Aspects of the present disclosure relate generally to systems and methods for use in the implementation and/or operation of quantum information processing (QIP) systems including an ion trap and a multiple-zone addressing system, and more particularly, to a large field-of-view Raman system having a micro-or metalens array. In some aspects, the ion trap is configured to confine at least a first trapped ion chain and a second trapped ion chain. In some aspects, the multiple zone addressing system includes a first optical addresser, a second optical addresser, and a combining region.

TECHNICAL FIELD

Aspects of the present disclosure relate generally to systems and methods for use in the implementation, operation, and/or use of quantum information processing (QIP) systems.

BACKGROUND

Trapped atoms are one of the leading implementations for quantum information processing or quantum computing. Atomic-based qubits may be used as quantum memories, as quantum gates in quantum computers and simulators, and may act as nodes for quantum communication networks. Qubits based on trapped atomic ions enjoy a rare combination of attributes. For example, qubits based on trapped atomic ions have very good coherence properties, may be prepared and measured with nearly 100% efficiency, and are readily entangled with each other by modulating their Coulomb interaction with suitable external control fields such as optical or microwave fields. These attributes make atomic-based qubits attractive for extended quantum operations such as quantum computations or quantum simulations.

It is therefore important to develop new techniques that improve the design, fabrication, implementation, control, and/or functionality of different QIP systems used as quantum computers or quantum simulators, and particularly for those QIP systems that handle operations based on atomic-based qubits.

SUMMARY

This disclosure describes various aspects of quantum information processing (QIP) systems that include large field-of-view (FOV) Raman systems configured to address large fields of view. For example, such systems may be configured to address multiple discrete sub-FOVs within a large FOV using a multi-aperture approach. Such systems are suitable for addressing ion traps that include more than one chain of trapped ions.

In some aspects, a QIP system includes an ion trap and a multiple-zone addressing system. The ion trap is configured to confine at least a first trapped ion chain and a second trapped ion chain. The multiple-zone addressing system includes a first optical addresser, a second optical addresser, and a combining region. The first optical addresser is configured to control a first beam configured to address a first addressing zone including the first trapped ion chain. The second optical addresser is configured to control a second beam configured to address a second addressing zone including the second trapped ion chain. The combining region is configured to reduce a fill factor of the first beam and the second beam while maintaining spatial separation of the first beam and the second beam.

In some aspects, a QIP system includes an ion trap and an addressing system. The ion trap includes at least one addressing zone including a trapped ion chain. The addressing system is configured to address the at least one addressing zone of the ion trap. The addressing system includes an optical addresser and a microlens array or a metalens array. The optical addresser is configured to control a beam configured to address the at least one addressing zone including the trapped ion chain. The microlens array includes a microlens configured to focus the beam on the trapped ion chain. The metalens array includes a metalens configured to focus the beam on the trapped ion chain.

DETAILED DESCRIPTION

The detailed description set forth below in connection with the appended drawings or figures is intended as a description of various configurations or implementations and is not intended to represent the only configurations or implementations in which the concepts described herein may be practiced. The detailed description includes specific details for the purpose of providing a thorough understanding of various concepts. However, it will be apparent to those skilled in the art that these concepts may be practiced without these specific details or with variations of these specific details. In some instances, well known components are shown in block diagram form, while some blocks may be representative of one or more well-known components.

Scaling up quantum information processing (QIP) systems will ultimately involve coupling quantum computing chips into a quantum network (e.g., including photonic interconnects). It is desirable to increase a number of qubits per chip when scaling up QIP systems. However, the chains of trapped ions used in the ion traps of current QIP systems experience a decrease in stability as the length of the trapped ion chains increases. Therefore, increasing the number of qubits on a chip is not a matter of simply increasing the number of ions in a trapped ion chain. Instead of increasing the length of the trapped ion chains, multiple trapped ion chains (also called “cores”) may be incorporated in a single quantum computing chip (e.g., ion trap). These multiple trapped ion chains may be entangled with each other via transport and swap operations, which can allow the multiple trapped ion chains to act like a network of ion chains. In some aspects, photonic interconnects may be used to entangle ion chains within each other via transport and swap operations, or via photonic interconnects within a single quantum computing chip.

When implemented in a multiple chain configuration, the multiple trapped ion chains of the ion trap will be in close proximity to each other. Therefore, the optical addressers for addressing individual qubits and performing gate operations of QIP systems that include ion traps having multiple chains of trapped ions are modified (e.g., different from optical addressers used in single ion chain systems). For example, in order to avoid optical crosstalk between adjacent ions in a single ion chain, addressing beams should have a beam waist of much less than the ion spacing. For example, in an ion chain with an ion spacing of 3 microns (μm), the addressing beams may have a beam waist of less than 1.5 μm (i.e. a beam diameter of less than 30 μm). In another example, in order to avoid optical crosstalk between adjacent trapped ion chains, the trapped ion chains may be separated by a distance great enough to mitigate the effects of spontaneous emission. For example, for an ion chain of 64 ions and an ion spacing of 3 μm, a center-to-center spacing of adjacent trapped ion chains may be at least 1080 μm. In some aspects, such configurations may have a minimum center-to-center spacing of adjacent trapped ions that may be at least 400 μm. Given these size constraints, a “fill factor” of the addressing zone would only be about 20% for an example system including trapped ion chains that are 200 μm long and have 1080 μm of chain separation. As used herein the phrase “fill factor” refers to a collective beam diameter of the beams formed by a particular addresser relative to the spacing of the addressing zones. In an example including four trapped ion chains, an addressing window would therefore be about 4 mm. If the optical addressing system were to uniformly address the full 4 mm FOV, it would be inefficient in terms of entendue (e.g., amount of beam spreading) required and fill factor being used.

However, conventional QIP systems have a single addressing region for addressing ions that typically has less than a 200 μm field of view (FOV). Therefore, this conventional addressing region is too small for addressing multiple chains of trapped ions.

Solutions to the issues described above are explained in more detail in connection withFIGS.1-8, withFIGS.1-3providing a background of QIP systems or quantum computers, and more specifically, of atomic-based QIP systems or quantum computers.

FIG.1illustrates a diagram100with multiple atomic ions or ions106(e.g., ions106a,106b, . . . ,106c, and106d) trapped in a linear crystal or chain110using a trap (not shown; the trap can be inside a vacuum chamber as shown inFIG.2). The trap maybe referred to as an ion trap. The ion trap shown may be built or fabricated on a semiconductor substrate, a dielectric substrate, or a glass die or wafer (also referred to as a glass substrate). The ions106may be provided to the trap as atomic species for ionization and confinement into the chain110. Some or all of the ions106may be configured to operate as qubits in a QIP system.

In the example shown inFIG.1, the trap includes electrodes for trapping or confining multiple ions into the chain110laser-cooled to be nearly at rest. The number of ions trapped can be configurable and more or fewer ions may be trapped. The ions can be Ytterbium ions (e.g.,171Yb+ions), for example. The ions are illuminated with laser (optical) radiation tuned to a resonance in171Yb+and the fluorescence of the ions is imaged onto a camera or some other type of detection device (e.g., photomultiplier tube (PMT)). In this example, ions may be separated by a few microns (m) from each other, although the separation may vary based on architectural configuration. The separation of the ions is determined by a balance between the external confinement force and Coulomb repulsion and does not need to be uniform. Moreover, in addition to Ytterbium ions, neutral atoms, Rydberg atoms, or other types of atomic-based qubit technologies may also be used. Moreover, ions of the same species, ions of different species, and/or different isotopes of ions may be used. The trap may be a linear RF Paul trap, but other types of confinement devices may also be used, including optical confinements. Thus, a confinement device may be based on different techniques and may hold ions, neutral atoms, or Rydberg atoms, for example, with an ion trap being one example of such a confinement device. The ion trap may be a surface trap, for example.

FIG.2illustrates a block diagram that shows an example of a QIP system200. The QIP system200may also be referred to as a quantum computing system, a quantum computer, a computer device, a trapped ion system, or the like. The QIP system200may be part of a hybrid computing system in which the QIP system200is used to perform quantum computations and operations and the hybrid computing system also includes a classical computer to perform classical computations and operations. The quantum and classical computations and operations may interact in such a hybrid system.

Shown inFIG.2is a general controller205configured to perform various control operations of the QIP system200. These control operations may be performed by an operator, may be automated, or a combination of both. Instructions for at least some of the control operations may be stored in memory (not shown) in the general controller205and may be updated over time through a communications interface (not shown). Although the general controller205is shown separate from the QIP system200, the general controller205may be integrated with or be part of the QIP system200. The general controller205may include an automation and calibration controller280configured to perform various calibration, testing, and automation operations associated with the QIP system200. These calibration, testing, and automation operations may involve, for example, all or part of an algorithms component210, all or part of an optical and trap controller220and/or all or part of a chamber250.

The QIP system200may include the algorithms component210mentioned above, which may operate with other parts of the QIP system200to perform or implement quantum algorithms, quantum applications, or quantum operations. The algorithms component210may be used to perform or implement a stack or sequence of combinations of single qubit operations and/or multi-qubit operations (e.g., two-qubit operations) as well as extended quantum computations. The algorithms component210may also include software tools (e.g., compilers) that facilitate such performance or implementation. As such, the algorithms component210may provide, directly or indirectly, instructions to various components of the QIP system200(e.g., to the optical and trap controller220) to enable the performance or implementation of the quantum algorithms, quantum applications, or quantum operations. The algorithms component210may receive information resulting from the performance or implementation of the quantum algorithms, quantum applications, or quantum operations and may process the information and/or transfer the information to another component of the QIP system200or to another device (e.g., an external device connected to the QIP system200) for further processing.

The QIP system200may include the optical and trap controller220mentioned above, which controls various aspects of a trap270in the chamber250, including the generation of signals to control the trap270. The optical and trap controller220may also control the operation of lasers, optical systems, and optical components that are used to provide the optical beams that interact with the atoms or ions in the trap. Optical systems that include multiple components may be referred to as optical assemblies. The optical beams are used to set up the ions, to perform or implement quantum algorithms, quantum applications, or quantum operations with the ions, and to read results from the ions. Control of the operations of laser, optical systems, and optical components may include dynamically changing operational parameters and/or configurations, including controlling positioning using motorized mounts or holders. When used to confine or trap ions, the trap270may be referred to as an ion trap. The trap270, however, may also be used to trap neutral atoms, Rydberg atoms, and other types of atomic-based qubits. The lasers, optical systems, and optical components can be at least partially located in the optical and trap controller220, an imaging system230, and/or in the chamber250.

The QIP system200may include the imaging system230. The imaging system230may include a high-resolution imager (e.g., CCD camera) or other type of detection device (e.g., PMT) for monitoring the ions while they are being provided to the trap270and/or after they have been provided to the trap270(e.g., to read results). In an aspect, the imaging system230can be implemented separate from the optical and trap controller220, however, the use of fluorescence to detect, identify, and label ions using image processing algorithms may need to be coordinated with the optical and trap controller220.

In addition to the components described above, the QIP system200can include a source260that provides atomic species (e.g., a plume or flux of neutral atoms) to the chamber250having the trap270. When atomic ions are the basis of the quantum operations, that trap270confines the atomic species once ionized (e.g., photoionized). The trap270may be part of what may be referred to as a processor or processing portion of the QIP system200. That is, the trap270may be considered at the core of the processing operations of the QIP system200since it holds the atomic-based qubits that are used to perform or implement the quantum operations or simulations. At least a portion of the source260may be implemented separate from the chamber250.

It is to be understood that the various components of the QIP system200described inFIG.2are described at a high-level for ease of understanding. Such components may include one or more sub-components, the details of which may be provided below as needed to better understand certain aspects of this disclosure.

Aspects of this disclosure may be implemented at least partially using the optical lasers, optical systems, optical components, and ion trap270described above.

Referring now toFIG.3, an example of a computer system or device300is shown. The computer device300may represent a single computing device, multiple computing devices, or a distributed computing system, for example. The computer device300may be configured as a quantum computer (e.g., a QIP system), a classical computer, or to perform a combination of quantum and classical computing functions, sometimes referred to as hybrid functions or operations. For example, the computer device300may be used to process information using quantum algorithms, classical computer data processing operations, or a combination of both. In some instances, results from one set of operations (e.g., quantum algorithms) are shared with another set of operations (e.g., classical computer data processing). A generic example of the computer device300implemented as a QIP system capable of performing quantum computations and simulations is, for example, the QIP system200shown inFIG.2.

The computer device300may include a processor310for carrying out processing functions associated with one or more of the features described herein. The processor310may include a single processor, multiple set of processors, or one or more multi-core processors. Moreover, the processor310may be implemented as an integrated processing system and/or a distributed processing system. The processor310may include one or more central processing units (CPUs)310a, one or more graphics processing units (GPUs)310b, one or more quantum processing units (QPUs)310c, one or more intelligence processing units (IPUs)310d(e.g., artificial intelligence or Al processors), or a combination of some or all those types of processors. In one aspect, the processor310may refer to a general processor of the computer device300, which may also include additional processors310to perform more specific functions (e.g., including functions to control the operation of the computer device300). Quantum operations may be performed by the QPUs310c. Some or all of the QPUs310cmay use atomic-based qubits, however, it is possible that different QPUs are based on different qubit technologies.

The computer device300may include a memory320for storing instructions executable by the processor310to carry out operations. The memory320may also store data for processing by the processor310and/or data resulting from processing by the processor310. In an implementation, for example, the memory320may correspond to a computer-readable storage medium that stores code or instructions to perform one or more functions or operations. Just like the processor310, the memory320may refer to a general memory of the computer device300, which may also include additional memories320to store instructions and/or data for more specific functions.

It is to be understood that the processor310and the memory320may be used in connection with different operations including but not limited to computations, calculations, simulations, controls, calibrations, system management, and other operations of the computer device300, including any methods or processes described herein.

Further, the computer device300may include a communications component330that provides for establishing and maintaining communications with one or more parties utilizing hardware, software, and services. The communications component330may also be used to carry communications between components on the computer device300, as well as between the computer device300and external devices, such as devices located across a communications network and/or devices serially or locally connected to computer device300. For example, the communications component330may include one or more buses, and may further include transmit chain components and receive chain components associated with a transmitter and receiver, respectively, operable for interfacing with external devices. The communications component330may be used to receive updated information for the operation or functionality of the computer device300.

Additionally, the computer device300may include a data store340, which can be any suitable combination of hardware and/or software, which provides for mass storage of information, databases, and programs employed in connection with the operation of the computer device300and/or any methods or processes described herein. For example, the data store340may be a data repository for operating system360(e.g., classical OS, or quantum OS, or both). In one implementation, the data store340may include the memory320. In an implementation, the processor310may execute the operating system360and/or applications or programs, and the memory320or the data store340may store them.

The computer device300may also include a user interface component350configured to receive inputs from a user of the computer device300and further configured to generate outputs for presentation to the user or to provide to a different system (directly or indirectly). The user interface component350may include one or more input devices, including but not limited to a keyboard, a number pad, a mouse, a touch-sensitive display, a digitizer, a navigation key, a function key, a microphone, a voice recognition component, any other mechanism capable of receiving an input from a user, or any combination thereof. Further, the user interface component350may include one or more output devices, including but not limited to a display, a speaker, a haptic feedback mechanism, a printer, any other mechanism capable of presenting an output to a user, or any combination thereof. In an implementation, the user interface component350may transmit and/or receive messages corresponding to the operation of the operating system360. When the computer device300is implemented as part of a cloud-based infrastructure solution, the user interface component350may be used to allow a user of the cloud-based infrastructure solution to remotely interact with the computer device300.

In connection with the systems described inFIGS.1-3, a Raman zone optical system having multiple addressing zones is described below. Each of the addressing zones is configured to address one of the trapped ion chains of the ion trap270, while limiting crosstalk with neighboring trapped ion chains of the ion trap270.

FIG.4illustrates a multiple-zone Raman optical system400that includes metalenses or microlenses according to example aspects.FIGS.5,6, and7illustrate enlarged portions of the multiple-zone Raman optical system400. In the example embodiment illustrated inFIG.4, the optical system400is telecentric in the ion plane and the ion trap270is configured to confine four ion chains that are spaced approximately 1 millimeter (mm) apart. In other aspects, the ion trap270may be configured to confine more or fewer ion chains. It should be appreciated that the ion chains can correspond to ion chain100inFIG.1. Moreover, the optical system400can be implemented as a component of the optical and trap controller220configured to control the ion chain(s) in trap270ofFIG.2accordingly to an exemplary aspect.

The system400includes an optical addresser404aconfigured control a first beam412ato address a first addressing region including the first ion chain406a(e.g.,FIG.7), a second optical addresser404bconfigured to control a second beam412bto address a second addressing region including the second ion chain406b(e.g.,FIG.7), a third optical addresser404cconfigured to control a third beam412cto address a third addressing region including the third ion chain406c(e.g.,FIG.7), and a fourth optical addresser404dconfigured to control a fourth beam412dto address a fourth addressing region including the fourth ion chain406d(e.g.,FIG.7). Each of the optical addressers404a-404dare substantially similar to each other, so the second, third, and fourth optical addressers404b-404dare only described in detail herein to the extent that they differ from the first optical addresser404a. Like numbering will be used to discuss like parts of the optical addressers404a-404d, with the letter “a” used to indicate components of the first optical addresser, the letter “b” used to indicate components of the second optical addresser, the letter “c” used to indicate components of the third optical addresser, and the letter “d” used to indicate components of the fourth optical addresser. It is noted that each of the optical addressers can be considered a configuration or arrangement that includes a plurality of optical components for addressing a respective ion as described in detail herein.

As shown inFIGS.4and5, the optical addresser404aemits a divergent beam412a. In some aspects, the optical addresser404amay include an optical fiber408aconfigured to emit the divergent beam412a. In some aspects, the optical addresser404amay use free-space optics. A fiber collimator416ais positioned downstream of the optical fiber408aand is configured to collimate the beam412a. The optical addresser404amay include an acousto-optic deflector (AOD)420a. In such aspects, the AOD420ais configured to generate an angle range for the beam412abased on a radiofrequency (RF) signal injected into a crystal of the AOD420a. For example, the AOD420amay deflect the collimated rays of the portion of the beam412aentering the AOD420asuch that the rays of the beam412aexiting the AOD420aare deflected by a range of angles determined based on the RF signal injected into the crystal420aof the AOD. In other aspects, the optical addresser404amay include multiple AODs, two-dimensional AODs with crossed deflection axes, or other types of scanning devices.

A doublet of lenses424aand an optional singlet lens428aare configured to focus the beam412aon a first image plane432a. The optional singlet lens428amay be a meniscus lens configured to introduce a field curvature to the beam412a. In some aspects, the lens428amay be configured to adjust the field curvature of the beam412asuch that a field curvature of the beam412ais approximately equal to the Rayleigh range (“ZRayleigh”) of the beam412ain the intermediate image plane432aand is less than 0.01*ZRayleighin the focal plane of the ion trap270. In some aspects, the field curvature may be used to compensate for the effects of a microlens, as described in greater detail below.

Referring now toFIGS.4and6, a cylindrical lens436ais configured to shape the beam412ainto an anamorphic beam. As shown inFIGS.4and6, the cylindrical lens436ais a single cylindrical lens (e.g., is not paired with a second cylindrical lens in a telescope configuration). For example, the cylindrical lens436amay be configured to shape the beam412ainto an elliptical beam. In the illustrated embodiment, the anamorphic beam may have an aspect ratio of up to 1:20 (expressed as the ratio of focal spot size along the high numerical aperture (NA) axis relative to focal spot size the low NA axis). In such an aspect, this produces a 20 times smaller focal spot size along the high NA axis in a focal plane after a focusing lens. For example in some aspects, the aspect ratio of the anamorphic beam may be at least 1:2. For example in some aspects, the aspect ratio of the anamorphic beam may be at least 1:5. In another example, the aspect ratio may be between 1:2 to 1:10. In another example, the aspect ratio may be between 1:3 to 1:6. The cylindrical lens436ais configured to shape the beam412such that the shaped beam has a high numerical aperture (NA) in an axis oriented along the axis of the ion chain. This configuration produces a narrow cross-section along the axis oriented along the axis of the ion chain, which reduces the likelihood of addressing ions adjacent to a target ion when addressing the target ion (i.e., optical crosstalk). The shaped beam has a lower NA in an axis oriented substantially transverse to the axis of the ion chain. This produces a wider cross-section in the axis oriented substantially transverse to the axis of the ion chain, which allows the shaped beam to clear the ion trap270close to a surface of the ion trap270and to clear a predetermined width of the ion trap270, as required to target the desired ions in the ion trap270. This wider cross-section also makes the beam412aless susceptible to misalignment along the axis oriented substantially transverse to the axis of the ion chain. The width of the low NA portion of the shaped beam, however, should be narrow enough so that the shaped beam can pass through aperture(s) in the cryostat and/or trap housing(s) and/or travel past other components of the optical components of the QIP system200without being clipped.

As further shown, a doublet of lenses440ais configured to collimate the beam412aand focus the beam412aon an intermediate image plane (not shown).

The beams412a-412dthen progress downstream to a combining region442or prism table that is configured to reduce a distance between the beams412a-412dwhile maintaining spatial separation of the beams412a-412d. For example, the combining region442may be configured to orient the beams412a-412dso that the beams412a-412doverlap in a same plane but are spatially separated. As illustrated inFIG.6in an example aspect, deflector pairs444a-444dare aligned with the beams412a-412d, respectively, and are configured to deflect the beams412a-412dto reduce an overall spacing between the beams412a-412d. As also shown inFIG.6, each of the paired deflectors444a-444dare oriented parallel to each other. In some aspects, the deflector pairs444a-444dmay be mirrors or prisms.

In the illustrated configuration, the combining region442is oriented at a relayed entrance of a pupil plane of each of microlens472a-472dof the microlens array468. As used herein, the phrase “pupil plane” refers to a plane in which divergent beams come together (e.g., converge). In such a configuration, the beams are collimated in the pupil plane, and all of the beams produced by a particular addresser (e.g., the addresser404a,404b,404c, or404d) overlap. This overlap allows for simultaneous compensation (e.g., for field-independent aberrations) and/or position adjustment of all of the beams produced by a particular addressor. These pupil planes for each of the addressers404a-404dare relayed to the entrance of the pupil plane of the corresponding microlens or metalens sub-aperture. This allows the clean separation of the beams412a-412dfor each of the different addressing zones in the combining region442to translate to clean separation of the beam for the different addressing zones in the entrance pupil planes of the microlenses or metalens sub-apertures.

In other aspects, the combining region442may be oriented near an intermediate image plane. In other aspects, the combining region442may be oriented at a relayed image plane.

As is best shown inFIG.6, the beams412a-412dcollectively have a fill factor F1before entering the combining region442(e.g., before being deflected by the deflector pairs444a-444d) and a second fill factor F2after exiting the combining region442(e.g., after being deflected by the deflector pairs444a-444d). As used herein, the phrase “fill factor” refers to a collective beam diameter of the beams412a-412dformed by a particular addresser404a-404d. The first fill factor F1is lower than the second fill factor F2. In some aspects, the first fill factor F1may be 5 times smaller than the second fill factor F2. In some aspects, the first fill factor F1may be 4 times smaller than the second fill factor F2. This increase in fill factor in the combining region442is advantageous because such a configuration allows both bulky centimeter-scale optics and components to be used on a first (e.g., upstream) end of the multi-scale optical assembly and then taper the size of the assembly down to a very compact assembly with higher optical fill factor at a second (e.g., downstream) end of the optical assembly.

Moreover, according to an example aspect, an objective lens, shown as doublet448, is positioned downstream of the combining region442and is configured to form a demagnifying relay with the lens doublet440. The demagnifying relay formed by the doublets448,440is configured to focus the beams412a-412don a second intermediate image plane452.

A lens doublet456is configured to direct the beams412a-412dthrough a window460in a cryostat housing such that the beams412a-412dcan interact with the ion chains confined by the ion trap270.

Referring now toFIG.7, an entrance of the pupil plane of the microlens array464is shown by the line464. The microlens array468includes a plurality of microlenses472. In the illustrated embodiment, the microlens array468includes four microlenses, microlenses472a-472d. In the example embodiment, the microlenses472a-472dhave working distances of about 1.5 mm. In the example embodiment, a shape of the microlenses472a-472dis low order aspheric. As used herein, the phrase “low order aspheric” refers to lens that is up to a 4thorder lens. A conical term may be added to the spherical surface of the microlenses472a-472dto achieve a M2value of 1.05 or less across the FOVs for each of the microlenses472a-472d. In aspects in which the microlenses472a-472dhave different working distances, higher order aspheric shapes of the microlenses472a-472dmay be required. Such higher order aspheric shapes may be defined with 4thorder or higher polynomials.

In other embodiments, the plurality of microlenses472may include more or fewer microlenses. The number of microlenses472corresponds to the number of addressing beams412and the number of ion chains406. The microlens array468is positioned a distance d2 from the ion trap270. In some aspects, the distance d2 is from about 2 mm to about 5 mm. In some aspects, the microlens array468is coupled to the ion trap270. For example, some aspects, the microlens array468may be optically bonded to the ion trap270. In another example, the microlens array468may be mounted to the ion trap270by a micro-mechanical assembly configured to adjust the microlens array468relative to the ion trap270. In such aspects, coupling the microlens array468to the ion trap270may result in the microlens array468being tightly referenced to the ion chains406a-406d. This can reduce sensitivity to drift, noise (e.g., due to vibrations, thermal contraction, air currents, and so forth), and so forth.

As shown inFIG.7, each of the microlenses472a-472dis aligned with one of the beams412a-412d, respectively. Each of the microlenses472a-472dis configured to focus the beams412a-412d, respectively, onto the corresponding ion chains406a-406d. The focused beams412a-412dare illustrated schematically inFIG.7as three “collections” of rays, which indicates that a full addressing range (e.g., of angled rays) of the beams412a-412dis focused on each of the respective ion chains406a-406d. As shown in the illustrated embodiment, although the beams412a-412dare very close together, the beams412a-412dare sufficiently separated so that the beams412a-412ddo not address neighboring ion chains. In the illustrated embodiment, adjacent ion chains are a distance d1 apart. In some aspects, the distance d1 is 1 mm. In such aspects, a total addressing region is 4 mm wide. However, each of the individual optical addressers404a-404dis configured to address a much smaller addressing region than the total addressing region. In the illustrated embodiment, the ion chains may be 189 μm long. In other aspects, the total region addressing region may be larger or smaller based on a number of individual addressing regions included in the total addressing region.

In the illustrated aspect, the microlenses472a-472dare configured to produce beams having a beam waist of less than 1.5 μm along the axis of the trapped ion chains406a-406d, a diameter of less than 30 μm along an orthogonal axis, and having a beam propagation ratio M2of less than 1.1. As used herein the orthogonal axis is orthogonal to both the axis of the trapped ion chains and the beam propagation direction.

For large addressing windows, such as the 4 mm addressing window of the present disclosure, it is advantageous to use a plurality of microlenses instead of one larger lens. For example, when addressing a 4 mm addressing region spaced 2 mm from an ion trap with a single beam, the angle of the beam is approximately 1 radian. Such an angle would require a very high NA. However, errors introduced by optics such as lenses typically increase with NA, reducing the accuracy of the addressing beam. In contrast, each of the microlenses472a-472dis configured to address the first, second, third, or fourth addressing regions, respectively. In the illustrated aspect, each of the first, second, third, and fourth addressing regions is 200 μm. Since the first, second, third, and fourth addressing regions are each spaced 1 mm from each other, in this example, a total addressing region is 4 mm.

The multiple-zone Raman optical system400described herein facilitates producing QIP systems200that have more qubits per quantum chip. For example, the system400includes optical addressers404a-404dthat can be used to address different trapped ion chains406a-406dof the ion trap270. In some aspects, the system400can be controlled (e.g., by the general controller205, the optical and trap controller220, and so forth) to address the different ion chains406a-406dsimultaneously. Since the trapped ion chains406a-406dmay be entangled with each other via transport and swap operations and/or photonic interconnects, the system400can allow the multiple trapped ion chains to act like a network of ion chains406a-406d.

In the examples described above, the trapped ion chains406a-406dmay be in close proximity to each other within the ion trap270. In these examples, the optical addressers404a-404ddescribed herein are configured to reduce the likelihood of optical crosstalk between adjacent trapped ions within a single ion chain by having a beam waist of much less than the ion spacing. For example, in an ion chain with an ion spacing of 3 μm, the addressing beam may have a beam waist of less than 1.5 μm along the axis of the trapped ion chains, with a diameter of less than 30 μm along an orthogonal axis. In some aspects, the diameter may be less than 60 μm along an orthogonal axis. In some aspects, the addressing beam may have a beam waist of 1.5 μm along the axis of the trapped ion chains and 4.5 μm-12 μm along the orthogonal axis. Such configurations may produce beam diameters of 3 μm along the axis of the trapped ion chains and 9 μm-24 μm along the orthogonal axis. Further, the optical addressers404a-404ddescribed herein are configured to reduce the likelihood of optical crosstalk between adjacent trapped ion chains406a-406d, the trapped ion chains406a-406dmay be separated by a distance large enough to mitigate the effects of spontaneous transmission. For example, the addressing beams produced by the system400have a beam waist of less than 1.5 μm, with a diameter of less than 30 μm. For example, in order to avoid optical crosstalk between adjacent trapped ion chains, for an ion chain of 64 ions and an ion spacing of 3 μm, a center-to-center spacing of adjacent trapped ion chains may be at least 1080 μm.

Although the system400is described as having four trapped ion chains406a-406dand four optical addressers404a-404d, in other aspects, the system400may include more or fewer trapped ion chains and optical addressers (i.e., the system400may be scaled up or down accordingly as long as there are at least two optical addressers). For example, variants of the system400can have as few as two trapped ion chains and two optical addressers. Variants of the system400can have as many as 64 trapped ion chains and 64 optical addressers.

In the configuration shown above, the system400may include conventional size lenses (e.g., not microlenses or metalenses) for the lenses424a-424d,428a-428d,436a-436d,440a-440d,448a-448d, and456a-456d. In other aspects, one or more of the lenses424a-424d,428a-428d,436a-436d,440a-440d,448a-448d, and456a-456dmay be microlenses and/or metalenses. In other aspects, all of the lenses424a-424d,428a-428d,436a-436d,440a-440d,448a-448d, and456a-456dmay be microlenses and/or metalenses.

Advantages of using microlenses and/or metalenses include the removal of large, bulky lenses, which can reduce the footprint of the system400.

FIG.8illustrates a detail view of a portion of a variant of system400that includes a metalens868instead of a microlens array468. Except the differences described below, the variant of the system400that includes the metalens468is the same as described above. In some aspects, the system400may include a metalenses868including a plurality of sub-lenses872a-872d. The metalens868and sub-lenses872a-872dare flat lenses. In some aspects, the metalens868may be configured as a continuous repeated pattern of sub-lenses872a-872din a single long lens. For example, the metalens868may form a periodic concentric pattern, with each pattern repeat forming a sub-lens872a-872dconcentrically centered around the center of one of the addressing zones of the ion trap270. Therefore, configurations that include metalenses may not include the singlet lenses428a-428d.

In some aspects, it may be advantageous to use metalenses868because metalenses have fewer optical aberrations and may eliminate the need for aspheric surface forms.

Further, although the beams412a-412dare shown in substantially linear configurations inFIGS.4-8, in some aspects, the system400may include mirrors and/or prisms configured to fold the beams412a-412d. In some variants, at least a portion of the components upstream of the of the combining region442may be positioned on a module or card. In such aspects, the components for each of the beams412a-412dmay be on separate cards or modules. In the variants of the system400described herein, the system400is configured so that the combining region442is oriented such that the beams412a-412ddo not overlap downstream of the combining region442.