Radio frequency signal processing device for cryogenic ion trap

Abstract

The embodiment of the present invention provides a radio frequency signal processing device for a low-temperature ion trap, which can be applied to the field of quantum computing technology. The radio frequency signal processing device includes: a noise suppression circuit and a resonance unit in the low-temperature ion trap, wherein the noise suppression circuit is configured to perform waveform transformation processing on the initial radio frequency signal generated by the signal source to obtain a square wave signal corresponding to the initial radio frequency signal; the noise suppression circuit is also configured to perform noise suppression processing on the square wave signal and output a noise suppression signal; the resonance unit is configured to perform passive amplification processing on the noise suppression signal, and utilize low temperature to greatly improve the quality factor of the resonance unit, and output a target radio frequency signal with extremely low amplitude noise to the low-temperature ion trap. The device is also configured to utilize a capacitive voltage divider unit to separate a low-power radio frequency signal from the low-temperature ion trap, perform rectification, low-noise differential amplification, and phase inversion before mixing with the signal source, thereby suppressing the slow drift of the radio frequency signal amplitude.

Description

Technical Field

[0001] The present invention relates to the field of quantum computing technology, and more specifically, to a radio frequency signal processing device for a low-temperature ion trap. Background Art

[0002] As an important development direction of ion trap quantum information processing technology, the low-temperature ion trap system can significantly improve the ion lifetime in the ion trap and reduce the heating rate of the ions, thereby improving the performance and stability of the ion trap system. It is the development direction of ion trap quantum information processing technology.

[0003] The existing technology mainly generates the high-voltage radio frequency signal required by the ion trap through a resonant cavity. The efficient amplification of the resonant cavity depends on precise impedance matching, which is usually achieved by mechanically adjusting the distance between the coils. However, in a cryogenic system, this mechanical adjustment becomes extremely difficult due to changes in the physical properties of the material and the freezing of the mechanical components. In addition, the voltage gain of the resonant cavity is limited, and an RF amplifier needs to be introduced to meet the demand. However, the use of an RF amplifier will introduce a large amount of RF amplitude noise, and complex precision temperature control is also required. Summary of the invention

[0004] In view of this, the present invention provides a radio frequency signal processing device for a low-temperature ion trap.

[0005] One aspect of the present invention provides a radio frequency signal processing device for a low-temperature ion trap, the radio frequency signal processing device comprising: a noise suppression circuit and a resonance unit, wherein the input end of the noise suppression circuit is connected to a signal source, and the noise suppression circuit is configured to perform waveform transformation processing on an initial radio frequency signal generated by the signal source to obtain a square wave signal corresponding to the initial radio frequency signal; the noise suppression circuit is also configured to perform noise suppression processing on the square wave signal to output a noise suppression signal; the input end of the resonance unit is connected to the output end of the noise suppression circuit, and the resonance unit is configured to perform passive amplification processing on the noise suppression signal to output a target radio frequency signal to the low-temperature ion trap.

[0006] According to an embodiment of the present invention, the noise suppression circuit includes a signal processing unit and a filtering unit; wherein the signal processing unit is configured to convert the initial RF signal into the square wave signal; and the filtering unit performs filtering processing on the high-order harmonic components included in the frequency spectrum of the square wave signal to obtain the noise suppression signal.

[0007] According to an embodiment of the present invention, the noise suppression circuit further includes a first power supply unit; wherein the first power supply unit is connected to the signal processing unit, and the first power supply unit is configured to supply power to the signal processing unit through a plurality of linear regulators and a voltage reference.

[0008] According to an embodiment of the present invention, the above-mentioned radio frequency signal processing device also includes an impedance matching circuit, wherein the input end of the above-mentioned impedance matching circuit is connected to the output end of the above-mentioned noise suppression circuit, and the output end of the above-mentioned impedance matching circuit is connected to the input end of the above-mentioned resonance unit; the above-mentioned impedance matching circuit includes multiple groups of variable capacitance diodes, and the above-mentioned impedance matching circuit is configured to adjust the capacitance values ​​of the above-mentioned multiple groups of variable capacitance diodes so that the impedance value of the impedance matching circuit is matched with the output impedance of the above-mentioned signal source and the input impedance of the above-mentioned resonance unit respectively.

[0009] According to an embodiment of the present invention, the impedance matching circuit further includes a second power supply unit and an isolation unit, and the second power supply unit is configured to supply power to the plurality of groups of varactor diodes via the isolation unit.

[0010] According to an embodiment of the present invention, the RF signal processing device further includes a mixer and a feedback control circuit; wherein the input end of the mixer is respectively connected to the output end of the feedback control circuit and the output end of the noise suppression circuit, the output end of the mixer is connected to the input end of the resonance unit, and the input end of the feedback control circuit is connected to the output end of the resonance unit; the feedback control circuit is configured to sequentially perform voltage division processing, rectification processing and noise amplification processing on the target RF signal to obtain a feedback RF signal, reversely process the DC signal phase of the feedback RF signal to obtain a feedback signal, and send the feedback signal to the mixer; the mixer is configured to perform mixing processing on the feedback signal and the noise suppression signal to obtain a mixed signal, wherein the mixed signal is passively amplified by the resonance unit and then output to the low-temperature ion trap.

[0011] According to an embodiment of the present invention, the resonance unit is configured as a resonance cavity, and the impedance matching circuit and the resonance cavity are arranged in an ion trap cavity.

[0012] According to an embodiment of the present invention, the resonant cavity comprises a coil, a ceramic fixture and a cold plate, wherein the coil is connected to the ceramic fixture by a winding process, and the ceramic fixture is connected to the cold plate by a thermal anchoring process.

[0013] According to an embodiment of the present invention, the above-mentioned resonant cavity includes a high-temperature superconducting material, a substrate, a ceramic fixing and a cold plate, wherein the above-mentioned high-temperature superconducting material is etched on the above-mentioned substrate by an induced ion beam etching process to obtain a resonant cavity chip, the above-mentioned resonant cavity chip is fixedly connected to the ceramic fixing, and the above-mentioned ceramic fixing is connected to the above-mentioned cold plate by a thermal anchoring process.

[0014] According to an embodiment of the present invention, the ion trap cavity is configured such that the bottom of the cavity is connected to the impedance matching circuit and the resonant cavity through an insulating material.

[0015] According to the RF signal processing device of the cryogenic ion trap provided by the embodiment of the present invention, the input sine wave signal is converted into a square wave signal of the corresponding frequency by using a noise suppression circuit, and then the high-order harmonics are passively filtered out, thereby further effectively suppressing the integral amplitude noise in the initial RF signal, improving the purity and signal-to-noise ratio of the signal. At the same time, since the passive filtering does not require an additional power supply, no additional active noise is introduced. In addition, the resonance unit is used instead of the RF amplifier for passive amplification processing, which increases the voltage amplitude of the input signal and outputs the target RF signal that meets the driving requirements of the cryogenic ion trap, thereby getting rid of the influence of the temperature drift and thermal noise of the RF amplifier on the system performance, which helps to improve the accuracy and stability of the RF signal processing device. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The above and other objects, features and advantages of the present invention will become more apparent through the following description of the embodiments of the present invention with reference to the accompanying drawings, in which:

[0017] Figure 1 A schematic structural diagram of a radio frequency signal processing device for a low-temperature ion trap according to an embodiment of the present invention is shown.

[0018] Figure 2 A schematic structural diagram of a radio frequency signal processing device for a low-temperature ion trap according to another embodiment of the present invention is shown.

[0019] Figure 3 A schematic structural diagram of an impedance matching circuit according to a specific embodiment of the present invention is shown.

[0020] Figure 4 A schematic structural diagram of a radio frequency signal processing device for a low-temperature ion trap according to yet another embodiment of the present invention is shown. DETAILED DESCRIPTION

[0021] Below, embodiments of the present invention will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the present invention. In the following detailed description, for ease of explanation, many specific details are set forth to provide a comprehensive understanding of embodiments of the present invention. However, it is apparent that one or more embodiments may also be implemented without these specific details. In addition, in the following description, descriptions of known structures and technologies are omitted to avoid unnecessary confusion of concepts of the present invention.

[0022] The terms used herein are only for describing specific embodiments and are not intended to limit the present invention. The terms "comprise", "include", etc. used herein indicate the existence of the features, steps, operations and / or components, but do not exclude the existence or addition of one or more other features, steps, operations or components.

[0023] All terms (including technical and scientific terms) used herein have the meanings commonly understood by those skilled in the art unless otherwise defined. It should be noted that the terms used herein should be interpreted as having a meaning consistent with the context of this specification and should not be interpreted in an idealized or overly rigid manner.

[0024] When using expressions such as "at least one of A, B, and C, etc.", they should generally be interpreted according to the meaning of the expression commonly understood by those skilled in the art (for example, "a system having at least one of A, B, and C" should include but is not limited to a system having A alone, B alone, C alone, A and B, A and C, B and C, and / or A, B, C, etc.).

[0025] As a cutting-edge technology in the field of quantum information processing, the core of the ion trap quantum computing system is to use radio frequency electric fields to trap ions to achieve the manipulation of quantum bits. In this process, the amplitude stability of the radio frequency signal plays a decisive role in the manipulation accuracy of the ion quantum bits.

[0026] As an important development direction of ion trap quantum information processing technology, low-temperature ion trap systems can significantly increase the lifetime of ions in ion traps and reduce the heating rate of ions, thereby improving the performance and stability of ion trap systems. In large-scale, long-ion-chain ion trap quantum computing systems, low-temperature ion trap systems are essential technologies.

[0027] However, there are many challenges in generating high-voltage and high-stability RF signals in a cryogenic environment. First, the total efficiency of the RF signal in a cryogenic environment needs to be strictly controlled below the cooling capacity to avoid adversely affecting the performance of the cryostat. Secondly, the problem of adjusting the impedance matching of the resonant cavity in the cryostat is also a major problem. As the physical properties of the material change at low temperatures, the impedance characteristics of the resonant cavity also change. Therefore, it is necessary to accurately adjust the impedance matching of the resonant cavity in a cryogenic environment to ensure the effective transmission and amplification of the RF signal. In addition, suppressing the amplitude noise of the RF signal is also an important challenge in a cryogenic ion trap system. Because the performance and stability of electronic devices are affected in a low-temperature environment, and the interference of the external environment to the system is enhanced, the amplitude noise of the RF signal is difficult to completely eliminate.

[0028] In addition, it takes longer to decouple the ion chain motion mode, and the noise of the motion mode will contribute more to the logic gate error rate. If >99.9% dual-ion logic gate fidelity is to be achieved in long ion chain experiments, suppressing the ion motion mode noise, that is, increasing the ion motion coherence time, is the biggest bottleneck.

[0029] The existing technology mainly generates the high-voltage radio frequency signal required by the ion trap through a resonant cavity. The resonant cavity can be regarded as a bandpass filter to filter out the radio frequency noise outside 1 MHz near the resonant frequency, so that the low-frequency and high-frequency noise of the ion trap frequency are suppressed at the same time. However, the efficient amplification of the resonant cavity depends on precise impedance matching, which is usually achieved by mechanically adjusting the distance between the coils. However, in a cryogenic system, this mechanical adjustment becomes extremely difficult due to changes in the physical properties of the material (such as thermal expansion and contraction) and the freezing of mechanical parts. In addition, the existing methods mainly rely on large-volume antennas to achieve impedance matching with the previous circuit, and the position needs to be manually controlled for fine adjustment. The impedance-matched radio frequency will drift over a long time scale, affecting the transition frequency of the quantum logic gate. At the same time, the voltage gain of the resonant cavity is limited, and an RF amplifier needs to be introduced to meet the demand. However, the use of an RF amplifier will introduce a large amount of RF amplitude noise, and because the power gain is very sensitive to the temperature of the device, complex precision temperature control is also required to stabilize the amplifier temperature at 10 mK.

[0030] Based on the above problems, an embodiment of the present invention provides a radio frequency signal processing device for a cryogenic ion trap, which converts the input sinusoidal wave signal into a square wave signal of the corresponding frequency by using a noise suppression circuit, and then passively filters out high-order harmonics, thereby further effectively suppressing the integrated amplitude noise in the initial radio frequency signal, and improving the purity and signal-to-noise ratio of the signal. Since passive filtering does not require an additional power supply, no additional active noise is introduced. In addition, a resonance unit is used instead of an radio frequency amplifier for passive amplification processing, which increases the voltage amplitude of the input signal, so that the target radio frequency signal output by the radio frequency signal processing device has a sufficiently high passive gain, thereby making the input power of the cryogenic system less than the refrigeration power, while getting rid of the influence of the temperature drift and thermal noise of the radio frequency amplifier on the performance of the cryogenic system, and improving the accuracy and stability of the radio frequency signal processing device.

[0031] Specifically, an embodiment of the present invention provides a radio frequency signal processing device for a low-temperature ion trap, and the radio frequency signal processing device includes: a noise suppression circuit and a resonance unit, wherein the input end of the noise suppression circuit is connected to a signal source, and the noise suppression circuit is configured to perform waveform transformation processing on an initial radio frequency signal generated by the signal source to obtain a square wave signal corresponding to the initial radio frequency signal; the noise suppression circuit is also configured to perform noise suppression processing on the square wave signal and output a noise suppression signal; the input end of the resonance unit is connected to the output end of the noise suppression circuit, and the resonance unit is configured to perform passive amplification processing on the noise suppression signal and output a target radio frequency signal to the low-temperature ion trap.

[0032] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings.

[0033] Figure 1 A schematic structural diagram of a radio frequency signal processing device for a low-temperature ion trap according to an embodiment of the present invention is shown.

[0034] like Figure 1 As shown, the radio frequency signal processing device of the low temperature ion trap includes a noise suppression circuit 2 and a resonance unit 3. Among them, the input end of the noise suppression circuit 2 is connected to the signal source 1 to receive the initial radio frequency signal generated by the signal source 1, the input end of the resonance unit 3 is connected to the output end of the noise suppression circuit 2 to receive the noise suppression signal output by the noise suppression circuit 2, and the output end of the resonance unit 3 is connected to the low temperature ion trap 4 to output the target radio frequency signal to the low temperature ion trap 4.

[0035] According to an embodiment of the present invention, since the initial RF signal generated by the signal source 1 is a sinusoidal waveform signal, the noise suppression circuit 2 can use the signal processing unit to perform signal conversion processing on the initial RF signal, and convert the sinusoidal waveform signal into a square wave signal corresponding to the frequency of the initial RF signal. The signal processing unit can implement signal conversion processing based on the threshold voltage characteristics of the CMOS transistor. For example, when the input signal exceeds or falls below the threshold voltage, the CMOS transistor switches between the on and off states, thereby generating a square wave output.

[0036] According to an embodiment of the present invention, the noise suppression circuit 2 can also use a filtering unit to perform passive noise suppression processing on the converted square wave signal to filter the integrated amplitude noise generated by the signal source in the frequency range near DC, thereby outputting a noise suppression signal. Specifically, the filtering unit can filter out the high-order harmonic components generated during the waveform conversion process based on a bandpass filter, retain the fundamental frequency components, and convert the retained fundamental frequency components into a sine wave signal as a noise suppression signal and output it to the resonance unit 3.

[0037] According to an embodiment of the present invention, the resonance unit 3 can be used to perform passive amplification processing on the received noise suppression signal, thereby increasing the voltage amplitude of the signal while avoiding the introduction of additional noise and power consumption. After the input noise suppression signal is passively amplified, the resonance unit 3 outputs the processed target RF signal to the cryogenic ion trap 4 to meet the driving requirements of the cryogenic ion trap 4. The resonance frequency of the resonance unit 3 is configured to match the RF signal frequency required by the cryogenic ion trap 4 to ensure that the target signal can be effectively amplified and noise of other frequencies can be suppressed.

[0038] Based on this, the embodiment of the present invention converts the input sine wave signal into a square wave signal of the corresponding frequency by using CMOS transistors, and passively filters out high-order harmonics through a bandpass filter, thereby further effectively suppressing the integrated amplitude noise in the initial RF signal, improving the purity and signal-to-noise ratio of the signal, and at the same time, since passive filtering does not require an additional power supply, it has lower power consumption and higher energy efficiency. In addition, since the resonance unit has a higher quality factor and better performance in a low-temperature environment, the resonance unit can replace the RF amplifier, and use its passive amplification processing function to increase the voltage amplitude of the input signal, so that the target RF signal output by the RF signal processing device has a sufficiently high passive gain, and the quality factor of the resonance unit is greatly improved by using low temperature, and the target RF signal with extremely low amplitude noise is output to the low-temperature ion trap, thereby making the input power of the low-temperature system less than the refrigeration power, while getting rid of the influence of the temperature drift and thermal noise of the RF amplifier on the performance of the low-temperature system, the accuracy and stability of the RF signal processing device are improved.

[0039] According to an embodiment of the present invention, the noise suppression circuit further includes a first power supply unit, which can be connected to the signal processing unit and supply power to the signal processing unit to ensure that the square wave signal output by the signal processing unit does not introduce additional amplitude noise.

[0040] Specifically, the first power supply unit may include at least a voltage reference and a plurality of linear regulators. Among them, in the noise suppression circuit, the power supply quality of the signal processing unit such as the CMOS transistor will directly affect the noise level of the output signal. Therefore, it is necessary to ensure that the voltage provided by the first power supply unit is stable and low-noise. Based on this, the voltage reference and the plurality of linear regulators included in the first power supply unit can adopt devices with ultra-low noise characteristics. For example, the ultra-low noise voltage reference can provide a stable and low-noise voltage reference for the power supply unit to reduce the noise introduced by noise fluctuations. The ultra-low noise linear regulator can ensure a high power supply ripple rejection ratio (PSRR) over a wide frequency range to filter out noise from the voltage source.

[0041] According to an embodiment of the present invention, in order to further improve the stability and noise suppression capability of the power supply system, two ultra-low noise linear regulators can be used in series. The first ultra-low noise linear regulator can be used for preliminary voltage stabilization and filtering, and the second ultra-low noise linear regulator can be used to further reduce noise and provide the final required output voltage to the signal processing unit. Specifically, the input end of the first ultra-low noise linear regulator can be connected to the output end of the ultra-low noise voltage reference, and the output voltage of the first ultra-low noise linear regulator is set to meet the input voltage requirement of the second ultra-low noise linear regulator.

[0042] Based on this, an embodiment of the present invention adds a first power supply unit consisting of a voltage reference with ultra-low noise characteristics and multiple linear regulators to the noise suppression circuit to power the signal processing unit, so as to ensure that the signal processing unit obtains a stable and low-noise power supply voltage, thereby improving the passive amplitude noise suppression capability of the noise suppression circuit. At the same time, it does not depend on the signal quality of the signal source. Even if the signal source has certain fluctuations or noise, the signal processing unit can offset the noise influence of the signal source through the stability of the output voltage and the noise suppression capability of the power supply unit, thereby improving the stability of the noise suppression circuit.

[0043] Figure 2 A schematic structural diagram of a radio frequency signal processing device for a low-temperature ion trap according to another embodiment of the present invention is shown.

[0044] like Figure 2 As shown, the radio frequency signal processing device of the low temperature ion trap further includes an impedance matching circuit 5, and the input end of the impedance matching circuit 5 is connected to the output end of the noise suppression circuit 2. By adjusting the impedance value of the impedance matching circuit 5, it is matched with the output impedance of the signal source 1 and the input impedance of the resonance unit 3 respectively, thereby ensuring that the radio frequency signal will not be reflected or attenuated during the transmission process, thereby improving the efficiency and stability of signal transmission.

[0045] Figure 3 A schematic structural diagram of an impedance matching circuit according to a specific embodiment of the present invention is shown.

[0046] like Figure 3 As shown, the impedance matching circuit 5 includes multiple groups of varactor diodes 51, an isolation unit 52 and a second power supply module 53. The multiple groups of varactor diodes 51 can achieve impedance matching by adjusting their capacitance values. The impedance matching circuit 5 also includes a second power supply unit 53 and an isolation unit 52. The second power supply unit 53 supplies power to the multiple groups of varactor diodes 51 through the isolation unit 52 to ensure their normal operation.

[0047] Specifically, Figure 3 As shown, in a specific embodiment of the present invention, the impedance matching circuit 5 can use four groups of back-to-back varactor diodes, which are connected in parallel to the front stage of the resonant unit 3. When different control voltages are applied, the capacitance value of the varactor diodes will change, thereby allowing the impedance matching circuit to adapt to different impedance conditions. For example, by applying a reverse voltage of 0-20V to the four groups of back-to-back varactor diodes, their capacitance values ​​can be dynamically adjusted to achieve impedance matching.

[0048] Among them, since the capacitance value of a single varactor diode is inversely proportional to the control voltage, when at least two varactor diodes are connected in reverse series in a back-to-back manner, the total capacitance value of the varactor diode can be linearly proportional to the control voltage. This linear control relationship is more conducive to realizing active feedback of impedance matching, thereby providing more stable impedance matching performance.

[0049] In a specific embodiment of the present invention, the isolation unit is connected in series to the front stage of multiple groups of varactor diodes to prevent the second power supply unit from interfering with the radio frequency signal and ensure that the varactor diodes are supplied with stable and clean power. Figure 3 As shown, the isolation unit 52 is composed of three identical resistor and inductor series circuits connected in parallel. The resistors and inductors can be used to form a low-pass filter to filter out high-frequency noise and interference signals and only allow low-frequency DC or control signals to pass, thereby improving the isolation effect and power supply stability.

[0050] like Figure 3 As shown, the second power supply unit 53 is used to provide a stable power supply for the four groups of back-to-back varactor diodes to ensure the normal operation of the varactor diodes. Since the capacitance value of the varactor diode is controlled by voltage, the stability and accuracy of the second power supply unit 53 are crucial to the effect of impedance matching. Wherein, C1 is a filter capacitor.

[0051] Based on this, the embodiment of the present invention adds an impedance matching circuit between the noise suppression circuit and the resonance unit to ensure that the radio frequency signal is not reflected or attenuated during the transmission process, thereby improving the efficiency and stability of signal transmission.

[0052] Figure 4 A schematic structural diagram of a radio frequency signal processing device for a low-temperature ion trap according to yet another embodiment of the present invention is shown.

[0053] like Figure 4 As shown, the RF signal processing device also includes a feedback control circuit and a mixer 6. The input end of the mixer 6 is connected to the output end of the feedback control circuit and the output end of the noise suppression circuit 2 respectively to receive the output signal and the noise suppression signal from the feedback control circuit. The output end of the mixer 6 is connected to the input end of the resonance unit 3 to mix the feedback signal and the noise suppression signal and output the mixed signal to the resonance unit.

[0054] Among them, the input end of the feedback control circuit is connected to the output end of the resonance unit 3 to perform voltage division processing, rectification processing and noise amplification processing on a part of the target RF signal in sequence to obtain a feedback RF signal, and reversely process the DC signal phase of the feedback RF signal to obtain a feedback signal and send the feedback signal to the mixer 6.

[0055] Specifically, Figure 4 As shown, the feedback control circuit includes a capacitor voltage divider unit 7, a rectifier unit 8, a differential amplifier unit 9 and a control unit 10, wherein the capacitor voltage divider unit 7 can be used to separate part of the low-power radio frequency signal from the target radio frequency signal output by the resonance unit 3 for feedback, the rectifier unit 8 can be used to convert the amplitude of part of the low-power radio frequency signal into a DC signal voltage value, and the differential amplifier unit 9 can be used to perform low-noise differential amplification on the DC signal to obtain a feedback radio frequency signal. The control unit 10 can be used to generate a reverse signal with a phase opposite to that of the feedback radio frequency signal, and input the reverse signal into the mixer 6 to mix with the noise suppression signal, thereby suppressing the slow drift of the radio frequency signal amplitude. After the mixing process, a radio frequency signal with less noise can be obtained, and the radio frequency signal is passively amplified by the resonance unit 3 and then output to the low-temperature ion trap 4 to drive the low-temperature ion trap 4.

[0056] According to an embodiment of the present invention, the resonance unit may be configured as a resonance cavity, so as to utilize the low temperature effect to improve the quality factor of the resonance cavity and reduce the attenuation of the radio frequency signal.

[0057] Specifically, in a specific embodiment of the present invention, the resonant cavity may include a coil, a ceramic fixture, a cold plate, and a shell, etc. The coil may be wound and connected with the ceramic fixture through a winding process, and the ceramic fixture after the coil is wound may be fixed on the 4K cold plate through a thermal anchoring process and placed in the shell to prepare a low-temperature ion trap system resonant cavity, thereby ensuring the stability of the resonant cavity in a low-temperature environment.

[0058] Among them, the coil can be a high-purity copper coil, which can be configured as a vacuum enameled wire, and the vacuum enameled wire can be made of polyimide film (Kapton) material to ensure that the circuit in the cavity will not short-circuit and has an ultra-high vacuum degree (for example, the vacuum degree is maintained at less than 1×10^-8 mbar), thereby ensuring high insulation and low gas outflow rate, and being able to maintain stable coil performance in a low temperature environment. When winding the coil, the number of turns, diameter and shape of the coil can be controlled to ensure that the performance of the resonant cavity meets the requirements of the resonant unit. In addition, the coil can be fixed to the ceramic fixture by vacuum thermal conductive glue, and the ceramic fixture can be thermally anchored to the pure copper 4K cold plate with pure copper screws or silver-plated copper screws to further improve the thermal conductivity and ensure that the low-temperature cold is effectively transferred to the coil to cool the entire RF line after impedance matching, thereby greatly reducing the resistance of the line and greatly improving the quality factor of the resonant circuit, thereby greatly improving the passive voltage gain.

[0059] In this specific embodiment, one end of the copper coil can be connected to the impedance matching circuit board, and the other end can be connected to the intracavity relay circuit by hot plugging.

[0060] In another specific embodiment of the present invention, the resonant cavity may include a high-temperature superconducting material, a substrate, a ceramic fixing, a cold plate, and a shell. Among them, the high-temperature superconducting material may be etched on the substrate by a thin film preparation technology such as inductive ion beam etching to form a high-temperature superconducting coil on the substrate as a resonant cavity chip. The substrate etched with the coil may be fixed on a 4K cold plate by a thermal anchoring process and placed in a shell to prepare a high-temperature superconducting resonant cavity.

[0061] Among them, the high-temperature superconducting material can be yttrium barium copper oxide (YBCO), which can exhibit extremely low resistivity at low temperatures, and can even reach a zero resistance state. Therefore, in a low-temperature environment of 4K, the resistance of yttrium barium copper oxide is almost zero, resulting in a greatly improved quality factor of the resonant cavity to reduce the loss of energy during the transmission of the resonant cavity. In addition, the substrate can be made of sapphire or ceramic material. Among them, the thickness of the yttrium barium copper oxide coil etched on the sapphire substrate can be configured to be 300 nanometers (nm) to ensure that the coil has sufficient current carrying capacity and stability in the superconducting state. In order to improve the conductivity and corrosion resistance of the coil, a layer of gold about 200 nanometers thick can be plated on the surface of the coil, which not only provides good conductivity, but also protects the coil from damage by low-temperature environmental factors.

[0062] In this specific embodiment, the prepared high temperature superconducting coil can be connected to an external circuit through a wire bonding process.

[0063] According to an embodiment of the present invention, since the quality factor can reflect the ratio of energy stored in the resonant cavity to energy lost. The higher the quality factor, the stronger the energy storage capacity of the resonant cavity and the smaller the loss. Since the resistance is inversely proportional to the quality factor, the reduction in resistance can directly lead to an increase in the quality factor. Therefore, in a low temperature environment of 4K, the resistance of the copper coil and the high-temperature superconducting material will be significantly reduced, so that the quality factor of the resonant cavity is significantly improved. In addition, the ceramic fixture with the coil is fixed on the 4K cold plate through a thermal anchoring process to ensure good thermal contact between the ceramic fixture and the cold plate, so that the resistance of the subsequent circuit of the resonant cavity will jump down, and the quality factor will be improved, ensuring the stability and reliability of the resonant cavity in a low temperature environment, and helping to reduce the impact of thermal noise and temperature drift on system performance.

[0064] According to a specific embodiment of the present invention, based on the preparation method of the resonant cavity, the resonant cavity is tested, and the test results show that in a low temperature environment of 4K, the quality factor of the resonant cavity can reach 421, which is 2.7 times the quality factor of 160 at room temperature. At the same time, the resonant frequency is 68 MHz and the well load is 8 pF. In this case, when the initial RF signal output by the signal source is greater than 16 dBm, the peak value of the RF signal applied to the ion can be amplified to 100 V by using only the resonant cavity without using an RF amplifier, thereby getting rid of the temperature drift and thermal noise problems of the RF amplifier to improve the stability and accuracy of the system.

[0065] According to an embodiment of the present invention, both the impedance matching circuit and the resonant cavity can be arranged in the vacuum ion trap cavity to shield the electromagnetic radiation interference in the space. In addition, according to the relationship between thermal noise and temperature, the thermal noise limit of the circuit will decrease in a square root relationship with the Kelvin temperature. Therefore, the low temperature environment can be used to reduce the thermal noise limit of the above circuit. In a low temperature environment of 4K, the background noise of multiple circuits in the cavity will be reduced, thereby improving the overall performance of the system.

[0066] According to an embodiment of the present invention, since the radio frequency system is prone to coupling electromagnetic noise from the environment, part of it comes from electromagnetic radiation, and the other part comes from the ground loop. The noise of the ground loop mainly includes 50 Hz harmonic noise introduced by the mains. Since this harmonic noise is difficult to filter with a filter, the bottom of the ion trap cavity can be configured to be connected to the impedance matching circuit and the resonant cavity included in the cavity through insulating materials such as ceramics, so that the vacuum ion trap cavity is floated to improve the impact of the ground loop noise and reduce the background noise level of the device.

[0067] According to an embodiment of the present invention, the bottom of the vacuum ion trap cavity can also be configured to be fixedly connected to the external optical platform through stainless steel material, and the ground wire of the vacuum ion trap cavity is connected to the inside of the cavity through insulating material, thereby achieving isolation between the intra-cavity circuit and the external optical platform.

[0068] According to an embodiment of the present invention, before the initial RF signal is input into the vacuum ion trap cavity, a capacitor may be connected in series between the signal line and the ground line to form a high-pass filter, allowing high-frequency RF signals to pass through and effectively isolating low-frequency noise (<100 kHz) in the ground loop to prevent such noise from interfering with the RF signal.

[0069] According to an embodiment of the present invention, the impedance matching circuit can be configured to use a low outgassing rate material as a substrate to ensure the ultra-high vacuum degree inside the vacuum ion trap cavity. In addition, the substrate can also use a material with a low loss tangent to reduce the loss of the radio frequency signal; the substrate is not provided with a solder mask layer, which is also to ensure the ultra-high vacuum degree inside the vacuum ion trap cavity; in addition, one side of the circuit can be configured to be covered with ground copper to provide a good electromagnetic shielding layer, reduce the impact of the external electromagnetic field on the circuit, further optimize the electromagnetic shielding effect, and reduce unnecessary capacitance effects and signal interference. In addition, copper on one side can also minimize the capacitance between the radio frequency signal line and the ground. Specifically, since the formation of this capacitance is related to the distance and area between the two conductors. In the radio frequency circuit, the capacitance formed between the signal line and the ground will affect the transmission quality of the signal and the stability of the circuit. Therefore, by copper on one side, the area between the signal line and the ground can be reduced, thereby reducing the size of this capacitance. When the capacitance is small, the energy loss of the circuit at the resonant frequency will be reduced. Therefore, the quality factor is improved by this method, thereby improving the performance and stability of the circuit. At the same time, by increasing the thickness of the circuit board (for example, greater than 1.5 mm) to change the distance between the capacitor plates, the performance of the circuit is improved by reducing parasitic capacitance and inductance.

[0070] According to an embodiment of the present invention, the impedance matching circuit can also be configured to gold-plate the surface of the pad, which can reduce the resistance at the circuit connection and improve the conductivity while reducing the surface roughness, thereby reducing the thermal stress during the welding process and improving the connectivity and reliability of the circuit.

[0071] Reduce signal loss. The copper wire thickness is configured to 2Oz (ounces), which makes the circuit have higher current carrying capacity and lower resistance, which helps to reduce heat loss and improve signal transmission efficiency. In addition, two screw adjustment capacitors (160 pF dynamic range) and four groups of back-to-back voltage-controlled capacitor diodes (40 pF dynamic range) can be used in the impedance matching circuit to achieve precise adjustment of impedance by adjusting the capacitance value without replacing components. It should be noted that in an embodiment of the present invention, the number of voltage-controlled capacitor diodes can also be set to multiple groups to further improve the dynamic adjustment range of the impedance matching circuit.

[0072] According to a specific embodiment of the present invention, a reverse voltage of 0~20V is applied to the above four groups of back-to-back voltage-controlled capacitor diodes (40 pF dynamic range). After testing, the dynamic range of the impedance matching circuit is 40pF, which means that the impedance matching circuit can be adjusted within a larger capacitance value range to meet different impedance matching requirements. In addition, it is calculated that the electrical noise of the reverse voltage will not introduce significant amplitude noise into the ion RF signal. Taking the commonly used DAC chip AD3551R as an example, when the reverse voltage is 5V and the bandwidth is 100kHz, the amplitude noise corresponding to the ion RF is only 0.2ppm. This shows that the active impedance matching circuit can maintain a low electrical noise level while adjusting the impedance, and will not have a significant impact on the quality of the RF signal.

[0073] According to an embodiment of the present invention, the noise suppression circuit can be configured as an external part of the ion trap cavity and connected to the internal circuit of the ion trap cavity through a signal line. The noise suppression circuit is tested using an analog RF signal generator and a DC power supply. The test results show that the noise suppression circuit can reduce the amplitude noise of the signal source from a higher 43 ppm to a lower 9 ppm in the DC~100 kHz frequency band.

[0074] Based on this, the embodiment of the present invention uses a noise suppression circuit to convert the input sinusoidal wave signal into a square wave signal of the corresponding frequency, and then passively filters out high-order harmonics, thereby further effectively suppressing the integral amplitude noise in the initial RF signal, improving the purity and signal-to-noise ratio of the signal. At the same time, since passive filtering does not require an additional power supply, it has lower power consumption and higher energy efficiency. In addition, a resonance unit is used instead of an RF amplifier for passive amplification processing, which increases the voltage amplitude of the input signal and outputs a target RF signal that meets the low-temperature ion trap drive requirements, thereby getting rid of the influence of the temperature drift and thermal noise of the RF amplifier on the system performance, which helps to improve the accuracy and stability of the RF signal processing device. In a specific embodiment of the present invention, the coherence time of the ion motion can be increased to more than 100 ms, and the integral amplitude noise of the signal source in the DC~100 kHz frequency band can be ensured to be less than 10 ppm.

[0075] So far, the embodiments of the present invention have been described in detail in conjunction with the accompanying drawings. It should be noted that the implementation methods not shown or described in the drawings or the body of the specification are all forms known to ordinary technicians in the relevant technical field and are not described in detail. In addition, the above definitions of each element and method are not limited to the various specific structures, shapes or methods mentioned in the embodiments, and ordinary technicians in the field can simply change or replace them.

[0076] Throughout the drawings, the same elements are represented by the same or similar reference numerals. Conventional structures or configurations will be omitted when they may cause confusion in understanding the present invention.

[0077] Moreover, the shapes and sizes of the components in the figures do not reflect the real size and proportion, but only illustrate the contents of the embodiments of the present invention. In addition, in the claims, any reference symbols between brackets shall not be construed as limiting the claims.

[0078] Unless otherwise indicated, the numerical parameters in this specification and the appended claims are approximate values ​​and can vary according to the desired properties obtained through the content of the present invention. In particular, all numbers used in the specification and claims to express the content of the composition, reaction conditions, etc., should be understood to be modified by the term "about" in all cases. Furthermore, the word "comprising" does not exclude the presence of elements or steps not listed in the claims. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements.

[0079] The ordinal numbers used in the specification and claims, such as "first", "second", "third", etc., to modify the corresponding elements, do not themselves mean that the elements have any ordinal numbers, nor do they represent the order of one element and another element, or the order in the manufacturing method. The use of these ordinal numbers is only used to clearly distinguish a component with a certain name from another component with the same name.

[0080] It will be appreciated by those skilled in the art that the features described in the various embodiments of the present invention may be combined and / or combined in various ways, even if such combinations or combinations are not explicitly described in the present invention. In particular, without departing from the spirit and teachings of the present invention, the features described in the various embodiments of the present invention may be combined and / or combined in various ways. All of these combinations and / or combinations fall within the scope of the present invention.

[0081] The embodiments of the present invention are described above. However, these embodiments are only for the purpose of illustration, and are not intended to limit the scope of the present invention. Although each embodiment is described above, it does not mean that the measures in each embodiment cannot be used in combination advantageously. Without departing from the scope of the present invention, those skilled in the art may make various substitutions and modifications, which should all fall within the scope of the present invention.

Claims

1. A radio frequency signal processing device for a low temperature ion trap, characterized in that: The radio frequency signal processing device comprises: a noise suppression circuit and a resonance unit, The input end of the noise suppression circuit is connected to a signal source, and the noise suppression circuit is configured to perform waveform transformation processing on an initial radio frequency signal generated by the signal source to obtain a square wave signal corresponding to the initial radio frequency signal; The noise suppression circuit is further configured to perform noise suppression processing on the square wave signal and output a noise suppression signal; The input end of the resonance unit is connected to the output end of the noise suppression circuit, and the resonance unit is configured to perform passive amplification processing on the noise suppression signal and output a target radio frequency signal to the low-temperature ion trap.

2. The radio frequency signal processing device according to claim 1, characterized in that: The noise suppression circuit includes a signal processing unit and a filtering unit; The signal processing unit is configured to convert the initial radio frequency signal into the square wave signal; the filtering unit performs filtering processing on the high-order harmonic components included in the frequency spectrum of the square wave signal to obtain the noise suppression signal.

3. The radio frequency signal processing device according to claim 2, characterized in that: The noise suppression circuit also includes a first power supply unit; The first power supply unit is connected to the signal processing unit, and is configured to supply power to the signal processing unit through a plurality of linear regulators and a voltage reference.

4. The radio frequency signal processing device according to claim 1, characterized in that: The radio frequency signal processing device further includes an impedance matching circuit. Wherein, the input end of the impedance matching circuit is connected to the output end of the noise suppression circuit, and the output end of the impedance matching circuit is connected to the input end of the resonance unit; The impedance matching circuit includes a plurality of groups of varactor diodes, and the impedance matching circuit is configured to adjust the capacitance values ​​of the plurality of groups of varactor diodes so that the impedance value of the impedance matching circuit matches the output impedance of the signal source and the input impedance of the resonance unit respectively.

5. The radio frequency signal processing device according to claim 4, characterized in that: The impedance matching circuit further includes a second power supply unit and an isolation unit, wherein the second power supply unit is configured to supply power to the plurality of groups of varactor diodes via the isolation unit.

6. The radio frequency signal processing device according to claim 1, characterized in that: The radio frequency signal processing device also includes a mixer and a feedback control circuit; The input end of the mixer is connected to the output end of the feedback control circuit and the output end of the noise suppression circuit respectively, the output end of the mixer is connected to the input end of the resonance unit, and the input end of the feedback control circuit is connected to the output end of the resonance unit; The feedback control circuit is configured to sequentially perform voltage division processing, rectification processing and noise amplification processing on the target RF signal to obtain a feedback RF signal, perform reverse processing on the DC signal phase of the feedback RF signal to obtain a feedback signal, and send the feedback signal to the mixer; The mixer is configured to perform mixing processing on the feedback signal and the noise suppression signal to obtain a mixed signal, wherein the mixed signal is passively amplified by the resonance unit and then output to the low-temperature ion trap.

7. The radio frequency signal processing device according to claim 4, characterized in that: The resonance unit is configured as a resonance cavity, and the impedance matching circuit and the resonance cavity are arranged in an ion trap cavity.

8. The radio frequency signal processing device according to claim 7, characterized in that: The resonant cavity comprises a coil, a ceramic fixture and a cold plate, wherein the coil is connected to the ceramic fixture by a winding process, and the ceramic fixture is connected to the cold plate by a thermal anchoring process.

9. The radio frequency signal processing device according to claim 7, characterized in that: The resonant cavity comprises a high-temperature superconducting material, a substrate, a ceramic fixing and a cold plate, wherein the high-temperature superconducting material is etched on the substrate by an induction ion beam etching process to obtain a resonant cavity chip, the resonant cavity chip is fixedly connected to the ceramic fixing, and the ceramic fixing is connected to the cold plate by a thermal anchoring process.

10. The radio frequency signal processing device according to claim 7, characterized in that: The ion trap cavity is configured such that the bottom of the cavity is connected to the impedance matching circuit and the resonant cavity through an insulating material.

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