arXiv subjects

Robert J. Niffenegger

Publications and source records attributed to Robert J. Niffenegger.

11 recordsLinked to original sources

arXiv2026

Single- and Two-Qubit Gates Driven by an Integrated Photonic Laser

Trapped ions are a leading technology for quantum computing, but their reliance on bespoke tabletop laser and optical systems remains a major obstacle to scaling and robustness. Integrated silicon nitride lasers, compatible with future monolithic integration with surface electrode ion traps, have recently demonstrated frequency-selective qubit state preparation and measurement as well as interrogation of an optical clock transition. However, coherent qubit gates driven by integrated laser sources have not yet been demonstrated because coherent quantum logic imposes substantially more stringent performance requirements on the laser. Here, we use a visible-wavelength integrated Brillouin laser stabilized to an integrated coil resonator to drive coherent single- and two-qubit gates with $^{88}$Sr$^+$ optical qubits. We measure an average single-qubit fidelity of 99.61% $\pm$ 0.03% per Clifford gate with randomized benchmarking and use a two-qubit Mølmer-Sørensen interaction to generate an entangled Bell state with a fidelity of 92.35% $\pm$ 1.50%. The qubit exhibits a bare Ramsey coherence time of 660 $\pm$ 9 $μ$s, extended to 1.750 $\pm$ 0.033 ms by spin echo. These results demonstrate that integrated visible-wavelength narrow-linewidth photonic lasers can meet the phase-noise requirements for coherent trapped ion quantum logic, providing a path for scalable optical systems integrated within trapped ion quantum processors.

quant-ph↗

arXiv2026

Qubit operations using a modular optical system engineered with PyOpticL: a code-to-CAD optical layout tool

Complex optical design is hindered by conventional piecewise setup, which prevents modularization and therefore abstraction of subsystems at the circuit level. This limits multiple fields that require complex optics systems, including quantum computing with atoms and trapped ions, because their optical systems are not scalable. We present an open-source Python library for optical layout (PyOpticL) which uses beam-path simulation and dynamic beam-path routing for quick and easy optical layout by placing optical elements along the beam path without a priori specification, enabling adaptive, path-based layouts with automatic routing and connectivity. We use PyOpticL to create modular `drop-in' optical baseplates for common optical subsystems used in atomic and molecular optics (AMO) experiments including laser sources, frequency and intensity modulation, and locking to an atomic reference for stabilization. We demonstrate this minimal working example of a dynamic full laser system for strontium trapped ions by using it for laser cooling, qubit state detection, and over 99% fidelity single-qubit gates with 3D printed baseplates. This enables a new paradigm of design abstraction layers for engineering optical systems leveraging modular baseplates, as they can be used for any wavelength in the system and enables scaling up the underlying optical systems for quantum computers. This new open-source hardware and software code-to-CAD library seeks to foster open-source collaborative hardware and systems design across numerous fields of research including AMO physics and quantum computing with neutral atoms and trapped ions.

quant-ph↗

arXiv2025

Octave Spanning Visible to SWIR Integrated Coil-Stabilized Brillouin Lasers

Narrow linewidth stabilized lasers are central to precision applications that operate across the visible to short-wave infrared wavelengths, including optical clocks, quantum sensing and computing, ultra-low noise microwave generation, and fiber sensing. Today, these spectrally pure sources are realized using multiple external cavity tabletop lasers locked to bulk-optic free-space reference cavities. Integration of this technology will enable portable precision applications with improved reliability and robustness. Here, we report wavelength-flexible design and operation, over more than an octave span, of an integrated coil-resonator-stabilized Brillouin laser architecture. Leveraging a versatile two-stage noise reduction approach, we achieve low linewidths and high stability with chip-scale laser designs based on the ultra-low-loss, CMOS-compatible silicon nitride platform. We report operation at 674 and 698 nm for applications to strontium neutral and trapped-ion clocks, quantum sensing and computing, and at 1550 nm for applications to fiber sensing and ultra-low phase noise microwave generation. Over this range we demonstrate frequency noise reduction from 1 Hz to 10 MHz resulting in 1.0 Hz -17 Hz fundamental and 181 Hz - 630 Hz integral linewidths and an Allan deviation of 6.5 x 10-13 at 1 ms for 674 nm, 6.0 x 10-13 at 15 ms for 698 nm, and 2.6 x10-13 at 15 ms for 1550 nm. This represents the lowest achieved linewidths and highest stability for integrated stabilized Brillouin lasers over an order of magnitude improvement in operating wavelength range. These results unlock the potential of integrated, ultra-low-phase-noise stabilized lasers for precision applications and further integration in systems-on-chip solutions.

physics.optics↗

arXiv2024

Trapped ion qubit and clock operations with a visible wavelength photonic coil resonator stabilized integrated Brillouin laser

Integrating precise, stable, ultra-low noise visible light lasers into atomic systems is critical for advancing quantum information sciences and improving scalability and portability. Trapped ions are a leading approach for high-fidelity quantum computing, high-accuracy optical clocks, and precision quantum sensors. However, current ion-based systems rely on bulky, lab-scale precision lasers and optical stabilization cavities for optical clock and qubit operations, constraining the size, weight, scalability, and portability of atomic systems. Chip-scale integration of ultra-low noise lasers and reference cavities operating directly at optical clock transitions and capable of qubit and clock operations will represent a major transformation in atom and trapped ion-based quantum technologies. However, this goal has remained elusive. Here we report the first demonstration of chip-scale optical clock and qubit operations on a trapped ion using a photonic integrated direct-drive visible wavelength Brillouin laser stabilized to an integrated 3-meter coil-resonator reference cavity and the optical clock transition of a $^{88}$Sr$^+$ ion trapped on a surface electrode chip. We also demonstrate for the first time, to the best of our knowledge, trapped-ion spectroscopy and qubit operations such as Rabi oscillations and high fidelity (99%) qubit state preparation and measurement (SPAM) using direct drive integrated photonic technologies without bulk optic stabilization cavities or second harmonic generation. Our chip-scale stabilized Brillouin laser exhibits a 6 kHz linewidth with the 0.4 Hz quadrupole transition of $^{88}$Sr$^+$ and a self-consistent coherence time of 60 $μ$s via Ramsey interferometry on the trapped ion qubit. Furthermore, we demonstrate the stability of the locked Brillouin laser to 5$\times10^{-13}/ \sqrtτ$ at 1 second using dual optical clocks.

quant-ph↗

arXiv2023

A fully packaged multi-channel cryogenic module for optical quantum memories

Realizing a quantum network will require long-lived quantum memories with optical interfaces incorporated into a scalable architecture. Color centers quantum emitters in diamond have emerged as a promising memory modality due to their optical properties and compatibility with scalable integration. However, developing a scalable color center emitter module requires significant advances in the areas of heterogeneous integration and cryogenically compatible packaging. Here we report on a cryogenically stable and network compatible quantum-emitter module for memory use. This quantum-emitter module is a significant development towards advanced quantum networking applications such as distributed sensing and processing.

quant-ph↗

arXiv2022

High-Fidelity Ion State Detection Using Trap-Integrated Avalanche Photodiodes

Integrated technologies greatly enhance the prospects for practical quantum information processing and sensing devices based on trapped ions. High-speed and high-fidelity ion state readout is critical for any such application. Integrated detectors offer significant advantages for system portability and can also greatly facilitate parallel operations if a separate detector can be incorporated at each ion-trapping location. Here we demonstrate ion quantum state detection at room temperature utilizing single-photon avalanche diodes (SPADs) integrated directly into the substrate of silicon ion trapping chips. We detect the state of a trapped $^{88}\text{Sr}^{+}$ ion via fluorescence collection with the SPAD, achieving $99.92(1)\%$ average fidelity in 450 $μ$s, opening the door to the application of integrated state detection to quantum computing and sensing utilizing arrays of trapped ions.

quant-ph↗

arXiv2021

Integrated multi-wavelength control of an ion qubit

Monolithic integration of control technologies for atomic systems is a promising route to the development of quantum computers and portable quantum sensors. Trapped atomic ions form the basis of high-fidelity quantum information processors and high-accuracy optical clocks. However, current implementations rely on free-space optics for ion control, which limits their portability and scalability. Here we demonstrate a surface-electrode ion-trap chip using integrated waveguides and grating couplers, which delivers all the wavelengths of light required for ionization, cooling, coherent operations, and quantum-state preparation and detection of Sr+ qubits. Laser light from violet to infrared is coupled onto the chip via an optical-fiber array, creating an inherently stable optical path, which we use to demonstrate qubit coherence that is resilient to platform vibrations. This demonstration of CMOS-compatible integrated-photonic surface-trap fabrication, robust packaging, and enhanced qubit coherence is a key advance in the development of portable trapped-ion quantum sensors and clocks, providing a way toward the complete, individual control of larger numbers of ions in quantum information processing systems.

quant-ph↗

arXiv2019

Spin current generation and relaxation in a quenched spin-orbit-coupled Bose-Einstein condensate

Understanding the effects of spin-orbit coupling (SOC) and many-body interactions on spin transport is important in condensed matter physics and spintronics. This topic has been intensively studied for spin carriers such as electrons but barely explored for charge-neutral bosonic quasiparticles (including their condensates), which hold promises for coherent spin transport over macroscopic distances. Here, we explore the effects of synthetic SOC (induced by optical Raman coupling) and atomic interactions on the spin transport in an atomic Bose-Einstein condensate (BEC), where the spin-dipole mode (SDM, actuated by quenching the Raman coupling) of two interacting spin components constitutes an alternating spin current. We experimentally observe that SOC significantly enhances the SDM damping while reducing the thermalization (the reduction of the condensate fraction). We also observe generation of BEC collective excitations such as shape oscillations. Our theory reveals that the SOC-modified interference, immiscibility, and interaction between the spin components can play crucial roles in spin transport.

cond-mat.quant-gas↗

arXiv2017

Stueckelberg interferometry using periodically driven spin-orbit coupled Bose-Einstein condensates

We study the single-particle dispersion of a spin-orbit coupled (SOC) Bose-Einstein condensate (BEC) under the periodical modulation of the Raman coupling. This modulation introduces a further coupling of the SOC dressed eigenlevels, thus creating a second generation of modulation-dressed eigenlevels. Theoretical calculations show that these modulation-dressed eigenlevels feature a pair of avoided crossings and a richer spin-momentum locking, which we observe using BEC transport measurements. Furthermore, we use the pair of avoided crossings to engineer a tunable Stueckelberg interferometer that gives interference fringes in the spin polarization of BECs.

physics.atom-ph↗

arXiv2014

Tunable Landau-Zener transitions in a spin-orbit coupled Bose-Einstein condensate

The Landau-Zener (LZ) transition is one of the most fundamental phenomena in quantum dynamics. It describes nonadiabatic transitions between quantum states near an avoided crossing that can occur in diverse physical systems. Here we report experimental measurements and tuning of LZ transitions between the dressed eigenlevels of a Bose-Einstein condensate (BEC) that is synthetically spin-orbit (SO) coupled. We measure the transition probability as the BEC is accelerated through the SO avoided crossing and study its dependence on the coupling between the diabatic (bare) states, eigenlevel slope, and eigenstate velocity--the three parameters of the LZ model that are independently controlled in our experiments. Furthermore, we performed time-resolved measurements to demonstrate the breaking down of the spin-momentum locking of the spin-orbit-coupled BEC in the nonadiabatic regime, and we determined the diabatic switching time of the LZ transitions. Our observations show quantitative agreement with the LZ model and numerical simulations of the quantum dynamics in the quasimomentum space. The tunable LZ transition may be exploited to enable a spin-dependent atomtronic transistor.

cond-mat.quant-gas↗

arXiv2013

Optimizing the efficiency of evaporative cooling in optical dipole traps

We present a combined computational and experimental study to optimize the efficiency of evaporative cooling for atoms in optical dipole traps. By employing a kinetic model of evaporation, we provide a strategy for determining the optimal relation between atom temperature, trap depth, and average trap frequency during evaporation given experimental initial conditions. We then experimentally implement a highly efficient evaporation process in an optical dipole trap, showing excellent agreement between the theory and experiment. This method has allowed the creation of pure Bose-Einstein condensates of $^{87}$Rb with 2$\times 10^4$ atoms starting from only $5\times 10^5$ atoms initially loaded in the optical dipole trap, achieving an evaporation efficiency, $γ_{eff}$, of 4.0 during evaporation.

cond-mat.quant-gas↗