About

Professor Robert Niffenegger is an Assistant Professor in Electrical and Computer Engineering and an Adjunct Professor in the Physics Department at the University of Massachusetts Amherst. His research focuses on trapped ion quantum computing and photonics. Prior to joining UMass Amherst as faculty, he completed a postdoctoral position at MIT Lincoln Laboratory where he worked on trapped ions and integrated photonics, achieving full photonic control of a trapped ion qubit. Before his postdoctoral work, he was employed at Intel as a 7nm Integration and Yield Engineer, where he patented a new metal gate process. Professor Niffenegger earned his PhD in Physics from Purdue University, conducting quantum simulations with Bose-Einstein Condensates (BECs), and holds an undergraduate degree in Physics from Michigan Technological University.

Research topics

• Quantum mechanics
• Physics
• Materials science
• Optoelectronics
• Optics
• Atomic physics

Selected publications

• Integrated multi-wavelength control of an ion qubit

  Nature · 76 citations

  1st authorCorresponding
  • Optoelectronics
  • Physics
  • Materials science

  Abstract Monolithic integration of control technologies for atomic systems is a promising route to the development of quantum computers and portable quantum sensors1–4. Trapped atomic ions form the basis of high-fidelity quantum information processors5, 6 and high-accuracy optical clocks7. 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 chip8, 9 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-fibre 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 towards the complete, individual control of larger numbers of ions in quantum information processing systems.

  DOI

• Octave spanning operation of visible to SWIR integrated coil-stabilized Brillouin lasers

  Light Science & Applications · 2026-01-02 · 1 citations

  articleOpen access

  Abstract 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 to 10 MHz resulting in 1.0–17 Hz fundamental and 181–630 Hz integral linewidths and an Allan deviation of 6.5 × 10 −13 at 1 ms for 674 nm, 6.0 × 10 −13 at 15 ms for 698 nm, and 2.6 × 10 −13 at 15 ms for 1550 nm. This work demonstrates the lowest fundamental and integral linewidths and highest stability achieved to date for stabilized Brillouin lasers with integrated coil-resonator references, with over an order of magnitude improvement in the visible 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.

  PublisherOA PDFDOI

• Chip scale coil stabilized Brillouin laser driving a room temperature trapped ion qubit

  Nature Communications · 2026-03-03

  articleOpen access

  Abstract Photonic integrated stable, ultra-low-noise lasers are essential for scalable and portable quantum information systems. Trapped ions are a leading modality for quantum computing and optical clocks, with room-temperature operation enabling portable applications. Current systems rely on free-space lasers and stabilization cavities, frequency conversion, and cryogenic infrastructure, limiting size, weight, and power. We demonstrate a chip-scale coil-stabilized 674 nm Brillouin laser driving qubit state preparation and measurement and the optical clock transition in a room-temperature surface electrode trapped 88 Sr + ion without a bulk-optic reference cavity. The CMOS compatible silicon nitride integrated 3-meter coil and Brillouin laser achieve 8.8×10 -13 stability at 20 ms, sufficient to interrogate the 0.4 Hz quadrupole optical clock transition. The ion-disciplined laser achieves 5.3 $$\times {10}^{-13}/\sqrt{\tau }$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mo>×</mml:mo> <mml:msup> <mml:mrow> <mml:mn>10</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>13</mml:mn> </mml:mrow> </mml:msup> <mml:mo>/</mml:mo> <mml:msqrt> <mml:mrow> <mml:mi>τ</mml:mi> </mml:mrow> </mml:msqrt> </mml:math> stability, spectroscopy with 1.5 kHz linewidths, and 99.6% qubit state preparation and measurement fidelity. These results light the way towards integration of stabilized lasers with trapped-ion chips for portable and robust quantum technologies.

  PublisherOA PDFDOI

• Integrated visible light coil-resonator stabilized Brillouin lasers for Sr neutral and trapped-ion clock and qubit transitions

  2025-01-01

  article

  We demonstrate stabilization of 698 and 674 nm integrated Brillouin lasers to integrated 3-m coil resonators for neutral and trapped-ion strontium clock applications, achieving record-low 17 Hz fundamental and 660 Hz integral linewidths.

  PublisherDOI

• A modular and compact trapped ion quantum computer

  2025-01-01

  articleSenior author

  We demonstrate a compact and modular trapped ion quantum computer based on modular optical baseplates and subsystems created using a beam-path based optical layout tool, PyOpticL. These same baseplates and subsystems have direct applications to all AMO experiments including neutral atom quantum computers.

  PublisherDOI

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

  ArXiv.org · 2025-01-24

  preprintOpen accessSenior author

  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 dynamic 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 99.9% 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.

  PublisherOA PDFDOI

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

  arXiv (Cornell University) · 2024-02-26 · 11 citations

  preprintOpen access

  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.

  PublisherOA PDFDOI

• Development of a compact trapped ion quantum computer

  Quantum 2.0 Conference and Exhibition · 2024-01-01

  articleSenior author

  We report progress developing a compact trapped ion quantum computer and optical clock, based on a photonic integrated direct-drive visible wavelength Brillouin laser stabilized to an integrated 3-meter coil-resonator reference cavity.

  PublisherDOI

• High-fidelity trapped-ion state detection with an integrated avalanche photodiode

  2023-03-08 · 3 citations

  article

  Integrated technologies represent a key enabling capability for future compact and portable atomic physics systems, including optical clocks and other sensors. In this talk, I will discuss our recent demonstration of high-fidelity detection of the state of a trapped Sr+ ion with a single-photon avalanche detector (SPAD) integrated into a microfabricated surface-electrode trap. Using an adaptive technique, we achieve ion state detection in 450 us with 99.92(1)% average fidelity. I will also discuss ongoing efforts to combine integrated detectors with integrated photonics to enable ion traps that completely eliminate the need for free-space optics for light delivery and collection.

  PublisherDOI

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

  arXiv (Cornell University) · 2023-02-24

  preprintOpen access

  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.

  PublisherOA PDFDOI

Frequent coauthors

• Dave Kharas

  Massachusetts Institute of Technology

  26 shared

• Jules Stuart

  24 shared

• Colin Bruzewicz

  24 shared

• John Chiaverini

  Massachusetts Institute of Technology

  22 shared

• Robert McConnell

  21 shared

• David Reens

  MIT Lincoln Laboratory

  20 shared

• Abraham Olson

  Purdue University West Lafayette

  17 shared

• Jeremy Sage

  17 shared

Labs

• Niffenegger LabPI

Awards & honors

• NSF CAREER Award