Patent Description:
Ion trap quantum computing uses highly precise alignment of the final "atom imager" objective lens. For example, this may include thirty-two telecentric beams targeting an array of thirty-two individual atoms. The location in all three axes (x, y, z) is desirable controlled to within <<NUM>, for example. In addition, the beam angle in the x and y direction (pitch and yaw) may be controlled within 10mrad.

System architecture often means that these beams travel horizontally to skim the top of the ion trap. A relatively small (e.g., <NUM>) spot size uses a relatively high numerical aperture (NA) objective lens. Further, there may be significant restriction of physical space for the mechanism typically used to adjust the alignment.

Previous systems attempted to address these problems by using a Gough-Stewart Platform (hexapod) mounted outside the vacuum chamber. Beams were directed to enter the vacuum chamber from below using a relatively large reentrant window. The vertical beam orientation may be desirable to eliminate the overhanging loads (moments) and to center the center of gravity of the lens above the manipulator.

Despite the existence of such configurations, further advancements in optical systems may be desirable in certain applications, such as quantum computing, for example. An example for a lens positioner with five degrees of freedom is disclosed in the document <CIT>. An example for an optical system with an adjustment stage is disclosed in the document <CIT>. Further, an example for a precision retroreflector positioning apparatus is disclosed in the document <CIT>.

An optical system for use with a vacuum chamber may include a target to be positioned within the vacuum chamber, a laser source, and an optical assembly to be positioned within the vacuum chamber between the target and the laser source. The optical assembly is according to claim <NUM>.

The optical assembly may also comprise a plurality of translation actuators coupled between the housing and the frame. For example, the flexure actuators and the translation actuators may be configured to provide five degrees of freedom (DOF) movement for adjustment of the lens.

The frame may include a pair of elongate passageways orthogonal to one another. Each translation actuator may comprise a motor having an eccentric output shaft received within a respective elongate passageway. Similar to the flexure actuators, the plurality of translation actuators may also be carried within the housing.

The frame may have a rectangular shape defining four corners, for example. In this embodiment, the proximal end of each spiral flexure is coupled to the frame at a respective corner.

In some embodiments, the target may comprise an atom trap. In other embodiments, the target may comprise a semiconductor mask. Of course, the optical assembly may be used in other applications as well.

A method aspect is directed to a method of steering a laser beam from a laser source to a target within a vacuum chamber according to claim <NUM>.

The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention, as defined by the claims, to those skilled in the art.

Ion trap quantum computing requires highly precise alignment of the final "atom imager" objective lens of an optical assembly. There is a desire to move away from re-entrant windows in large vacuum chambers and toward more compact, highly integrated designs having the objective lens inside the vacuum chamber. Thus, minimizing chamber size may be critical to system performance. The optical assembly may need to be as small as possible as operation inside the vacuum chamber would typically use remote operation of the lens mount adjustments.

Referring initially to <FIG>, an optical system is generally designated <NUM> and is part of a quantum computer <NUM>. The optical system <NUM> includes an optical assembly <NUM>, a laser source and associated acousto-optic modulator (AOM) <NUM>, and a target in the form of atoms (e.g. ions) <NUM> within an atom trap <NUM>. An objective lens <NUM> is aligned between the laser source <NUM> and the target <NUM>. The optical system <NUM> satisfies tightly controlled telecentricity, distortion, and spot size requirements. The optical system <NUM> may also be adapted to fiber-coupling for acousto-optic (AO) devices. The ability to provide fiber-coupled acousto-optic modulators (AOMs) may become increasingly important as the quantum computing industry grows.

Examples of acousto-optic modulator devices and similar acousto-optic systems are disclosed in the documents <CIT>, <CIT>, <CIT>, <CIT>, <CIT> and <CIT>. Accordingly, the optical system <NUM> allows operation over a large spectrum. The optical system <NUM> may accordingly provide advantages with respect to numerous different types of targets.

The optical system <NUM> may provide five degrees of freedom of movement for adjustment, and comprises a parallel flexure system for final objective lens mounting as described in more detail below. The z-axis is defined in the direction of the laser source <NUM> to the target <NUM>. The laser source <NUM> generates a plurality of laser beams <NUM> that are aimed through the lens <NUM> to the target <NUM>.

The optical assembly <NUM> includes a housing <NUM>, a frame <NUM>, the lens <NUM> carried by the frame <NUM>, and a plurality of spiral flexures 124a, 124b, 124c, 124d, each having a respective proximal end coupled to the frame <NUM> as shown in <FIG>. The spiral flexures 124a, 124b, 124c, 124d operate both as pseudo-spherical joints and as prismatic joints. Accordingly, the five degrees of freedom of movement are advantageously managed in a single stage, as opposed to serially in stacked stages, for example. The optical assembly <NUM> may be cube shaped and have a dimension of approximately <NUM> millimeters on each side. The optical assembly <NUM> is space-efficient and may be more tightly integrated with the vacuum chamber <NUM> than current approaches and can also be adapted to fiber-coupling of acousto-optic devices.

In addition, the spiral flexures 124a, 124b, 124c, 124d have a high effective aspect ratio, allowing for a large adjustment range of Δx, Δy, Δz: ±. <NUM>" (<NUM>) and θx, θy: ±<NUM>°. A precision of adjustment of the optical assembly <NUM> is driven in part by the controls design.

Referring now to <FIG>, the optical assembly <NUM> features high precision and includes kinematically adjustments for each degree of freedom. In particular, the optical assembly <NUM> includes a plurality of flexure actuators 126a, 126b, 126c, 126d, where each flexure actuator is coupled between the housing <NUM> and a distal end of a respective spiral flexure. Each of the flexure actuators 126a, 126b, 126c, 126d comprises a respective threaded flexure tube 128a, 128b, 128c, 128d coupled to a distal end of each of the plurality of spiral flexures. Each flexure actuator also comprises a motor 130a, 130b, 130c, 130d having a rotatable threaded output shaft 132a, 132b, 132c, 132d coupled to a respective threaded flexure tube. In some embodiments, the flexure actuators may be carried within the housing <NUM> as shown in the illustrated embodiment.

The optical assembly <NUM> may also comprise a plurality of translation actuators 134a, 134b coupled between the housing <NUM> and the frame <NUM>. For example, the flexure actuators 126a, 126b, 126c, 126d and the translation actuators 134a, 134b are configured to provide the five degrees of freedom (DOF) movement for adjustment of the lens <NUM>.

The frame <NUM> may include a pair of elongate passageways 136a, 136b orthogonal to one another. Each translation actuator 134a, 134b may comprise a respective motor 140a, 140b having an eccentric output shaft 138a, 138b received within a respective elongate passageway 136a, 136b. Similar to the flexure actuators, the plurality of translation actuators 134a, 134b may also be carried within the housing <NUM>. The frame <NUM> may have a rectangular shape defining four corners, for example. In this embodiment, the distal end of each of the spiral flexures 124a, 124b, 124c, 124d is coupled to the frame <NUM> at a respective corner.

Referring now to <FIG>, the elongate passageway 136a is configured to engage the eccentric output shaft 138a to shift the frame <NUM> in the directions 142a, 142b along the x-axis. For example, in operation the frame <NUM> is configured to move in the direction 142a as the eccentric output shaft 138a rotates counter-clockwise. In a similar manner, the frame is configured to move in the direction 142b as the eccentric output shaft 138b rotates in the opposing clockwise direction. As those of ordinary skill in the art can appreciate, the frame <NUM> can similarly be adjusted along the y-axis.

With additional reference to <FIG>, the eccentric output shaft <NUM> is offset from the center of the translation actuator 134a. Accordingly, the eccentric output shaft <NUM> is configured to move in one of the directions 142a, 142b and consequently moves the frame <NUM> and lens <NUM> in the desired direction as the motor 140a rotates.

The spiral flexure 124a is also shown in a partial cross-sectional view in <FIG>. The respective corner of the frame <NUM> is raised or lowered dependent on the direction the threaded output shaft 132a is rotated by the motor 130a. In a particular aspect, the threaded flexure tube 128a rides upwards on the threaded output shaft 132a and away from the housing <NUM> as the threaded output shaft 132a is rotated in the counter-clockwise direction. As the threaded output shaft 132a is rotated in the clockwise direction, the threaded flexure tube 128a rides down on the threaded output shaft 132a and towards the housing <NUM>. The result of raising or lowering the spiral flexure 124a is to cause the frame <NUM> and lens <NUM> to be adjusted. As those of ordinary skill in the art can appreciate, the direction of rotation and threading of the threaded flexure tube 128a and output shaft 132a could be reversed to operate similarly.

The frame <NUM> is illustrated in <FIG> without the lens <NUM> or the spiral or translation actuators. As explained above, the frame <NUM> combines five degrees of freedom of movement into one stage. The focus of the lens <NUM> is adjusted by actuating one or more of the spiral flexures 124a, 124b, 124c, 124d. For example, as spiral flexure 124c is raised as illustrated in <FIG>, the frame <NUM> moves accordingly to adjust the focus of the lens <NUM>. As those of ordinary skill in the art can appreciate, the frame <NUM> and consequently the lens <NUM> can be adjusted in the Δz, θx, θy directions using the spiral flexures 124a, 124b, 124c, 124d alone or in combination with each other.

Typically, the alignment of the lens <NUM> would require three to five stages in series to achieve the alignment of the lens <NUM>. However, the frame <NUM> achieves synergistic travel and moves similar to a Gough-Stewart platform discussed above. Linearity is driven by force balance among the spiral flexures, not kinematics, and having a relatively high specific stiffness (stiffness per unit mass). In addition, the spiral flexures 124a, 124b, 124c, 124d allow for relatively large adjustment range in both translation and rotation while efficiently distributing stress. In addition, the spiral flexures 124a, 124b, 124c, 124d have a unique aspect ratio and may desirably have a specific stiffness due to being almost a full diameter in thickness.

With reference to <FIG>, the optical system <NUM>' may be used in an application where the target comprises a semiconductor mask <NUM>'. The laser source <NUM>' is directed to the semiconductor mask <NUM>' with the optical lens assembly <NUM>' therebetween.

Referring now to the flowchart <NUM> of <FIG>, in accordance with another aspect, is a method of steering a laser beam from a laser source to a target within a vacuum chamber. The method includes operating a plurality of flexure actuators of an optical assembly within the vacuum chamber between the target and the laser source. The optical assembly comprises a housing, a frame, a lens carried by the frame, and a plurality of spiral flexures each having a respective proximal end coupled to the frame. The optical assembly also has a plurality of flexure actuators with each flexure actuator coupled between the housing and a distal end of a respective spiral flexure. In addition, the optical assembly may include a plurality of translation actuators where the flexure actuators and the translation actuators provide five degrees of freedom (DOF) of movement for adjustment of the lens.

Claim 1:
An optical assembly (<NUM>) to be used between a target positioned within a vacuum chamber (<NUM>) and a laser source (<NUM>), the optical assembly comprising:
a housing (<NUM>);
a frame (<NUM>);
a lens (<NUM>) carried by the frame (<NUM>);
a plurality of spiral flexures (124a, 124b, 124c, 124d) each having a respective proximal end coupled to the frame; and
a plurality of flexure actuators (126a, 126b, 126c, 126d), each flexure actuator coupled between the housing and a distal end of a respective spiral flexure; and
wherein the optical assembly is characterized in that it comprises
a respective threaded flexure tube (128a, 128b, 128c, 128d) coupled to a distal end of each of the plurality of spiral flexures (124a, 124b, 124c,124d), and wherein each flexure actuator (126a, 126b, 126c, 126d) comprises a motor (130a, 130b, 130c, 130d) having a rotatable threaded output shaft (132a, 132b, 132c, 132d) coupled to a respective threaded flexure tube (128a, 128b, 128c, 128d).