photonic-chip sources for applications, spanning from timekeeping to optical-frequency synthesis and ranging. Broad optical bandwidth, brightness, coherence, and frequency stability have made frequency combs important to directly probe atoms and molecules, especially in trace gas detection, multiphoton light-atom interactions, and spectroscopy in the extreme ultraviolet. Here, we explore direct microcomb atomic spectroscopy, using a cascaded, two-photon 1529-nm atomic transition in a rubidium micromachined cell. Fine and simultaneous repetition rate and carrier-envelope offset frequency control of the soliton enables direct sub-Doppler and hyperfine spectroscopy. Moreover, the entire set of microcomb modes are stabilized to this atomic transition, yielding absolute optical-frequency fluctuations at the kilohertz level over a few seconds and

Complex systems are a proving ground for fundamental interactions between components and their collective emergent phenomena. Through intricate design, integrated photonics offers intriguing nonlinear interactions that create new patterns of light. In particular, the canonical Kerr-nonlinear resonator becomes unstable with a sufficiently intense traveling-wave excitation, yielding instead a Turing pattern composed of a few interfering waves. These resonators also support the localized soliton pulse as a separate nonlinear stationary state. Kerr solitons are remarkably versatile for applications, but they cannot emerge from constant excitation. Here, we explore an edge-less photonic-crystal resonator (PhCR) that enables spontaneous formation of a soliton pulse in place of the Turing pattern. We design a PhCR in the regime of single-azimuthal-mode engineering to re-balance Kerr-nonlinear frequency shifts in favor of the soliton state, commensurate with how group-velocity dispersion balances nonlinearity. Our experiments establish PhCR solitons as mode-locked pulses by way of ultraprecise optical-frequency measurements, and we characterize their fundamental properties. Our work shows that sub-wavelength nanophotonic design expands the palette for nonlinear engineering of light., Comment: main text 6 pages, 4 figures; supplemental 4 pages, 2 figures

We introduce edgeless photonic-crystal resonators, creating photonic bandgap atop one azimuthal mode. The bandgap affects re-balancing of resonator Kerr-shift to enable spontaneous soliton generation, which we demonstrate by tuning laser onto resonance with the mode.

Microglia (MG), a heterogeneous population of phagocytic cells, play important roles in central nervous system (CNS) homeostasis and neural plasticity. Under steady-state conditions, MG maintain homeostasis by producing antiinflammatory cytokines and neurotrophic factors, support myelin production, and remove synapses and cellular debris, as well as participating in "cross-correction," a process that supplies neurons with key factors for executing autophagy-lysosomal function. As sentinels for the immune system, MG also detect "danger" signals (pathogenic or traumatic insult), become activated, produce proinflammatory cytokines, and recruit monocytes and dendritic cells to the site of damage through a breached blood-brain barrier or via brain lymphatics. Failure to effectively resolve MG activation can be problematic and can lead to chronic inflammation, a condition proposed to underlie CNS pathophysiology in heritable brain disorders and age-related neurodegenerative and cognitive decline. Here, we show that APOBEC1-mediated RNA editing occurs within MG and is key to maintaining their resting status. Like bone marrow-derived macrophages, RNA editing in MG leads to overall changes in the abundance of edited proteins that coordinate the function of multiple cellular pathways. Conversely, mice lacking the APOBEC1 editing function in MG display evidence of dysregulation, with progressive age-related signs of neurodegeneration, characterized by clustering of activated MG, aberrant myelination, increased inflammation, and lysosomal anomalies that culminate in behavioral and motor deficiencies. Collectively, our study identifies posttranscriptional modification by RNA editing as a critical regulatory mechanism of vital cellular functions that maintain overall brain health.

We predict subharmonic entrainment of breather-soliton oscillations to a periodic perturbation at the round-trip time ${T}_{R}$ in Kerr-nonlinear optical resonators; an integer ratio ${T}_{b}/{T}_{R}=N\ensuremath{\gg}1$ results for breathing period ${T}_{b}$. Rigid entrainment is observed with intermediate finesse ($\mathcal{F}\ensuremath{\sim}30--40$) for $N$ up to 20, and we propose a way to realize higher entrainment ratios at higher finesse. This nontrivial synchronization across the widely separated timescales of the photon lifetime and round-trip time points to a new direction for research in this field and may find application, for example, in the measurement of a pulse train repetition rate that is electronically inaccessible.

Precise measurements of the frequencies of light waves have become common with mode-locked laser frequency combs1. Despite their huge success, optical frequency combs currently remain bulky and expensive laboratory devices. Integrated photonic microresonators are promising candidates for comb generators in out-of-the-lab applications, with the potential for reductions in cost, power consumption and size. Such advances will significantly impact fields ranging from spectroscopy and trace gas sensing to astronomy, communications and atomic time-keeping. Yet, in spite of the remarkable progress shown over recent years, microresonator frequency combs (‘microcombs’) have been without the key function of direct f–2f self-referencing, which enables precise determination of the absolute frequency of each comb line. Here, we realize this missing element using a 16.4 GHz microcomb that is coherently broadened to an octave-spanning spectrum and subsequently fully phase-stabilized to an atomic clock. We show phase-coherent control of the comb and demonstrate its low-noise operation.

Subharmonic resonance behaviors are investigated for the classical hydrogen atom, with classical radiation damping and circularly polarized light acting on the classical electron. This study is intended for both potential experimental applications as well as for deeper theoretical purposes. Long resonant states are predicted for realistic Rydberg atoms and highly excited hydrogen states. Several previously undiscovered physical effects are predicted. First, the semimajor axis remains relatively constant when in subharmonic resonance; second, the eccentricity steadily increases until a maximum, critical value is reached, at which point orbital decay sets in. If the initial orbit is circular, this critical eccentricity value is shown to always be the same for each subharmonic condition, regardless of the initial orbital radius. An analytic derivation for this result is presented. The illustrated dynamics are of interest for the classical theory of stochastic electrodynamics (SED) regarding whether SED can fundamentally describe more of quantum phenomena, particularly atomic excited state behavior and related emission and absorption spectra. Also of interest are how classical resonances can be imposed on a near continuum of quantum states. Finally, there may be future technological applications, such as “reading” and “writing” information into Rydberg atoms in the form of subharmonic resonances.

We experimentally demonstrate a versatile technique for performing dual-comb interferometry using a single frequency comb. By rapid switching of the repetition rate, the output pulse train can be delayed and heterodyned with itself to produce interferograms. The full speed and resolution of standard dual-comb interferometry is preserved while simultaneously offering a significant experimental simplification and cost savings. We show that this approach is particularly suited for absolute distance metrology due to an extension of the non-ambiguity range as a result of the continuous repetition-rate switching.

We demonstrate direct generation of Kerr-microresonator solitons with measured 100 percent success rate using an increasing-frequency scan of a phase-modulated pump laser. A reversed soliton step is observed. The phase modulation controls the solitons' properties.

We show how microresonators driven by optical pulses enable the efficient, low-power generation of Kerr solitons and potentially open the door to new nonlinear regimes. We observe two new kinds of low-noise Kerr frequency combs.

The use of proteasome inhibitors (PI) as targeted chemotherapeutics have significantly improved survival in patients with multiple myeloma (MM). However, rare and serious cardiovascular complications have occurred as a result of their use, most commonly congestive heart failure, hypertension, and arrhythmias. MM occurs in an aged population with many concurrent cardiovascular risk factors. The primary disease process also contributes to cardiovascular complications. Furthermore, many MM patients have prior exposure to cardiotoxic chemotherapy such as anthracyclines. Because of these occurrences, the identification, prevention, and management of cardiovascular complications is made increasingly difficult. Various clinical studies and case reports have documented cardiotoxicity among all 3 of the currently approved PIs, bortezomib, carfilzomib, and ixazomib. Carfilzomib has shown the highest rates of cardiotoxicity, whereas there is conflicting evidence regarding bortezomib's role in producing cardiotoxicity. However, various case reports have documented the existence of adverse cardiac effects. Higher frequencies of complications have also been seen in "real-life" populations with cardiovascular co-morbidities who were originally excluded from clinical studies. Ixazomib, the most recently approved PI, has also been proposed to cause cardiotoxicity, elucidating a possible class effect. PIs are thought to cause cardiotoxicity through the unfolded protein response, leading to apoptosis in cardiac myocytes. Apremilast and rutin have been used in an animal model to reverse this signaling. Standardized guidelines identifying patients at greatest risk, to prevent and manage complications, have not yet been developed. Efforts have been made to prioritize patients older than 60 years with anthracycline exposure, cardiovascular risk factors, or amyloidosis. Withholding medication, using slower-infusion times, limiting fluids and providing supportive therapy have been successful. Screening echocardiograms have not been proven effective.

Using silicon nitride and aluminum nitride chip-integrated waveguides, we demonstrate supercontinuum spanning 500-4000 nm. We detect the carrier-envelope-offset frequency using total optical power below 15 mW, or, alternatively, directly from the waveguide output.

Using aluminum-nitride photonic-chip waveguides, we generate optical frequency comb supercontinuum spanning 500 to 4000 nm. We detect and stabilize the offset frequency of the compact laser comb oscillator directly using the waveguide output.

Interferometric scattering microscopy (iSCAT) is a light scattering-based imaging modality that offers a unique combination of imaging speed and precision for tracking nanoscopic labels and enables label-free optical sensing down to the single-molecule level. In contrast to fluorescence, iSCAT does not suffer from limitations associated with dye photochemistry and photophysics, or the requirement for fluorescent labeling. Here we present a protocol for constructing an iSCAT microscope from commercially available optical components and demonstrate its compatibility with simultaneously operating single-molecule, objective-type, total internal reflection fluorescence microscopy. Given an intermediate level of experience with optics and microscopy, for instance graduate-level familiarity with laser beam steering and optical components, this protocol can be completed in a time frame of 2 weeks.

Epigenetic alterations are necessary for the establishment of functional and phenotypic diversity in the populations of immune cells of the monocytic lineage. The epigenetic status of individual genes at different time points defines their transcriptional responses throughout development and in response to environmental stimuli. Epigenetic states are defined at the level of DNA modifications, chromatin modifications, as well as at the level of RNA base changes through RNA editing. Drawing from lessons regarding the epigenome and epitranscriptome of cells of the monocytic lineage in the periphery, and from recently published RNAseq data deriving from brain-resident monocytes, we discuss the impact of modulation of these epigenetic states and how they affect processes important for the development of a healthy brain, as well as mechanisms of neurodegenerative disease and aging. An understanding of the varied brain responses and pathologies in light of these novel gene regulatory systems in monocytes will lead to important new insights in the understanding of the aging process and the treatment and diagnosis of neurodegenerative disease.

Self-organized solitons confined to an optical resonator would offer unique capabilities for experiments in communication, computation and sensing with light. Here, we report the observation of soliton crystals in monolithic Kerr microresonators—spontaneously and collectively ordered ensembles of co-propagating solitons whose interactions discretize their allowed temporal separations. We unambiguously identify and characterize soliton crystals through analysis of their ‘fingerprint’ optical spectra, which arise from spectral interference between the solitons. We identify a rich space of soliton crystals exhibiting crystallographic defects and we perform time-domain measurements to directly confirm our inference of their crystal structure. Soliton crystallization is explained by long-range soliton interactions mediated by resonator mode degeneracies, and we probe the qualitative difference between soliton crystals and the disorganized soliton liquid that would form in the absence of these interactions. Our work explores the physics of monolithic Kerr resonators in a regime of dense soliton occupation and offers a way to increase the efficiency of Kerr combs. Furthermore, the extreme degeneracy of the configuration space of soliton crystals suggests an implementation for an on-chip optical buffer. The observation of soliton crystals in monolithic Kerr microresonators is reported. The physics of such resonators is explored in a regime of dense soliton occupation, offering a way to increase the efficiency of Kerr combs.

We explore ordered soliton ensembles in Kerr microresonators. These soliton crystals are stabilized through collective soliton interactions mediated by defects in resonator mode structure, and require only adiabatic tuning of the pump for generation.

We explore highly ordered configurations of up to 24 Kerr-cavity solitons in a silica disk microresonator. Our work relaxes thermal stability requirements for Kerr-soliton generation, and suggests a mechanism that mediates soliton interactions.

To guide experimental efforts, we employ numerical simulations to design tapered silicon nitride waveguides for broadband supercontinuum generation from low-energy femtosecond pulses. A three-stage broadening scheme provides coherent supercontinuum with picosecond pulses, enabling chip-scale broadband sources.

We explore highly ordered configurations of up to 27 Kerr-cavity solitons in a silica disk microresonator. Our work relaxes thermal stability requirements for Kerr-soliton generation, and suggests a mechanism that mediates soliton interactions.

We demonstrate dispersion control in optical resonators over an octave of optical bandwidth. Dispersion is engineered lithographically and Q factor is maintained above 100 million, which is critical for efficient nonlinear devices such as microcombs.

Optical frequency combs based on solitons in nonlinear microresonators open up new regimes for optical metrology and signal processing across a range of expanding and emerging applications. In this work, we advance these combs toward applications by demonstrating protected single-soliton formation and operation in a Kerr-nonlinear microresonator using a phase-modulated pump laser. Phase modulation gives rise to spatially/temporally varying effective loss and detuning parameters, leading to an operation regime in which multi-soliton degeneracy is lifted and a single soliton is the only observable behavior. We achieve direct, on-demand excitation of single solitons as indicated by reversal of the characteristic “soliton step.” Phase modulation also enables precise, high bandwidth control of the soliton pulse train’s properties, and we measure dynamics that agree closely with simulations. We show that the technique can be extended to high-repetition-frequency Kerr solitons through subharmonic phase modulation. These results will facilitate straightforward generation and control of Kerr-soliton microcombs for integrated photonics systems.