Time sequence control system for quantum energy level transition

Abstract

The invention discloses a time sequence control system for quantum energy level transition, which belongs to the technical field of quantum computing and comprises a radio frequency signal source module for generating frequency-adjustable radio frequency signals, a radio frequency microwave coaxial switch module for switching channel switches through TTL (transistor-transistor logic) signals, and a time sequence control module for quantum energy level transition. The radio frequency power amplification module is used for amplifying a radio frequency signal and driving the acousto-optic modulator; and the sequential control optical path comprises a plurality of stages of acousto-optic modulators which can be independently controlled. According to the technical scheme provided by the invention, the multi-stage acousto-optic modulator is controlled by the radio frequency channel switched by the TTL signal through the modularly designed sequential control system, so that not only can the frequency, the light extraction rate and the light intensity of each laser beam be independently controlled, but also nanosecond-level rapid switching can be carried out, and the controllability of trapping ions by the ion trap is enhanced.

Description

Technical Field

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

[0002] The key to quantum computing is to build a quantum computer, and the ion trap is the core component of the quantum computer architecture. Ion trap quantum computers use the internal energy levels of ions to encode quantum bits, and use laser beams to manipulate the 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, lasers are usually used to Doppler cool the trapped ions. However, due to the collision and recoil effects during photon radiation, there are theoretical limits to Doppler cooling, and trapped ions cannot be cooled to the ground state of motion. Therefore, electromagnetically induced transparency (EIT) cooling technology is needed to continue to cool the trapped ions more deeply. Generally, EIT cooling has high requirements on the accuracy and stability of the laser frequency. Therefore, in order to cool the trapped ions to the ground state of motion, the laser needs to be able to switch quickly and stably.

[0003] In the prior art, Chinese invention patent CN116757289B discloses a time-division multiplexing control method, which uses an optical modulation module to modulate the seed laser to generate a laser with the required sideband, and after the seed laser is converted into a laser of the target band by a frequency conversion module, a laser separation module is used to separate lasers of different frequencies, and finally the operation module controls the timing and spatial distribution of the laser. However, the above scheme has low control accuracy for RF signals, slow signal switching response, and cannot meet the needs 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 0th-order diffracted light through a double-pass optical path, and combines multiple groups of acousto-optic modulators, RF microwave coaxial switch modules and RF signal source modules to achieve efficient RF signal regulation, precise laser modulation and fast timing control.

[0005] In order to achieve the above-mentioned purpose, the present invention provides a timing control system for quantum energy level transition. The timing control system includes: a radio frequency signal source module, which is used to generate a frequency-adjustable radio frequency signal; a radio frequency microwave coaxial switch module, which is connected to the radio frequency signal source module and switches the channel through an external TTL signal; a radio frequency power amplifier module, which is connected to an acousto-optic modulator and is used to amplify the radio frequency signal to drive the acousto-optic modulator; a timing control optical path, including a laser and the acousto-optic modulator, through which the laser output by the laser is tuned and controlled 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 driving light and EIT cooling detection 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 diffraction light of the first acousto-optic modulator is output to the first coupler to form the Doppler-assisted cooling light.

[0006] Furthermore, the AOM also includes a second AOM, the +1st order diffraction light of the first AOM is output to the second AOM, and the -1st order diffraction light of the second AOM is output to a second coupler to form the Doppler cooling light.

[0007] Furthermore, the AOM also includes a third AOM and a fourth AOM; the 0th order diffraction light of the second AOM is output to the third AOM; the +1st order diffraction light of the third AOM is output to a third coupler to form the EIT cooling driving light; the 0th order diffraction light of the third AOM is output to the fourth AOM; the +1st order diffraction light of the fourth AOM is output to a fourth coupler to form the EIT cooling detection light.

[0008] Preferably, the RF microwave coaxial switch module includes a plurality of switch units, each of which 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.

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

[0010] Preferably, each of the switch units also includes a hexagonal switch and an indicator light, the hexagonal switch is used to switch the working mode of the switch unit, 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 also includes a wavelength meter for measuring the frequency of the laser; and a frequency stabilization optical path, wherein the frequency stabilization optical path adopts an FP optical cavity for stabilizing the frequency of the laser.

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

[0013] The present invention achieves the following beneficial effects through the above technical solution:

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

[0015] 2) The multi-level acousto-optic modulator is controlled by a modular laser timing control system, which can not only independently and accurately control the frequency, light output rate and light intensity of each laser beam, but also perform rapid switching at the nanosecond level according to the needs of ion trap quantum operations, thereby enhancing the controllability of ion trap trapped ions.

[0016] 3) The RF microwave coaxial switch module combines hexagonal switches and indicator lights to achieve multi-mode flexible switching of the switch unit, improve the real-time response capability of the system, simplify the system debugging and maintenance process, enable users to intuitively observe the switch status, and improve the availability and ease of use of the equipment.

[0017] 4) The RF signal source module uses multiple direct digital frequency synthesizers to improve the control accuracy of the RF signal, ensure the stable operation of the acousto-optic modulator, and provide high-quality laser timing control for the quantum transition process. BRIEF 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 amplifier 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 of an embodiment of the present invention.

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

[0022] Figure 5 40Ca of the embodiment of the present invention + Schematic diagram of the energy levels of ions.

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

[0024] The numbers in the figure represent: 1. laser; 2. timing control optical path; 3. wavelength meter; 4. frequency stabilization optical path; 5. RF microwave coaxial switch module; 6. RF power amplifier 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 Mirror; 209, first D-type mirror; 210, third reflecting mirror; 211, fourth reflecting mirror; 212, second AOM; 213, third aperture; 214, fifth reflecting mirror; 215, second D-type mirror; 216, third AOM; 217, fourth aperture; 218, third D-type mirror; 219, third coupler; 220, fourth AOM; 221, fifth aperture; 222, fourth D-type mirror; 223, fourth coupler; 224, beam collector; 225, second coupler; 226, fifth D-type mirror; 227, first coupler. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical scheme and advantages of the present invention more clear, the specific implementation of the present invention is further described in detail below in conjunction with examples. It should be understood that the embodiments described herein are only used to explain the present invention, but are not used to limit the scope of the present invention.

[0026] Please see attached Figure 1 , Figure 1: is a schematic diagram of the circuit module structure of the timing control system of the 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 amplifier module 6, and a timing control optical path 2 including a multi-level acousto-optic modulator. Among them, the radio frequency signal source module is used to generate a frequency-adjustable radio frequency signal, which is output 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 switching through an external TTL signal to output the selected radio frequency signal to the radio frequency power amplifier module 6. In particular, in an embodiment of the present invention, the radio frequency power amplifier module 6 is connected to an acousto-optic modulator (AOM) to amplify the radio frequency signal to drive the acousto-optic modulator. The laser output by the laser 1 is tuned and controlled in strength, switching, and frequency by the acousto-optic modulator of the timing control optical path 2 to generate multiple target laser beams suitable for the quantum transition. In an embodiment of the present invention, the multiple target laser beams include Doppler auxiliary cooling light, Doppler cooling light, EIT cooling driving light, and EIT cooling detection light. In one or other embodiments of the present invention, the multi-target laser further includes a state detection laser or a state initialization laser. In the embodiment of the present invention, the acousto-optic modulator includes a first acousto-optic modulator 205 using a double-pass optical path, and the incident laser generates 0th order and 1st order diffracted light after passing through the first acousto-optic modulator 205. The embodiment of the present invention outputs the 0th order diffracted light to the first coupler 227 to form the Doppler-assisted cooling light.

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

[0028] Exemplarily, in an embodiment of the present invention, the RF microwave coaxial switch module 5 includes 8 switch units, each of which includes a TTL signal channel, a first input channel, a second input channel, a signal output channel, a hexagonal switch, and a signal lamp. The TTL signal channel in the switch unit is used to connect 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, so that the path switching of the RF signal is faster and more accurate, and the signal switching within nanoseconds is realized, which improves the real-time response capability of the system and helps to achieve accurate timing control. In an embodiment of the present invention, the first input channel is connected to the RF signal source module for inputting the RF signal, and the second input channel is vacant at this time. In one or other embodiments of the present invention, the first input channel is vacant, and the second input channel is connected to the RF signal source module for inputting the RF signal. There are two connection states of the signal output channel of the switch unit, 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 hexagonal switch in the RF 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 signal output channel is quickly switched to be connected to the first input channel or the second input channel through a TTL signal. Since one of the two input channels is always in an idle state, it is possible to control whether the RF signal is output or not, and further control the working state of the acousto-optic modulator, thereby realizing rapid switching of the laser.

[0030] In an embodiment of the present invention, the RF signal is connected to the first input channel of the RF microwave coaxial switch module 5, and the switch unit of the RF microwave coaxial switch module 5 has two methods of use. First, by toggling the hexagonal switch to the upper gear, the signal light turns red, and the corresponding working mode of the switch unit is the first direct connection mode, and its signal output channel is the signal of the first input channel in the first connection state, or the hexagonal switch is toggled to the middle gear, the signal light is not on, and the working mode corresponding to the switch unit is the second direct connection mode, so that its signal output channel is the signal of the second input channel in the second connection state. Second, the hexagonal switch is toggled to the lower gear, the signal light turns blue, and the signal selection of the signal output channel is controlled by an external TTL signal. When the TTL signal is at a low level, the signal output channel is the signal of the first input channel in the first connection state, and when the TTL signal is at a high level, the signal output channel is 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. The use of the signal light in the embodiment of the present invention allows the user to intuitively observe the switch status, thereby improving the availability and usability of the device.

[0031] In the embodiment of the present invention, the RF power amplifier module 6 is composed of 8 RF power amplifier submodules, each of which is composed of an input channel, an output channel, a switch and a signal light. When the switch is adjusted to the upper gear, the signal light is red, and the module can enhance the power of the input signal by about 30dbm, so that the power of the RF signal reaches the power required for the normal operation of the acousto-optic modulator. When the switch is modulated to the lower gear, the signal light is not on and the module does not work.

[0032] In one or other embodiments of the present invention, an attenuator is provided between the RF signal source module and the RF microwave coaxial switch module 5, so that even at the highest output of the RF signal, the signal strength transmitted to the AOM is only slightly higher than the standard operating power of the AOM, and the AOM can still work normally, thereby ensuring the safe use of the AOM.

[0033] Please see attached Figure 2 , Figure 2Schematic diagram of the channel structure of the coaxial switch module and the power amplifier module of the embodiment of the present invention. In the embodiment of the present invention, the connection of each group of modules of the timing control system follows the principle of a single RF signal source module-a single RF microwave coaxial switch module 5-a single RF power amplifier module 6-a single acousto-optic modulator. As can be seen from the figure, in the embodiment of the present invention, the RF signal source module adopts the Ad9912 signal source and is connected to the first input channel of the RF 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 RF microwave coaxial switch module 5 is connected to the input channel of the RF power amplifier module 6, and the RF signal output by the output channel of the RF power amplifier module 6 is connected to the acousto-optic modulator. When the hexagonal switch of the RF microwave coaxial switch module 5 is turned to the upper gear, the signal light of the module is red, and the output channel of the module outputs the RF signal input by the first output channel. When the hexagonal switch of the RF microwave coaxial switch module 5 is turned to the middle gear, the signal light of the module is not on, and the output channel output 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 hexagonal switch of the RF microwave coaxial switch module 5 is turned to the lower gear, the signal light 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 module output channel to output the RF signal connected to the first input channel. The high level of the TTL signal causes the module output channel to output the signal connected to the second input channel. In the embodiment of the present invention, the second input channel is vacant, so when the TTL signal is at a high level, the output channel of the RF microwave coaxial switch module 5 is vacant.

[0034] In the embodiment of the present invention, in addition to the above modules, the timing control system also includes a timing control optical path 2 of a four-level acousto-optic modulator. Exemplarily, the acousto-optic modulator is equipped with piezoelectric ceramics, and the acousto-optic effect is used to periodically change the refractive index of the medium in the acousto-optic modulator to form a refractive index grating, so that light diffracts when passing through the medium of the acousto-optic modulator, and the intensity, frequency and direction of the diffracted light will change with the change of the signal source. In the embodiment 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, and controlling 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 achieved.

[0035] Please see attached Figure 3 , Figure 3It is a schematic diagram of the overall optical path structure of the timing control system of an embodiment of the present invention. As can be seen from the figure, the entire timing control system includes a laser 1, a wavelength meter 3 and a frequency stabilization optical path 4 in addition to the timing control optical path 2 of the multi-level acousto-optic modulator. The laser emitted by the laser 1 is separated into two beams of laser light 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 laser frequency, and the ratio of the two separated laser beams can be adjusted. Specifically, in an embodiment of the present invention, the reflection and transmittance ratio of the laser through the first polarization beam splitter 102 is adjusted by the first half-wave plate 101 to achieve proportional adjustment of the two laser beams. A beam of laser light transmitted by the first polarization beam splitter 102 is selected, and it passes through the second reflector 201 to change the propagation direction, and is connected to the timing control optical path 2 through the third half-wave plate 202 to generate multiple target laser beams. A beam of laser light reflected by the first polarizer beam splitter enters the second half-wave plate 103 and the second polarization beam splitter 104. The reflected laser light of the second polarization beam splitter 104 is selected and coupled into the wavelength meter 3 to read the wavelength of the laser light for real-time monitoring of the laser frequency. The transmitted laser light of the second polarization beam splitter 104 changes its propagation direction through the first reflector 105 and is coupled into the frequency stabilization optical path 4, which uses an FP optical cavity for stabilizing the frequency of the laser light.

[0036] Please see attached 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 is a 4-level acousto-optic modulator 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 is only transmitted but not reflected when passing through the third polarization beam splitter 203. After that, the laser is first diffracted by the first acousto-optic modulator 205, and the second aperture 206 is set to allow the diffracted 0th order diffracted light and +1st order diffracted light to pass through, blocking other orders of diffracted light. The fourth half-wave plate 207 and the first convex lens 208 are set so that the 0th order diffracted light and +1st order diffracted light that pass through the first acousto-optic modulator 205 for the first time propagate parallel to the main optical axis. At this time, the 0th order diffracted light is reflected by the first D-type mirror 209 and enters the first coupler 227 to be used as Doppler auxiliary cooling light for ion cooling, while the +1st order diffracted light returns to the original path after passing through the third reflector 210 perpendicular to the incident plane and passes through the first acousto-optic modulator 205 again. At this time, the +1st order diffracted light overlaps with the main optical axis. The first aperture 204 is set to filter the remaining diffracted light except the +1st order diffracted light. The +1st order diffracted light emitted through 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 is only reflected but not transmitted when passing through the third polarization beam splitter 203, thereby changing the propagation direction of the laser and entering the second acousto-optic modulator 212 through the fourth reflector 211. The third aperture 213 is set so that only the 0th order diffraction light and the -1st order diffraction light pass through the diffraction light of the second acousto-optic modulator 212, and the -1st order diffraction light enters the second coupler 225 through the fifth D-type mirror 226 for Doppler cooling light for ion cooling. In an embodiment of the present invention, the Doppler cooling light and the Doppler auxiliary cooling light irradiate the trapped ions from different directions, which enhances the uniformity of cooling and improves the cooling efficiency. In other embodiments of the present invention, the Doppler cooling light and the Doppler auxiliary cooling light can also be combined and output to cool the trapped ions. The technical solution of the present invention improves the laser cooling efficiency and enhances the cooling effect by using the 0th order diffraction light of the first-order acousto-optic modulator for auxiliary cooling, so that the trapped ions in the ion trap are more stable. The 0th order diffraction light emitted 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-type mirror 215. The fourth aperture 217 is set so that only the 0th order diffraction light and the +1st order diffraction light of the diffracted light of the third acousto-optic modulator 216 pass through, and the +1st order diffraction light enters the third coupler 219 through the third D-type mirror 218 as EIT cooling driving 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. +Ions, in addition to achieving Doppler cooling and EIT cooling, can also further achieve state initialization and state detection by modulating the frequency of 397nm laser.

[0039] For example, due to the collision and recoil effects during photon radiation, Doppler cooling has a theoretical limit and cannot cool ions to the ground state of motion. In order to cool ions to the ground state of motion, EIT cooling is required. In an ion trap system, EIT cooling requires two 397nm laser beams. The 397nm Polarized light is used to couple the ground state and excited state The Rabi frequency is , called EIT cooling probe light. 397nm Polarized light is used to drive The corresponding Rabi frequency is , called EIT cooling driving light. The two laser beams for EIT cooling should meet two conditions: First, the detuning amount of the two beams is the same and much larger than the excited state linewidth. Second, the intensity of the driving light is much larger than the intensity of the detection light, and the AC Stark frequency shift caused by the driving 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 greater than the blue sideband intensity, and the carrier transition is completely suppressed. It is this feature that ensures the cooling effect of EIT on the motion mode, thereby achieving a lower cooling limit.

[0040] In one or other embodiments of the present invention, in addition to being used to form Doppler auxiliary cooling light, Doppler cooling light, EIT cooling driving light and EIT cooling detection light to achieve Doppler cooling and EIT cooling, the timing control system can also be used to generate 397nm Polarized light is used 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. Transfer to state and transfers to state, so that all electrons are in the ground state to achieve state initialization. In addition, 397nm laser is often used to detect 40Ca + The quantum state of ions can be distinguished between two electronic states with nearly 100% efficiency through electron shelving technology.

[0041] Please see attached Figure 5 , Figure 5 40Ca of the embodiment of the present invention + Schematic diagram of the energy levels of ions. As can be seen from the figure, if State and The two states of the quantum bit are the ground state Coupling to the excited state through 397nm laser strong transition If the ion is in state, no fluorescence is observed, and if the ions are state, photons in Based on the above principle, by repeatedly preparing atomic states and measuring fluorescence, it is possible to determine State and The population of the state is crucial for achieving precise quantum operations and reading of quantum information.

[0042] Please see attached Figure 6 , Figure 6 It is a schematic diagram of multi-laser timing control of an embodiment of the present invention. As can be seen from the figure, the multi-laser includes 866nm laser, Doppler auxiliary cooling light, Doppler cooling light, EIT cooling driving light, EIT cooling detection light, 729nm laser and 854nm laser. In the embodiment of the present invention, the 0th order diffraction light emitted by the first acousto-optic modulator 205 (AOM1), that is, the Doppler auxiliary cooling light, is used to continuously act on the trapped ions on the one hand, so that the trapped ions can be stabilized in the ion trap and prevent the trapped ions from overheating and evaporation. On the other hand, it works together with the Doppler cooling light of the -1st order diffraction light of the second acousto-optic modulator 212 (AOM2) to perform preliminary cooling on the trapped ions. The embodiment of the present invention independently controls each laser beam through a timing control system, and the control accuracy reaches the nanosecond level. It can be further seen from the figure that in a timing control column, the embodiment of the present invention can accurately control the light emission time of the Doppler cooling light, that is, the moment from 1ms to 2ms. Moreover, from 2 ms to 3.08 ms, the embodiment of the present invention controls the third AOM 216 (AOM3) to generate Polarized light is used as the EIT cooling driving light. The EIT cooling driving light of the embodiment of the present invention is also used to make The trapped ion transitions to Energy level state, complete the state initialization of the trapped ions, in preparation for subsequent ion operations. Therefore, the emission time of the EIT cooling driving light of the embodiment of the present invention is greater than the EIT cooling detection light. Specifically, the timing control system of the embodiment of the present invention controls the RF output through the TTL signal, so that the emission time of the EIT cooling detection light modulated by the fourth acousto-optic modulator 220 (AOM4) lasts between 2.04ms and 3.04ms. In this way, during the entire EIT cooling process, the EIT cooling driving light modulated by the third acousto-optic modulator 216 simultaneously initializes the state of the trapped ions for subsequent state operations. After the EIT cooling is completed, the timing design of the embodiment of the present invention is the quantum state operation of the pulsed light. Then, the timing control system of the present invention controls the RF signal, and the -1 order diffraction light is modulated by the fourth acousto-optic modulator 220 to emit light at 3.10ms, that is, 397nm π polarized light is still used, and the trapped ions after the quantum state operation are detected by fluorescence detection technology. For example, the embodiment of the present invention can be further expanded by timing controlling the 854nm laser to emit light at 4.08ms, The electrons in the energy level are excited to energy level, using its rapid decay characteristics to make the electron jump to energy level to ensure the sustainability of subsequent cooling, state initialization and state detection processes.

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

[0044] In the embodiment of the present invention, a 397nm laser 1 provides a relatively stable and strong 397nm laser, and 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 diffraction light of the first acousto-optic modulator 205 forms Doppler auxiliary cooling light, and its frequency is the same as the initial 397nm laser frequency. The +1st order diffraction light passes through the first acousto-optic modulator 205 for the second time due to the reflection of the second reflector 201, and is output to the second acousto-optic modulator 212. The -1st order diffraction light is selected to enter the second coupler 225 to form Doppler cooling light, and its frequency is increased by 220MHz after two modulations of the first acousto-optic modulator 205, and then reduced by 180MHz after one modulation of the second acousto-optic modulator 212, so the frequency of the Doppler cooling light is increased by 40MHz compared with the initial 397nm laser frequency. 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 frequency of the resonance between 397nm and the energy level. According to the Doppler principle, it can cool trapped ions in a larger speed range, further improving the cooling efficiency of Doppler cooling. The 0th order diffraction light of the second acousto-optic modulator 212 is selected to enter the third acousto-optic modulator 216, and the generated +1st order diffraction light is output to the third coupler 219 to form the EIT cooling driving light. In the embodiment of the present invention, the frequency of the EIT cooling driving light is increased by 220MHz after the first acousto-optic modulator 205, remains unchanged when passing through the second acousto-optic modulator 212, and increases by 180MHz after passing through the third acousto-optic modulator 216. Compared with the initial 397nm laser frequency, the frequency of the EIT cooling driving light is increased by 400MHz. The 0th order diffraction light of the third acousto-optic modulator 216 is selected to enter the fourth acousto-optic modulator 220, and the +1st order diffraction light after diffraction is selected to be output to the fourth coupler 223 to form the EIT cooling detection light. The frequency of the EIT cooling detection light increases by 220 MHz after passing through the first AOM 205, remains unchanged after passing through the second AOM 212 and the third AOM 216, and increases by 180 MHz after passing through the fourth AOM 220, and its frequency is equal to that of the EIT cooling driving light.

[0045] Finally, it should be noted that the above specific implementation methods are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the spirit and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A timing control system for quantum energy level transition, used for timing control of ion trap quantum transition, characterized in that: The timing control system comprises: A radio frequency signal source module, used for generating a frequency-adjustable radio frequency signal; A radio frequency microwave coaxial switch module is connected to the radio frequency signal source module and switches the channel through an external TTL signal; A radio frequency power amplification module, connected to the acousto-optic modulator, for amplifying the radio frequency signal to drive the acousto-optic modulator; A timing control optical path includes a laser and the acousto-optic modulator, wherein the laser output by the laser is tuned and controlled by the acousto-optic modulator to generate multiple target laser beams suitable for the quantum transition; The multiple target laser beams include Doppler-assisted cooling light, Doppler cooling light, EIT cooling driving light and EIT cooling detection 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 diffraction light of the first acousto-optic modulator is output to the first coupler to form the Doppler-assisted cooling light.

2. The timing control system according to claim 1, characterized in that: The AOM also includes a second AOM, the +1st order diffraction light of the first AOM is output to the second AOM, and the -1st order diffraction light of the second AOM 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 0th order diffraction light of the second AOM is output to the third AOM; the +1st order diffraction light of the third AOM is output to the third coupler to form the EIT cooling driving light; The 0th order diffraction light of the third AOM is output to the fourth AOM; the +1st order diffraction light of the fourth AOM is output to the fourth coupler to form the EIT cooling detection light.

4. The timing control system according to claim 1, characterized in that: The radio frequency microwave coaxial switch module includes a plurality of switch units, each of which 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 RF signal source module for inputting the RF signal, and the second input channel is vacant; or the first input channel is vacant, and the second input channel is connected to the RF signal source module for inputting the RF signal.

6. The timing control system according to claim 4, characterized in that: Each of the switch units further comprises a hexagonal switch and an indicator light, wherein the hexagonal switch is used to switch the working mode of the switch unit, wherein the working modes comprise 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 also includes a wavelength meter for measuring the frequency of the laser; and A frequency stabilizing optical path, wherein the frequency stabilizing optical path adopts an FP optical cavity and is used to stabilize 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, each of which 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.

Images