Timing control system for quantum energy level transition

Abstract

The present invention discloses a timing control system for quantum energy level transitions, belonging to the technical field of quantum computing. It includes a radio frequency signal source module for generating tunable radio frequency signals, a radio frequency microwave coaxial switch module that switches channel switches through TTL signals, a radio frequency power amplification module for amplifying radio frequency signals and driving an acousto-optic modulator, and a timing control optical path including a multi-stage acousto-optic modulator that can be independently controlled. The technical solution provided by the present invention uses a modular-designed timing control system to control the multi-stage acousto-optic modulator through radio frequency channel switching by TTL signals, which can not only independently control the frequency, light output rate, and light intensity of each laser beam, but also perform rapid switching at the nanosecond level, enhancing the controllability of ion trapping ions in an ion trap.

Description

Technical Field

[0001] The present invention belongs to the technical field of quantum computing, and particularly relates to a timing control system for quantum energy level transitions. Background Art

[0002] The key to quantum computing is to build a quantum computer, and an ion trap is a core component of the architecture of a quantum computer. An ion trap quantum computer encodes the internal energy levels of ions as qubits, and uses laser beams to manipulate specific energy levels of ions in the ion trap, thereby realizing quantum operations such as quantum entanglement gates. Before performing quantum operations on trapped ions, Doppler cooling of the trapped ions is usually performed using lasers. However, due to the collision and recoil effects during the photon radiation process, Doppler cooling has a theoretical limit and cannot cool the trapped ions to the motional ground state. Therefore, it is necessary to use electromagnetically induced transparency (EIT) cooling technology to continue to cool the trapped ions more deeply. Generally, EIT cooling has high requirements for the accuracy and stability of the laser frequency. Therefore, in order to cool the trapped ions to the motional ground state, the laser needs to be switched quickly and stably in frequency.

[0003] In the prior art, Chinese invention patent CN116757289B discloses a time-division multiplexing control method. This method uses an optical modulation module to modulate a seed laser to generate a laser with the required sidebands, and after converting the seed laser into a laser in the target wavelength band through a frequency conversion module, uses a laser separation module to separate lasers with different frequencies, and finally the operation module controls the timing and spatial distribution of the lasers. However, the above solution has low regulation accuracy for radio frequency signals, slow signal switching response, and cannot meet the requirements of high-precision multi-channel fast switching. Summary of the Invention

[0004] Based on this, the timing control system provided by the technical solution of the present invention utilizes the 0th-order diffracted light through a double-pass optical path, and combines multiple acousto-optic modulators, a radio frequency microwave coaxial switch module, and a radio frequency signal source module to achieve efficient radio frequency signal regulation, precise laser modulation, and fast timing control.

[0005] To achieve the above object, the present invention provides a timing control system for quantum level transitions. The timing control system includes: a radio frequency signal source module for generating a radio frequency signal with adjustable frequency; a radio frequency microwave coaxial switch module connected to the radio frequency signal source module, and the channel switching is performed through an external TTL signal; a radio frequency power amplification module connected to an acousto-optic modulator for amplifying the radio frequency signal to drive the acousto-optic modulator; a timing control optical path including a laser and the acousto-optic modulator, and the laser output by the laser is tuned and controlled through the acousto-optic modulator to generate multiple target lasers suitable for the quantum transition. Among them, the multiple target lasers include Doppler-assisted cooling light, Doppler cooling light, EIT cooling drive light, and EIT cooling probe light; the acousto-optic modulator includes a first acousto-optic modulator, and the first acousto-optic modulator adopts a double-pass optical path; the 0th-order diffracted light of the first acousto-optic modulator is output to a first coupler to form the Doppler-assisted cooling light.

[0006] Further, the acousto-optic modulator further includes a second acousto-optic modulator, the +1st-order diffracted light of the first acousto-optic modulator is output to the second acousto-optic modulator, and the -1st-order diffracted light of the second acousto-optic modulator is output to a second coupler to form the Doppler cooling light.

[0007] Furthermore, the acousto-optic modulator further includes a third acousto-optic modulator and a fourth acousto-optic modulator; the 0th-order diffracted light of the second acousto-optic modulator is output to the third acousto-optic modulator; the +1st-order diffracted light of the third acousto-optic modulator is output to a third coupler to form the EIT cooling drive light; the 0th-order diffracted light of the third acousto-optic modulator is output to the fourth acousto-optic modulator; the +1st-order diffracted light of the fourth acousto-optic modulator is output to a fourth coupler to form the EIT cooling probe light.

[0008] Preferably, the radio frequency microwave coaxial switch module includes a plurality of switch units, and each switch unit includes a TTL signal channel, a first input channel, a second input channel, and a signal output channel; the TTL signal channel is used to connect the external TTL signal, and the switch unit switches the connection state of the signal output channel according to the high and low levels of the external TTL signal; among them, the connection state of the signal output channel includes a first connection state and a second connection state; the first connection state is that the signal output channel is connected to the first input channel; the second connection state is that the signal output channel is connected to the second input channel.

[0009] Specifically, the first input channel is connected to the radio frequency signal source for inputting the radio frequency signal, and the second input channel is vacant; or the first input channel is vacant, and the second input channel is connected to the radio frequency signal source for inputting the radio frequency signal.

[0010] Preferably, each of the switch units further includes a hexagonal switch and an indicator light. The hexagonal switch is used to switch the working mode of the switch unit, and the working modes include a first direct connection mode, a second direct connection mode, and a TTL signal control mode. The first direct connection mode corresponds to the first connection state of the signal output channel. The second direct connection mode corresponds to the second connection state of the signal output channel. In the TTL signal control mode, the connection state of the signal output channel is controlled by the external TTL signal.

[0011] Furthermore, the timing control optical path further includes a wavemeter for measuring the frequency of the laser, and a frequency stabilization optical path. The frequency stabilization optical path adopts an F-P optical cavity for stabilizing the frequency of the laser.

[0012] Specifically, the RF signal source module includes a plurality of channel units. Each channel unit includes a direct digital frequency synthesizer for synthesizing and outputting the RF signal. The frequency and intensity of the RF signal are adjustable, and the frequency range of the RF signal is set between 0 - 400 MHz.

[0013] The beneficial effects achieved by the present invention through the above technical solutions are as follows:

[0014] 1) The first acousto-optic modulator uses a double-pass optical path to use the +1 order diffracted light as the Doppler cooling light, and recycles the 0 order diffracted light discarded in the traditional technology as the Doppler assisted cooling light. The two laser beams act together on the trapped ions in the ion trap, which not only improves the utilization efficiency of the cooling laser, but also Doppler cools the trapped ions from different directions, making the cooling more uniform and the frequency range of the trapped ions being cooled wider.

[0015] 2) By controlling the multi-stage acousto-optic modulator through a modular laser timing control system, not only can the frequency, light output rate, and light intensity of each laser beam be independently and precisely controlled, but also a nanosecond-level fast switching can be performed according to the requirements of ion trap quantum operations, enhancing the controllability of the trapped ions in the ion trap.

[0016] 3) The RF microwave coaxial switch module combines a hexagonal switch and an indicator light, realizing flexible multi-mode switching of the switch unit, improving the real-time response ability of the system, simplifying the system debugging and maintenance process, enabling users to intuitively observe the switch state, and improving the usability and ease of use of the device.

[0017] 4) The RF signal source module adopts a plurality of direct digital frequency synthesizers, improving the regulation accuracy of the RF signal, ensuring the stable operation of the acousto-optic modulator, and providing high-quality laser timing regulation for the quantum transition process. Description of the Drawings

[0018] Figure 1 It is a schematic diagram of the circuit module structure of the timing control system according to an embodiment of the present invention.

[0019] Figure 2 It is a schematic diagram of the channel structure of the coaxial switch module and the power amplification module according to an embodiment of the present invention.

[0020] Figure 3 It is a schematic diagram of the overall optical path structure of the timing control system according to an embodiment of the present invention.

[0021] Figure 4 It is a schematic diagram of the timing control optical path structure according to an embodiment of the present invention.

[0022] Figure 5 It is the energy level schematic diagram of 40Ca + ions according to an embodiment of the present invention.

[0023] Figure 6 It is a schematic diagram of multi-laser timing control according to an embodiment of the present invention.

[0024] In the figure, each label represents: 1. Laser; 2. Timing control optical path; 3. Wavemeter; 4. Frequency stabilization optical path; 5. RF microwave coaxial switch module; 6. RF power amplification module; 101. First half-wave plate; 102. First polarization beam splitter; 103. Second half-wave plate; 104. Second polarization beam splitter; 105. First reflector; 201. Second reflector; 202. Third half-wave plate; 203. Third polarization beam splitter; 204. First aperture; 205. First acousto-optic modulator; 206. Second aperture; 207. Fourth half-wave plate; 208. First convex lens; 209. First D-shaped mirror; 210. Third reflector; 211. Fourth reflector; 212. Second acousto-optic modulator; 213. Third aperture; 214. Fifth reflector; 215. Second D-shaped mirror; 216. Third acousto-optic modulator; 217. Fourth aperture; 218. Third D-shaped mirror; 219. Third coupler; 220. Fourth acousto-optic modulator; 221. Fifth aperture; 222. Fourth D-shaped mirror; 223. Fourth coupler; 224. Beam collector; 225. Second coupler; 226. Fifth D-shaped mirror; 227. First coupler. Detailed implementation manners

[0025] In order to make the objectives, technical solutions, and advantages of the present invention clearer and more understandable, the following further describes in detail the specific implementation manners of the present invention in conjunction with embodiments. It should be understood that the embodiments described herein are only used to explain the present invention, but not to limit the scope of the present invention.

[0026] Please refer to the attached Figure 1 , Figure 1It is a schematic diagram of the circuit module structure of the timing control system according to an embodiment of the present invention. As can be seen from the figure, the timing control system includes a radio frequency signal source module, a radio frequency microwave coaxial switch module 5, a radio frequency power amplification module 6, and a timing control optical path 2 including a multi-stage acousto-optic modulator. Among them, the radio frequency signal source module is used to generate a radio frequency signal with adjustable frequency and output it to the radio frequency microwave coaxial switch module 5 connected to the radio frequency signal source module. The switch module has a number of input channels and performs multi-channel switch switching through an external TTL signal to output the selected radio frequency signal to the radio frequency power amplification module 6. In particular, in the embodiment of the present invention, the radio frequency power amplification module 6 is connected to an acousto-optic modulator (AOM) and is used to amplify the radio frequency signal to drive the acousto-optic modulator. The acousto-optic modulator of the timing control optical path 2 tunes and controls the intensity, switch, and frequency of the laser output by the laser 1 to generate multiple target lasers suitable for the quantum transition. In the embodiment of the present invention, the multiple target lasers include Doppler-assisted cooling light, Doppler cooling light, EIT cooling drive light, and EIT cooling probe light. In one or other embodiments of the present invention, the multi-target lasers further include state detection lasers or state initialization lasers. In the embodiment of the present invention, the acousto-optic modulator includes a first acousto-optic modulator 205 using a double-pass optical path. After the incident laser passes through the first acousto-optic modulator 205, 0th-order and 1st-order diffraction lights are generated. In the embodiment of the present invention, the 0th-order diffraction light is output to the first coupler 227 to form the Doppler-assisted cooling light.

[0027] Exemplarily, in the embodiment of the present invention, the radio frequency signal source module for synthesizing and outputting radio frequency signals includes 8 channel units. Each channel unit includes a direct digital frequency synthesizer (AD9912) integrated with a 14-bit digital-to-analog converter and a main control board, and can output a sinusoidal signal with a frequency range of 0 - 400 MHz and adjustable intensity, so as to greatly improve the regulation accuracy of the radio frequency signal, thereby ensuring the stable operation of the acousto-optic modulator and providing high-quality laser regulation during the quantum transition process. In the embodiment of the present invention, the channel unit can be manually set through the main control board or support program control by dedicated software, so as to meet the requirements for the quality of radio frequency signals in different experimental environments.

[0028] Exemplarily, in an embodiment of the present invention, the radio frequency microwave coaxial switch module 5 includes eight switch units, and each switch unit includes a TTL signal channel, a first input channel, a second input channel, a signal output channel, a hexagon switch, and a signal lamp. The TTL signal channel in the switch unit is used to connect to an external TTL signal, so that the switch unit can switch the connection state of the signal output channel according to the high and low levels of the external TTL signal, making the switching of the radio frequency signal path faster and more accurate, realizing signal switching within nanoseconds, improving the real-time response ability of the system, and helping to achieve precise timing control. In an embodiment of the present invention, the first input channel is connected to the radio frequency signal source module and is used to input a radio frequency signal, and at this time, the second input channel is vacant. In one or other embodiments of the present invention, the first input channel is vacant, and the second input channel is connected to the radio frequency signal source module and is used to input the radio frequency signal. The connection state of the signal output channel of the switch unit has two types, including a first connection state and a second connection state. The first connection state is that the signal output channel is connected to the first input channel. The second connection state is that the signal output channel is connected to the second input channel.

[0029] Exemplarily, the hexagon switch in the radio frequency microwave coaxial switch module 5 is used to switch the working mode of the switch unit. The working modes of the switch unit include a first direct connection mode, a second direct connection mode, and a TTL signal control mode. The first direct connection mode corresponds to the signal output channel being connected to the first input channel. The second direct connection mode corresponds to the signal output channel being connected to the second input channel. In the TTL signal control mode, the connection state of the signal output channel is controlled by an external TTL signal. Specifically, in an embodiment of the present invention, the connection of the signal output channel to the first input channel or the second input channel is quickly switched through the TTL signal. Since one of the two input channels is always in a vacant state, the output of the radio frequency signal can be controlled, and further the working state of the acousto-optic modulator can be controlled, thereby realizing the rapid switching of the laser.

[0030] In the embodiment of the present invention, a radio frequency signal is connected to the first input channel of the radio frequency and microwave coaxial switch module 5. The switch unit of the radio frequency and microwave coaxial switch module 5 has two usage methods. First, by toggling the hexagon switch to the upper position, the signal lamp lights up red. The corresponding working mode of the switch unit is the first direct connection mode, and its signal output channel outputs the signal of the first input channel in the first connection state. Or toggle the hexagon switch to the middle position, the signal lamp does not light up, and the corresponding working mode of the switch unit is the second direct connection mode, so that its signal output channel outputs the signal of the second input channel in the second connection state. Second, toggle the hexagon switch to the lower position, the signal lamp lights up blue, and the signal output by its signal output channel is controlled by an external TTL signal. When the TTL signal is at a low level, the signal output channel outputs the signal of the first input channel in the first connection state. When the TTL signal is at a high level, the signal output channel outputs the signal of the second input channel in the second connection state. By controlling the high and low level timing of the external TTL signal, the timing control of the connection state of the signal output channel can be realized, and then the timing control of the output signal can be realized. In the embodiment of the present invention, the use of the signal lamp facilitates the user to intuitively observe the switch state and improves the usability and ease of use of the device.

[0031] In the embodiment of the present invention, the radio frequency power amplification module 6 is composed of 8 radio frequency power amplification sub-modules. Each sub-module is composed of an input channel, an output channel, a switch and a signal lamp. When the switch is turned to the upper position, the signal lamp lights up red, and the module can enhance the power of the input signal by about 30 dbm, so that the power of the radio frequency signal reaches the power required for the normal operation of the acousto-optic modulator. When the switch is turned to the lower position, the signal lamp does not light up and the module does not work.

[0032] In one or other embodiments of the present invention, an attenuator is provided between the radio frequency signal source module and the radio frequency and microwave coaxial switch module 5, so that even in the case of the highest output of the radio frequency signal, the signal intensity transmitted to the acousto-optic modulator is only slightly higher than the standard working power of the acousto-optic modulator, and the acousto-optic modulator can still work normally, thus ensuring the use safety of the acousto-optic modulator.

[0033] Please refer to the appendix Figure 2 , Figure 2Schematic diagram of the channel structure of the coaxial switch module and the power amplifier module according to the embodiments of the present invention. In the embodiments of the present invention, the connection of each module of the timing control system follows the principle of a single radio frequency signal source module - a single radio frequency microwave coaxial switch module 5 - a single radio frequency power amplifier module 6 - a single acousto-optic modulator. As can be seen from the figure, in the embodiments of the present invention, the radio frequency signal source module uses an Ad9912 signal source and is connected to the first input channel of the radio frequency microwave coaxial switch module 5. The TTL signal is connected to the TTL signal channel, and the second input channel is vacant. The output channel of the radio frequency microwave coaxial switch module 5 is connected to the input channel of the radio frequency power amplifier module 6, and the radio frequency signal output from the output channel of the radio frequency power amplifier module 6 is connected to the acousto-optic modulator. When the hexagon switch of the radio frequency microwave coaxial switch module 5 is turned to the upper position, the signal lamp of the module lights up red, and the output channel of the module outputs the radio frequency signal input from the first output channel. When the hexagon switch of the radio frequency microwave coaxial switch module 5 is turned to the middle position, the signal lamp of the module does not light up, and the output channel of the module is connected to the second input channel. Since the second input channel is vacant, the output channel is also vacant. When the hexagon switch of the radio frequency microwave coaxial switch module 5 is turned to the lower position, the signal lamp of the module lights up blue, and the output channel of the module is connected to the TTL signal channel. The low level of the TTL signal causes the output channel of the module to output the radio frequency signal connected to the first input channel. The high level of the TTL signal causes the output channel of the module to output the signal connected to the second input channel. In the embodiments of the present invention, the second input channel is vacant, so when the TTL signal is high, the output channel of the radio frequency microwave coaxial switch module 5 is vacant.

[0034] In the embodiments of the present invention, in addition to the above modules, the timing control system further includes a timing control optical path 2 including a four-stage acousto-optic modulator. Exemplarily, a piezoelectric ceramic is provided inside the acousto-optic modulator. Using the acousto-optic effect, the refractive index of the medium in the acousto-optic modulator is periodically changed to form a refractive index grating, so that light diffracts when passing through the medium of the acousto-optic modulator. The intensity, frequency, direction, etc. of the diffracted light will change with the change of the signal source. In the embodiments of the present invention, the radio frequency signal is the signal source connected to the acousto-optic modulator. By establishing a radio frequency signal source module, a radio frequency microwave coaxial switch module 5, and a radio frequency power amplifier module 6 to control the radio frequency signal, the working state of the acousto-optic modulator can be controlled, and the control of the laser entering the acousto-optic modulator can be realized.

[0035] Please refer to the appendix Figure 3 , Figure 3It is a schematic diagram of the overall optical path structure of the timing control system according to an embodiment of the present invention. As can be seen from the figure, in addition to the timing control optical path 2 including multiple acousto-optic modulators, the entire timing control system further includes a laser 1, a wavelength meter 3, and a frequency stabilization optical path 4. The laser emitted by the laser 1 is separated into two beams of laser by the first polarization beam splitter 102. One beam is used to read the laser wavelength, and the other beam is used to stabilize the frequency of the laser. Moreover, the ratio of the two separated beams of laser can be adjusted. Specifically, in the embodiment of the present invention, the reflection and transmission ratio of the laser passing through the first polarization beam splitter 102 is adjusted by the first half-wave plate 101 to achieve the adjustment of the ratio of the two beams of laser. Select one beam of laser transmitted by the first polarization beam splitter 102, and make it pass through the second mirror 201 to change the propagation direction, and access the timing control optical path 2 through the third half-wave plate 202 to generate multiple target lasers. One beam of laser reflected by the first polarizer beam splitter enters the second half-wave plate 103 and the second polarization beam splitter 104. Select the reflected laser of the second polarization beam splitter 104 to be coupled into the wavelength meter 3 to read the wavelength of the laser, which is used to monitor the frequency of the laser in real time. The transmitted laser of the second polarization beam splitter 104 changes the propagation direction through the first mirror 105 and is coupled into the frequency stabilization optical path 4. The frequency stabilization optical path 4 adopts an F-P optical cavity and is used to stabilize the frequency of the laser.

[0036] Please refer to the appendix Figure 4 , Figure 4It is a schematic diagram of the timing control optical path structure of an embodiment of the present invention. As can be seen from the figure, the laser of the laser 1 enters the timing control optical path 2 through the second reflector 201, and there are 4 acousto-optic modulators in the timing control optical path 2. The first acousto-optic modulator 205 is used to build a double-pass optical path. The third half-wave plate 202 is adjusted so that the laser only transmits and does not reflect when passing through the third polarization beam splitter 203. Then the laser first diffracts through the first acousto-optic modulator 205, and the second aperture 206 is set to allow the 0th-order diffracted light and the +1st-order diffracted light of the diffraction to pass through, and other-order diffracted lights are blocked. The fourth half-wave plate 207 and the first convex lens 208 are set so that the 0th-order diffracted light and the +1st-order diffracted light that first pass through the first acousto-optic modulator 205 propagate parallel to the principal optical axis. At this time, the 0th-order diffracted light is reflected by the first D-shaped mirror 209 and enters the first coupler 227 to be used as the Doppler-assisted cooling light for ion cooling, while the +1st-order diffracted light is perpendicularly incident on the third reflector 210 of the plane and returns along the original path, and passes through the first acousto-optic modulator 205 again. At this time, the +1st-order diffracted light overlaps with the principal optical axis. The first aperture 204 is set to filter the remaining diffracted lights other than the +1st-order diffracted light. The +1st-order diffracted light emerging from the double-pass optical path of the first acousto-optic modulator 205 passes through the third polarization beam splitter 203 again. By adjusting the third half-wave plate 202, the light beam only reflects and does not transmit when passing through the third polarization beam splitter 203, so as to change the propagation direction of the laser and enter the second acousto-optic modulator 212 through the fourth reflector 211. The third aperture 213 is set so that only the 0th-order diffracted light and the -1st-order diffracted light in the diffracted light of the second acousto-optic modulator 212 pass through, and the -1st-order diffracted light enters the second coupler 225 through the fifth D-shaped mirror 226 to be used as the Doppler cooling light for ion cooling. In the embodiment of the present invention, the Doppler cooling light and the Doppler-assisted cooling light irradiate the trapped ions from different directions, enhancing the cooling uniformity and improving the cooling efficiency. In other embodiments of the present invention, the Doppler cooling light and the Doppler-assisted cooling light can also be combined and output to cool the trapped ions. The technical solution of the present invention uses the 0th-order diffracted light of the first-order acousto-optic modulator for auxiliary cooling, improving the laser cooling efficiency, enhancing the cooling effect, and making the trapped ions in the ion trap more stable. The 0th-order diffracted light emerging from the second acousto-optic modulator 212 changes the propagation direction through the fifth reflector 214 and enters the third acousto-optic modulator 216 through the second D-shaped mirror 215. The fourth aperture 217 is set so that only the 0th-order diffracted light and the +1st-order diffracted light in the diffracted light of the third acousto-optic modulator 216 pass through, and the +1st-order diffracted light enters the third coupler 219 through the third D-shaped mirror 218 as the EIT cooling drive light.The 0th order diffracted light emitted from the third AOM 216 enters the fourth AOM 220 through the fourth D-type mirror 222 for diffraction, and the fifth aperture 221 is set so that only the 0th order diffracted light and the +1st order diffracted light pass through the diffracted light of the fourth AOM 220, and the +1st order diffracted light enters the fourth coupler 223 as the EIT cooling detection light, and the 0th order diffracted light is collected by the beam collector 224 to prevent dangerous accidents. In the embodiment of the present invention, the 0th order diffracted light is fully utilized through the coordinated use of the AOMs at various levels, which greatly improves the utilization efficiency of the laser compared to directly blocking the 0th order light before.

[0037] In one or other embodiments of the present invention, the RF signal source module, the RF microwave coaxial switch module 5, and the RF power amplifier module 6 are all modularized and overload protected, which can effectively improve the stability of the system, reduce the impact of external interference on system performance, and enhance the flexibility and scalability of the system, reduce the space occupied by the circuit system, and each module is independent and has clear functions, which simplifies installation and operation. In addition, the RF microwave coaxial switch module 5 and the RF power amplifier module 6 are both added with signal lights and corresponding switches, so that users can easily distinguish and control the working status of the system.

[0038] In the embodiment of the present invention, 40Ca is selected + Laser timing control in ground state cooling of ions. + Ion The energy level transition between them corresponds to the 397nm wavelength laser. By modulating the frequency of the 397nm laser, Doppler cooling and electromagnetic induced transparency (EIT) cooling are realized respectively, and a timing control system is used to switch the above-mentioned multi-beam target lasers at high speed. Doppler cooling is a widely used method for cooling neutral atoms and ions. In trapped ion systems, it is often used for purposes such as ion trapping and preliminary cooling of ion motion. When a red-detuned laser meets an ion moving in opposite directions, due to the Doppler effect, the ion absorbs a photon, resulting in a transition, and its own momentum is reduced. Because the excited state corresponding to the 397nm laser The lifetime is usually very short, and the ion will then emit a photon through spontaneous radiation. Considering that the spontaneous radiation process is isotropic, the average momentum change of the ion in this process is almost 0. In the continuous absorption-radiation process, the momentum of the ion will continue to decrease, and the temperature will decrease accordingly, thus achieving a cooling effect. The energy level transition rate is in the nanosecond level. EIT cooling requires a high accuracy of the laser frequency. Therefore, in order to complete the above series of operations, the 397nm laser must be able to switch quickly and have a stable frequency. +The ions can be modulated by the frequency of the 397 nm laser to achieve not only Doppler cooling and EIT cooling, but also further state initialization and state detection.

[0039] Exemplarily, due to the collision and recoil effects during the photon radiation process, Doppler cooling has a theoretical limit and cannot cool the ions to the motional ground state. To cool the ions to the motional ground state, EIT cooling needs to be continued. In the ion trap system, two 397 nm lasers are required for EIT cooling. Among them, the polarized light is used to couple the ground state and the excited state transition, and the Rabi frequency is , which is called the EIT cooling probe light. The polarized light of 397 nm is used to drive the transition, and the corresponding Rabi frequency is , which is called the EIT cooling drive light. The two lasers for EIT cooling should meet two conditions: First, the detuning amounts of the two beams of light are the same and much larger than the excited state linewidth. Second, the intensity of the drive light is much larger than that of the probe light, and the AC Stark frequency shift caused by the drive light field should be consistent with the ion trapping frequency. In this case, the intensity of the red sideband process of the ion transition is much larger than that of the blue sideband, and the carrier transition is completely suppressed. It is this feature that ensures the cooling effect of EIT on the motion mode, thus achieving a lower cooling limit.

[0040] In one or other embodiments of the present invention, the timing control system can not only be used to form the Doppler-assisted cooling light, Doppler cooling light, EIT cooling drive light, and EIT cooling probe light to achieve Doppler cooling and EIT cooling, but also use the polarized light of 397 nm to achieve state initialization. State initialization is the first step in the quantum computing process, ensuring that the ions are in a known and controllable quantum state, thus laying the foundation for subsequent quantum operations. Through the operation of optical pumping, the electrons are transferred from the state to the state and then transferred to the state via spontaneous emission, so that all electrons are in the ground state to achieve state initialization. In addition, the 397 nm laser is often used to detect the quantum state of 40Ca + ions, and through the electron shelving technique, the two electron states can be distinguished with an efficiency close to 100%.

[0041] Please refer to the attached Figure 5 , Figure 5 is the energy level schematic diagram of 40Ca + ions in the embodiments of the present invention. As can be seen from the figure, assuming that the state and the state are used as the two states of the qubit, the ground state Coupled to the excited state by strong transitions of 397 nm laser . If the ion is in the state, no fluorescence will be observed, while if the ion is in the state, photons transition between the energy levels and emit photons. Based on the above principle, by repeatedly preparing the atomic state and measuring fluorescence, the populations of the state and the state can be determined, which is crucial for achieving precise quantum operations and reading quantum information.

[0042] Please refer to the appendix Figure 6 , Figure 6 which is a schematic diagram of the multi-laser timing control of the embodiment of the present invention. As can be seen from the figure, the multi-laser includes 866 nm laser, Doppler-assisted cooling light, Doppler cooling light, EIT cooling drive light, EIT cooling probe light, 729 nm laser and 854 nm laser. In the embodiment of the present invention, the 0th order diffracted light emitted by the first acousto-optic modulator 205 (AOM1), that is, the Doppler-assisted cooling light, on the one hand, is used to continuously act on the trapped ions to keep the trapped ions stable in the ion trap and prevent the trapped ions from overheating and evaporating. On the other hand, it acts together with the Doppler cooling light of the -1st order diffracted light of the second acousto-optic modulator 212 (AOM2) to preliminarily cool the trapped ions. The embodiment of the present invention independently controls each beam of laser through a timing control system, and the control accuracy reaches the nanosecond level. Further, as can be seen from the figure, in a timing control column, the embodiment of the present invention can precisely control the light output time of the Doppler cooling light, that is, from 1 ms to start outputting light until the moment of 2 ms. Moreover, from 2 ms to 3.08 ms, the embodiment of the present invention controls the third acousto-optic modulator 216 (AOM3) to generate polarized light as the EIT cooling drive light. The EIT cooling drive light of the embodiment of the present invention is also used to make the trapped ions in the energy level state transition to the Energy level state to complete the state initialization of the trapped ions for subsequent ion operations. Therefore, in the embodiment of the present invention, the light output time of the EIT cooling driving light is greater than that of the EIT cooling probing light. Specifically, the timing control system in the embodiment of the present invention controls the radio frequency output through a TTL signal, so that the light output time of the EIT cooling probing light generated by modulating the fourth acousto-optic modulator 220 (AOM4) lasts between 2.04 ms and 3.04 ms. In this way, during the entire EIT cooling process, the EIT cooling driving light modulated and emitted by the third acousto-optic modulator 216 simultaneously performs state initialization on the trapped ions for subsequent state operations. After the EIT cooling is completed, the timing design in the embodiment of the present invention is for the quantum state operation of the pulsed light. Immediately, the timing control system of the present invention controls the radio frequency signal, and modulates the -1st order diffracted light through the fourth acousto-optic modulator 220 to output light at 3.10 ms, that is, still using the π-polarized light of 397 nm, and uses the fluorescence detection technology to detect the state of the trapped ions after the quantum state operation. Exemplarily, the embodiment of the present invention can be further extended. By controlling the timing, the 854 nm laser outputs light at 4.08 ms, and the electrons staying in the ion energy level are excited to energy level, and by virtue of its fast decay characteristic, the electrons jump to energy level to ensure the sustainability of the subsequent cooling, state initialization, and state detection processes.

[0043] In an embodiment of the present invention, 40Ca + ions are selected for the laser in the ground state cooling for timing control. The signal source frequency of the first acousto-optic modulator in the double-pass optical path is 110 MHz, and the frequency adjustment range is 20 MHz, the intensity can be adjusted downward to 1 W, and the diffraction efficiency of the +1st order diffracted light is about 50%. The signal source frequency of the second acousto-optic modulator 212 is 180 MHz, and the frequency adjustment range is 20 MHz, the intensity can be adjusted downward to 1 W, and the diffraction efficiency of the -1st order diffracted light is 60%. The signal source frequency of the third acousto-optic modulator 216 is 180 MHz, and the frequency adjustment range is 20 MHz, the intensity can be adjusted downward to 1 W, and the diffraction efficiency of the +1st order diffracted light is 60%. The signal source frequency, frequency adjustment range, and intensity adjustment range of the fourth acousto-optic modulator 220 are the same as those of the third acousto-optic modulator 216. The difference is that the diffraction efficiency of the +1st order diffracted light of the fourth acousto-optic modulator 220 is 80%.

[0044] In the embodiment of the present invention, a relatively stable and intense 397 nm laser is provided by a 397 nm laser 1. The laser entering the timing control system first passes through the first acousto-optic modulator 205 of the double-pass optical path. The 0th-order diffracted light of the first acousto-optic modulator 205 forms Doppler-assisted cooling light, and its frequency is the same as the frequency of the initial 397 nm laser. The +1st-order diffracted light passes through the first acousto-optic modulator 205 for the second time due to the reflection of the second mirror 201, and is output to the second acousto-optic modulator 212. The -1st-order diffracted light is selected to enter the second coupler 225 to form Doppler cooling light. Its frequency is increased by 220 MHz after being modulated twice by the first acousto-optic modulator 205, and is decreased by 180 MHz after being modulated once by the second acousto-optic modulator 212. Therefore, the frequency of the Doppler cooling light is increased by 40 MHz compared with the frequency of the initial 397 nm laser. And because the frequency of the Doppler-assisted cooling light is lower than the frequency of the Doppler cooling light, the Doppler-assisted cooling light is also farther from the resonance frequency between 397 nm and the energy level. According to the Doppler principle, trapped ions in a larger velocity range can be cooled, further improving the cooling efficiency of Doppler cooling. The 0th-order diffracted light of the second acousto-optic modulator 212 is selected to enter the third acousto-optic modulator 216, and the generated +1st-order diffracted light is output to the third coupler 219 to form EIT cooling drive light. In the embodiment of the present invention, the frequency of the EIT cooling drive light is increased by 220 MHz by the first acousto-optic modulator 205, remains unchanged when passing through the second acousto-optic modulator 212, and is increased by 180 MHz by the third acousto-optic modulator 216. Compared with the frequency of the initial 397 nm laser, the frequency of the EIT cooling drive light is increased by 400 MHz. The 0th-order diffracted light of the third acousto-optic modulator 216 is selected to enter the fourth acousto-optic modulator 220, and the diffracted +1st-order diffracted light is selected and output to the fourth coupler 223 to form EIT cooling probe light. The frequency of the EIT cooling probe light is increased by 220 MHz by the first acousto-optic modulator 205, remains unchanged when passing through the second acousto-optic modulator 212 and the third acousto-optic modulator 216, and is increased by 180 MHz by the fourth acousto-optic modulator 220, and its frequency is equal to that of the EIT cooling drive light.

[0045] Finally, it should be noted that the above specific embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention, and they should all be covered within the scope of the claims of the present invention.

Claims

1. A timing control system for quantum energy level transitions, which is used to perform timing control on ion trap quantum transitions, and is characterized in that, The timing control system includes: a radio frequency signal source module for generating a radio frequency signal with adjustable frequency; a radio frequency microwave coaxial switch module connected to the radio frequency signal source module, and performing channel switching through an external TTL signal; a radio frequency power amplification module connected to an acousto-optic modulator for amplifying the radio frequency signal to drive the acousto-optic modulator; a timing control optical path including a laser and the acousto-optic modulator, tuning and controlling the laser output by the acousto-optic modulator to generate multiple target lasers applicable to the quantum transition; wherein the multiple target lasers include Doppler-assisted cooling light and Doppler cooling light, and the acousto-optic modulator includes a first acousto-optic modulator; the zero-order diffracted light of the first acousto-optic modulator forms the Doppler-assisted cooling light, and the non-zero-order diffracted light of the first acousto-optic modulator forms the Doppler cooling light; the Doppler-assisted cooling light and the Doppler cooling light are used to jointly irradiate the trapped ions for Doppler cooling of the trapped ions.

2. The timing control system according to claim 1, wherein The acousto-optic modulator further includes a second acousto-optic modulator, the +1-order diffracted light of the first acousto-optic modulator is output to the second acousto-optic modulator, and the -1-order diffracted light of the second acousto-optic modulator is output to a second coupler to form the Doppler cooling light.

3. The timing control system according to claim 2, characterized in that, The acousto-optic modulator further includes a third acousto-optic modulator and a fourth acousto-optic modulator; the 0-order diffracted light of the second acousto-optic modulator is output to the third acousto-optic modulator; the +1-order diffracted light of the third acousto-optic modulator is output to a third coupler to form the EIT cooling drive light; the 0-order diffracted light of the third acousto-optic modulator is output to the fourth acousto-optic modulator; the +1-order diffracted light of the fourth acousto-optic modulator is output to a fourth coupler to form the EIT cooling probe light.

4. The timing control system according to claim 1, wherein The radio frequency microwave coaxial switch module includes a plurality of switch units, and each switch unit includes a TTL signal channel, a first input channel, a second input channel, and a signal output channel; the TTL signal channel is used to connect the external TTL signal, and the switch unit switches the connection state of the signal output channel according to the high and low levels of the external TTL signal; wherein, the connection state of the signal output channel includes a first connection state and a second connection state; the first connection state is that the signal output channel is connected to the first input channel; the second connection state is that the signal output channel is connected to the second input channel.

5. The timing control system according to claim 4, characterized in that The first input channel is connected to the radio frequency signal source module for inputting the radio frequency signal, and the second input channel is vacant; or the first input channel is vacant, and the second input channel is connected to the radio frequency signal source module for inputting the radio frequency signal.

6. The timing control system according to claim 4, characterized in that Each switch unit further includes a hexagonal switch and an indicator light, and the hexagonal switch is used to switch the working mode of the switch unit, and the working mode includes a first direct connection mode, a second direct connection mode, and a TTL signal control mode; the first direct connection mode corresponds to the first connection state of the signal output channel; the second direct connection mode corresponds to the second connection state of the signal output channel; In the TTL signal control mode, the connection state of the signal output channel is controlled by the external TTL signal.

7. The timing control system according to claim 1, characterized in that The timing control optical path further includes a wavemeter for measuring the frequency of the laser; and a frequency stabilization optical path which adopts an F-P optical cavity for stabilizing the frequency of the laser.

8. The timing control system according to claim 1, characterized in that, The RF signal source module includes a plurality of channel units, and each of the channel units includes a direct digital frequency synthesizer for synthesizing and outputting the RF signal. The frequency and intensity of the RF signal are adjustable, and the frequency range of the RF signal is set between 0 and 400 MHz.

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