COMPACT GONIOMETER MOUNT

Aspects of the present disclosure relate generally to systems and methods for using a goniometer mount system for use with a quantum information processing (QIP) system. The goniometer mount system includes a mounting bracket comprising a base plate and a back plate having a plurality of slots radially disposed about a center of the back plate. The goniometer mount system includes a rotary mounting plate that is rotatably coupled to the mounting bracket and configured to rotate about an axis extending through the center of the back plate that is circumscribed by the plurality of slots.

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 a goniometer mount system configured to change an angular position of a device coupled to the goniometer mount system. The goniometer mount system is operable within a small footprint. In some aspects, an acousto-optic deflector may be mounted to the goniometer mount system.

In some aspects, a goniometer mount system for use with a quantum information processing (QIP) system includes a mounting bracket and a rotary mounting plate. The mounting bracket includes a base plate and a back plate having a plurality of slots radially disposed about a center of the back plate. The rotary mounting plate is rotatably coupled to the mounting bracket and configured to rotate about an axis extending through the center of the back plate that is circumscribed by the plurality of slots.

In some aspects, a quantum information processing (QIP) system includes an acousto-optical deflector (AOD), a mounting system, and an actuator. The AOD includes a crystal configured to deflect an incoming beam from an optical addressing system onto one or more trapped ions. The mounting system includes a mounting bracket comprising a base plate and a back plate and a rotary mounting plate rotatably coupled to the back plate about a first axis of rotation. The AOD is mounted to the rotary mounting plate such that a center of the crystal is aligned with the first axis of rotation. The actuator is rotatably coupled to the back plate and seated against a surface of the rotary mounting plate. The actuator is configured to rotate about a second axis, which rotates the rotary mounting plate about the first axis.

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.

As is described in greater detail below, quantum computing (QIP) systems conduct computing operations using multiple atomic ions trapped in a linear crystal or chain using a trap. The trap may be referred to as an ion trap. Some or all of the trapped ions may be configured to operate as qubits in a QIP system. Such QIP systems may use one or more acousto-optic deflectors (AODs) to direct laser beams to illuminate the trapped ions. For example, the AODs may be used to dynamically direct laser beams that drive quantum gates towards individual ions.

In operation, a crystal within the AOD is aligned to a beam produced by an optical addressing system of the QIP system. The beams produced by the optical addressing system interact with the atoms or ions in the trap. Therefore, precise control of an orientation of the AOD (and therefore the crystal inside the AOD) is advantageous. In aspects described in greater detail herein, the AOD is mounted to a goniometer to enable adjustment of the AOD's position. However, due to the large size of the AOD relative to other nearby components, it is advantageous to couple the AOD to a compact goniometer, particularly a goniometer that is compact in a direction parallel to an axis of rotation of the goniometer. Conventional goniometer and/or gimbaled designs are typically thick in the direction of the axis of rotation. In contrast, the goniometer mount system of the present disclosure is compact in the direction of the axis of rotation. In some configurations, due to the size of the AOD, the goniometer may need to be positioned within a recess.

Solutions to the issues described above are explained in more detail in connection withFIGS.1-11, 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 or PMT). In this example, ions may be separated by a few microns (μm) 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 facility 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 with the optical assemblies, for example to position one or more AODs used to direct the optical beams that interact with the atoms or ions in the trap. 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.

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 AI 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, the goniometer mount system400described herein is configured to control the angular position of AODs (or other devices) coupled to the goniometer mount system400. The goniometer mount system400is configured to have a small footprint such that the goniometer mount system400can fit within a sterically constrained space.

For example, as shown schematically inFIG.8, due to the large size of an AOD402relative to other nearby components, it is advantageous to couple the AOD402to a compact goniometer mount system400. For example, the blocks401a-dschematically indicate components of laser, optical systems, optical components, and mechanical components that are used in the QIP system200. As shown inFIG.8, the goniometer mount system400is positioned in a sterically constrained space. It is therefore advantageous to minimize thickness in the direction indicated by the line403.

FIG.4illustrates a front perspective view of an example of a goniometer mount system400for an acousto-optical deflector (AOD)402according to aspects of the present disclosure.FIG.9illustrates a perspective view of the goniometer mount system400coupled to the AOD402.FIG.10shows a side view of the goniometer mount system400coupled to the AOD402. The goniometer mount system400is configured to reposition the AOD402to align the optical beams. In some aspects, the goniometer mount system400is used to reposition the AOD402to align the optical beams during configuration of the QIP system200. In some aspects, the goniometer mount system is used to reposition the AOD402to re-align the optical beams to long-term drift.

As shown inFIGS.4and9-10, the goniometer mount system400may include a base404, a back plate408, an AOD mounting plate412, and a knob416. As is described in greater detail below, the back plate408is fixedly coupled to the base404. The AOD mounting plate412is movably coupled to the back plate408and is configured to rotate relative to the back plate408and the base404about the axis A via actuation of the knob416. The AOD402is fixedly coupled to the AOD mounting plate412and rotates with the AOD mounting plate412about the axis A. As is best shown inFIG.8, the goniometer mount system400is compact in the direction parallel to the axis A (as indicated by the line403. The AOD402includes an acousto-optical crystal configured to deflect an incoming light beam aligned with the axis A. The AOD402is mounted to the AOD mounting plate412, such that the center of the acousto-optical crystal is aligned with the axis A. Advantageously, this configuration can prevent translation of the AOD crystal when making angular adjustments of the AOD mounting plate412according to an exemplary aspect. In some aspects, the goniometer mount system400may be positioned within a cavity so that the AOD402is aligned with the beam.

Although the goniometer mount system400is described herein with respect to the AOD402, it is contemplated that the goniometer mount system400can be used for other types of deflectors and other types of components of the QIP system200. The AOD mounting plate412may be interchangeably referred to herein as a rotary mounting plate.

As shown inFIG.4, the base404includes a substantially planar surface420, a first arm422, and a second arm424. The first arm422and the second arm424may be substantially perpendicular to the planar surface420. Each arm422,424may include a plurality of holes426. As is described in greater detail below, each of the holes426may receive a fastener (not shown) to couple the base404to the back plate408. The substantially planar surface420includes a first surface428and a second surface428opposite the first surface428. The first surface428includes a first cutout432and a second cutout436. The first cutout432is configured to accommodate rotation of the AOD402. The second cutout436is configured to accommodate rotation of the AOD mounting plate412(FIG.11). In some aspects, the AOD mounting plate412may rotate from substantially −7 degrees to substantially +7 degrees about the axis A. The base404includes holes418configured for mounting the base404to a housing of the QIP system200. The base404and the back plate408may be collectively referred to herein as a mounting bracket.

As shown inFIGS.5and6, the back plate408is substantially planar and includes a first surface440and a second surface444(FIG.6) opposite the second surface440. The back plate408includes a mounting hole448and a plurality of mounting slots452a-452cspaced from and radially surrounding the mounting hole448. In the illustrated embodiment, the back plate408includes three slots,452a,452b,452cthat extend through the back plate408. In other embodiments, the back plate408may include more than three slots. The slots452a,452b,452care curved, such that each slot452a,452b,452c, at least partially circumscribes a circle (or circular shape) having a radius at the mounting hole448. In other words, the plurality of slot452a,452b,452ccan be equidistantly spaced from each other and each spaced an equal distance from the mounting hole448according to an exemplary aspect. In some aspects, the slots452a,452b,452cmay be dimensioned such that the AOD mounting plate412may rotate from substantially −7 degrees to substantially +7 degrees about the axis A (e.g., relative to a zero position in which the fasteners512a-care substantially centered in the slots452a-c).

As is best shown inFIG.5, the first surface440of the back plate408includes a recess456configured to receive a spring460. In the illustrated aspect, the spring460is a helical spring. In other aspects, the spring460may be a different type of spring, such as, for example, a leaf spring. A first end464of the spring460may be coupled to the back plate408and a second end466of the spring460may be coupled to the AOD mounting plate412, such that the spring460biases the AOD mounting plate412in the direction shown by the arrow A (FIG.5). A mounting arm472may be coupled to a top side476of the back plate408. The mounting arm472may include an opening480configured to receive the knob416. In the illustrated aspect, the knob416may be threadedly coupled to the mounting arm472via the opening480.

As further shown inFIG.4, the AOD mounting plate412is substantially planar and includes a first surface484and a second surface488(FIG.6) opposite the first surface484. The AOD mounting plate412includes AOD mounting holes492, a mounting hole496, a plurality of radial mounting holes500a,500b,500cand a bearing arm504. The AOD402may be mounted to the AOD mounting plate412via fasteners (not shown) secured to the AOD mounting holes492. The AOD mounting plate412has chamfered corners506. The chamfered corners506proximate the first surface428of the base404allow the AOD mounting plate412to rotate relative to the base404and the back plate408. The chamfered corners506proximate the top of the AOD mounting plate412may prevent interference with the knob416and/or the back plate408as the AOD mounting plate412rotates. As is best shown inFIG.6, the second surface488includes a cutout510to allow the AOD mounting plate412to rotate past the mounting arm472of the back plate408.

The mounting hole496is configured to align with the mounting hole448of the back plate408when the AOD mounting plate412is aligned with the back plate408such that the AOD mounting plate412can be coupled to the back plate408by a fastener508engaged with the holes448and496.FIG.7illustrates a section view taken through the AOD mounting plate412, the back plate408, and the fastener508. At least a portion of the mounting hole496is threaded and configured to threadedly engage the fastener508. As shown inFIG.7, in some aspects, a bearing542may be engaged with the fastener508to reduce friction as the AOD mounting plate412rotates. In some aspects, the bearing542is a low-friction sleeve bearing. The bearing542prevents motion of the AOD mounting plate412as the fastener508is tightened (e.g., moved from the first position to the second position). The bearing542and the fastener508keep the rotation of the AOD mounting plate412centered about the axis A and referenced to the back plate408. In such aspects, the mounting hole496may include a shoulder546that is configured to seat the bearing542.

Returning toFIGS.5-6, the plurality of radial mounting holes500a,500b,500care configured to align with a portion of the slots452a,452b,452cof the back plate408when the AOD mounting plate412is aligned with the back plate408. The AOD mounting plate412is coupled to the back plate408by fasteners512engaged with the slots452a,452b,452cand the radial mounting holes500a,500b,500c. At least a portion of each of the radial mounting holes500a,500b,500cis threaded and configured to threadedly engage one of the fasteners512a,512b,512c, similar to what is shown inFIG.7with respect to the mounting hole496. In some aspects, bearings544a,544b,544cmay be engaged with the fasteners512a,512b,512c, respectively similar to what is described above with regard toFIG.7. The bearings544a,544b,544cprevent motion of the AOD mounting plate412as the fasteners512a,512b,512care tightened (e.g., moved from the first position to the second position). In the illustrated aspect, the plurality of radial mounting holes includes three radial mounting holes500a,500b,500c. In other aspects, the plurality of radial mounting holes may include more or fewer radial mounting holes.

The knob416is configured to engage a surface516of the bearing arm504and rotate the AOD mounting plate412. In the illustrated aspect, the bearing arm504is secured to a side of the AOD mounting plate412by fasteners520. In other aspects, the bearing arm504may be integrally formed with the AOD mounting plate412.

Referring now toFIG.5, in the illustrated aspect, the knob416has an elongated shaft that is threadably coupled with the opening480of the mounting arm472. In some aspects, the opening480is formed in a high-thread-per inch bushing coupled to the mounting arm472. The knob416is rotatable about an axis B in a first direction and a second direction opposite the first direction. The axis B is substantially perpendicular to the axis A. Rotation of the knob416in the first direction causes the knob416to move towards the bearing arm504, as indicated by the arrow B. The knob416exerts a force on the on the bearing arm504, also indicated by the arrow B, which causes the AOD mounting plate412to rotate against the bias of the spring460in the direction indicated by the arrow C. Rotation of the knob416in the second direction causes the knob416to move away from the bearing arm504, as indicated by the arrow D. This reduces the amount of force exerted by the knob416on the bearing arm504, and the bias of the spring460causes the AOD mounting plate412to rotate in the direction indicated by the arrow A. The spring constant of the spring460is high enough that the spring460is configured to maintain engagement between the bearing arm504and the knob416, thereby preventing backlash as the direction of rotation of the knob416is changed. In some aspects, the knob416may be actuated by hand. In some aspects, a motor may be coupled to the knob416and configured to actuate the knob416.

As shown inFIGS.5and6, a bearing528is secured between the back plate408and the AOD mounting plate412. The bearing528is centered about the axis A. In the illustrated aspect, the bearing528is a needle-roller thrust bearing. The needle-roller thrust bearing is compact in the direction of the axis A. The needle roller thrust bearing provides compact, low-friction gimbaled pitch adjustment (e.g., rotation) about the axis A. Since the axis A is centered at the center of the crystal of the AOD402, the needle-roller thrust bearing also provides compact, low-friction gimbaled pitch adjustment (e.g., rotation) about the center of the crystal of the AOD402. The profile of the needle roller thrust bearing does not substantially increase the thickness of the back plate408or the AOD mounting plate412. This allows the AOD mounting plate412to rotate about the axis A without adding bulk in a direction parallel to the axis A. In other aspects, other types of bearings528may be used. The bearing528is configured to provide low friction rotation about the axis A.

As shown inFIGS.5and6, the axis A extends through the centers of the mounting holes448and496. The fastener508extends through the mounting holes448and496such that the threads of the fastener508engage threads of the mounting hole496to couple the back plate408to the AOD mounting plate412. The fastener508is movable between a first position in which the AOD mounting plate412can rotate relative to the back plate408and a second (e.g., locking) position in which the AOD mounting plate412is prevented from rotating relative to the back plate408. A spring washer532and a low friction washer534are positioned between the fastener508and the second surface444of the back plate408.

The fasteners512a,512b,512cextend through the slots452a,452b,452cand the radial mounting holes500a,500b,500c, respectively, such that the threads of the fasteners512engage threads of the mounting holes500a,500b,500cto couple the back plate408to the AOD mounting plate412. As shown inFIG.6, the fasteners512a,512b,512ccan slide along the slots452a,452b,452c, respectively, as the AOD mounting plate412rotates about the axis A. The AOD mounting plate412may be continuously positionable between a first position in which the fasteners512a,512b,512care adjacent a first end of the slots452a,452b,452cand a second position in which the fasteners512a,512b,512care adjacent a second end of the slots452a,452b,452c. The fasteners512a,512b,512care movable between a first position in which the AOD mounting plate412can rotate relative to the back plate408and a second (e.g., locking) position in which the AOD mounting plate412is prevented from rotating relative to the back plate408. Spring washers536a,536b,536cand low friction washers538a,538b,538care positioned between the fasteners512a,512b,512cand the second surface444of the back plate408.

The spring washers532and536a,536b,536care biased to urge the AOD mounting plate412toward the back plate408even when the fasteners508,512a,512b,512chave been loosened to allow rotation of the AOD mounting plate412about the axis A. This bias helps seat the bearing528between the AOD mounting plate412and the back plate408as the AOD mounting plate412is rotated about the axis A. In some aspects, the spring washers532and536a,536b,536cmay be Belleville washers. In other aspects, other suitable types of spring washers may be used. The low friction washers534,538a,538b,538care configured to allow smooth rotation of the AOD mounting plate412about the axis A and to prevent movement of the AOD mounting plate412relative to the back plate as the fastener508is tightened. In some aspects, the low friction washers534,538a,538b,538cmay be polytetrafluoroethylene (PTFE). In other aspects, other suitable materials may be used. In the illustrated aspect, the fasteners508and512b,512care shoulder screws. In other aspects, other types of fasteners may be used. In the illustrated aspect, the fastener512ais a thumb screw. In other aspects, more or fewer of the fasteners may be thumb screws.

To position or re-position the AOD402mounted to the goniometer mount system400, an operator loosens the fasteners508,512a,512b,512c. The bias of the spring washers532,536a,536b,536cpushes the AOD mounting plate412and the back plate408together even when the fasteners508,512a,512b,512chave been loosened. The operator then grasps the knob416and rotates the knob416in either the first direction or the second direction to rotate the AOD mounting plate412about the axis A. Rotating the knob416in the first direction increases the force exerted by the knob416on the bearing arm504in the direction indicated by the arrow B, thereby rotating the AOD mounting plate412about the axis A in the direction indicated by the arrow C against the bias of the spring460. Rotating the knob416in the second direction moves the knob416in the direction indicated by the arrow D, which decreases the force exerted by the knob416on the bearing arm504. The bias of the spring460urges the AOD mounting plate412to rotate about the axis A in the direction indicated by the arrow A as the knob416moves in the direction indicated by the arrow D. The stiffness of the spring460is configured to hold the bearing arm504in contact with the knob416, preventing backlash in AOD mounting plate412as the knob416is rotated. The bearing528facilitates smooth rotation of the AOD mounting plate412as the AOD mounting plate412rotates about the axis A. The bearings542,544a,544b,544cand the low friction washers534,538a,538b,538cfacilitate smooth rotation of the AOD mounting plate412.

FIG.11illustrates the goniometer mount system400in a configuration in which the AOD mounting plate412has been rotated about the axis A (e.g., relative to the configuration illustrated inFIG.5). To position the AOD mounting plate412as shown inFIG.11, the knob416has been rotated in the direction indicated by the arrow B, which exerted a force on the bearing arm504, causing the AOD mounting plate412to rotate in the direction indicated by the arrow C.

After the operator has positioned the AOD mounting plate412in a desired orientation, the operator tightens the fasteners508,512a,512b,512c. The bearings542,544a,544b,544cand the low friction washers534,538a-cprevent motion of the AOD mounting plate412as the fasteners508,512a,512b,512care tightened, locking the AOD mounting plate412into the desired position. In some aspects in which the fastener512ais a thumb screw, the fasteners508and512a-cmay be partially tightened when the goniometer mount system400is installed in the QIP system200. In such aspects, the AOD mounting plate412may be rotated about the axis A after the goniometer mount system400has been installed in the QIP system200. The fastener512amay be tightened after the position of the AOD mounting plate412has been adjusted to lock the AOD mounting plate412into position.

InFIG.11, a portion of the base404has been cutaway. As shown inFIG.11, the cutouts436allow the AOD mounting plate412to rotate about the axis A without interference from the sides of the base404.