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Bulletin of the American Physical Society

Holographic optical manipulation of trapped ions for quantum simulation

Chung-You Shih, Sainath Motlakunta, Manas Sajjan, Nikhil Kotibhaskar, Thiago Bergamaschi, Roland Hablützel, Rajibul Islam

Published Jun 4, 2020• 0 citations
OpenAlex

Abstract

Trapped ion is one of the leading platforms for quantum simulation experiment due to its long coherence time and high fidelity state initialization, detection, and manipulation. To individually address ions at a single-ion level, it requires sophisticated optical engineering. In the thesis, we present a novel single qubit addressing system that is immune to imperfections of optical imaging and can scale to different size of the system. The technique is based on digital light processing with a commercially available digital micro-mirror device (DMD). \n \nA DMD is a 2D array that consists of tiny micro-mirrors that can be individually manipulated. It is commonly used in movie projectors to modulate the intensity of the light to create the desired image. However, using this technology to ions will require more sophisticated controls over optical wavefronts of the laser beams, for example, the necessity to manipulate the optical phase. It can be achieved by using the DMD as a programmable hologram, which can then be used to characterize and compensate for any imaging imperfections as well. We developed a new iterative Fourier transform algorithm (IFTA) for calculating the holograms. In the simulation, our algorithm shows more than one order of magnitude improvement in accuracy comparing to previously proposed algorithms. We experimentally demonstrated this holographic beam shaping technique with the optical aberration being compensated. The laser we used in the experiment is in the ultraviolet (UV) regime that is close to the optical transition used for manipulating $^{171}\\mathrm{Yb}^+$ qubits. The short wavelength makes it more susceptible to environmental disturbance. \n \nAlso, we proposed and experimentally demonstrated a new scheme that enables holographic controls over lights with multiple laser frequencies simultaneously by combing the DMD with an acousto-optical modulator (AOM). The AOM splits the light and illuminates different zones of the DMD. Each zone has its own hologram forming one frequency channel for addressing. This opens the possibility to engineer more complex Hamiltonian for quantum simulation. For example, we can engineer arbitrary spin-spin interaction graphs by applying the M\\o lmer-S\\o rensen scheme on this new setup.

Related papers

Reprogrammable and high-precision holographic optical addressing of trapped ions for scalable quantum control

Chung-You Shih, Sainath Motlakunta, Nikhil Kotibhaskar +3 more

Abstract High-precision, individually programmable manipulation of quantum particles is crucial for scaling up quantum information processing (QIP) systems such as laser-cooled trapped-ions. However, restricting undesirable “crosstalk” in optical manipulation of ion qubits is fundamentally challenging due to micron-level inter-ion separation. Further, inhomogeneous ion spacing and high susceptibility to aberrations at UV wavelengths suitable for most ion-species pose severe challenges. Here, we demonstrate high-precision individual addressing ( λ = 369.5 nm) of Yb + using a reprogrammable Fourier hologram. The precision is achieved through in-situ aberration characterization via the trapped ion, and compensating (to λ /20) with the hologram. Using an iterative Fourier transformation algorithm (IFTA), we demonstrate an ultra-low (<10 −4 ) intensity crosstalk error in creating arbitrary pair-wise addressing profiles, suitable for over fifty ions. This scheme relies on standard commercial hardware, can be readily extended to over a hundred ions, and adapted to other ion-species and quantum platforms.

npj Quantum Information•Apr 8, 2021•32 citations

Manipulating single atoms with optical tweezers

Dustin Stuart

Single atoms are promising candidates for physically implementing quantum bits, the fundamental unit of quantum information. We have built an apparatus for cooling, trapping and imaging single rubidium atoms in microscopic optical tweezers. The traps are formed from a tightly focused off-resonant laser beam, which traps atoms using the optical dipole force. The traps have a diameter of ~1 μm and a depth of ~1 mK. The novelty of our approach is the use a digital mirror device (DMD) to generate multiple independently movable tweezers from a single laser beam. The DMD consists of an array of micro-mirrors that can be switched on and off, thus acting as a binary amplitude modulator. We use the DMD to imprint a computer-generated hologram on the laser beam, which is converted in to the desired arrangement of traps in the focal plane of a lens. We have developed fast algorithms for calculating binary holograms suitable for the DMD. In addition, we use this method to measure and correct for errors in the phase of the wavefront caused by optical aberrations, which is necessary for producing diffraction-limited focal spots. Using this apparatus, we have trapped arrays of up to 20 atoms with arbitrary geometrical arrangements. We exploit light-assisted collisions between atoms to ensure there is at most one atom per trapping site. We measure the temperature of the atoms in the traps to be 12 μK, and their lifetime to be 1.4 s. Finally, we demonstrate the ability to select individual atoms from an array and transport them over a distance of 14μm with laser cooling, and 5 μm without.

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Achieving $10^{-5}$ level relative intensity crosstalk in optical holographic qubit addressing via a double-pass digital micromirror device

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Holographic beam shaping is a powerful approach for generating individually addressable optical spots for controlling atomic qubits, such as those in trapped-ion quantum processors. However, its application in qubit control is limited by residual intensity crosstalk at neighboring sites and by a nonzero background floor in the far wings of the addressing beam, leading to accumulated errors from many exposed qubits. Here, we present an all-optical scheme that mitigates both effects using a single digital micromirror device (DMD) operated in a double-pass configuration, in which light interacts with two separate regions of the same device. In the first pass, one region of the DMD is placed in a Fourier plane and implements a binary-amplitude hologram for individual addressing, while in the second pass a different region serves as a programmable intermediate image-plane aperture for spatial filtering. By multiplexing the Fourier-plane hologram to include secondary holograms, we generate weak auxiliary fields that interfere destructively with unwanted light at selected sites, while image-plane filtering suppresses the residual tail at larger distances. Together, these techniques maintain relative intensity crosstalk at or below $10^{-5}$ ($-50\,\mathrm{dB}$) across the full field of view relevant for qubit addressing, and further reduce the far-wing background to approximately $10^{-6}$ at large distances from the addressed qubit, approaching the detection limit. These results provide a compact, DMD-based solution for low-crosstalk optical holographic qubit addressing that is directly applicable to trapped ions and other spatially ordered quantum systems.

quant-pharXiv:2512.13882•Dec 17, 2025•0 citations

Single-atom trapping and transport in DMD-controlled optical tweezers

Dustin Stuart, Axel Kuhn

We demonstrate the trapping and manipulation of single neutral atoms in reconfigurable arrays of optical tweezers. Our approach offers unparalleled speed by using a Texas instruments digital micro-mirror device as a holographic amplitude modulator with a frame rate of 20 000 per second. We show the trapping of static arrays of up to 20 atoms, as well as transport of individually selected atoms over a distance of 25 μ m with laser cooling and 4 μ m without. We discuss the limitations of the technique and the scope for technical improvements.

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Developing theoretical and experimental tools for a hybrid quantum simulator based on trapped ions

Sainath Motlakunta

Quantum simulation is the process of using a highly controllable quantum system to simulate another less controllable system. Quantum simulation can provide insights into the properties and dynamics of complex many-body systems. Trapped ion platform is one of the leading candidates for a quantum simulator due to its properties such as ease of isolation, preparation and manipulation. Simulating high dimensional spin systems enables us to study the various physical phenomena in higher geometries. Previous proposals for simulating higher dimensions require experimental resources that don't scale favourably with the system. In this thesis, we propose a hybrid (digital-analog) approach to simulate an effective 2D lattice from a 1D chain of trapped ions. In the initial geometry, the ions interact with each other through a flip-flop kind of interactions generated using a global Molmer-Sorensen scheme. A series of single qubit gates are used to rescale and suppress the interactions in the initial chain to simulate the target geometry. These gates are applied using a laser field gradient which generates a site-dependent AC stark shift. I discuss the construction of this protocol in detail and the theoretical results for the case of 6, 9 and 16 ions. I also show that the number of gates and also the Stark gradient scale linearly with the system size. \n \nExperimental implementation of an ion trap quantum simulator has various challenges, one of the which is the laser frequency stabilization within a fraction of transition linewidth. Traditionally, this is done by locking the lasers to an atomic transition. In this thesis, I discuss two alternative schemes for locking the laser frequencies used to build a 171Yb+ ion quantum simulator. One of these solutions uses a commercial wavemeter as a measuring device for the frequency and feedbacks the lasers based on this measurement. I discuss the layout of this scheme and some results. Other solution uses a Fabry Perot (FP) cavity to transfer the stability of a stable laser to an unstable laser. In this thesis, I discuss the construction, optical layout and transmission measurements of a home-built FP cavity.

•Sep 5, 2018•0 citations

Quantum Information Processing with Trapped Ion Chains

T.A. Manning

Trapped atomic ion systems are currently the most advanced platform for quantum information processing. Their long coherence times, pristine state initialization and detection, and precisely controllable and versatile interactions make them excellent quantum systems for experiments in quantum computation and quantum simulation. One of the more promising schemes for quantum computing consists of performing single and multi-qubit quantum gates on qubits in a linear ion crystal. Some of the key challenges of scaling such a system are the individual addressing of arbitrary subsets of ions and controlling the growing complexity of motional mode interactions as the number of qubits increases or when the gates are performed faster. Traditional entangling quantum gates between ion qubits use laser pulses to couple the qubit states to the collective motion of the crystal, thereby generating a spin-spin interaction that can produce entanglement between selected qubits. The intrinsic limitations on the performance of gates using this method can be alleviated by applying optimally shaped pulses instead of pulses with constant amplitude. This thesis explains the theory behind this pulse shaping scheme and how it is implemented on a chain of Yb ions held in a linear radiofrequency `Paul' trap. Several experiments demonstrate the technique in chains of two, three, and five ions using various types of pulse shapes. A tightly focused individual addressing beam allows us to apply the entangling gates to a target pair of ions, and technical issues related to such tight focusing are discussed. Other advantages to the pulse shaping scheme include a robustness against detuning errors and the possibility of suppressing undesirable coupling due to optical spillover on neighboring ions. Combined with ion shuttling, we harness these features to perform sequential gates to different qubit pairs in order to create genuine tripartite entangled states and demonstrate the programmable quantum information processing capability of our system.

•Jan 1, 2014•1 citation
Trapped ion is one of the leading platforms for quantum simulation experiment due to its long coherence time and high fidelity state initialization, detection, and manipulation. To individually address ions at a single-ion level, it requires sophisticated optical engineering. In the thesis, we present a novel single qubit addressing system that is immune to imperfections of optical imaging and can scale to different size of the system. The technique is based on digital light processing with a commercially available digital micro-mirror device (DMD). \n \nA DMD is a 2D array that consists of tiny micro-mirrors that can be individually manipulated. It is commonly used in movie projectors to modulate the intensity of the light to create the desired image. However, using this technology to ions will require more sophisticated controls over optical wavefronts of the laser beams, for example, the necessity to manipulate the optical phase. It can be achieved by using the DMD as a programmable hologram, which can then be used to characterize and compensate for any imaging imperfections as well. We developed a new iterative Fourier transform algorithm (IFTA) for calculating the holograms. In the simulation, our algorithm shows more than one order of magnitude improvement in accuracy comparing to previously proposed algorithms. We experimentally demonstrated this holographic beam shaping technique with the optical aberration being compensated. The laser we used in the experiment is in the ultraviolet (UV) regime that is close to the optical transition used for manipulating 171mathrmYb+^{171}\\mathrm{Yb}^+171mathrmYb+ qubits. The short wavelength makes it more susceptible to environmental disturbance. \n \nAlso, we proposed and experimentally demonstrated a new scheme that enables holographic controls over lights with multiple laser frequencies simultaneously by combing the DMD with an acousto-optical modulator (AOM). The AOM splits the light and illuminates different zones of the DMD. Each zone has its own hologram forming one frequency channel for addressing. This opens the possibility to engineer more complex Hamiltonian for quantum simulation. For example, we can engineer arbitrary spin-spin interaction graphs by applying the M\o lmer-S\o rensen scheme on this new setup.
Abstract High-precision, individually programmable manipulation of quantum particles is crucial for scaling up quantum information processing (QIP) systems such as laser-cooled trapped-ions. However, restricting undesirable “crosstalk” in optical manipulation of ion qubits is fundamentally challenging due to micron-level inter-ion separation. Further, inhomogeneous ion spacing and high susceptibility to aberrations at UV wavelengths suitable for most ion-species pose severe challenges. Here, we demonstrate high-precision individual addressing ( λ = 369.5 nm) of Yb + using a reprogrammable Fourier hologram. The precision is achieved through in-situ aberration characterization via the trapped ion, and compensating (to λ /20) with the hologram. Using an iterative Fourier transformation algorithm (IFTA), we demonstrate an ultra-low (<10 −4 ) intensity crosstalk error in creating arbitrary pair-wise addressing profiles, suitable for over fifty ions. This scheme relies on standard commercial hardware, can be readily extended to over a hundred ions, and adapted to other ion-species and quantum platforms.
Single atoms are promising candidates for physically implementing quantum bits, the fundamental unit of quantum information. We have built an apparatus for cooling, trapping and imaging single rubidium atoms in microscopic optical tweezers. The traps are formed from a tightly focused off-resonant laser beam, which traps atoms using the optical dipole force. The traps have a diameter of ~1 μm and a depth of ~1 mK. The novelty of our approach is the use a digital mirror device (DMD) to generate multiple independently movable tweezers from a single laser beam. The DMD consists of an array of micro-mirrors that can be switched on and off, thus acting as a binary amplitude modulator. We use the DMD to imprint a computer-generated hologram on the laser beam, which is converted in to the desired arrangement of traps in the focal plane of a lens. We have developed fast algorithms for calculating binary holograms suitable for the DMD. In addition, we use this method to measure and correct for errors in the phase of the wavefront caused by optical aberrations, which is necessary for producing diffraction-limited focal spots. Using this apparatus, we have trapped arrays of up to 20 atoms with arbitrary geometrical arrangements. We exploit light-assisted collisions between atoms to ensure there is at most one atom per trapping site. We measure the temperature of the atoms in the traps to be 12 μK, and their lifetime to be 1.4 s. Finally, we demonstrate the ability to select individual atoms from an array and transport them over a distance of 14μm with laser cooling, and 5 μm without.
Achieving 10−510^{-5}10−5 level relative intensity crosstalk in optical holographic qubit addressing via a double-pass digital micromirror device
Holographic beam shaping is a powerful approach for generating individually addressable optical spots for controlling atomic qubits, such as those in trapped-ion quantum processors. However, its application in qubit control is limited by residual intensity crosstalk at neighboring sites and by a nonzero background floor in the far wings of the addressing beam, leading to accumulated errors from many exposed qubits. Here, we present an all-optical scheme that mitigates both effects using a single digital micromirror device (DMD) operated in a double-pass configuration, in which light interacts with two separate regions of the same device. In the first pass, one region of the DMD is placed in a Fourier plane and implements a binary-amplitude hologram for individual addressing, while in the second pass a different region serves as a programmable intermediate image-plane aperture for spatial filtering. By multiplexing the Fourier-plane hologram to include secondary holograms, we generate weak auxiliary fields that interfere destructively with unwanted light at selected sites, while image-plane filtering suppresses the residual tail at larger distances. Together, these techniques maintain relative intensity crosstalk at or below 10−510^{-5}10−5 (−50 dB-50\,\mathrm{dB}−50dB) across the full field of view relevant for qubit addressing, and further reduce the far-wing background to approximately 10−610^{-6}10−6 at large distances from the addressed qubit, approaching the detection limit. These results provide a compact, DMD-based solution for low-crosstalk optical holographic qubit addressing that is directly applicable to trapped ions and other spatially ordered quantum systems.
We demonstrate the trapping and manipulation of single neutral atoms in reconfigurable arrays of optical tweezers. Our approach offers unparalleled speed by using a Texas instruments digital micro-mirror device as a holographic amplitude modulator with a frame rate of 20 000 per second. We show the trapping of static arrays of up to 20 atoms, as well as transport of individually selected atoms over a distance of 25 μ m with laser cooling and 4 μ m without. We discuss the limitations of the technique and the scope for technical improvements.
Quantum simulation is the process of using a highly controllable quantum system to simulate another less controllable system. Quantum simulation can provide insights into the properties and dynamics of complex many-body systems. Trapped ion platform is one of the leading candidates for a quantum simulator due to its properties such as ease of isolation, preparation and manipulation. Simulating high dimensional spin systems enables us to study the various physical phenomena in higher geometries. Previous proposals for simulating higher dimensions require experimental resources that don't scale favourably with the system. In this thesis, we propose a hybrid (digital-analog) approach to simulate an effective 2D lattice from a 1D chain of trapped ions. In the initial geometry, the ions interact with each other through a flip-flop kind of interactions generated using a global Molmer-Sorensen scheme. A series of single qubit gates are used to rescale and suppress the interactions in the initial chain to simulate the target geometry. These gates are applied using a laser field gradient which generates a site-dependent AC stark shift. I discuss the construction of this protocol in detail and the theoretical results for the case of 6, 9 and 16 ions. I also show that the number of gates and also the Stark gradient scale linearly with the system size. \n \nExperimental implementation of an ion trap quantum simulator has various challenges, one of the which is the laser frequency stabilization within a fraction of transition linewidth. Traditionally, this is done by locking the lasers to an atomic transition. In this thesis, I discuss two alternative schemes for locking the laser frequencies used to build a 171Yb+ ion quantum simulator. One of these solutions uses a commercial wavemeter as a measuring device for the frequency and feedbacks the lasers based on this measurement. I discuss the layout of this scheme and some results. Other solution uses a Fabry Perot (FP) cavity to transfer the stability of a stable laser to an unstable laser. In this thesis, I discuss the construction, optical layout and transmission measurements of a home-built FP cavity.
Trapped atomic ion systems are currently the most advanced platform for quantum information processing. Their long coherence times, pristine state initialization and detection, and precisely controllable and versatile interactions make them excellent quantum systems for experiments in quantum computation and quantum simulation. One of the more promising schemes for quantum computing consists of performing single and multi-qubit quantum gates on qubits in a linear ion crystal. Some of the key challenges of scaling such a system are the individual addressing of arbitrary subsets of ions and controlling the growing complexity of motional mode interactions as the number of qubits increases or when the gates are performed faster. Traditional entangling quantum gates between ion qubits use laser pulses to couple the qubit states to the collective motion of the crystal, thereby generating a spin-spin interaction that can produce entanglement between selected qubits. The intrinsic limitations on the performance of gates using this method can be alleviated by applying optimally shaped pulses instead of pulses with constant amplitude. This thesis explains the theory behind this pulse shaping scheme and how it is implemented on a chain of Yb ions held in a linear radiofrequency `Paul' trap. Several experiments demonstrate the technique in chains of two, three, and five ions using various types of pulse shapes. A tightly focused individual addressing beam allows us to apply the entangling gates to a target pair of ions, and technical issues related to such tight focusing are discussed. Other advantages to the pulse shaping scheme include a robustness against detuning errors and the possibility of suppressing undesirable coupling due to optical spillover on neighboring ions. Combined with ion shuttling, we harness these features to perform sequential gates to different qubit pairs in order to create genuine tripartite entangled states and demonstrate the programmable quantum information processing capability of our system.