WO2023040615A1

WO2023040615A1 - Laser transmission device and ion trap system

Info

Publication number: WO2023040615A1
Application number: PCT/CN2022/114677
Authority: WO
Inventors: 杨超; 胡铁; 易飞
Original assignee: 华为技术有限公司
Priority date: 2021-09-18
Filing date: 2022-08-25
Publication date: 2023-03-23
Also published as: CN115826135A

Abstract

The present application discloses a laser transmission device and an ion trap system. The laser transmission device is applied to an ion trap system, and comprises a spatial spot-size converter and an array of diffractive elements. The spatial spot-size converter and the array of diffractive elements are located in different planes in space. The spatial spot-size converter is used for irradiating multiple laser beams to the array of diffractive elements. The array of diffractive elements is used for independently irradiating the multiple laser beams to corresponding ions, respectively. After passing through the diffractive elements, a column of laser beams emitted along a direction perpendicular to an ion chain are not parallel to each other. In this solution, since the array of diffractive elements is not coplanar with the spatial spot-size converter, the arrangement mode and number of the diffractive elements are not limited by the spatial spot-size converter, and the array of diffractive elements is easy to expand; moreover, the non-coplanar design eliminates the need for optical fibers to be directly coupled to a chip, thereby avoiding the limitation of chip size on the number of optical fibers; and the array arrangement of the diffractive elements is beneficial to increasing the numerical apertures of the diffractive elements, increasing the focusing capability of the diffractive elements, and outputting high-quality focused small light spots, thereby reducing crosstalk.

Description

A laser transmission device and ion trap system

Cross References to Related Applications

This application claims the priority of the Chinese patent application with the application number 202111101860.0 and the application name "A Laser Transmission Device and Ion Trap System" submitted to the China Patent Office on September 18, 2021, the entire contents of which are incorporated herein by reference Applying.

technical field

The present application relates to the technical field of quantum computing, in particular to a laser transmission device and an ion trap system.

Background technique

With the development of information technology, quantum computing has attracted more and more attention. The special feature of quantum computing is that the superposition of quantum states makes large-scale "parallel" computing possible. This is because the basic principle of quantum computing is to use qubits (ie ions) to encode information, where the state of a single qubit not only has two classical states of 0 and 1, but also a superposition state of 0 and 1 (as shown in As shown in 1, the qubit can be in the 0 state with half the probability and the 1 state with half the probability), and n qubits can be in the superposition state of 2 ⁿ quantum states at the same time. Each quantum algorithm performs different quantum operations on different numbers of qubits. The larger the number of qubits, the stronger its parallel acceleration capability, and the faster it can solve the same problem.

In terms of the physical realization of quantum computers, the current international mainstream solution is to use ion trap systems or superconducting systems. Among them, the basic process of using the ion trap system for quantum computing is as follows: the outer shell electrons of the heated atoms are ionized to form ions; in the vacuum chamber, the alternating radio frequency electric field and DC electric field generated by the ion trap integrated chip trap the ions into ions chain; the ions cooled by the cooling light interact with the control light emitted from the ion trap integrated chip to achieve a specific quantum state; quantum computing is realized through the manipulation of the quantum state.

In the multi-ion scenario, the manipulation of the quantum state of ions is achieved by independently manipulating light onto different ions. The manipulation of ion quantum state is achieved by striking different ions with independent focused lasers (arrows); the quantum state detection device is realized by imaging optical path and CCD, PMT, etc. to read fluorescence. The quantum gate operation is completed by controlling the duration of the manipulation of the laser through the peripheral timing control unit.

However, the current ion trap system is limited by the size and arrangement of optical components, making it difficult to achieve small spot focusing and expand the scale of long ion chains, thus affecting the computing power of quantum computers.

Contents of the invention

The embodiment of the present application provides a laser transmission device and an ion trap system, which can solve the problem that the number of ions in the ion trap system is difficult to expand.

In a first aspect, an embodiment of the present application provides a laser transmission device, which is applied in an ion trap system. Specifically, the device includes a spatial mode converter and a diffraction element array, and the spatial mode converter and the diffraction element array are located on different planes in space; the spatial mode converter is used to irradiate multiple laser beams to the diffraction element array The diffraction element array is used to independently irradiate the multi-path lasers to the corresponding ions, and part of the lasers in the multi-path lasers are not parallel to each other after passing through a row of diffraction elements in the diffraction element array along the direction perpendicular to the ion chain, Each path of laser light after passing through the diffraction element array corresponds to an ion in the ion chain, and the above ion chain is a one-dimensional long chain including multiple ions.

In the traditional ion trap system, the optical fiber is directly coupled to the chip, and the waveguide and diffraction elements are all set on the chip. Due to the limitation of the arrangement and chip size, it is difficult to expand the number of optical fibers and diffraction elements. In the above scheme of the present application, the diffraction elements are arranged in a two-dimensional array at first, and the spatial pattern converter and the diffraction element array are placed on a plane different from that of the diffraction element array. Therefore, if the diffraction element array is still If placed on the chip, the spatial pattern converter is located outside the chip, which can greatly increase the number of diffraction elements; in addition, since the spatial mode converter is located outside the chip, the optical fiber used to provide the laser light source is directly connected to the space The coupling of the mode spot converter makes it unnecessary for the optical fiber to be directly coupled to the chip, thereby avoiding the limitation of the number of optical fibers by the size of the chip; because the above-mentioned device greatly reduces the limitation on the number of optical fibers and the number of diffraction elements, so that more independent lasers can be realized Irradiating the ions on the ion chain separately can increase the number of ions in the ion trap system and improve the computing power of quantum computing. On the other hand, the array arrangement of the diffraction elements is beneficial to increase the numerical aperture of the diffraction elements, increase the focusing ability of the diffraction elements, output high-quality focused small light spots, and reduce crosstalk.

In a possible implementation, the above-mentioned device also includes a collimator array, which is used to collimate the multi-path laser light provided by the fiber array, and the collimator array is located between the fiber array and the spatial mode spot converter, so that after The collimated multi-channel laser light can be irradiated to the spatial mode spot converter. Collimating the laser is beneficial to improve the focusing effect of the laser. Especially for the laser with a large diffraction angle after passing through the diffraction element, the quality of the spot will be reduced due to the large diffraction angle; after the laser is collimated, it is beneficial to improve the quality of the spot irradiated to the ions.

In a possible implementation manner, the diffraction element is a metasurface structure formed by a plurality of micro-nano units processed and prepared from a dielectric material. The metasurface structure can realize the flexible and effective control of electromagnetic wave polarization, amplitude, phase, polarization mode, propagation mode and other characteristics, and it is more convenient to control the laser irradiated to the ion chain.

In a possible implementation manner, in the diffraction element array, there are shared micro-nano units along two adjacent diffraction elements parallel to the direction of the ion chain. The micro-nano unit shared by two adjacent diffraction elements parallel to the direction of the ion chain can make the array of diffraction elements more compact and further increase the number of diffraction elements; the adjacent two lasers along the direction parallel to the ion chain will It will be irradiated on the shared micro-nano unit, but due to the diffraction element of the metasurface structure, the polarization of the laser can be adjusted. Setting the two laser beams to different polarizations can make the same irradiation on the two shared micro-nano units The emitting directions of the laser light are inconsistent, so that the corresponding ions are irradiated.

In a possible implementation manner, the collimator array is composed of a plurality of collimator lenses, and the focal lengths of the plurality of collimator lenses along a direction perpendicular to the ion chain are different. After a row of laser beams passes through a row of diffraction elements, the diffraction angle is different, and the larger the diffraction angle, the quality of the outgoing laser spot will be reduced. Therefore, the focusing ability of the lens can be enhanced by setting a larger focal length of the collimator lens to improve The quality of the emitted laser spot can make up for the problem that the quality of the spot is reduced due to the large diffraction of the laser after passing through the diffraction element.

In a possible implementation manner, the collimator array includes a grating coupler array, or includes an end face coupler array. The grating coupler or end coupler is coupled with the optical fiber, so that the laser transmitted in the fiber continues to propagate along the grating coupler or end coupler, which is beneficial to improve the coupling efficiency of the laser and reduce the loss of laser energy.

In a possible implementation manner, the spatial mode converter includes a plurality of confocal lenses; or, the spatial mode converter is an optical waveguide array. At least two confocal lenses or lens groups can realize "zooming" of the laser light, so that the emitted laser light array matches the diffraction element array. The optical waveguide array can guide light waves to propagate therein, and each optical waveguide corresponds to a diffraction element, so that the laser array is transmitted to the corresponding diffraction element array.

In a possible implementation manner, the optical waveguide is a tapered optical waveguide. The tapered optical waveguide helps to increase the size of the mode spot and reduce the output divergence angle, thereby achieving amplitude matching and phase matching with the diffractive optical element.

In a possible implementation manner, the tapered optical waveguide is an arc-shaped slope structure. The tapered optical waveguide with the curved slope structure can make the conversion of the mode spot smoother, effectively reduce the influence of the diffraction effect and reduce the required length of the tapered region.

In a possible implementation manner, the device further includes a rectangular waveguide array, configured to transmit the multi-channel laser light to the spatial mode spot converter. The rectangular optical waveguide array can be arranged between the collimator array and the spatial mode spot converter to realize the transmission of the laser array; if the laser transmission device does not include the collimator array, the rectangular optical waveguide array can be arranged between the optical fiber array and the Between the spatial mode spot converters, it is used to realize the transmission of the laser array.

In a possible implementation manner, the device is located in a vacuum chamber. Arranging the optical device in the vacuum chamber can effectively avoid the multi-stage amplification of the light beam and reduce the size of the light spot, thereby helping to reduce the size of the ion trap system.

In the second aspect, the embodiment of the present application provides an ion trap system, including an optical fiber array and the laser transmission device as described in the first aspect or any one of the first aspect, the plurality of optical fibers in the optical fiber array are connected to the diffraction A plurality of diffraction elements in the element array correspond to each other. The restriction on the number of optical fibers and the number of diffraction elements of the ion system is greatly reduced, so that a larger number of independent lasers can be irradiated separately on the ions on the ion chain, which can increase the number of ions in the ion trap system and improve the calculation of quantum computing. ability. On the other hand, the array arrangement of the diffraction elements is beneficial to increase the numerical aperture of the diffraction elements, increase the focusing ability of the diffraction elements, output high-quality focused small light spots, and reduce crosstalk.

In a possible implementation manner, the foregoing optical fiber is a thermally expanded core optical fiber. When the numerical aperture of the diffraction element gradually increases from the middle to both sides, and/or the focal length of the collimator lens gradually increases from the middle to both sides, the use of TEC fiber can achieve a higher quality outgoing laser that matches the diffraction element.

Description of drawings

Fig. 1 provides the principle schematic diagram of qubit for the embodiment of the present application;

Fig. 2 is a schematic structural diagram of a traditional ion trap system provided by the embodiment of the present application;

Figure 3a and Figure 3b are schematic structural diagrams of another traditional ion trap system provided by the embodiment of the present application;

Fig. 4 is the enlarged schematic view of area D' in Fig. 3a provided by the embodiment of the present application;

Fig. 5 is a structural diagram of the multi-ion arrangement based on the ion trap system shown in Fig. 3a and Fig. 3b provided by the embodiment of the present application;

FIG. 6 is a schematic structural diagram of a laser transmission device provided in an embodiment of the present application;

FIG. 7 is a schematic diagram of the arrangement of the diffraction element array provided in the embodiment of the present application;

Fig. 8 is a schematic structural diagram of another laser transmission device provided in the embodiment of the present application;

Fig. 9a is a schematic diagram of a grating coupler array provided by an embodiment of the present application;

Fig. 9b is a schematic diagram of an array of end face couplers provided by the embodiment of the present application;

Fig. 10 is a schematic diagram of shared micro-nano units in two diffraction elements provided by the embodiment of the present application;

Fig. 11a is a schematic structural diagram of a tapered optical waveguide provided by an embodiment of the present application;

Fig. 11b is a schematic diagram of the matching of the optical waveguide and the diffractive optical element array provided by the embodiment of the present application;

Fig. 12 is a schematic structural diagram of a laser delivery device in a specific embodiment provided by the embodiment of the present application;

Fig. 13 is a spot effect diagram based on the laser transmission device shown in Fig. 12 provided by the embodiment of the present application;

Fig. 14a is a schematic structural diagram of a laser transmission device in another specific embodiment provided by the embodiment of the present application;

Fig. 14b is a schematic structural diagram of a laser delivery device in another specific embodiment provided by the embodiment of the present application;

Fig. 15 is a spot effect diagram based on the laser transmission device shown in Fig. 14a provided by the embodiment of the present application;

Fig. 16 is a schematic diagram of an ion trap system provided by an embodiment of the present application.

Detailed ways

In one ion trap system shown in Figure 2, conventional optics are used for focusing and addressing. Specifically, N ions are imprisoned into a one-dimensional long chain in a vacuum, and the control light is divided into two paths, namely the global Raman light and the independent Raman light. address; the independent Raman light is split by a beam splitter, modulated by a multi-channel acousto-optic modulator, and then focused by a lens with a large numerical aperture (NA) to accurately hit the ion chain. Among them, the modulator controls the switch and frequency of the light, which can realize the manipulation of the ion quantum state. However, the field angle of the aberration-ablation lens group composed of traditional optical lenses is limited, which leads to a limited number of independent Raman lights used for addressing and poor scalability; and the multi-stage amplification of beams makes the ion trap quantum computer The volume is on the order of meters.

3a and 3b are a top view and a side view of another ion trap system, respectively. As shown in Figure 3a, the two RF electrodes 01 and the DC electrode 02 are connected to the power supply. After the power is turned on, the RF electrode 01 can generate an alternating RF electric field, and the DC electrode 02 can generate a DC electric field. The RF electric field and the DC electric field are used together to generate A trapping potential well for trapping ions. Fig. 3b is a side view of the ion trap integrated chip 001 at B'-B' in Fig. 3a. The ion trap integrated chip 001 is connected to the optical fiber 002, and the optical fiber 002 transmits manipulated light of a specific frequency and polarization. The control light is coupled from the optical fiber 002 into the ion trap integrated chip 001, transmitted through the waveguide 03 and then coupled to the grating region C', and the focused integrated beam hits the trapped ions to realize quantum state manipulation.

Fig. 4 is an enlarged schematic view of area D' in Fig. 3a. As shown in FIG. 4 , small balls 1 and 2 are two examples of ions, and each grating 04 in FIG. 4 corresponds to one ion. FIG. 5 is a top view of the arrangement of multiple ions realized based on the ion trap integrated chip 001 shown in FIG. 3a and FIG. 3b . Exemplarily, the number of ions and the number of gratings 04 are both five. Combining with Figure 3a, Figure 3b, Figure 4 and Figure 5, it can be seen that the optical fiber is directly coupled to the chip, and the waveguide and diffraction elements are all set on the chip. The number of diffraction elements that can be set on the chip and the number of optical fibers that can be coupled to the chip are limited, thereby limiting the number of ions in the ion trap and reducing the computing power of the quantum computing system where the ion trap is located.

In view of this, an embodiment of the present application provides a laser transmission device that can be applied to an ion trap system to solve the problem that the number of diffraction elements is difficult to expand, so as to realize the expansion of the number of ions in the ion trap system.

Figure 6 is a schematic structural diagram of the laser transmission device provided by the embodiment of the present application. As shown in the figure, the laser transmission device provided by the embodiment of the present application includes a spatial pattern converter 61 and a diffraction element array 62, and the spatial pattern converter 61 and the diffractive element array 62 are located on a spatially different plane.

When the laser beam passes through the laser transmission device as shown in Figure 6, it first passes through the spatial pattern converter 61 in the Z-axis direction, and then passes through the diffraction element array 62. On the plane of , specifically means that the spatial pattern converter 61 and the diffraction element array 62 are not located on the same XOY plane, that is, the Z coordinates are different. In addition, although the spatial pattern converter 61 and the diffraction element array 62 are located on mutually parallel XOY planes in FIG. 6 , in some embodiments, their planes may not be parallel to each other. It should be understood that the above-mentioned spatial pattern converter 61 and the diffraction element array 62 are located on different spatial planes, which do not limit the length of the device in the Z-axis direction.

Specifically, the spatial pattern converter 61 is used to irradiate multiple laser beams to the diffraction element array, so that each laser beam is irradiated to one diffraction element of the diffraction element array 62 . For example, the size of the optical fiber array is usually larger than that of the diffraction element array. Therefore, the multiple laser beams can be scaled as a whole by the spatial mode spot converter 61, so that each laser beam can be irradiated to the corresponding diffraction element.

The diffraction element array 62 is used to independently irradiate multiple laser beams to corresponding ions in the ion chain, so as to realize quantum state manipulation. The diffraction element array 62 includes several diffraction elements. In a specific embodiment, the diffraction element array 62 can be shown in FIG. Laser beams are irradiated to each ion of the ion chain respectively. A and b in FIG. 7 exemplarily provide two arrangements of the diffraction element array 62 , and in practical applications, the arrangement of the diffraction element array 62 is not limited to this, and other arrangements are also possible. In addition, the number of rows and columns of the diffraction elements in the diffraction element array 62 in FIG. 7 is only an example, which is not limited in the present application.

The ion chain is a one-dimensional long chain, including several ions. In the embodiment shown in Figure 6, the one-dimensional ion chain is located on a straight line parallel to the X axis (because the X axis is perpendicular to the paper direction in Figure 6, so The ion chain only shows one ion in Fig. 6), and the diffraction element array 62 is arranged on the plane parallel to the XOY plane, since the multi-path lasers passing through the diffraction element array 62 need to be independently irradiated to the corresponding ions in the ion chain, so a column After the laser light passes through a row of diffraction elements in the diffraction element array 62 along the direction perpendicular to the ion chain (along the Y-axis direction), the emitted laser light is not parallel to each other. In the embodiment shown in Fig. 6, on the Y-axis direction, the ion chain is located in the middle of the diffraction element array 62, so after the laser passes through the diffraction element in the middle of the Y-axis direction in the diffraction element array 62, the diffraction angle The diffraction angle of the laser light is relatively large after passing through the diffraction elements on both sides of the diffraction element array 62 along the Y-axis direction.

In the above embodiments, since the spatial pattern converter 61 and the diffraction element array 62 are located on different planes in space, the spatial pattern converter 61 will not affect the arrangement of the diffraction elements. If the diffraction element array 62 is placed on the chip, the spatial pattern converter 61 is located outside the chip, and the spatial pattern converter 61 does not need to occupy a limited position on the chip, which is beneficial to increase the number of diffraction elements. In addition, since the spatial mode spot converter 61 is located outside the chip, no matter whether the optical fiber used to provide the laser light source is directly coupled with the spatial mode spot converter, the optical fiber does not need to be directly coupled with the chip, thereby avoiding the impact of the chip size on the number of optical fibers. limits.

On the other hand, since the diffraction elements are arranged in an array, referring to a in Figure 7, if the 5 diffraction elements in the first row correspond to ions 1-5 on the ion chain from top to bottom, then the 5 diffraction elements in the second row The first diffraction element and the second diffraction element in the first row correspond to 1 and 6 on the ion chain respectively from top to bottom, so each diffraction element The diameter of can be set to 5d, where d represents the ion distance. In FIG. 7 , it is taken that each column of the diffraction element array 62 includes 5 diffraction elements as an example. If each column includes N diffraction elements, the radius of the diffraction element can be set as N*d. Therefore, the above embodiments are beneficial to increase the numerical aperture of the diffraction element, thereby helping to increase the focusing capability of the diffraction element, and output high-quality focused small light spots. In addition, the diffraction element array has no overlap in space and adopts an off-axis design, that is, the beams perpendicular to the direction of the ion chain are not parallel to each other, and the crosstalk between channels is low.

Since the limitation of the above-mentioned device on the number of optical fibers and the number of diffraction elements is greatly reduced, a larger number of independent lasers can irradiate the ions on the ion chain separately, thereby increasing the number of ions in the ion trap system and improving the calculation of quantum computing. ability; in addition, it is also possible to irradiate high-quality focused small spots to ion chains to improve the performance of quantum computing systems.

Further, the above-mentioned laser transmission device may also include a collimator array 63 as shown in FIG. 8 . The collimator array 63 is used to collimate the multiple laser beams transmitted by the fiber array, and irradiate the collimated multiple laser beams to the spatial mode spot converter 61 . The collimator array 63 can collimate the laser light, and can adjust the size of the output light spot at the same time, which is beneficial to improve the focusing effect of the laser light.

The multiple collimators included in the collimator array 63 correspond to the multiple diffractive elements included in the diffractive element array 62 one by one, that is, after passing through the collimator, one path of laser light is irradiated to corresponding diffraction elements in the diffraction element array 62 and illuminate corresponding ions. In addition, the multiple collimators included in the collimator array 63 are also in one-to-one correspondence with the multiple optical fibers included in the fiber array, that is, each optical fiber corresponds to a collimator, and each collimator corresponds to a diffraction element, Each diffraction element corresponds to an ion, so each laser beam will be irradiated on its corresponding ion.

In a possible design, the collimator array 63 may be composed of a collimator lens array, and each collimator lens corresponds to an optical fiber in an optical fiber array, and is used for collimating the laser light transmitted by the optical fiber. The focal length of the collimating lens array needs to be matched with the spatial pattern converter 61 . If the focal length of the collimating lens needs to be larger, the collimating lens may not be provided, and the optical fiber array is directly coupled to the spatial mode converter 61 .

The arrangement of collimating lenses may also be as shown in FIG. 7 . The arrangement of the collimating lens array can be consistent with that of the diffractive element array, so that the laser light passing through the collimating lens can be irradiated to the corresponding diffractive element after passing through the spatial mode spot converter. The aperture of a collimator lens is usually greater than the aperture of a diffraction element, that is, the area occupied by the collimator array 63 is greater than the area occupied by the diffraction element array 62; if there is no space between the collimator array 63 and the diffraction element array 62 The speckle converter 61 cannot independently irradiate the multiple laser beams passing through the collimator array 63 to the corresponding diffraction elements. The spatial pattern converter 61 performs overall scaling of multiple laser beams, so as to irradiate each laser beam to a corresponding diffraction element.

In the collimating lens array, the focal length of a row of collimating lenses (ie, collimating lenses along the direction perpendicular to the ion chain) can be different. As mentioned above, after a row of laser beams passes through a row of diffraction elements, the diffraction angles are different. Take the ion chain at the middle position of the diffraction element array 62 as an example, so the diffraction angle of the laser light is smaller after passing through the diffraction elements at the middle position of a row of diffraction elements; The larger the diffraction angle, the larger the diffraction angle will reduce the quality of the outgoing laser spot. At this time, a collimator lens with a smaller focal length may be arranged in the middle of a row of collimator lenses, and a collimator lens with a larger focal length may be arranged at the upper and lower sides of a row of collimator lenses. A collimating lens with a larger focal length can enhance the focusing ability of the lens and improve the quality of the outgoing laser spot, thereby compensating for the problem that the laser spot is degraded due to large diffraction after passing through the diffraction element. In addition, setting different focal lengths is also beneficial to reduce the complexity of the spatial mode spot converter, especially when the diffraction elements of the diffraction element array are not completely the same, the output spot size can be adjusted by the different focal lengths of the collimator. Improve the diffraction efficiency of the diffraction element.

In another possible design, the collimator array 63 may also include a grating coupler array, as shown in FIG. 9a; or, the collimator array 63 may also include an end face coupler array, as shown in FIG. 9b. Fig. 9 a and Fig. 9 b only provide the schematic diagram of a collimator in the collimator array 63 by way of example, as shown in the figure, the grating coupler or the end face coupler is coupled with the optical fiber, so that the laser light transmitted in the optical fiber is coupled along the grating The grating coupler or end coupler also has a collimating effect on the laser. If the collimator array 63 is a grating coupler array or an end face coupler array, the laser emitted from the fiber array propagates along the medium in the collimator array 63, which is beneficial to improve the coupling efficiency of the laser and reduce the energy loss of the laser.

The grating coupler can use an on-chip grating coupler to achieve high coupling efficiency through reasonable grating parameter design and material selection. The end-face coupler can adopt the reciprocal structure of the three-dimensional conical mode spot converter, and achieve higher coupling efficiency by adopting the arc-shaped conical structure.

In a possible implementation manner, the diffraction elements in the above-mentioned diffraction element array 62 may be metasurface structures formed by a plurality of micro-nano units processed and prepared from dielectric materials. For example, the diffraction element can be a metalens with a metasurface structure, and each metalens can include several electromagnetic micro-nano units, and the electromagnetic micro-nano units are located in various structures such as elliptical cylinders, annular cylinders, polygonal cylinders, etc., to expand the focusing aperture, Outputs long chains of densely focused spots. The numerical apertures of multiple metalens in a closely arranged metalens array can be equal or unequal. As mentioned above, the diffraction angles of a row of superlenses perpendicular to the direction of the ion chain are different, and the quality of the outgoing laser spot will be reduced due to the large diffraction angle. Therefore, in order to compensate for the inconsistent quality of the light spot caused by the diffraction angle, you can A metalens with a larger numerical aperture is used for a diffraction element with a larger diffraction angle to improve its focusing ability and enhance the quality of the outgoing light spot, and a metalens with a smaller numerical aperture is used for a diffraction element with a smaller diffraction angle. Taking the ion chain at the center of the diffraction element array 62 in the Y-axis direction as an example, then the diffraction element array 62 is in the Y-axis direction, and the numerical aperture of the diffraction element gradually increases from the middle to both sides.

Since the diffraction element can be a metasurface structure formed by a plurality of micro-nano units, in order to make the arrangement of the diffraction element array 62 more compact, and further increase the number of diffraction elements, it is also possible to make the adjacent two along the direction parallel to the ion chain Diffraction elements, there are shared micro-nano units. In the specific embodiment shown in FIG. 10 , each solid circle represents a diffraction element, and the shaded part represents a shared micro-nano unit. It should be understood that FIG. 10 is only a specific example, and in practical application, two diffraction elements may share a proportion of micro-nano units, which may be more or less than that shown in FIG. 10 . Due to the diffraction element of the metasurface structure, the polarization and wavelength of the laser can be adjusted. Therefore, two adjacent laser beams along the direction parallel to the ion chain can be set to different polarizations or different wavelengths, so that although the two laser beams are both Irradiate to the shared micro-nano unit, but because the micro-nano unit of the metasurface structure can adjust the polarization and wavelength, the lasers with different polarizations or different wavelengths are emitted in different directions, thus irradiating different ions. For example, different types of ions may have different wavelength requirements for controlling the laser. If there are different types of ions in the ion chain, the activation of different wavelengths can be set, which can meet the requirements for ion control and realize multi-channel laser. When it irradiates the shared micro-nano unit, it can emit in different directions.

In order to make the laser beam irradiated to the ions have a better focusing effect, the distance between the ion chain and the diffraction element array (the distance on the Z axis as shown in Figure 6 and Figure 8) can be set as the focal length of the diffraction element, so that This enables the laser to focus on the ions.

In a possible implementation manner, the foregoing spatial pattern converter 61 may be a plurality of confocal lenses. Specifically, the spatial mode spot converter 61 may include at least two confocal lenses or lens groups to achieve “zooming” of the laser light, so that the emitted laser light array matches the diffraction element array 62 .

In another possible implementation manner, the foregoing spatial mode speckle converter 61 may also be an optical waveguide array. An optical waveguide is a dielectric device that guides light waves to propagate in it, also known as a dielectric optical waveguide. The optical waveguide array can be used to transmit the laser array, and realize the pitch conversion from the collimator array 63 to the diffraction element array 62 , or the pitch conversion from the optical fiber array to the diffraction element array 62 . When the laser transmission device includes a collimator array 63, each optical waveguide is coupled with a collimator, and transmits the collimated laser light to a corresponding diffraction element; when the laser transmission device does not include a collimator array 63 , the spatial mode spot converter 61 can be directly coupled with the fiber array, that is, each optical waveguide is coupled with an optical fiber, and transmits the laser light to a corresponding diffraction element.

Each optical waveguide in the optical waveguide array may be a tapered optical waveguide. The tapered optical waveguide helps to increase the size of the mode spot and reduce the output divergence angle, thereby achieving amplitude matching and phase matching with the diffractive optical element. Further, the tapered waveguide can adopt an on-chip three-dimensional tapered waveguide solution, as shown in Figure 11a, wherein the dark part is the optical waveguide, and the light part is the medium. The structure of the optical waveguide includes the input single-mode waveguide (coupling part with the collimator, that is, the dark and slender part of the front end in Fig. 11a), the symmetrical horizontal tapered converter to realize the expansion of the mode width direction, and the on-chip The vertical tapered converter and the final output waveguide (for outputting the laser spot to the ion chain). Further, the tapered slope surface can be an arc surface, so that the transition of the mold spot is smoother, which can effectively reduce the influence of the diffraction effect and reduce the required length of the tapered region. Figure 11b further illustrates the matching structure of the tapered waveguide and the diffractive optical element array in this embodiment, and Figure 11b takes 2 rows and 2 columns as an example, the polarization of the laser light transmitted by the two optical waveguides in the horizontal direction (parallel to the direction of the ion chain) They are different, represented by TE and TM respectively. Therefore, although the corresponding diffraction element has a common part, and the common part is irradiated by the laser light transmitted by the two optical waveguides, but because the superlens has a regulating effect on the polarization of light, the two laser beams After passing through the common part, the laser beams with different polarizations will emerge in different directions to irradiate corresponding ions.

Optionally, the above-mentioned laser transmission device may also include a rectangular optical waveguide array or an optical waveguide array of other shapes, which is arranged between the collimator array 63 and the spatial mode spot converter 61 to realize the transmission of the laser array; if the laser If the transmission device does not include the collimator array 63, the rectangular optical waveguide array can be arranged between the optical fiber array and the spatial mode spot converter 61 to realize the transmission of the laser array.

In order to further improve the quality of the light spot, the above-mentioned laser transmission device can all be arranged in a vacuum cavity. In the traditional ion trap system shown in Figure 2, since the optical components are all outside the vacuum chamber, multi-stage amplification of the beam is inevitable, making the volume of the ion trap quantum computer reach the order of meters. However, in the embodiment of the present application, the optical device can be arranged in the vacuum chamber, which can effectively avoid the multi-stage amplification of the light beam and reduce the size of the spot, thereby helping to reduce the size of the ion trap system.

In order to understand the above-mentioned embodiments of the present application more clearly, examples are described below in conjunction with the accompanying drawings.

Referring to Fig. 12, it is a specific embodiment provided by this application. In the specific embodiment shown in FIG. 12 , the laser delivery device includes a collimator array 63 , a spatial pattern converter 61 and a diffraction element array 62 , all of which are located in the vacuum chamber of the ion trap system. Wherein, the collimator array 63 is a collimating lens array, and each optical fiber of the fiber array transmits the laser light to a corresponding collimating lens in the collimating lens array, and the collimating lens collimates the laser light, and transmits the laser light to the space Pattern converter 61. The spatial mode spot converter 61 includes two confocal lenses (groups) for irradiating the laser array to the corresponding diffraction element array 62 . The diffraction element array 62 is a metalens array, and the metalens in the metalens array do not have shared micro-nano units. A row of lasers in the laser array (lasers arranged perpendicular to the direction of the ion chain), after passing through a corresponding row of metalens in the metalens array (the metalens arranged perpendicular to the direction of the ion chain), are not parallel to each other, so that Each path of laser light is irradiated on the corresponding ion in the one-dimensional long chain of ions.

What Fig. 12 shows is the schematic cross-sectional view of the laser transmission device on the YOZ plane. On this cross-section, the collimator array 63 can only show one column of collimators, and the diffraction element array 62 can only show one column of diffraction elements. In the figure, Each column contains 5 collimators and 5 diffraction elements as an example, in actual application, each column can be provided with more or less collimators and diffraction elements than those shown in Figure 12. It should be understood that several columns of collimators and corresponding columns of diffraction elements may also be arranged in a direction perpendicular to the paper. For example, the arrangement of the optical fiber array, the collimator array 63 and the diffraction element array on the plane parallel to the YOZ plane may be as shown in FIG. 7 . Similarly, only one ion can be shown in Fig. 12 because the ion chain is also located in the direction perpendicular to the paper. A row of laser beams passes through a row of diffraction elements and irradiates successive different ions in the ion chain.

Simulation calculations have been carried out based on the specific embodiment shown in Figure 12. Taking each array as an example with 2 rows and 2 columns, the simulation experiment data of the laser spot for ion control of ions that is finally output by the diffraction element array can be shown in the figure 13. As shown in Table 1 and Table 2.

Table 1

Table 2

It can be seen from FIG. 13 that the size of the final output light spot is smaller and the focusing effect is better. The above Table 1 shows the coupling efficiency and crosstalk matrix of each laser. As shown in Table 1, the coupling efficiency of each channel is above 50%. Compared with the traditional ion trap system, the coupling efficiency is significantly improved and the crosstalk between channels is reduced.

Referring to Fig. 14a and Fig. 14b, it is another specific embodiment provided by the present application. In the specific embodiment shown in Fig. 14a and Fig. 14b, the laser delivery device includes a collimator array 63, a spatial mode spot converter 61 and a diffraction element array 62, all of which are located in the vacuum chamber of the ion trap system. In Fig. 14a, the collimator array 63 is a grating coupler array, and each grating coupler is coupled with an optical fiber in the fiber array, and transmits the laser light to the spatial mode spot converter 61; in Fig. 14b, the collimator The array 63 is an end-face coupler, and each end-face coupler is coupled with one fiber in the fiber array, and transmits the laser light to the spatial mode spot converter 61 . The end face coupler 61 includes an optical waveguide array for irradiating the laser array transmitted by the grating coupler array (or the end face coupler array) to the one-to-one corresponding diffraction element array 62 . The diffraction element array 62 is a metalens array, and there are shared micro-nano units between adjacent metalens in the metalens array along the direction parallel to the ion chain. A row of lasers in the laser array (lasers arranged perpendicular to the direction of the ion chain), after passing through a corresponding row of metalens in the metalens array (the metalens arranged perpendicular to the direction of the ion chain), are not parallel to each other, so that Each path of laser light is irradiated on the corresponding ion in the one-dimensional long chain of ions.

Figures 14a and 14b are schematic cross-sectional views of the laser transmission device on the XOY plane. On this cross-section, the collimator array 63 can only show a row of grating couplers or a row of end-face couplers, and the spatial mode spot converter 61 can only show One row of optical waveguides can be shown, and the array of diffractive elements can only show one row of diffractive elements. It should be understood that several rows of grating couplers (or end face couplers), corresponding rows of optical waveguides and corresponding rows of diffraction elements may also be arranged in a direction perpendicular to the paper.

Simulation calculations have been carried out based on the specific embodiment shown in Figure 14a. Taking each array including 2 rows and 2 columns as an example, the experimental data of the laser spot that is finally output by the diffraction element array for ion control can be shown in Figure 15 , Table 3 and Table 4.

table 3

Table 4

It can be seen from FIG. 15 that the size of the final output light spot is smaller and the focusing effect is better. The above Table 3 shows the coupling efficiency and crosstalk matrix of each laser. As shown in Table 3, the coupling efficiency of each channel is above 50%. Compared with the traditional ion trap system, the coupling efficiency is significantly improved and the crosstalk between channels is reduced.

Based on the same technical idea, an embodiment of the present application also provides an ion trap system, which may include an optical fiber array, and the laser transmission device in any of the foregoing embodiments.

In a possible implementation manner, the optical fibers in the foregoing optical fiber array may be thermally expanded core (TEC) optical fibers. Especially when the numerical aperture of the diffraction element gradually increases from the middle to both sides, and/or the focal length of the collimator lens gradually increases from the middle to both sides, the use of TEC fiber can achieve a higher quality output laser that matches the diffraction element .

Figure 16 exemplarily provides an ion trap system, as shown in the figure, the ion trap system includes a vacuum system 16-1, a laser system 16-2, a trapping electromagnetic field generating device 16-3, a detection device 16-4 and a control system System 16-5. The laser system 16-2 includes the laser transmission device 16-2-1 provided in the above-mentioned embodiments of the present application, which is arranged in the vacuum chamber O provided by the vacuum system 16-1.

Further, the laser system 16-2 also includes manipulation light, detection light, ionization, cooling, and pumping light. The laser system 16-2 is connected to the ion trap integrated chip 100 through the laser transmission device 16-2-1; the trapping electromagnetic field generates The device 16-3 is electrically connected with the ion trap integrated chip 100 to control the ion trap integrated chip 100 to generate a trapping potential well; the detection device 16-4 is composed of an imaging optical path, a charge coupled device image sensor (charge coupled device, CCD) and a photoelectric The photomultiplier tube (photomultiplier tube, PMT) and other components are used to detect the quantum state of ions; the control system 16-5 generates timing and switches to control other parts. Specifically, the control system 16-5 is respectively connected with the laser system 16-2, the trapping electromagnetic field generating device 16-3 and the detection device 16-4 in signal connection.

The working process of the above-mentioned ion trap system is: when the trapping electromagnetic field generating device 16-3 is turned on, in the vacuum chamber O, the ion trap integrated chip 100 provided by the embodiment of the present application is powered on, and the alternating radio frequency electric field in the ion trap integrated chip 100 and The DC electric field generates a trapping electromagnetic field, which traps ions (formed after the heated atoms’ outer shell electrons are ionized) into ion chains, and the ionized ions are trapped at tens of microns above the ion trap integrated chip 100; the laser system 16- The cooling light and pumping light in 2 cool and initialize the ions, so that the ions reach a specific quantum state; then, carry out sideband cooling on the ions, and control the manipulation in the laser system 16-2 through the control system 16-5 The light passes through the laser transmission device 16-2-1 to perform coherent operations on the quantum states of the ions; after the operation is completed, the detection light emitted by the laser system 16-2 and the detection device 16-4 measure the results of the operations on the quantum states.

In addition, it should be understood that in the description of this application, terms such as "first", "second", and "third" are only used for the purpose of distinguishing descriptions, and should not be understood as indicating or implying relative importance. Neither should it be construed as indicating or implying an order. Reference to "one embodiment" or "some embodiments" or the like in this specification means that a particular feature, structure, or characteristic described in connection with the embodiment is included in one or more embodiments of the present application. Thus, appearances of the phrases "in one embodiment," "in some embodiments," "in other embodiments," "in other embodiments," etc. in various places in this specification are not necessarily All refer to the same embodiment, but mean "one or more but not all embodiments" unless specifically stated otherwise. The terms "including", "comprising", "having" and variations thereof mean "including but not limited to", unless specifically stated otherwise.

The above is only the specific implementation of the application, but the scope of protection of the application is not limited thereto. Any person familiar with the technical field can think of changes or replacements based on the technical solution of the application within the technical scope disclosed in the application. All should be covered within the scope of protection of this application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

A laser transmission device, which is applied in an ion trap system, is characterized in that the laser transmission device includes: a spatial mode spot converter and a diffraction element array, and the spatial mode spot converter and the diffraction element array lie on different planes in space;

The spatial mode spot converter is used to irradiate multiple laser beams to the diffraction element array;

The diffraction element array is used to independently irradiate the multiple laser beams to corresponding ions in the ion chain, and part of the laser light in the multiple laser beams passes through the diffraction element array along a direction perpendicular to the ion chain A row of diffraction elements in the direction is not parallel to each other, and each path of laser light passing through the array of diffraction elements corresponds to an ion in the ion chain, and the ion chain is a one-dimensional long chain including multiple ions.
The laser delivery device according to claim 1, wherein the device further comprises a collimator array, and a plurality of collimators in the collimator array are connected to a plurality of diffraction elements in the diffraction element array one-to-one correspondence;

The collimator array is used to collimate the multiple laser beams transmitted by the fiber array, and irradiate the collimated multiple laser beams to the spatial mode spot converter.
The laser transmission device according to claim 1 or 2, characterized in that the diffraction element is a metasurface structure formed by a plurality of micro-nano units processed and prepared from dielectric materials.
The laser transmission device according to claim 3, characterized in that, in the diffraction element array, there are shared micro-nano units along two adjacent diffraction elements parallel to the direction of the ion chain.
The laser delivery device according to any one of claims 1-4, wherein the collimator array is composed of a plurality of collimator lenses, and the focal lengths of the plurality of collimator lenses perpendicular to the direction of the ion chain different.
The laser transmission device according to any one of claims 1-4, wherein the collimator array includes a grating coupler array, or includes an end face coupler array.
The laser transmission device according to any one of claims 1-6, wherein the spatial mode spot converter comprises a plurality of confocal lenses; or

The spatial mode speckle converter is an optical waveguide array.
The laser transmission device according to claim 7, wherein the optical waveguide is a tapered optical waveguide.
The laser transmission device according to claim 8, wherein the tapered optical waveguide is an arc-shaped slope structure.
The laser transmission device according to any one of claims 7-9, characterized in that the device further comprises a rectangular waveguide array for transmitting the multi-channel laser light to the spatial mode spot converter.
The laser delivery device according to any one of claims 1-10, characterized in that the device is located in a vacuum chamber.
An ion trap system, characterized in that it comprises an optical fiber array and the laser transmission device according to any one of claims 1-11, the plurality of optical fibers in the optical fiber array and the plurality of diffractive elements in the diffraction element array One-to-one correspondence of components.
The ion trap system according to claim 12, wherein the optical fiber is a thermally expanded core TEC optical fiber.