Crosstalk reduction in multichannel acousto-optic modulators.

Abstract

Aspects of the present disclosure describe a technique for controlling coherent crosstalk errors occurring in a multi-channel acousto-optic modulator (AOM) by applying cancellation tones to reduce or eliminate the crosstalk errors. For example, a method and system are described that include applying a first radio frequency (RF) tone to generate a first acoustic wave in a first channel of the multi-channel AOM, where a portion of the first acoustic wave interacts with a second channel to cause a crosstalk effect, and applying a second RF tone to generate a second acoustic wave in the second channel, where the second acoustic wave reduces or eliminates the crosstalk effect caused by the portion of the first acoustic wave.

Description

[Technical field]

[0001] [CROSS REFERENCE TO RELATED APPLICATIONS] This application claims priority to and the benefit of U.S. Non-Provisional Patent Application No. 17 / 150,909, entitled "CROSSTALK REDUCTION IN MULTI CHANNEL ACOUSTO-OPTIC MODULATORS," filed on January 15, 2021, and U.S. Provisional Patent Application No. 62 / 965,091, entitled "CROSSTALK REDUCTION IN MULTI-CHANNEL ACOUSTO-OPTIC MODULATORS," filed on January 23, 2020, the entire contents of which are incorporated herein by reference.

[0002] [Government Licensing Rights] This invention was made with United States Government support under Contract No. W911NF1610082 awarded by the Intelligence Advanced Research Projects Activity. The United States Government has certain rights in this invention. [Background technology]

[0003] Aspects of the present disclosure relate generally to cancellation of crosstalk noise in near channels of a trapped ion quantum computer, and more specifically, the present disclosure describes techniques used to control coherent crosstalk errors in a multi-channel acousto-optic modulator (AOM) using cancellation tones.

[0004] Trapped atoms are one of the main implementations of quantum information processing (QIP) or quantum computing. Atomic-based qubits can be used as quantum memories, as quantum gates in quantum computers and simulators, and can act as nodes in quantum communication networks. Qubits based on trapped atomic ions have a rare combination of attributes. For example, qubits based on trapped atomic ions have exceptional coherence properties, can be prepared and measured with nearly 100% efficiency, and are easily entangled with each other by modulating the Coulomb interaction with a suitable external control field, such as an optical or microwave field. These attributes make atom-based qubits attractive for extended quantum operations, such as quantum computation or quantum simulation.

[0005] The precision with which the atom-based qubits are manipulated is important to avoid systematic errors during quantum operations. In a trapped ion quantum computer, the AOM is used to control a light beam that is deflected from it and then used to control the atom-based qubit. In a multi-channel AOM, where each channel may correspond to an individual light beam and its atom-based qubit, the application of radio frequency (RF) energy or RF signals in one channel may inadvertently affect one or more other channels. For example, turning on one channel may unintentionally turn on adjacent or nearby channels. In some instances, some of the RF energy and / or acoustic energy associated with one channel in a multi-channel AOM may "leak" into one or more neighboring channels. The "leak" may cause crosstalk noise or errors that may adversely affect the operation and / or control of the AOM. It is therefore important to minimize the impact of crosstalk noise on neighboring channels in a multi-channel AOM to avoid unintended impacts of such crosstalk noise on non-targeted atom-based qubits. Summary of the Invention [Means for solving the problem]

[0006] The following presents a simplified summary of one or more aspects in order to provide a basic understanding of such aspects. This summary is not an exhaustive overview of all contemplated aspects, and is not intended to identify key or critical elements of all aspects or to delineate the scope of any or all aspects. Its sole purpose is to present some concepts of one or more aspects in a simplified form as a prelude to the more detailed description that is presented later.

[0007] In one aspect of the disclosure, a method includes applying a first radio frequency (RF) tone to generate a first acoustic wave in a first channel of a multi-channel AOM, where the first acoustic wave interacts with a second channel of the multi-channel AOM causing a crosstalk effect on the second channel, and applying a second RF tone to generate a second acoustic wave in the second channel, where the second acoustic wave reduces or eliminates the crosstalk effect caused by a portion of the first acoustic wave.

[0008] In some embodiments of the present disclosure, an acousto-optic modulator (AOM) system includes an AOM crystal, a first transducer disposed above a first channel of the AOM crystal, a second transducer disposed above a second channel of the AOM crystal, a first waveform generator configured to apply a first radio frequency (RF) tone to generate a first acoustic wave in a first channel of the multi-channel AOM, where the first acoustic wave interacts with a second channel of the multi-channel AOM causing a crosstalk effect on the second channel, and a second waveform generator configured to apply a second RF tone to generate a second acoustic wave in the second channel, where the second acoustic wave reduces or eliminates crosstalk effects caused by a portion of the first acoustic wave.

[0009] In another aspect of the disclosure, a quantum information processing (QIP) system includes an AOM crystal, a first transducer disposed over a first channel of the AOM crystal, a second transducer disposed over a second channel of the AOM crystal, a first waveform generator configured to apply a first radio frequency (RF) tone to activate the first transducer to generate a first acoustic wave in the first channel, where a portion of the first acoustic wave interacts with the second channel to cause a crosstalk effect on the second channel, a second waveform generator configured to apply a second RF tone to activate the second transducer to generate a second acoustic wave in the second channel, where the second acoustic wave reduces or eliminates the crosstalk effect caused by the portion of the first acoustic wave, trapped ions, and a light source configured to shine light through the AOM crystal to change a state of the trapped ions.

[0010] In another aspect of the disclosure, a method of operating a multi-channel AOM includes calculating an initial RF tone to be applied to a plurality of channels of the AOM; calculating, in response to application of the initial RF tone, a compensating RF tone to be added to the initial RF tone to at least partially correct for undesirable crosstalk effects; and calculating, in response to application of the initial RF tone and the compensating RF tone, a subsequent compensating RF tone to be added to the initial RF tone until crosstalk effects in each of the plurality of channels are below a threshold.

[0011] To the accomplishment of the foregoing and related ends, the one or more aspects comprise the features hereinafter fully described and particularly pointed out in the claims. The following description and the annexed drawings set forth in detail certain illustrative features of the one or more aspects. These features are indicative, however, of but a few of the various ways in which the principles of the various aspects may be employed and the description is intended to include all such aspects and their equivalents.

[0012] The disclosed aspects are hereinafter described in conjunction with the accompanying drawings, which are provided to illustrate, but not to limit, the disclosed aspects, and in which like reference numerals refer to like elements. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 shows a diagram of a vacuum chamber housing electrodes for trapping atomic ions in a linear crystal, according to an embodiment of the present disclosure. [Diagram 2] FIG. 2 is a diagram illustrating an example of a Raman beam geometry according to an embodiment of the present disclosure. [Diagram 3] FIG. 3 is a diagram illustrating an example of a multi-channel acousto-optic modulator (AOM) with crosstalk compensation according to an embodiment of the present disclosure. [Figure 4] FIG. 4 is a diagram illustrating an example AOM system that uses cancellation tones to suppress crosstalk according to an embodiment of the disclosure. [Diagram 5] FIG. 5 illustrates an example AOM system for measuring channel crosstalk according to an embodiment of the disclosure. [Figure 6] FIG. 6 is a flow diagram illustrating suppressing crosstalk using cancellation or compensation tones in channels of an AOM according to an embodiment of the disclosure. [Figure 7] FIG. 7 is a flow diagram illustrating the use of cancellation tones in compensating for tones applied to an AOM to suppress crosstalk, according to an embodiment of the disclosure. [Figure 8] FIG. 8 is a block diagram illustrating an example of a quantum information processing (QIP) system according to an embodiment of the present disclosure. [Figure 9] FIG. 9 illustrates an example computing device according to an embodiment of the disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] The detailed description set forth below in conjunction with the accompanying drawings is intended as a description of various configurations and is not intended to represent the only configurations in which the concepts described herein may be implemented. The detailed description includes specific details for the purpose of providing a thorough understanding of the various concepts. However, it will be apparent to those skilled in the art that these concepts may be implemented without these specific details. In some instances, well-known components are shown in block diagram form to avoid obscuring such concepts.

[0015] As mentioned above, trapped atoms can be used to implement quantum information processing systems or quantum computers. Atom-based quantum bits can be used as different types of devices, including, but not limited to, quantum memories, quantum gates in quantum computers and simulators, and nodes for quantum communication networks. As used in this disclosure, the terms "atomic ion," "atom," and "ion" can be used interchangeably to describe particles that will be or are actually confined in a trap to form a crystal or similar arrangement or configuration.

[0016] Individual addressing of each ion trapped in the ion trap may be required to control phase, frequency, and / or amplitude, and also polarity, as required by the particular quantum gate or quantum operation implemented with the ions. One or more light beams may be used to individually address the trapped ions, and in some examples, a global light beam may be applied to all trapped ions. These counter-propagating optical beams, called Raman optical beams or simply Raman beams, may be generated using a multi-channel AOM, which is a crystal that has various piezoelectric transducers patterned with radio-frequency antennas, traces, or electrodes on one side and a radio-frequency absorber on the other side that deflects the light beam and shifts its frequency. The interaction with each light beam may be separately controlled by a radio-frequency (RF) waveform generator and a piezoelectric transducer in each channel of the multi-channel AOM.

[0017] Problems arise in multi-channel AOMs when application of RF energy or RF signals in one channel may inadvertently affect another channel. For example, turning on one channel may unintentionally turn on adjacent or nearby channels, e.g., unintentionally deflecting an optical beam in that channel. In some examples, some of the RF and / or acoustic energy associated with one channel in a multi-channel AOM may "leak" into one or more neighboring channels. The "leak" may cause crosstalk noise and / or errors that may adversely affect the operation and / or control of the atom-based quantum bits controlled by the multi-channel AOM (e.g., causing unintentional changes in the state of trapped ions). To reduce or eliminate crosstalk between individual channels, additional compensation tones may be applied to each channel of the AOM. The compensation tones may cancel / reduce the crosstalk signals that "leak" from neighboring channels. It will be appreciated that in some cases, the compensation tones themselves may generate crosstalk, and thus the process may need to be repeated until the overall effect of crosstalk is reduced in the various channels of the multi-channel AOM.

[0018] A solution to the above mentioned problem is explained in more detail with reference to FIGS.

[0019] FIG. 1 shows a diagram 100 illustrating a number of atomic ions 106 trapped in a linear crystal or chain 110 using a linear RF Paul trap (the linear crystal 110 can be in a vacuum chamber, not shown). In the example shown in FIG. 1, the vacuum chamber of the quantum system contains a number (e.g., N=20) of atomic Ytterbium ions (e.g., 171 Yb +The number of trapped atomic ions is configurable and more or fewer atomic ions may be trapped. The atoms are 171 Yb + The atomic ions are illuminated with laser (optical) radiation tuned to the resonance of the ion trap, and the fluorescence of the atomic ions is imaged on a camera. In this example, the atomic ions are separated from each other by a distance of about 5 microns (μm). The separation of the atomic ions is determined by the balance between the external confinement force and the Coulomb repulsion and does not have to be uniform. Furthermore, in addition to atomic Ytterbium ions, neutral atoms, Rydberg atoms, other atomic ions or species of atomic ions may also be used. Instead of a linear RF Paul trap, optical or other forms of confinement may be used. Thus, the confinement device may be based on different technologies and may hold ions, neutral atoms, or Rydbergs, etc., and the ion trap is one example of such a confinement device.

[0020] FIG. 2 shows a diagram 200 illustrating examples of Raman light beam shapes for use in an ion trap type system in which individual light beams 210 and a global optical beam 220 are directed to a chain 110 with atomic ion qubits to control the atomic ion qubits and perform quantum operations. Light beams in the same direction may be referred to as co-propagating optical beams, and light beams in different or opposite directions may be referred to as non-co-propagating or counter-propagating optical beams, respectively. The individual light beams 210 (co-propagating) are focused optical beams that address ions individually, whereas the global light beam 220 (counter-propagating with respect to the individual beams 210 as shown) may be an unfocused or focused optical beam that impinges on all ions. In some examples, additional individual light beams 210 may be used instead of the global light beam 220. As used herein, the terms laser beam, light beam, beam, optical field, and field may be used interchangeably. Each of the individual light beams 210 may be controlled, for example, by a different channel in a multi-channel AOM. The global light beam 220 may also be controlled by a respective channel in the AOM.

[0021] Referring to FIG. 3, an example of a system 300 including a multi-channel acousto-optic modulator (AOM) 310 configured to enable crosstalk compensation is shown. For simplicity, the light source and transmitted beams are not shown. The AOM 310 may include one or more channels. Each channel may include a waveform generator to modulate (e.g., change the characteristics) of the light beam deflected by the channel. For example, each channel may include a waveform generator that applies an RF signal (or "tone") to a transducer (e.g., a trace or electrode of the AOM crystal), which then applies acoustic waves to the channel (e.g., forming a corresponding acoustic column for the channel in the AOM crystal). The applied acoustic waves may modulate the light beam passing through the channel by vibrating a portion of the channel and changing the refractive index of the portion of the channel. In other words, the transducer may modulate the light beam deflected by the channel by changing the amplitude and / or frequency of the acoustic waves. This modulation may also change the characteristics of the light beam transmitted through the respective channel.

[0022] In one example, the AOM 310 may be a multi-channel Bragg cell having piezoelectric transducers 312a-d that locally apply acoustic waves to the AOM 310. The piezoelectric transducers 312a-d may be controlled by a controller 320 (which may be part of an optical controller 820 described below in connection with FIG. 8) having waveform generators 322a-d. The waveform generators 322a-d may be arbitrary waveform generators (AWGs) and / or direct digital synthesizers. The waveform generators 322a-d may apply RF signals (or "tones") of specific frequencies to generate the acoustic waves. Individual beams 210a-d may be provided to separately irradiate some of the trapped ions 110, as shown above in connection with FIG. 2. The AOM 310 may be a multi-channel AOM and include multiple channels 330.

[0023] 3, in certain implementations, the frequency, amplitude, and / or phase of each of the individual beams 210a-d may be modulated by the AOM 310. For example, the waveform generator 322a may cause the transducer 312a to generate a first acoustic wave (e.g., a first acoustic column) having a first predetermined quality in the first channel 330a. The first acoustic wave generated by the transducer 312a may cause the deflected individual light beam 210a to have a first frequency, a first phase, and / or a first amplitude. In another example, the waveform generator 322b may cause the transducer 312b to generate a second acoustic wave (e.g., a second acoustic column) having a second predetermined quality in the second channel 330b. The second acoustic wave generated by the transducer 312b may cause the deflected individual light beams 210b to have a second frequency, a second phase, and / or a second amplitude. In another example, the waveform generator 322c may cause the transducer 312c to generate a third acoustic wave (e.g., a third acoustic column) having a third predetermined quality in the third channel 330c. The third acoustic wave generated by the transducer 312c may cause the deflected individual light beams 210c to have a third frequency, a third phase, and / or a third amplitude. In yet another example, the waveform generator 322d may cause the transducer 312d to generate a fourth acoustic wave (e.g., a fourth acoustic column) having a fourth predetermined quality in the fourth channel 330d. The fourth acoustic wave generated by transducer 312d may cause each deflected light beam 210d to have a fourth frequency, a fourth phase, and / or a fourth amplitude. The multi-channel AOM 310 may include as few as two channels or as many as 32 or more channels, each of which may have a corresponding waveform generator and transducer as described above.

[0024] In some aspects of the disclosure, when a waveform generator, such as any of the waveform generators 322, applies an RF tone to generate an acoustic wave in a channel, a portion of the RF tone and / or acoustic wave may "leak" into one or more neighboring channels (e.g., adjacent or nearby channels). For example, when the waveform generator 322b applies a second RF tone to generate a second acoustic wave in the second channel 330b, a portion of the second RF tone and / or a portion of the second acoustic wave may undesirably interact with the first channel 330a, the third channel 330c, and / or the fourth channel 330d. The portion of the second RF tone and / or a portion of the second acoustic wave that leaks into other channels may, for example, interfere with at least one of the frequency, phase, and / or amplitude of at least one of the individual optical beams 210a, 210c, and 210d.

[0025] In an illustrative example, a portion of the second RF tone and / or a portion of the second acoustic wave may undesirably interact with the third channel 330c causing what may be referred to as crosstalk effects, crosstalk noise, or crosstalk errors in the third channel 330c. The portion of the second RF tone that couples or interacts with the third channel 330c may be referred to as RF crosstalk, and the portion of the second acoustic wave that couples or interacts with the third channel 330c may be referred to as acoustic crosstalk. RF crosstalk may result from electronic coupling between traces or electrodes in the second channel 330b and traces or electrodes in the third channel 330c. Acoustic crosstalk may result from spatial overlap of wings or spread of acoustic columns formed in the second channel 330b and the third channel 330c. Some of the crosstalk may be coherent crosstalk. Incoherent crosstalk may also occur, but it tends to occur by a different mechanism than that described herein. In some examples, the crosstalk may appear as a coherent drive signal (e.g., a sine wave) in a neighboring channel (e.g., the third channel 330c). A portion of the second RF tone and / or a portion of the second acoustic wave may cause unintended vibration of the crystal in the third channel 330c, which in turn may undesirably change one or more of the frequency, phase, and / or amplitude of the individual beams 210c. In one example, the second channel 330b may be turned on, and crosstalk may cause the third channel 330c to be unintentionally turned on, for example, to deflect light. The waveform generator 322c may provide a compensating RF tone that reduces, cancels, or eliminates the crosstalk effect caused by a portion of the second RF tone and / or a portion of the second acoustic wave.In one aspect of the disclosure, the waveform generator 322c may provide a compensating RF tone that destructively interferes with the crosstalk effects caused by the second RF tone and / or a compensating acoustic wave that generates a compensating acoustic wave that destructively interferes with the crosstalk effects caused by the second acoustic wave (described in more detail below).

[0026] Referring to FIG. 4, an example of an AOM 400 illustrates suppressing crosstalk using cancellation tones according to an embodiment of the present disclosure. FIG. 4 illustrates a cross-sectional view of the AOM 400, which is a multi-channel AOM and is an example of the AOM 310 in the system 300 of FIG. 3. The AOM 400 may include a first channel 430a, a second channel 430b, and a third channel 430c, and additional channels may be present, all formed in the AOM crystal 410. The AOM 400 may include a first waveform generator 422a configured to transmit a first RF tone to the first transducer 412a (e.g., to a trace or electrode of the first transducer 412a) to generate a first acoustic wave. The AOM 400 may include a second waveform generator 422b configured to transmit a second RF tone to the second transducer 412b to generate a second acoustic wave. The AOM 400 may include a third waveform generator 422c configured to transmit a third RF tone to a third transducer 412c to generate a third acoustic wave.

[0027] During operation, in some examples, the second waveform generator 422b may transmit or apply a second RF tone to excite an acoustic column associated with the second acoustic wave generated in the second channel 430b. The exemplary acoustic column 450a (dashed line) is a narrow column that is separated or decoupled from another acoustic column, such as the adjacent acoustic column 450b, that may be separately excited in association with the third channel 430c. The second RF tone may inadvertently cause crosstalk effects in the third channel 430c. For example, application of the second RF tone to the second transducer 412b may cause RF crosstalk 460 and / or acoustic crosstalk 462 that interacts with the third channel 430c. That is, application of the second RF tone to the traces or electrodes of the second transducer 412b may result in RF coupling or RF crosstalk 460 with the traces or electrodes of the third transducer 412c. In this case, a signal that is small but proportional to the second RF tone appears to be applied to the third transducer 412c even though it is not generated by the third waveform generator 422c. This combined signal may be strong enough to, for example, inadvertently turn on the third channel 430c and excite the acoustic column 450b, or to change the properties of the acoustic column 450b when the third channel 430c is turned on.

[0028] In another example, the acoustic column associated with the second sound wave generated in the second channel 430b is not limited to the narrow acoustic column 450a (dashed line), but instead may have components across the wide acoustic column 450c (dotted line) that overlaps (shades) with the area in which the acoustic column 450b is formed. This overlap causes the second channel 430b to introduce acoustic crosstalk 462 into the third channel 430c by at least partially turning on the third channel 430c when the third channel 430c is turned off, or by changing the properties of the acoustic column 450b when the third channel 430c is turned on. Note that the effect of the acoustic crosstalk 462 varies depending on where the acoustic crosstalk 462 occurs in the third channel 430c. In this example, the acoustic crosstalk 462 occurs primarily on the left side of the third channel 430c, resulting in little or no acoustic crosstalk effect being seen on the right side of the third channel 430c. It will be appreciated that the RF and acoustic crosstalk discussed above may occur individually or in combination. The overall crosstalk contribution from the second channel 430b to the third channel 430c may be illustrated by signal 470.

[0029] To reduce the overall crosstalk impact on the third channel 430c caused by the RF crosstalk 460 and / or acoustic crosstalk 462 (e.g., to reduce the overall crosstalk indicated by the signal 470), the third waveform generator 422c may transmit or apply a compensatory RF tone. The compensatory RF tone may generate a compensatory acoustic tone. In one implementation, the compensatory RF tone and the compensatory acoustic tone generated from the compensatory RF tone may destructively interfere with the crosstalk impact and may cancel, reduce, or eliminate the crosstalk impact on the third channel 430c. This destructive interference may be indicated by a signal 475 used to cancel the signal 470 indicating the crosstalk impact. The signal 475 has approximately the same amplitude and opposite phase (i.e., 180° / π radians out of phase) as the crosstalk impact signal 470. This compensatory RF tone may be applied alone to turn the third channel "off" or may be applied together with the drive signal required for the third channel.

[0030] It will be appreciated that the compensation technique described in connection with FIG. 4 illustrates a simple scenario in which two channels interact with each other. A compensating RF tone applied to reduce crosstalk effects on one channel may itself cause crosstalk effects on adjacent or nearby channels. In such a situation, multiple channels need to iterate by calculating or computing compensating RF tones, applying these compensating RF tones alone or together with required drive signals, evaluating the effects of the compensating RF tones on the multiple channels, and, if necessary, calculating or computing new compensating RF tones until an acceptable overall crosstalk reduction is achieved (e.g., a certain threshold is met).

[0031] Referring to FIG. 5, an example of a system 500 for measuring channel crosstalk is shown. The system 500 may include an AOM 502, a light source 570, and a detector 572. The AOM 502 may be a multi-channel AOM and may be an example of the multi-channel AOMs 310 and 400 described above. The system 500 may include a first channel 530a and a second channel 530b. The system 500 may include a first waveform generator 522a configured to transmit a first RF tone to a first transducer 512a to generate a first acoustic wave associated with a corresponding acoustic column. The system 500 may include a second waveform generator 522b configured to transmit a second RF tone to a second transducer 512b to generate a second acoustic wave associated with a corresponding acoustic column.

[0032] During operation to measure channel crosstalk, the light source 570 may irradiate a light beam 574. It will be appreciated that the light beam 574 may pass through various optical and / or optoelectronic devices before reaching the AOM 502. The detector 572 may detect the light beam 574, including optical properties of the light beam 574, such as the amplitude, phase, and / or frequency of the light beam 574. In some examples, during channel crosstalk measurement, the first waveform generator 522a may apply a first RF tone (e.g., at the maximum power of the first waveform generator 522a) to the first channel 530a at a frequency f and zero phase (or some other reference phase). The first RF tone may be represented by the formula Asin(2πft+Φ), where A is the amplitude of the first RF tone and Φ is the phase (e.g., zero phase) of the first RF tone. The first RF tone may induce a crosstalk effect in the second channel 530b, which is currently turned off. As described above, this crosstalk effect may be caused by one or both of RF crosstalk (e.g., electrical coupling) or acoustic crosstalk (e.g., overlapping acoustic columns). The crosstalk effect on the second channel 530b may cause the optical properties of the optical beam 574 to change, such as the amplitude, phase, and / or frequency of the optical beam 574. The detector 572 may detect the change in the optical beam 574 and the optical properties of the optical beam 574. The second waveform generator 522b may apply a compensating RF tone at a frequency f to the second channel 530b to generate a corresponding compensating acoustic wave in the second channel 530b. The second waveform generator 522b may iteratively adjust (manually or automatically via feedback) the amplitude and / or phase of the compensating RF tone until the change in the optical properties of the optical beam 574 is minimized or substantially minimized for the case of frequency f. The compensating RF tone may be calculated according to the formula A(a 1→2 )sin(2πft+Φ+θ 1→2 ), wherein a 1→2 is the compensation RF tone amplitude adjustment factor, and θ 1→2is the phase adjustment factor of the compensation RF tone. In some examples, the above process may be repeated for one or more frequencies of the optical beam 574. In other non-limiting examples, the above process may be repeated for one or more channels of the AOM 502 (e.g., the first channel 530a).

[0033] In a particular implementation, the compensation RF tone may have an amplitude that is less than the amplitude of the first RF tone (i.e., a 1→2 is less than 1).

[0034] In some examples of the present disclosure, the compensating RF tone may compensate for RF and / or acoustic crosstalk from two or more channels. The compensating RF tone may superimpose multiple amplitude and / or phase adjustment factors from multiple channels.

[0035] In a particular implementation, the compensation RF tone may be superimposed on the second RF tone applied by the second waveform generator 522b.

[0036] In some aspects of the disclosure, the compensating RF tone may be adjusted depending on the position of the optical beam 574 in the second channel 530b. For example, if the optical beam 574 is closer to the first channel 530a (i.e., in a location with higher RF and / or acoustic crosstalk noise), the compensating RF tone may have higher energy. If the optical beam 574 is further from the first channel 530a (i.e., in a location with lower RF and / or acoustic crosstalk noise), the compensating RF tone may have lower energy.

[0037] In one implementation, detector 572 may be a photodiode, a photodetection system, atoms, or ions trapped in chains such as chains 110 described above. For example, detector 572 may be a photodiode that captures a large area, a photodiode that detects a portion of the field through an aperture, or a photodiode that responds to low light levels, such as a PIN photodiode or an avalanche photodiode or a photodiode with low responsivity.

[0038] In other implementations, the system 500 may be integrated into a quantum computer to perform on-site measurements / calibrations to generate compensating RF tones for each channel of the AOM 502. The compensating RF tones may reduce crosstalk between quantum gates of the quantum computer.

[0039] In some examples of the present disclosure, the compensating RF tones may cancel other crosstalk signals, such as crosstalk signals from non-adjacent (eg, spatially) channels within the AOM.

[0040] In one implementation, the signal measured by detector 572 may be smoothed or averaged to reduce measurement noise.

[0041] In certain implementations, the compensating RF tones may cancel coherent crosstalk noise due to physical mechanisms other than electronic coupling, acoustic overlap, or a combination of both, which may include ambient noise, temperature fluctuations, etc.

[0042] In a particular implementation, crosstalk measurements may be performed on one AOM and those measurements may be used on another similar AOM.

[0043] Additionally, aspects of system 500 may be applicable to the scenarios described above where a compensating RF tone applied to reduce crosstalk impact on one channel may itself cause crosstalk impact on adjacent or nearby channels; such situations may involve multiple channels and the need to repeatedly calculate or compute the compensating RF tone on multiple channels until an acceptable overall crosstalk reduction is achieved (e.g., the crosstalk impact on each channel is below a particular level).

[0044] 6, a method or flow diagram 600 illustrating applying cancellation or compensation tones to channels of an AOM to suppress crosstalk according to an embodiment of the disclosure is described. Method 600 may be performed on a computer system, such as computer device 900, which may perform the functions of method 600 using a processor 910, memory 920, data store 940, and / or operating system 960, etc., described below. Similarly, the functions of method 600 may be performed by one or more components of a QIP system, such as QIP system 800 and its components (e.g., optical controller 820, crosstalk controller 840, and / or subcomponents thereof), described below.

[0045] At block 602, the method 600 may include calculating RF waves or tones (e.g., initial RF waves or tones A calculated relative to channel and time) for all channels of the multi-channel AOM. At block 604, compensation RF waves (e.g., compensation RF waves or tones B calculated relative to compensation channel, excitation channel, and time) are calculated for these initial RF waves using compensation corrections such as those determined by the techniques described above with respect to Figures 4 and 5. These compensation RF waves or tones are then added to the initial RF waves or tones of each channel. At 608, this calculation of compensation RF waves or tones may be performed one or more times (e.g., repeatedly) since the compensation RF waves or tones themselves may generate crosstalk. Finally, at block 606, the calculated RF waves or tones (e.g., the initial RF waves or tones combined with the optimized compensation RF waves or tones) that reduce the impact of RF crosstalk and / or acoustic crosstalk on all channels may be applied to the multi-channel AOM.

[0046] 7, method 700 of operating a multi-channel AOM to compensate for coherent crosstalk noise may be performed in a computer system, such as computing device 900, which may perform the functions of method 700 using a processor 910, memory 920, data store 940, and / or operating system 960, etc., as described below. Similarly, the functions of method 700 may be performed by one or more components of a QIP system, such as QIP system 800 and its components (e.g., optical controller 820, crosstalk controller 840, and / or subcomponents thereof).

[0047] It will be appreciated that method 600 of FIG. 6 generally describes a scenario in which there are multiple channels and the compensating RF tone itself may cause crosstalk effects, whereas method 700 described below relates to a different, but related, scenario. Nonetheless, the same techniques described herein may be applied in conjunction with method 600 and method 700.

[0048] At block 702, the method 700 may include applying a first radio frequency (RF) tone to generate a first acoustic wave in a first channel of a multi-channel AOM, where the first acoustic wave interacts with a second channel of the multi-channel AOM to cause crosstalk effects on the second channel. For example, the second waveform generator 422b may apply a second RF tone to generate a second acoustic wave in the second channel 430b. Due to the application of the second RF tone, RF crosstalk and / or acoustic crosstalk may affect the third channel 430c.

[0049] At block 704, the method 700 may include applying a second RF tone to generate a second acoustic wave in the second channel, the second acoustic wave reducing or eliminating crosstalk effects caused by a portion of the first acoustic wave. For example, the third waveform generator 422c may apply a compensating RF tone to generate a compensating acoustic tone to reduce the effects of RF crosstalk and / or acoustic crosstalk on the third channel 430c.

[0050] In one aspect of method 700, a first channel includes electrical traces to which a first RF tone is applied to excite acoustic columns associated with a first acoustic wave, and a second channel includes electrical traces to which a second RF tone is applied to excite acoustic columns associated with a second acoustic wave, a portion of the first RF tone interacts with the second channel by coupling to the electrical traces of the second channel, and a portion of the first acoustic wave interacts with the second channel by overlapping the acoustic columns associated with the first acoustic wave and the second acoustic wave.

[0051] In another aspect of method 700, a first RF tone is applied to turn on a first channel, and a second RF tone is applied to reduce or eliminate crosstalk effects such that turning on the first channel does not inadvertently turn on a second channel with the first RF tone.

[0052] 8 is a block diagram illustrating an example of a QIP system 800 in which the techniques described above for controlling coherent crosstalk errors in a multi-channel AOM using cancellation tones can be implemented, according to an embodiment of the present disclosure. The QIP system 800 may also be referred to as a quantum computing system, a computing device, an ion trap type system, etc.

[0053] QIP system 800 can include a source 860 that provides an atomic species (e.g., a plume or flux of neutral atoms) to a chamber 850 having an ion trap 870 that traps the atomic species once ionized (e.g., photoionized) by source 860. Ion trap 870 can be part of a processor or processing unit of QIP system 800.

[0054] The imaging system 830 can include a high resolution imager (e.g., a CCD camera) for monitoring the atomic ions while they are being provided to the ion trap or after they have been delivered to the ion trap 870. In one embodiment, the imaging system 830 can be implemented separately from the optical controller 820, although the use of fluorescence to detect, identify, and label the atomic ions using image processing algorithms may need to be coordinated with the optical controller 820. The AOMs described above, as well as the photodetectors and light beam sources, may be part of the optical controller 820.

[0055] QIP system 800 may also include an algorithm component 810 that may operate with other parts of QIP system 800 (not shown) to perform quantum algorithms or operations, including a large number or series of combinatorial single qubit and / or multi-qubit operations (e.g., two-qubit operations) and extended quantum computation. As such, algorithm component 810 may provide instructions to various components of QIP system 800 (e.g., optical controller 820) to enable implementation of quantum algorithms or operations.

[0056] The QIP system 800 may also include a crosstalk controller 840 configured to perform the techniques described above for controlling coherent crosstalk errors in a multi-channel AOM using cancellation tones. In one example, the crosstalk controller 840 may apply appropriate cancellation tones based on information collected by measurements performed by the crosstalk controller 840 or information collected separately and stored in the crosstalk controller 840.

[0057] Referring to FIG. 9, an example of a computing device 900 according to an embodiment of the present disclosure is shown. The computing device 900 can represent, for example, a single computing device, multiple computing devices, or a distributed computing system. The computing device 900 may be configured as a quantum computer (e.g., a QIP system), a classical computer, or a combination of quantum and classical computing capabilities. For example, the computing device 900 may be used to process information using a quantum algorithm based on trapped ion type technology, and thus may implement a method of controlling coherent crosstalk errors in a multi-channel AOM using cancellation tones. A general example of a computing device 900 as a QIP system capable of implementing various compensation schemes described herein is shown in the example shown in FIG. 6.

[0058] In one example, the computing device 900 may include a processor 910 for performing processing functions associated with one or more of the features described herein. The processor 910 may include a single or multiple sets of processors or multi-core processors. Additionally, the processor 910 may be implemented as an integrated and / or distributed processing system. The processor 910 may include a central processing unit (CPU), a quantum processing unit (QPU), a graphics processing unit (GPU), or a combination of those types of processors. In one aspect, the processor 910 may refer to a general processor of the computing device 900, which may also include additional processors 910 to perform more specific functions, such as functions for individual beam control.

[0059] In one example, the computing device 900 may include a memory 920 that stores instructions executable by the processor 910 to perform functions described herein. In one implementation, for example, the memory 920 may correspond to a computer-readable storage medium that stores code or instructions for performing one or more functions or operations described herein. In one example, the memory 920 may include instructions for performing aspects of the method 600 and the method 700 described above in connection with FIG. 6 and FIG. 7. As with the processor 910, the memory 920 may refer to the general memory of the computing device 900, which may include additional memory 920 to store instructions and / or data for more specific functions, such as instructions and / or data for individual beam control.

[0060] Additionally, computing device 900 may include a communications component 930 that utilizes hardware, software, and services as described herein to provide for establishing and maintaining communications with one or more parties. Communications component 930 may perform communications both among components on computing device 900 and between computing device 900 and external devices, such as devices disposed over a communications network and / or devices serially or locally connected to computing device 900. For example, communications component 930 may include one or more buses and may further include transmit chain and receive chain components associated with transmitters and receivers, respectively, operable to interface with external devices.

[0061] Additionally, computing device 900 may include a data store 940, which may be any suitable combination of hardware and / or software that provides mass storage of information, databases, and programs used in connection with the implementations described herein. For example, data store 940 may be a data repository for operating system 960 (e.g., a classical OS or a quantum OS). In one implementation, data store 940 may include memory 920.

[0062] The computing device 900 may also include a user interface component 950 operable to receive input from a user of the computing device 900 and further operable to generate output for presentation to the user or to provide (directly or indirectly) to a different system. The user interface component 950 may include one or more input devices, including but not limited to a keyboard, a number pad, a mouse, a touch-sensitive display, a digitizer, navigation keys, function keys, a microphone, a voice recognition component, any other mechanism capable of receiving input from a user, or any combination thereof. Additionally, the user interface component 950 may 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 output to a user, or any combination thereof.

[0063] In one implementation, the user interface component 950 may send and / or receive messages corresponding to operations of the operating system 960. The processor 910 may also execute, and the memory 920 or the data store 940 may store, the operating system 960 and / or applications or programs.

[0064] When the computing device 900 is implemented as part of a cloud-based infrastructure solution, the user interface component 950 may be used to enable a user of the cloud-based infrastructure solution to remotely interact with the computing device 900. The foregoing description of the disclosure is provided to enable any person skilled in the art to make or use the disclosure. Various modifications to the disclosure will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other variations without departing from the spirit or scope of the disclosure. Furthermore, although elements of the described aspects may be described or claimed in the singular, the plural is contemplated unless limitation to the singular is expressly stated. Furthermore, unless otherwise stated, all or a portion of any aspect may be utilized with all or a portion of any other aspect. Thus, the disclosure should not be limited to the examples and designs described herein, but should be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. 1. A method of operating a multi-channel acousto-optic modulator (AOM), comprising the steps of: applying a first radio frequency (RF) tone to generate a first acoustic wave in at least a first channel of the multi-channel AOM, a portion of the first acoustic wave interacting with a second channel of the multi-channel AOM to cause undesirable crosstalk effects to the second channel; measuring a crosstalk effect of the portion of the first acoustic wave in the second channel; adjusting an amplitude of a second RF tone to be less than and proportional to an amplitude of the first RF tone based on the measurement of the crosstalk effect, and adjusting a phase of the second RF tone to be anti-phase of the crosstalk from the first RF tone; and applying the second RF tone to generate a second acoustic wave in the second channel, the second acoustic wave reducing or eliminating crosstalk effects caused by the portion of the first acoustic wave in the second channel.

2. the first channel includes an electrode to which the first RF tone is applied to excite an acoustic column associated with the first acoustic wave; the second channel includes an electrode to which the second RF tone is applied to excite an acoustic column associated with the second acoustic wave; the portion of the first RF tone interacts with the second channel by coupling the portion of the first RF tone to an electrode of the second channel; 2. The method of claim 1, wherein the portion of the first acoustic wave interacts with the second channel by overlapping an acoustic column associated with the first acoustic wave with an acoustic column associated with the second acoustic wave.

3. turning on the first channel by applying the first RF tone; 2. The method of claim 1, wherein the crosstalk effect is reduced or eliminated by applying the second RF tone such that turning on the first channel does not unintentionally turn on the second channel due to the first RF tone.

4. 2. The method of claim 1, further comprising the step of: prior to applying the second RF tone, adjusting an amplitude of the second acoustic wave to be less than and proportional to an amplitude of the first acoustic wave based on the measurement of the crosstalk effect, and adjusting a phase of the second acoustic wave to be anti-phase of crosstalk from the first acoustic wave.

5. 2. The method of claim 1 , wherein measuring the crosstalk effect further comprises measuring the crosstalk effect using a photodiode, a photodetection system, atoms, or trapped ions aligned to detect a light beam deflected from the second channel.

6. The step of measuring the crosstalk effect comprises: transmitting an optical beam through the second channel prior to applying the first RF tone to the first channel; measuring a change in one or more optical properties of the light beam due to application of the first RF tone; The method of claim 1 , further comprising: adjusting the second RF tone to minimize a change in one or more optical properties of the light beam.

7. The method of claim 6 , wherein the one or more optical properties include at least one of a phase, a frequency, or an amplitude of the light beam.

8. applying a third RF tone to generate a third acoustic wave in a third channel of the multi-channel AOM, a portion of the third acoustic wave interacting with the second channel to cause additional crosstalk effects to the second channel; 10. The method of claim 1, further comprising: applying a fourth RF tone to generate a fourth acoustic wave in the second channel, the fourth acoustic wave reducing or eliminating crosstalk effects caused by the portion of the third acoustic wave.

9. the third channel includes an electrode to which the third RF tone is applied to excite an acoustic column associated with the third acoustic wave; the second channel includes an electrode to which the second RF tone is applied to excite an acoustic column associated with the second acoustic wave; the portion of the third RF tone interacts with the second channel by coupling the portion of the third RF tone to an electrode of the second channel; 9. The method of claim 8, wherein the portion of the third acoustic wave interacts with the second channel by overlapping an acoustic column associated with the third acoustic wave with an acoustic column associated with the second acoustic wave.

10. 2. The method of claim 1, further comprising, in addition to applying the second RF tone to reduce or eliminate crosstalk effects to the second channel, applying an additional RF tone to the second channel to generate an additional acoustic wave in the second channel, the additional acoustic wave being superimposed on the second acoustic wave to control deflection of an optical beam from the second channel.

11. The method of claim 1 , wherein the first channel is immediately adjacent to the second channel in the multi-channel AOM.

12. The method of claim 1 , wherein the first channel is not directly adjacent to the second channel in the multi-channel AOM.

13. 1. A multi-channel acousto-optic modulator (AOM) system, comprising: An AOM crystal; a first transducer disposed above the AOM crystal and associated with a first channel of the multi-channel AOM system; a second transducer disposed above the AOM crystal and associated with a second channel of the multi-channel AOM system; a first waveform generator configured to apply a first radio frequency (RF) tone to activate the first transducer to generate a first acoustic wave in at least the first channel, a portion of the first acoustic wave interacting with the second channel to cause a crosstalk effect on the second channel; a photodetector configured to measure crosstalk effects of the portion of the first acoustic wave; a second waveform generator, adjusting the second RF tone based on the measurement of the crosstalk effect such that an amplitude of the second RF tone is less than and proportional to an amplitude of the first RF tone and a phase of the second RF tone is in anti-phase with the first RF tone; a second waveform generator configured to apply the second RF tone to activate the second transducer to generate a second acoustic wave in the second channel, the second acoustic wave reducing or eliminating crosstalk effects caused by the portion of the first acoustic wave in the second channel.

14. the first transducer includes an electrode to which the first RF tone is applied to excite an acoustic column associated with the first acoustic wave; the second transducer includes an electrode to which the second RF tone is applied to excite an acoustic column associated with the second acoustic wave; the portion of the first RF tone interacts with the second channel by coupling the portion of the first RF tone to an electrode of the second transducer; 14. The multi-channel AOM system of claim 13, wherein the portion of the first acoustic wave interacts with the second channel by overlapping an acoustic column associated with the first acoustic wave with an acoustic column associated with the second acoustic wave.

15. 14. The multi-channel AOM system of claim 13, further comprising a photodetector configured to measure crosstalk effects of the portion of the first acoustic wave from a deflected light beam from the second channel to the photodetector.

16. 16. The multi-channel AOM system of claim 15, wherein the second waveform generator is further configured to, prior to applying the second RF tone, adjust the second RF tone based on the measurement such that an amplitude of the second acoustic wave is less than and proportional to an amplitude of the first acoustic wave and a phase of the second acoustic wave is in anti-phase with the first acoustic wave.

17. a light source configured to illuminate a light beam passing through the second channel; the optical detector is configured to measure a change in one or more optical properties of the optical beam due to application of the first RF tone; 16. The multi-channel AOM system of claim 15, wherein the second waveform generator is configured to tune the second RF tone to minimize changes in one or more optical properties of the light beam.

18. 20. The multi-channel AOM system of claim 17, wherein the one or more optical properties include at least one of a phase, a frequency, or an amplitude of the light beam.

19. 14. The multi-channel AOM system of claim 13, further comprising an ion trap having at least one trapped ion configured to measure crosstalk effects due to at least one of a portion of the first RF tone or a portion of the first acoustic wave from a deflected light beam from the second channel to the at least one trapped ion.

20. a third transducer disposed above the AOM crystal and associated with a third channel of the multi-channel AOM system; a third waveform generator configured to apply a third RF tone to activate the third transducer to generate a third acoustic wave in the third channel, where at least one of a portion of the third RF tone or a portion of the third acoustic wave interacts with the second channel to cause an additional crosstalk effect on the second channel; 14. The multi-channel AOM system of claim 13, further comprising: a fourth waveform generator configured to apply a fourth RF tone to generate a fourth acoustic wave in the second channel, the fourth acoustic wave reducing or eliminating crosstalk effects caused by the portion of the third acoustic wave.

21. the third channel includes an electrode to which the third RF tone is applied to excite an acoustic column associated with the third acoustic wave; the second channel includes an electrode to which the second RF tone is applied to excite an acoustic column associated with the second acoustic wave; the portion of the third RF tone interacts with the second channel by coupling the portion of the third RF tone to an electrode of the second channel; 21. The multi-channel AOM system of claim 20, wherein the portion of the third acoustic wave interacts with the second channel by overlapping an acoustic column associated with the third acoustic wave with an acoustic column associated with the second acoustic wave.

22. a third transducer disposed above the AOM crystal and associated with a third channel of the multi-channel AOM system; 14. The multi-channel AOM system of claim 13, further comprising: a third waveform generator configured to apply a third RF tone to activate the third transducer to generate an additional acoustic wave in the second channel, the additional acoustic wave being superimposed on the second acoustic wave to control a deflection of an optical beam from the second channel.

23. 14. The multi-channel AOM system of claim 13, wherein the first channel is immediately adjacent to the second channel in the multi-channel AOM.

24. 14. The multi-channel AOM system of claim 13, wherein the first channel is not directly adjacent to the second channel in the multi-channel AOM.

25. a multi-channel acousto-optic modulator (AOM) having an AOM crystal; a first transducer disposed above the AOM crystal and associated with a first channel of the multi-channel AOM; a second transducer disposed above the AOM crystal and associated with a second channel of the multi-channel AOM; a first waveform generator configured to apply a first radio frequency (RF) tone to activate the first transducer to generate a first acoustic wave in at least the first channel, a portion of the first acoustic wave interacting with the second channel to cause a crosstalk effect on the second channel; a photodetector configured to measure crosstalk effects of the portion of the first acoustic wave; a second waveform generator, adjusting the second RF tone based on the measurement of the crosstalk effect such that an amplitude of the second RF tone is less than and proportional to an amplitude of the first RF tone and a phase of the second RF tone is in anti-phase with the first RF tone; a second waveform generator configured to apply the second RF tone to activate the second transducer to generate a second acoustic wave in the second channel, the second acoustic wave reducing or eliminating crosstalk effects caused by the portion of the first acoustic wave in the second channel; a containment device having at least one trapped ion, at least one neutral atom, or at least one Rydberg atom; a light source configured to illuminate one or more light beams that pass through respective channels of the AOM crystal to change the state of each of the at least one trapped ion, the at least one neutral atom, or the at least one Rydberg atom to perform a quantum operation.

26. the first transducer includes an electrode to which the first RF tone is applied to excite an acoustic column associated with the first acoustic wave; the second transducer includes an electrode to which the second RF tone is applied to excite an acoustic column associated with the second acoustic wave; the portion of the first RF tone interacts with the second channel by coupling the portion of the first RF tone to an electrode of the second channel; 26. The QIP system of claim 25, wherein the portion of the first acoustic wave interacts with the second channel by overlapping an acoustic column associated with the first acoustic wave with an acoustic column associated with the second acoustic wave.

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