The viability of neutral atom based quantum computers is dependent upon scalability to large numbers of qubits. Diffractive optical elements (DOEs) offer the possibility to scale up to many qubit systems by enabling the manipulation of light to collect signal or deliver a tailored spatial trapping pattern. DOEs have an advantage over refractive microoptics since they do not have measurable surface sag, making significantly larger numerical apertures (NA) accessible with a smaller optical component. The smaller physical size of a DOE allows the micro-lenses to be placed in vacuum with the atoms, reducing aberration effects that would otherwise be introduced by the cell walls of the vacuum chamber. The larger collection angle accessible with DOEs enable faster quantum computation speeds. We have designed a set of DOEs for collecting the 852 nm fluorescence from the D2 transition in trapped cesium atoms, and compare these DOEs to several commercially available refractive micro-lenses. The largest DOE is able to collect over 20% of the atom’s radiating sphere whereas the refractive micro-optic is able to collect just 8% of the atom’s radiating sphere.
The viability of neutral atom based quantum computers is dependent upon scalability to large numbers of qubits. Diffractive optical elements (DOEs) offer the possibility to scale up to many qubit systems by enabling the manipulation of light to collect signal or deliver a tailored spatial trapping pattern. DOEs have an advantage over refractive microoptics since they do not have measurable surface sag, making significantly larger numerical apertures (NA) accessible with a smaller optical component. The smaller physical size of a DOE allows the micro-lenses to be placed in vacuum with the atoms, reducing aberration effects that would otherwise be introduced by the cell walls of the vacuum chamber. The larger collection angle accessible with DOEs enable faster quantum computation speeds. We have designed a set of DOEs for collecting the 852 nm fluorescence from the D2 transition in trapped cesium atoms, and compare these DOEs to several commercially available refractive micro-lenses. The largest DOE is able to collect over 20% of the atom’s radiating sphere whereas the refractive micro-optic is able to collect just 8% of the atom’s radiating sphere.
We design and fabricate arrays of diffractive optical elements (DOEs) to realize neutral atom micro-traps for
quantum computing. We initialize a single atom at each site of an array of optical tweezer traps for a customized
spatial configuration. Each optical trapping volume is tailored to ensure only one or zero trapped atoms.
Specifically designed DOEs can define an arbitrary optical trap array for initialization and improve collection
efficiency in readout by introducing high-numerical aperture, low-profile optical elements into the vacuum
environment.
We will discuss design and fabrication details of ultra-fast collection DOEs integrated monolithically and coaxially
with tailored DOEs that establish an optical array of micro-traps through far-field propagation. DOEs, as mode
converters, modify the lateral field at the front focal plane of an optical assembly and transform it to the desired field
pattern at the back focal plane of the optical assembly. We manipulate the light employing coherent or incoherent
addition with judicious placement of phase and amplitude at the lens plane. This is realized through a series of
patterning, etching, and depositing material on the lens substrate. The trap diameter, when this far-field propagation
approach is employed, goes as 2.44λF/#, where the F/# is the focal length divided by the diameter of the lens
aperture. The 8-level collection lens elements in this presentation are, to our knowledge, the fastest diffractive
elements realized; ranging from F/1 down to F/0.025.
We developed techniques to design higher efficiency diffractive optical elements (DOEs) with large numerical apertures (NA) for quantum computing and quantum information processing.Large NA optics encompass large solid angles and thus have high collection efficiencies.Qubits in ion trap architectures are commonly addressed and read by lasers 1 .Large-scale ion-trap quantum computing 2 will therefore require highly parallel optical interconnects.Qubit readout in these systems requires detecting fluorescence from the nearly isotropic radiation pattern of single ions, so efficient readout requires optical interconnects with high numerical aperture.Diffractive optical element fabrication is relatively mature and utilizes lithography to produce arrays compatible with large-scale ion-trap quantum computer architectures.The primary challenge of DOEs is the loss associated with diffraction efficiency.This is due to requirements for large deflection angles, which leads to extremely small feature sizes in the outer zone of the DOE.If the period of the diffractive is between (the free space wavelength) and 10 the element functions in the vector regime.DOEs in this regime, particularly between 1.5 and 4 have significant coupling to unwanted diffractive orders, reducing the performance of the lens.Furthermore, the optimal depth of the zones with periods in the vector regime differs from the overall depth of the DOE.We will present results indicating the unique behaviors around the 1.5 and 4 periods and methods to improve the DOE performance.
We design and fabricate arrays of diffractive optical elements (DOEs) to realize neutral atom micro-traps for quantum computing.We initialize a single atom at each site of an array of optical tweezer traps for a customized spatial configuration.Each optical trapping volume is tailored to ensure only one or zero trapped atoms.Specifically designed DOEs can define an arbitrary optical trap array for initialization and improve collection efficiency in readout by introducing high-numerical aperture, low-profile optical elements into the vacuum environment.We will discuss design and fabrication details of ultra-fast collection DOEs integrated monolithically and coaxially with tailored DOEs that establish an optical array of micro-traps through far-field propagation.DOEs, as mode converters, modify the lateral field at the front focal plane of an optical assembly and transform it to the desired field pattern at the back focal plane of the optical assembly.We manipulate the light employing coherent or incoherent addition with judicious placement of phase and amplitude at the lens plane.This is realized through a series of patterning, etching, and depositing material on the lens substrate.The trap diameter, when this far-field propagation approach is employed, goes as 2.44λF/#, where the F/# is the focal length divided by the diameter of the lens aperture.The 8-level collection lens elements in this presentation are, to our knowledge, the fastest diffractive elements realized; ranging from F/1 down to F/0.025.
Designing and integrating micro-optical components into atom and ion traps are enabling steps toward miniaturizing trap dimensions in quantum computation applications.The micro-optic must have a high numerical aperture for precise illumination of the ion and should not introduce scatter.Due to the extreme optical efficiency requirements in trapped ion and atom-based quantum information processing, even slight losses from integrated micro-optics are detrimental.We have designed and fabricated aspheric micro-lenses through grayscale transfer into a fused silica in an effort to realize increased transmissive efficiency and decreased scatter compared to an equivalent diffractive optical element.The fabricated grayscale lens profile matched the desired lens profile well, and the measured and predicted optical performances were in good agreement.The pattern was transferred via coupled plasma reactive-ion etching smoothly into the fused silica with a RMS roughness ~35 nm.The micro-lens had a diameter of 88 um and 14.2 um sag, with an as-designed focal length of 149 um and spot diameter of 2.6 um.The maximum measured efficiency was ~80% (86% of theoretical, possibly due to rms roughness).This realized efficiency is superior to the equivalent diffractive lens efficiency, designed to the same use parameters.The grayscale approach demonstrated an increase in collection efficiency, at the desired optical focal length, providing the potential for further refinement.
The integration of optics for efficient light delivery and the collection of fluorescence from trapped ions in surface electrode ion traps is a key component to achieving scalability for quantum information processing.Diffractive optical elements (DOEs) present a promising approach as compared to bulk optics because of their small physical profile and their flexibility in tailoring the optical wavefront.The precise alignment of the optics for coupling fluorescence to and from the ions, however, poses a particular challenge.Excitation and manipulation of the ions requires a high degree of optical access, significantly restricting the area available for mounting components.The ion traps, DOEs, and other components are compact, constraining the manipulation of various elements.For efficient fluorescence collection from the ions the DOE must be have a large numerical aperture (NA), which results in greater sensitivity to misalignment.The ion traps are sensitive devices, a mechanical approach to alignment such as contacting the trap and using precision motors to back-off a set distance not only cannot achieve the desired alignment precision, but risks damage to the ion trap.We have developed a non-contact precision optical alignment technique.We use line foci produced by off-axis linear Fresnel zone plates (FZPs) projected on alignment targets etched in the top metal layer of the ion trap and demonstrate micron-level alignment accuracy.
The integration of optics for efficient light delivery and the collection of fluorescence from trapped ions in surface electrode ion traps is a key component to achieving scalability for quantum information processing. Diffractive optical elements (DOEs) present a promising approach as compared to bulk optics because of their small physical profile and their flexibility in tailoring the optical wavefront. The precise alignment of the optics for coupling fluorescence to and from the ions, however, poses a particular challenge. Excitation and manipulation of the ions requires a high degree of optical access, significantly restricting the area available for mounting components. The ion traps, DOEs, and other components are compact, constraining the manipulation of various elements. For efficient fluorescence collection from the ions the DOE must be have a large numerical aperture (NA), which results in greater sensitivity to misalignment. The ion traps are sensitive devices, a mechanical approach to alignment such as contacting the trap and using precision motors to back-off a set distance not only cannot achieve the desired alignment precision, but risks damage to the ion trap. We have developed a non-contact precision optical alignment technique. We use line foci produced by off-axis linear Fresnel zone plates (FZPs) projected on alignment targets etched in the top metal layer of the ion trap and demonstrate micron-level alignment accuracy.