Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

Optics Express

Bespoke mirror fabrication for quantum simulation with light in open-access microcavities

Benjamin T. Walker, Benjamin J. Ash, Aurelien A. P. Trichet, Jason M. Smith, Robert A. Nyman

Published Mar 9, 2021• 15 citations
Publisher

Abstract

In this work, we use focused ion beam (FIB) milling to generate custom mirror shapes for quantum simulation in optical microcavities. In the paraxial limit, light in multimode optical microcavities follows an equation of motion which is equivalent to Schrödinger’s equation, with the surface topography of the mirrors playing the role of the potential energy landscape. FIB milling allows us to engineer a wide variety of trapping potentials for microcavity light, through exquisite control over the mirror topography, including 2D box, 1D waveguide, and Mexican hat potentials. The 2D box potentials are sufficiently flat over tens of microns, that the optical modes of the cavity, found by solving Schrödinger’s equation on the measured cavity topography, are standing-wave modes of the box, rather than localised to deviations. The predicted scattering loss due to surface roughness measured using atomic force microscopy is found to be 177 parts per million, which corresponds to a cavity finesse of 2.2 × 104 once other losses have been taken into account. Spectra from dye-filled microcavities formed using these features show thermalised light in flat 2D potentials close to dye resonance, and spectrally-resolved cavity modes at the predicted frequencies for elliptical potentials. These results also represent a first step towards realising superfluid light and quantum simulation in arbitrary-shaped optical microcavities using FIB milling.

DOI
10.1364/oe.422127

Related papers

High precision micro-optical elements on fiber facets via focused-ion beam machining

Raman Kumar, Sebastian Will

Fiber-integrated micro-optical elements promise a scalable approach to photon collection and beam shaping for quantum information processing. Here, we demonstrate single-step micro-machining of micro-spherical, micro-spiral, and micro-axicon structures directly onto the core of single-mode optical fibers using focused-ion beam (FIB) machining with nanometer-scale precision. Atomic force microscopy reveals that micro-concave and micro-convex spherical surfaces achieve shape accuracies of $λ/50$ and $λ/33$ (at $λ= 633$~nm), respectively. Via optical characterization using a He-Ne laser (633~nm), we verify for the micro-spiral and -axicon structures the expected far-field donut beam patterns. Via Mach-Zehnder interferometry, we verify the azimuthal and radial phase structure of the light emitted from the spiral and axicon fibers, respectively. Surface metrology further shows that FIB processing introduces only a small increase in nanoscale roughness while preserving sub-nanometer RMS surface quality. The monolithically integrated fiber micro-optic elements demonstrated here enable broad use in quantum technology, for example, fiber micro-cavities for cavity quantum electrodynamics, beam shaping for neutral atom trapping, and the generation of structured light for free-space quantum network links.

physics.opticsCross-listedarXiv:2604.18426•Apr 21, 2026

Fabrication of optical nanofibre-based cavities using focussed ion-beam milling: a review

Priscila Romagnoli, Maki Maeda, Jonathan M. Ward +2 more

Abstract Nanofibre-based optical cavities are particularly useful for quantum optics applications, such as the development of integrated single-photon sources, and for studying fundamental light–matter interactions in cavity quantum electrodynamics (cQED). Although several techniques have been used to produce such cavities, focussed ion beam (FIB) milling is becoming popular; it can be used for the fabrication of complex structures directly in the nanofibre. However, it is challenging to mill insulating materials with highly curved geometries and large aspect ratios, such as silica nanofibres, due to charge accumulation in the material. In this article, we highlight the main features of nanofibres and briefly review cQED with nanofibre-based optical cavities. An overview of the milling process is given with a summary of different FIB milled devices and their applications. Finally, we present our technique to produce nanofibre cavities by FIB milling. To overcome the aforementioned challenges, we present a specially designed base plate with an indium tin oxide (ITO)-coated Si substrate and outline our procedure, which improves stability during milling and increases repeatability.

arXiv:2001.07881•Applied Physics B•May 31, 2020•36 citations

Fibre-tip microcavities for enhanced ion-photon coupling in scalable quantum information networks

Péter Horák, Nina Podoliak, Hiroki Takahashi +1 more

Scalable quantum information processing requires efficient coupling between stationary qubits (trapped atoms, ions, NV centres, etc.) via “flying” single-photon qubits. Here we investigate the optimisation and integration of fibre-tip microcavities into radiofrequency ion traps to achieve (i) high-fidelity transfer of ion qubits onto single photons, (ii) low-loss coupling of cavity photons into single-mode optical fibre, and (iii) achieving conditions (i) and (ii) without disturbing the ion trap. Our cavities are fabricated by laser micro-machining the ends of optical fibres and subsequent coating with a thin dielectric mirror, giving rise to cavity mirrors with a Gaussian profile. These cavities allow for small mode volume and thus large ion-photon coupling fulfilling requirement (i), while simultaneously providing intrinsic coupling to optical fibres, requirement (ii), as long as mode matching between the cavity mode and the fibre mode can be achieved at the cavity mirror. Using a semi-analytical numerical method, we show that Gaussian-shaped mirrors can in fact be used to enhance ion-photon coupling beyond what is possible with more common spherical cavity mirrors. Ion traps are notoriously sensitive to the presence of dielectric materials such as cavity mirrors near the trap centre, preventing requirement (iii) from being achieved. We performed an extensive numerical study of five different common ion traps to find the optimum configurations for integrating fibre-tip cavities with minimised effects on the trapping potentials. We discuss these results and present simple and effective design rules for realising optimum ion-cavity based quantum networks.

•Sep 20, 2016•0 citations

Optical cavities for quantum information processing with trapped neutral atoms

Thomas H. Doherty

A leading strategy for the creation of a scalable quantum computer is through a networked architecture. This would comprise stationary nodes for quantum information processing and photonic channels for their communication and entanglement distribution. In this scheme a coherent interface between light and matter is a critical component, facilitating the deterministic and reversible transfer of quantum information between stationary and travelling qubits. This requirement may be fulfilled by a high finesse optical cavity, whose radiation field is strongly coupled to a trapped quantised emitter. Neutral atoms are an ideal species for the development of such a device, given their inherent compatibility with dielectric mirror surfaces. However, an outstanding challenge in building an elementary network of neutral atom-cavity systems is in establishing a single atom dipole trap within each cavity mode. This thesis presents the development of an open-access cavity suitable for single atom localisation, whilst maintaining strong atom-cavity coupling, {g0,κ,γ} = {11,2.1,3} × 2πMHz, and the efficient extraction of generated photons, η=0.5. We consider cavity design methodology, deriving a connection between the physical properties of the optical resonator and its intended role in the production of single photons. An experimental platform is developed for the creation of cavity mirrors by laser ablation, with a high degree of geometrical control. This is used to produce a set of pyramidal micro-mirrors, demonstrated to represent a favourable alternative to the widespread adoption of fibre-tip cavities. These pyramidal mirrors are shown to support multi-feature resonators, allowing several atom-cavity interfaces to be formed using a pair of substrates. By developing a novel procedure for mirror alignment, a hybrid mirror cavity is fabricated and integrated into an experimental architecture tailored for atomic trapping. Suitability of the cavity for future experimentation is demonstrated by frequency stabilisation to an atomic resonance of 87Rb.

•Jan 1, 2021•0 citations

Microfabricated Surface Trap and Cavity Integration for Trapped Ion Quantum Computing

Van Rynbach, Jacques André

Atomic ions trapped in microfabricated surface traps can be utilized as a physical platform with which to build a quantum computer. They possess many of the desirable characteristics of such a device, including high fidelity state preparation and readout, universal logic gates, and long coherence times, and can be readily entangled with each other through photonic interconnects. The use of optical cavities integrated with trapped ion qubits as a photonic interface presents the possibility for order of magnitude improvements in performance in several key areas for their use in quantum computation. The first part of this thesis describes the design and fabrication of a novel surface trap for integration with an optical cavity. The trap is custom made on a highly reflective mirror surface and includes the capability of moving the ion trap location along all three trap axes with nanometer scale precision. The second part of this thesis demonstrates the suitability of small microcavities formed from laser ablated, fused silica substrates with radii of curvature in the 300-500 micron range for use with the mirror trap as part of an integrated ion trap cavity system. Quantum computing applications for such a system include dramatic improvements in the photon entanglement rate of up to 10 kHz, the qubit measurement time down to 1 microsecond, and the qubit measurement error rate down to the 1e-5 range. The final part of this thesis describes a performance simulator for exploring the physical resource requirements and performance demands to scale a quantum computer to sizes capable of implementing quantum algorithms beyond the limits of classical computation.

•Jan 1, 2016•0 citations

Advanced mirror shapes for mode enhancement in plano-concave cavities

William J. Hughes, Péter Horák

Optical cavities are frequently used in quantum technologies to enhance light matter interactions, with applications including single photon generation and entanglement of distant emitters. The Fabry-Pérot resonator is a popular choice for its high optical access and large emitter-mirror separation. A typical configuration, particularly for emitters that should not be placed close to the mirror surface like trapped ions and Rydberg atoms, features two spherical mirrors placed around a central emitter, but this arrangement can put demanding requirements on the mirror alignment. In contrast, plano-concave cavities are tolerant to mirror misalignment and only require the manufacture of one curved mirror, but have limited ability to focus light in the centre of the cavity. Here we show how mirror shaping can overcome this limitation of plano-concave cavities while preserving the key advantages. We demonstrate through numerical simulations that simple mirror shaping can increase coupling between a plano-concave cavity and a central emitter by an order of magnitude, even rivalling misalignment-sensitive concave-concave counterparts for achievable interaction strength. We use these observations to establish the conditions under which plano-concave cavities with shaped mirrors could improve the performance and practicality of emitter-cavity systems.

arXiv:2510.07251•Scientific Reports•Mar 11, 2026•0 citations
In this work, we use focused ion beam (FIB) milling to generate custom mirror shapes for quantum simulation in optical microcavities. In the paraxial limit, light in multimode optical microcavities follows an equation of motion which is equivalent to Schrödinger’s equation, with the surface topography of the mirrors playing the role of the potential energy landscape. FIB milling allows us to engineer a wide variety of trapping potentials for microcavity light, through exquisite control over the mirror topography, including 2D box, 1D waveguide, and Mexican hat potentials. The 2D box potentials are sufficiently flat over tens of microns, that the optical modes of the cavity, found by solving Schrödinger’s equation on the measured cavity topography, are standing-wave modes of the box, rather than localised to deviations. The predicted scattering loss due to surface roughness measured using atomic force microscopy is found to be 177 parts per million, which corresponds to a cavity finesse of 2.2 × 104 once other losses have been taken into account. Spectra from dye-filled microcavities formed using these features show thermalised light in flat 2D potentials close to dye resonance, and spectrally-resolved cavity modes at the predicted frequencies for elliptical potentials. These results also represent a first step towards realising superfluid light and quantum simulation in arbitrary-shaped optical microcavities using FIB milling.
Fiber-integrated micro-optical elements promise a scalable approach to photon collection and beam shaping for quantum information processing. Here, we demonstrate single-step micro-machining of micro-spherical, micro-spiral, and micro-axicon structures directly onto the core of single-mode optical fibers using focused-ion beam (FIB) machining with nanometer-scale precision. Atomic force microscopy reveals that micro-concave and micro-convex spherical surfaces achieve shape accuracies of λ/50λ/50λ/50 and λ/33λ/33λ/33 (at λ=633λ= 633λ=633~nm), respectively. Via optical characterization using a He-Ne laser (633~nm), we verify for the micro-spiral and -axicon structures the expected far-field donut beam patterns. Via Mach-Zehnder interferometry, we verify the azimuthal and radial phase structure of the light emitted from the spiral and axicon fibers, respectively. Surface metrology further shows that FIB processing introduces only a small increase in nanoscale roughness while preserving sub-nanometer RMS surface quality. The monolithically integrated fiber micro-optic elements demonstrated here enable broad use in quantum technology, for example, fiber micro-cavities for cavity quantum electrodynamics, beam shaping for neutral atom trapping, and the generation of structured light for free-space quantum network links.
Abstract Nanofibre-based optical cavities are particularly useful for quantum optics applications, such as the development of integrated single-photon sources, and for studying fundamental light–matter interactions in cavity quantum electrodynamics (cQED). Although several techniques have been used to produce such cavities, focussed ion beam (FIB) milling is becoming popular; it can be used for the fabrication of complex structures directly in the nanofibre. However, it is challenging to mill insulating materials with highly curved geometries and large aspect ratios, such as silica nanofibres, due to charge accumulation in the material. In this article, we highlight the main features of nanofibres and briefly review cQED with nanofibre-based optical cavities. An overview of the milling process is given with a summary of different FIB milled devices and their applications. Finally, we present our technique to produce nanofibre cavities by FIB milling. To overcome the aforementioned challenges, we present a specially designed base plate with an indium tin oxide (ITO)-coated Si substrate and outline our procedure, which improves stability during milling and increases repeatability.
Scalable quantum information processing requires efficient coupling between stationary qubits (trapped atoms, ions, NV centres, etc.) via “flying” single-photon qubits. Here we investigate the optimisation and integration of fibre-tip microcavities into radiofrequency ion traps to achieve (i) high-fidelity transfer of ion qubits onto single photons, (ii) low-loss coupling of cavity photons into single-mode optical fibre, and (iii) achieving conditions (i) and (ii) without disturbing the ion trap. Our cavities are fabricated by laser micro-machining the ends of optical fibres and subsequent coating with a thin dielectric mirror, giving rise to cavity mirrors with a Gaussian profile. These cavities allow for small mode volume and thus large ion-photon coupling fulfilling requirement (i), while simultaneously providing intrinsic coupling to optical fibres, requirement (ii), as long as mode matching between the cavity mode and the fibre mode can be achieved at the cavity mirror. Using a semi-analytical numerical method, we show that Gaussian-shaped mirrors can in fact be used to enhance ion-photon coupling beyond what is possible with more common spherical cavity mirrors. Ion traps are notoriously sensitive to the presence of dielectric materials such as cavity mirrors near the trap centre, preventing requirement (iii) from being achieved. We performed an extensive numerical study of five different common ion traps to find the optimum configurations for integrating fibre-tip cavities with minimised effects on the trapping potentials. We discuss these results and present simple and effective design rules for realising optimum ion-cavity based quantum networks.
A leading strategy for the creation of a scalable quantum computer is through a networked architecture. This would comprise stationary nodes for quantum information processing and photonic channels for their communication and entanglement distribution. In this scheme a coherent interface between light and matter is a critical component, facilitating the deterministic and reversible transfer of quantum information between stationary and travelling qubits. This requirement may be fulfilled by a high finesse optical cavity, whose radiation field is strongly coupled to a trapped quantised emitter. Neutral atoms are an ideal species for the development of such a device, given their inherent compatibility with dielectric mirror surfaces. However, an outstanding challenge in building an elementary network of neutral atom-cavity systems is in establishing a single atom dipole trap within each cavity mode. This thesis presents the development of an open-access cavity suitable for single atom localisation, whilst maintaining strong atom-cavity coupling, {g0,κ,γ} = {11,2.1,3} × 2πMHz, and the efficient extraction of generated photons, η=0.5. We consider cavity design methodology, deriving a connection between the physical properties of the optical resonator and its intended role in the production of single photons. An experimental platform is developed for the creation of cavity mirrors by laser ablation, with a high degree of geometrical control. This is used to produce a set of pyramidal micro-mirrors, demonstrated to represent a favourable alternative to the widespread adoption of fibre-tip cavities. These pyramidal mirrors are shown to support multi-feature resonators, allowing several atom-cavity interfaces to be formed using a pair of substrates. By developing a novel procedure for mirror alignment, a hybrid mirror cavity is fabricated and integrated into an experimental architecture tailored for atomic trapping. Suitability of the cavity for future experimentation is demonstrated by frequency stabilisation to an atomic resonance of 87Rb.
Atomic ions trapped in microfabricated surface traps can be utilized as a physical platform with which to build a quantum computer. They possess many of the desirable characteristics of such a device, including high fidelity state preparation and readout, universal logic gates, and long coherence times, and can be readily entangled with each other through photonic interconnects. The use of optical cavities integrated with trapped ion qubits as a photonic interface presents the possibility for order of magnitude improvements in performance in several key areas for their use in quantum computation. The first part of this thesis describes the design and fabrication of a novel surface trap for integration with an optical cavity. The trap is custom made on a highly reflective mirror surface and includes the capability of moving the ion trap location along all three trap axes with nanometer scale precision. The second part of this thesis demonstrates the suitability of small microcavities formed from laser ablated, fused silica substrates with radii of curvature in the 300-500 micron range for use with the mirror trap as part of an integrated ion trap cavity system. Quantum computing applications for such a system include dramatic improvements in the photon entanglement rate of up to 10 kHz, the qubit measurement time down to 1 microsecond, and the qubit measurement error rate down to the 1e-5 range. The final part of this thesis describes a performance simulator for exploring the physical resource requirements and performance demands to scale a quantum computer to sizes capable of implementing quantum algorithms beyond the limits of classical computation.
Optical cavities are frequently used in quantum technologies to enhance light matter interactions, with applications including single photon generation and entanglement of distant emitters. The Fabry-Pérot resonator is a popular choice for its high optical access and large emitter-mirror separation. A typical configuration, particularly for emitters that should not be placed close to the mirror surface like trapped ions and Rydberg atoms, features two spherical mirrors placed around a central emitter, but this arrangement can put demanding requirements on the mirror alignment. In contrast, plano-concave cavities are tolerant to mirror misalignment and only require the manufacture of one curved mirror, but have limited ability to focus light in the centre of the cavity. Here we show how mirror shaping can overcome this limitation of plano-concave cavities while preserving the key advantages. We demonstrate through numerical simulations that simple mirror shaping can increase coupling between a plano-concave cavity and a central emitter by an order of magnitude, even rivalling misalignment-sensitive concave-concave counterparts for achievable interaction strength. We use these observations to establish the conditions under which plano-concave cavities with shaped mirrors could improve the performance and practicality of emitter-cavity systems.