A nickel highly ionized ion optical clock and implementation method

Abstract

The present invention discloses a nickel highly ionized ion optical clock and a method for realizing the nickel highly ionized ion optical clock. 12+ As the reference system of optical clock, highly ionized ions have the characteristics of anti-interference ability and measurement accuracy superior to the current traditional low-valent ion optical clock. 12+ Highly ionized ions have two transition spectral lines at 498nm and 511nm, which can be used as optical clock transitions. The use of 498nm laser and 511nm laser can realize the output of two clock signals on an ion reference system and can verify each other. The frequency calibration performed by the two laser frequency values ​​can timely detect operational problems when the ratio suddenly changes, avoiding the problem of single-frequency optical clock being unable to detect problems in time when the signal reference deviates from the coordinated time during operation and outputting the wrong clock signal, thereby improving the stability of the optical clock output.

Description

Technical Field

[0001] The present invention belongs to the technical field of ion optical clocks, and in particular relates to a nickel highly ionized ion optical clock, and also relates to a method for realizing a nickel highly ionized ion optical clock, which is applicable to the field of highly ionized ion optical clocks. Background Art

[0002] Since its invention, atomic clocks have been the cornerstone of time and frequency standards. Traditional atomic clocks, particularly those based on microwave transitions in cesium and rubidium atoms, have been widely used in a variety of fields, such as satellite navigation, communication networks, and fundamental physics research. However, with the increasing demand for time precision, especially in navigation, precision measurement, gravitational wave detection, and the testing of fundamental physical constants, the accuracy and stability of microwave atomic clocks can no longer meet certain cutting-edge requirements. Therefore, optical clocks (atomic clocks based on optical frequencies) have become a hot topic in current scientific research and technological development.

[0003] Optical clocks achieve high theoretical accuracy and stability by locking the laser frequency to the electronic transition frequency of atoms or ions in the optical band. Optical clocks based on single ions, in particular, offer greater measurement stability and frequency accuracy due to their reduced susceptibility to external interference. Currently, the most representative ion optical clocks include those based on calcium, aluminum, and ytterbium ions. These low-ionization states can be stably stored in a vacuum environment, and high-precision time and frequency output can be achieved through laser detection and locking the laser to their transition frequency.

[0004] However, with the advancement of technology, traditional optical clocks with low-ionization ions have limitations in certain complex environments (such as strong magnetic fields and high energy). Therefore, optical clocks based on highly-ionized ions have become an important research direction for next-generation time and frequency standards. Highly-ionized ions are insensitive to the external environment and sensitive to changes in physical constants, thus theoretically providing higher anti-interference capabilities and measurement accuracy. This opens up new possibilities for applications in complex physical environments and extremely high-precision research, such as deep space exploration, gravitational wave detection, and fundamental research in quantum physics.

[0005] Currently, research on highly ionized ion optical clocks is still in its infancy and faces numerous technical challenges. For example, there are no highly ionized ion optical clocks with uncertainty indicators reaching or exceeding the E-18 level, nor are there any highly ionized ion optical clocks capable of simultaneously outputting two clock signals. Furthermore, when using a single clock for clock signal output, without real-time calibration from an external clock reference, it is impossible to self-determine the health of the optical clock. Summary of the Invention

[0006] The purpose of the present invention is to address the above-mentioned problems existing in the prior art and to provide a nickel highly ionized ion optical clock and a method for realizing the nickel highly ionized ion optical clock.

[0007] The above-mentioned purpose of the present invention is achieved by the following technical means:

[0008] A nickel highly ionized ion optical clock includes an optical clock system and an FPGA control system. The optical clock system includes a low-temperature ion trap system, a highly ionized ion source, an ion beam line system, an ultraviolet fluorescence collection system, a laser modulation system, a servo feedback circuit, an optical frequency comb, and a clock signal output system. The highly ionized ion source outputs a pulsed beam of nickel highly ionized ions to the ion beam line system, and the ion beam line system screens out Ni 12+ The pulsed beam of ions is collimated and decelerated and then output to the low-temperature ion trap system, which traps Ni 12+ ions, low-temperature ion trap systems also prepare and trap Be + ions, the laser modulation system outputs the swept laser to the low temperature ion trap system, and Ni 12+ ions are excited to an excited state, Ni 12+ Ions transmit external state information to Be + ion, Be + The ions emit a 313nm fluorescence signal, and the ultraviolet fluorescence collection system collects Be + ions emit a 313 nm fluorescence signal to obtain Ni 12+ The spectral line shape of the ion transition is output to the servo feedback circuit, which calculates the Ni 12+ The spectral line center value of the ion transition spectrum line type, the servo feedback circuit outputs an error signal to the laser modulation system according to the spectral line center value, and the laser modulation system shifts the output laser frequency according to the error signal, so that the laser frequency after frequency shift is locked to Ni 12+ At the center value of the spectral line of ion transition, the laser modulation system outputs the locked laser to the optical frequency comb, the optical frequency comb measures the laser frequency of the locked laser, the optical frequency comb outputs the measured laser frequency to the FPGA control system, the FPGA control system outputs the clock signal to the clock signal output system, the clock signal output system outputs the clock signal, and the FPGA control system is also connected to the low-temperature ion trap system, ion beam line system, ultraviolet fluorescence collection system, laser modulation system, optical frequency comb, and clock signal output system through timing control signal lines.

[0009] As mentioned above, the optical clock system also includes a 313nm Doppler cooling laser system, a 313nm pumping laser system, and a 313nm Raman sideband cooling laser system. The 313nm Doppler cooling laser system and the 313nm pumping laser system output 313nm Doppler cooling laser and 313nm pumping laser to the low temperature ion trap system to generate Be. + Ions undergo Doppler cooling, Ni 12+ The ions are cooperatively cooled; the 313nm Raman sideband cooling laser system outputs 313nm Raman sideband cooling laser to the low temperature ion trap system to cool the Be after Doppler + ions undergo Raman sideband cooling, Ni 12+ The ions are collaboratively cooled to the vibrational quantum ground state; the FPGA control system is also connected to the 313nm Doppler cooling laser system, 313nm back-pumping laser system, and 313nm Raman sideband cooling laser system through timing control signal lines.

[0010] As described above, the laser modulation system includes a first laser modulation module, which includes a first acousto-optic modulator and a 498nm narrow-linewidth laser. The 498nm narrow-linewidth laser outputs a 498nm narrow-linewidth laser to the laser input end of the first acousto-optic modulator. The servo feedback circuit outputs an error signal to the modulation input end of the first acousto-optic modulator. The laser output end of the first acousto-optic modulator outputs a 498nm narrow-linewidth swept laser or a 498nm narrow-linewidth frequency-shifted laser. The FPGA control system is also connected to the first acousto-optic modulator and the 498nm narrow-linewidth laser via a timing control signal line. When the first acousto-optic modulator and the 498nm narrow-linewidth laser are used, the FPGA control system outputs a first clock signal to the clock signal output system, and the clock signal output system outputs the first clock signal.

[0011] As described above, the laser modulation system also includes a second laser modulation module, which includes a second acousto-optic modulator and a 511nm narrow-linewidth laser. The 511nm narrow-linewidth laser outputs a 511nm narrow-linewidth laser to the laser input end of the second acousto-optic modulator. The servo feedback circuit outputs an error signal to the modulation input end of the second acousto-optic modulator. The laser output end of the second acousto-optic modulator outputs a 511nm narrow-linewidth swept laser or a 511nm narrow-linewidth frequency-shifted laser. The FPGA control system is also connected to the second acousto-optic modulator and the 511nm narrow-linewidth laser through a timing control signal line. When the second acousto-optic modulator and the 511nm narrow-linewidth laser are used, the FPGA control system outputs a second clock signal to the clock signal output system, and the clock signal output system outputs the second clock signal.

[0012] A method for realizing a nickel highly ionized ion optical clock, using the nickel highly ionized ion optical clock as described above, comprises the following steps:

[0013] Step S1: FPGA control system starts the low temperature ion trap system to prepare and trap Be + ion;

[0014] Step S2: The FPGA control system starts the 313nm Doppler cooling laser system and the 313nm pumping laser system to generate Be + The ions undergo Doppler cooling;

[0015] Step S3: The highly ionized ion source generates a pulse beam of nickel highly ionized ions, and the FPGA control system starts the ion beam line system to screen out Ni 12+ The pulsed beam of ions is collimated and decelerated and then output to the low-temperature ion trap system, which traps Ni 12+ ions, Ni 12+ ions are Be + Ion cooperative cooling;

[0016] Step S4: The FPGA control system starts the 313nm Raman sideband cooling laser system to cool the Be after Doppler cooling. + ions undergo Raman sideband cooling, Ni 12+ ions are Be + The ions are cooperatively cooled to a vibrational quantum ground state;

[0017] Step S5: The FPGA control system turns on the 498nm narrow linewidth laser generated by the 498nm narrow linewidth laser system and performs frequency shifting through the first acousto-optic modulator. The frequency-shifted 498nm narrow linewidth laser acts on the Ni in the vibration quantum ground state. 12+ ions, Ni 12+ ions are excited to the first excited state, Ni 12+ Ions transmit external state information to Be + ion, Be + The ions emit a 313 nm fluorescence signal;

[0018] Step S6: The FPGA control system starts the ultraviolet fluorescence collection system to detect and collect Be + The ion emits a 313nm fluorescence signal, and outputs the 313nm fluorescence signal to the servo feedback circuit;

[0019] Step S7: The FPGA control system controls the first acousto-optic modulator to sweep the 498nm narrow linewidth laser. The first acousto-optic modulator outputs the swept laser to the low-temperature ion trap system, and the ultraviolet fluorescence collection system synchronously detects and collects Be + The 313nm fluorescence signal emitted by the ion was obtained by Ni 12+ The spectral line shape of the ion's 498 nm transition;

[0020] Step S8, the ultraviolet fluorescence collection system collects Ni12+ The spectral line shape of the ion's 498nm transition is transmitted to the servo feedback circuit, which calculates Ni 12+ The servo feedback circuit calculates the deviation of the 313nm fluorescence signal from Ni based on the 313nm fluorescence signal in step S5. 12+ The error signal is fed back to the first acousto-optic modulator based on the center value of the 498nm transition spectrum of the ion. The acousto-optic modulator shifts the frequency of the 498nm narrow linewidth laser according to the error signal and locks the laser frequency of the 498nm narrow linewidth laser to Ni 12+ The center value of the ion's 498nm transition line;

[0021] Step S9: The first acousto-optic modulator outputs the 498nm narrow-linewidth laser light after the laser frequency is locked to the optical frequency comb for beat frequency, measures the laser frequency value of the 498nm narrow-linewidth laser light after the laser frequency is locked, and outputs it to the FPGA control system. The FPGA control system outputs a first clock signal to the clock signal output system, and the clock signal output system outputs the first clock signal.

[0022] Step S10: Setting an initial clock reference. The FPGA control system controls the optical clock system according to the initial clock reference to cycle steps S2 to S9 ten times in a set period.

[0023] Step S11: The FPGA control system switches the 498nm narrow-linewidth laser system to a 511nm narrow-linewidth laser system, switches the first acousto-optic modulator to a second acousto-optic modulator, the 511nm narrow-linewidth laser system generates a 511nm narrow-linewidth laser, and the second acousto-optic modulator performs frequency shifting and frequency sweeping on the 511nm narrow-linewidth laser, and repeats steps S1 to S10.

[0024] Step S12: Repeat steps S1 to S11. The clock signal output system alternately outputs the first clock signal and the second clock signal. The first clock signal and the second clock signal are mutually verified.

[0025] As described above, step S11 specifically includes the following process: the FPGA control system switches the 498nm narrow linewidth laser system to the 511nm narrow linewidth laser system, switches the first acousto-optic modulator to the second acousto-optic modulator, the 511nm narrow linewidth laser system generates a 511nm narrow linewidth laser, and the second acousto-optic modulator shifts and sweeps the 511nm narrow linewidth laser, repeats steps S1 to S5, and switches Ni 12+ ions are excited to the second excited state; steps S6 and S7 are repeated, and the ultraviolet fluorescence collection system obtains Ni 12+ Repeat step S7, and the servo feedback circuit calculates the Ni 12+The acousto-optic modulator locks the laser frequency of the 511 nm narrow linewidth laser to the center value of the 511 nm transition of Ni 12+ The center value of the spectral line of the 511nm transition of the ion; repeat steps S8 and S9, the FPGA control system outputs a second clock signal to the clock signal output system, and the clock signal output system outputs a second clock signal; repeat step S10, the FPGA control system uses the first clock signal as the clock reference to control the optical clock system to set the period cycle ten times.

[0026] When step S10 is executed for the first time, the FPGA control system outputs a first clock signal using the initial clock reference as the clock reference, and each subsequent output clock signal uses the previously output clock signal as the clock reference.

[0027] In step S11 as described above, the first clock signal and the second clock signal are mutually verified in the following manner:

[0028] The FPGA control system records the laser frequency value f1 of the locked 498nm narrow-linewidth laser and the laser frequency value f2 of the locked 511nm narrow-linewidth laser, respectively, and obtains the initial ratio R0 of f1 and f2 based on the laser frequency value f1 and laser frequency value f2 recorded for the first time. After that, the ratio R of the new f1 and the new f2 is calculated each time a new f2 is recorded, and checks whether R is equal to R0. If R is equal to R0, the verification is normal; if R is not equal to R0, the verification is faulty.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] (1) Using Ni 12+ As the reference system of optical clock, highly ionized ions have the characteristics of anti-interference ability and measurement accuracy superior to the current traditional low-valent ion optical clock. 12+ Highly ionized ions have two transition spectral lines at 498nm and 511nm, which can be used as optical clock transitions. The use of 498nm laser and 511nm laser can realize the output of two clock signals on an ion reference system and can verify each other. The frequency calibration performed by the two laser frequency values ​​can timely detect operational problems when the ratio suddenly changes, avoiding the problem of single-frequency optical clock being unable to detect problems in time when the signal reference deviates from the coordinated time during operation and outputting the wrong clock signal, thereby improving the stability of the optical clock output.

[0031] (2) Ni of the present invention 12+ The quality factor of the 498nm transition of the ion reaches 1.1×10 16 , based on Ni 12+ The uncertainty of the first clock signal output of the 498nm transition of the ion can be better than 5×10 -19, breaking through the highest level of existing optical clock uncertainty.

[0032] (3) In the present invention, highly ionized Ni is used for the first time. 12+ As an optical clock reference system, the dual clock transition consisting of 498nm clock transition and 511nm clock transition was selected to simultaneously realize two clock reference signals, which was the first implementation. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a structural schematic diagram of the device of the present invention;

[0034] Figure 2 Schematic diagram of alternately outputting and mutually verifying a first clock signal and a second clock signal in embodiment 2 of the present invention;

[0035] Reference numerals and corresponding component names:

[0036] 1—Cryogenic ion trap system; 2—Highly ionized ion source; 3—Ion beamline system; 4—Ultraviolet fluorescence collection system; 5—Servo feedback circuit; 6—First acousto-optic modulator; 7—498nm narrow-linewidth laser; 8—Second acousto-optic modulator; 9—511nm narrow-linewidth laser; 10—Optical frequency comb; 11—Clock signal output system; 12—FPGA control system; 13—313nm Doppler cooling laser system; 14—313nm pumping laser system; 15—313nm Raman sideband cooling laser system; 16—First clock signal; 17—Second clock signal. DETAILED DESCRIPTION

[0037] In order to facilitate those skilled in the art to understand and implement the present invention, the present invention is further described in detail below with reference to the embodiments. The embodiments described herein are only used to illustrate and explain the present invention and are not intended to limit the present invention.

[0038] Example 1:

[0039] A nickel highly ionized ion optical clock, comprising an optical clock system and an FPGA control system 12, wherein the optical clock system comprises a low-temperature ion trap system 1, a highly ionized ion source 2, and an ion beam line system 3, wherein the highly ionized ion source 2 prepares and generates nickel highly ionized ions, and the nickel highly ionized ions drawn from the highly ionized ion source 2 form a pulse beam, which is output to the ion beam line system 3, and the ion beam line system 3 screens out Ni 12+ The pulsed beam of ions is collimated and decelerated and then output to the low-temperature ion trap system 1, which is used to trap Ni 12+ ions, low temperature ion trap system 1 is also prepared and trapped for collaborative cooling of Ni 12+ Ionic Be + ion;

[0040] The optical clock system also includes an ultraviolet fluorescence collection system 4, a laser modulation system, and a servo feedback circuit 5. The laser modulation system outputs a frequency-sweeping laser to the low-temperature ion trap system 1, which transfers Ni 12+ ions are excited to an excited state, Ni 12+ Ions transmit external state information to Be + ion, Be + The ions emit a 313 nm fluorescence signal, and the UV fluorescence collection system 4 collects Be + The 313nm fluorescence signal emitted by the ion can be used to determine the Ni 12+ Whether the ions are successfully excited and Ni 12+ The spectral line shape of the ion transition is output to the servo feedback circuit 5, which calculates the Ni 12+ The spectral line center value of the ion transition line type, the servo feedback circuit 5 outputs an error signal to the laser modulation system according to the spectral line center value, and the laser modulation system shifts the output laser frequency according to the error signal, so that the laser frequency after frequency shift is locked to Ni 12+ At the center value of the spectral line of ion transition, due to Ni 12+ The center value of the transition spectrum of the ion is inherently constant, so when the 313nm fluorescence signal collected by the ultraviolet fluorescence is always at Ni 12+ When the center value of the transition spectrum line of the ion is 0.001, it indicates that the laser frequency output by the laser modulation system is completely locked to the Ni 12+ The center value of the ion's transition spectrum.

[0041] The optical clock system also includes an optical frequency comb 10 and a clock signal output system 11. The laser modulation system outputs the locked laser light to the optical frequency comb 10. The optical frequency comb 10 measures the laser frequency of the locked laser light. The optical frequency comb 10 outputs the measured laser frequency to the FPGA control system 12. The FPGA control system 12 outputs a clock signal to the clock signal output system 11. The clock signal output system 11 outputs the clock signal.

[0042] The optical clock system also includes a 313nm Doppler cooling laser system 13, a 313nm pumping laser system 14, and a 313nm Raman sideband cooling laser system 15. The 313nm Doppler cooling laser system 13 and the 313nm pumping laser system 14 output 313nm Doppler cooling laser and 313nm pumping laser to the low temperature ion trap system 1 for Be + Ions undergo Doppler cooling, Ni 12+ The ions are cooperatively cooled; the 313nm Raman sideband cooling laser system 15 outputs 313nm Raman sideband cooling laser to the low temperature ion trap system 1 to cool the Be after Doppler+ ions undergo Raman sideband cooling, Ni 12+ The ions are collaboratively cooled to the vibrational quantum ground state; the FPGA control system 12 is also connected to the 313nm Doppler cooling laser system 13, the 313nm back-pumping laser system 14, and the 313nm Raman sideband cooling laser system 15 through timing control signal lines.

[0043] In addition, the FPGA control system 12 is used to control the switching timing of each module of the optical clock system. The FPGA control system 12 is also connected to the low-temperature ion trap system 1, the ion beam line system 3, the ultraviolet fluorescence collection system 4, the laser modulation system, the optical frequency comb 10, and the clock signal output system 11 through timing control signal lines.

[0044] The laser modulation system includes two laser modulation modules, namely a first laser modulation module and a second laser modulation module. The first laser modulation module includes a first acousto-optic modulator 6 and a 498nm narrow-linewidth laser 7. The 498nm narrow-linewidth laser 7 outputs a 498nm narrow-linewidth laser to the laser input end of the first acousto-optic modulator 6. The servo feedback circuit 5 outputs an error signal to the modulation input end of the first acousto-optic modulator 6. The laser output end of the first acousto-optic modulator 6 outputs a 498nm narrow-linewidth swept laser or a 498nm narrow-linewidth frequency-shifted laser. The FPGA control system 12 is also connected to the first acousto-optic modulator 6 and the 498nm narrow-linewidth laser 7 via a timing control signal line.

[0045] The second laser modulation module includes a second acousto-optic modulator 8 and a 511nm narrow-linewidth laser 9. The 511nm narrow-linewidth laser 9 outputs a 511nm narrow-linewidth laser to the laser input end of the second acousto-optic modulator 8. The servo feedback circuit 5 outputs an error signal to the modulation input end of the second acousto-optic modulator 8. The laser output end of the second acousto-optic modulator 8 outputs a 511nm narrow-linewidth swept laser or a 511nm narrow-linewidth frequency-shifted laser. The FPGA control system 12 is also connected to the second acousto-optic modulator 8 and the 511nm narrow-linewidth laser 9 through a timing control signal line.

[0046] When the first acousto-optic modulator 6 and the 498 nm narrow-linewidth laser 7 are used, the FPGA control system 12 outputs the first clock signal 16 to the clock signal output system 11, and the clock signal output system 11 outputs the first clock signal 16. When the second acousto-optic modulator 8 and the 511 nm narrow-linewidth laser 9 are used, the FPGA control system 12 outputs the second clock signal 17 to the clock signal output system 11, and the clock signal output system 11 outputs the second clock signal 17.

[0047] In the present invention, the ions generated by the highly ionized state ion source 2 depend on the parameters of the placed atomic target and the ion source, and can simultaneously generate highly ionized state ions of different types with different valence states.

[0048] In the present invention, Ni 12+ The screening, collimation and deceleration of ions in the highly ionized ion beamline system 3 are achieved by real-time control of the voltage values ​​of the electrodes involved and the switching timing of the voltage values ​​by FPGA. 12+ The purity of ions can reach over 90%.

[0049] In the present invention, the 313nm Doppler cooling laser system 13, the 313nm pumping laser system 14, and the 313nm Raman sideband cooling laser system 15 all include components for polarization adjustment, laser frequency adjustment, and locking of the output laser, such as an acousto-optic modulator, a polarizer, a wave plate, and a laser output switch, and are all controlled in real time by the FPGA control system 12.

[0050] Example 2:

[0051] A method for realizing a nickel highly ionized ion optical clock, using the nickel highly ionized ion optical clock described in Example 1 above, comprises the following steps:

[0052] Step S1, FPGA control system 12 starts the low temperature ion trap system 1 to prepare and trap Ni 12+ Ionic Be + ion;

[0053] Step S2: The FPGA control system 12 turns on the 313nm Doppler cooling laser system 13 and the 313nm pumping laser system. The 313nm Doppler cooling laser system 13 and the 313nm pumping laser system 14 generate 313nm Doppler cooling laser and 313nm pumping laser respectively. The 313nm Doppler cooling laser and the 313nm pumping laser simultaneously act on the Be + ions, realize Be + Doppler cooling;

[0054] Step S3: The highly ionized ion source 2 generates a pulse beam of nickel highly ionized ions and outputs it to the ion beam line system 3. The FPGA control system 12 turns on the ion beam line system 3, and the ion beam line system 3 selects Ni 12+ The pulsed beam of ions is collimated and decelerated and then output to the low-temperature ion trap system 1, which traps Ni 12+ Ni in a pulsed beam of ions 12+ ions, Ni trapped in a cryogenic ion trap system 1 12+ Be ions are Doppler cooled + The ions cool cooperatively due to the Coulombic interaction between them;

[0055] Step S4: The FPGA control system 12 turns on the 313nm Raman sideband cooling laser system 15. The 313nm Raman sideband cooling laser system 15 generates a 313nm Raman sideband cooling laser. The 313nm Raman sideband cooling laser acts on the Be + ions, realize Be + The Raman sidebands of the ions are cooled, and Ni 12+ ions are Be + The ions are cooperatively cooled to a vibrational quantum ground state;

[0056] Step S5: The FPGA control system 12 turns on the 498nm narrow linewidth laser generated by the 498nm narrow linewidth laser 7 system. The 498nm narrow linewidth laser is output to the first acousto-optic modulator 6. The first acousto-optic modulator 6 applies the 498nm narrow linewidth laser to the Ni in the vibration quantum ground state. 12+ ions, Ni 12+ The ion is excited to the first excited state (specifically the excited state 3s 2 3p 4 3 P0), Ni 12+ Ions transmit external state information to Be + ion, Be + The ions emit a 313 nm fluorescence signal;

[0057] Step S6: FPGA control system 12 starts ultraviolet fluorescence collection system 4 to detect and collect Be + The 313nm fluorescence signal emitted by the ions is output to the servo feedback circuit 5;

[0058] Step S7, the FPGA control system 12 controls the first acousto-optic modulator 6 to sweep the 498nm narrow linewidth laser, and the first acousto-optic modulator 6 outputs the swept laser to the low-temperature ion trap system 1, and the ultraviolet fluorescence collection system 4 synchronously detects and collects Be + The 313nm fluorescence signal emitted by the ion was obtained by Ni 12+ The spectral line shape of the ion's 498 nm transition;

[0059] Step S8, the ultraviolet fluorescence collection system 4 collects Ni 12+ The spectral line shape of the ion's 498nm transition is transmitted to the servo feedback circuit 5, which calculates Ni 12+ The servo feedback circuit 5 calculates the deviation of the 313nm fluorescence signal from Ni based on the 313nm fluorescence signal in step S5. 12+The center value of the 498nm transition spectrum of the ion is measured, and the error signal is fed back to the first acousto-optic modulator 6. The acousto-optic modulator shifts the frequency of the 498nm narrow linewidth laser according to the error signal, and locks the laser frequency of the 498nm narrow linewidth laser to Ni 12+ The center value of the 498nm transition line of the ion, at this time Be + The ion emits the largest fluorescence signal;

[0060] Step S9: The first acousto-optic modulator 6 outputs the 498 nm narrow linewidth laser light after the laser frequency is locked to the optical frequency comb 10 for beat frequency, measures the laser frequency value of the 498 nm narrow linewidth laser light after the laser frequency is locked, and outputs it to the FPGA control system 12. The FPGA control system 12 outputs the first clock signal 16 to the clock signal output system 11, and the clock signal output system 11 outputs the first clock signal 16.

[0061] Step S10: Set an initial clock reference (such as Coordinated Universal Time (UTC) or National Atomic Time Standard (UTC(NIM))). The FPGA control system 12 controls the optical clock system to repeat steps S2 to S9 ten times with a period of 100 ms based on the initial clock reference.

[0062] Step S11, the FPGA control system 12 switches the 498nm narrow linewidth laser 7 system to the 511nm narrow linewidth laser 9 system, switches the first acousto-optic modulator 6 to the second acousto-optic modulator 8, the 511nm narrow linewidth laser 9 system generates a 511nm narrow linewidth laser, and the second acousto-optic modulator 8 performs frequency shifting and frequency sweeping on the 511nm narrow linewidth laser, repeating steps S1 to S5, and Ni 12+ The ion is excited to the second excited state (specifically the excited state 3s 2 3p 4 3 Repeat steps S6 and S7, and the ultraviolet fluorescence collection system 4 obtains Ni 12+ Repeat step S7, the servo feedback circuit 5 calculates Ni 12+ The acousto-optic modulator locks the laser frequency of the 511 nm narrow linewidth laser to the center value of the 511 nm transition of Ni 12+ Repeat steps S8 and S9, the FPGA control system 12 outputs the second clock signal 17 to the clock signal output system 11, and the clock signal output system 11 outputs the second clock signal 17; repeat step S10, the FPGA control system 12 uses the first clock signal 16 as the clock reference to control the optical clock system for ten cycles of 100ms;

[0063] Step S12, repeating steps S1 to S11, the clock signal output system 11 alternately outputs the first clock signal 16 and the second clock signal 17, wherein when step S10 is repeated, the FPGA control system 12 outputs the first clock signal 16 with the initial clock reference as the clock reference when step S10 is performed for the first time, and each subsequent output of the clock signal uses the previously output clock signal as the clock reference;

[0064] The FPGA control system 12 also records the laser frequency value f1 of the locked 498nm narrow-linewidth laser and the laser frequency value f2 of the locked 511nm narrow-linewidth laser, and obtains the initial ratio R0 of f1 and f2 based on the laser frequency value f1 and the laser frequency value f2 recorded for the first time. After that, the ratio R of the new f1 and the new f2 is calculated each time a new f2 is recorded, and it is checked whether R is equal to R0. If R is equal to R0, the verification is normal; if R is not equal to R0, the verification is faulty, thereby realizing mutual verification of the first clock signal 16 and the second clock signal 17.

[0065] In this embodiment, the FPGA control system 12 continuously switches the first laser modulation module and the second laser modulation module at a switching frequency of 1s, so that the clock signal output system 11 continuously switches and outputs the first clock signal 16 and the second clock signal 17. The first clock signal 16 and the second clock signal 17 are output alternately with a period of 2s and checked with each other.

[0066] The present invention can ensure that there is a clock signal output in real time, and can timely detect operating problems through frequency calibration performed by two laser frequency values ​​(laser frequency value f1 and laser frequency value f2), thereby avoiding the problem that when a single-frequency optical clock deviates from the coordinated time during operation, problems cannot be discovered in time and the clock signal is output incorrectly.

[0067] The present invention adopts Ni 12+ As the reference system of optical clock, highly ionized ions have the characteristics of anti-interference ability and measurement accuracy superior to the current traditional low-valent ion optical clock. 12+ Highly ionized ions have two transition spectral lines at 498nm and 511nm, which can be used as optical clock transitions. Using 498nm laser and 511nm laser at the same time can realize the output of two clock signals on an ion reference system and can verify each other.

[0068] It should be noted that the embodiments described herein are merely illustrative of the spirit of the present invention. Persons skilled in the art may make various modifications, additions, or substitutions to the described embodiments without departing from the spirit of the present invention or exceeding the scope of the appended claims.

Claims

1. A nickel highly ionized ion optical clock, comprising an optical clock system and an FPGA control system (12), characterized in that: The optical clock system includes a low-temperature ion trap system (1), a highly ionized ion source (2), an ion beam line system (3), an ultraviolet fluorescence collection system (4), a laser modulation system, a servo feedback circuit (5), an optical frequency comb (10), and a clock signal output system (11). The highly ionized ion source (2) outputs a pulse beam of nickel highly ionized ions to the ion beam line system (3), and the ion beam line system (3) screens out Ni 12+ The pulsed beam of ions is collimated and decelerated and then output to the low temperature ion trap system (1), which traps Ni 12+ ions, low temperature ion trap system (1) also prepares and traps Be + ions, the laser modulation system outputs the swept laser to the low temperature ion trap system (1), and the Ni 12+ ions are excited to an excited state, Ni 12+ Ions transmit external state information to Be + ion, Be + The ions emit a 313nm fluorescence signal, and the ultraviolet fluorescence collection system (4) collects Be + ions emit a 313 nm fluorescence signal to obtain Ni 12+ The spectral line shape of the ion transition is output to the servo feedback circuit (5), which calculates Ni 12+ The spectral line center value of the ion transition spectrum line type, the servo feedback circuit (5) outputs an error signal to the laser modulation system according to the spectral line center value, and the laser modulation system shifts the output laser frequency according to the error signal, so that the laser frequency after frequency shift is locked to Ni 12+ At the center value of the spectral line of the ion transition, the laser modulation system outputs the locked laser to the optical frequency comb (10), the optical frequency comb (10) measures the laser frequency of the locked laser, the optical frequency comb (10) outputs the measured laser frequency to the FPGA control system (12), the FPGA control system (12) outputs a clock signal to the clock signal output system (11), the clock signal output system (11) outputs the clock signal, and the FPGA control system (12) is also connected to the low-temperature ion trap system (1), the ion beam line system (3), the ultraviolet fluorescence collection system (4), the laser modulation system, the optical frequency comb (10), and the clock signal output system (11) through timing control signal lines.

2. A nickel highly ionized ion optical clock according to claim 1, characterized in that: The optical clock system further comprises a 313nm Doppler cooling laser system (13), a 313nm pumping laser system (14), and a 313nm Raman sideband cooling laser system (15). The 313nm Doppler cooling laser system (13) and the 313nm pumping laser system (14) respectively output 313nm Doppler cooling laser and 313nm pumping laser to the low temperature ion trap system (1) to generate Be. + Ions undergo Doppler cooling, Ni 12+ The ions are cooperatively cooled; the 313nm Raman sideband cooling laser system (15) outputs 313nm Raman sideband cooling laser to the low temperature ion trap system (1) to cool the Be after Doppler cooling. + ions undergo Raman sideband cooling, Ni 12+ The ions are collaboratively cooled to a vibration quantum ground state; the FPGA control system (12) is also connected to a 313nm Doppler cooling laser system (13), a 313nm back-pumping laser system (14), and a 313nm Raman sideband cooling laser system (15) through timing control signal lines.

3. A nickel highly ionized ion optical clock according to claim 2, characterized in that: The laser modulation system comprises a first laser modulation module, which comprises a first acousto-optic modulator (6) and a 498nm narrow linewidth laser (7). The 498nm narrow linewidth laser (7) outputs 498nm narrow linewidth laser light to the laser input end of the first acousto-optic modulator (6). The servo feedback circuit (5) outputs an error signal to the modulation input end of the first acousto-optic modulator (6). The laser output end of the first acousto-optic modulator (6) outputs 498nm narrow linewidth swept laser light or 498nm narrow linewidth frequency shifted laser light. The FPGA control system (12) is further connected to the first acousto-optic modulator (6) and the 498nm narrow linewidth laser (7) via a timing control signal line. When the first acousto-optic modulator (6) and the 498nm narrow linewidth laser (7) are used, the FPGA control system (12) outputs a first clock signal (16) to the clock signal output system (11), and the clock signal output system (11) outputs the first clock signal (16).

4. A nickel highly ionized ion optical clock according to claim 3, characterized in that: The laser modulation system further comprises a second laser modulation module, which comprises a second acousto-optic modulator (8) and a 511 nm narrow linewidth laser (9). The 511 nm narrow linewidth laser (9) outputs 511 nm narrow linewidth laser light to the laser input end of the second acousto-optic modulator (8). The servo feedback circuit (5) outputs an error signal to the modulation input end of the second acousto-optic modulator (8). The laser output end of the second acousto-optic modulator (8) outputs 511 nm narrow linewidth swept laser light or 511 nm narrow linewidth frequency shifted laser light. The FPGA control system (12) is further connected to the second acousto-optic modulator (8) and the 511 nm narrow linewidth laser (9) via a timing control signal line. When the second acousto-optic modulator (8) and the 511 nm narrow linewidth laser (9) are used, the FPGA control system (12) outputs a second clock signal (17) to the clock signal output system (11), and the clock signal output system (11) outputs the second clock signal (17).

5. A method for realizing a nickel highly ionized ion optical clock, using the nickel highly ionized ion optical clock according to claim 4, characterized in that: The following steps are involved: Step S1, FPGA control system (12) starts the low temperature ion trap system (1) to prepare and trap Be + ion; Step S2, the FPGA control system (12) turns on the 313nm Doppler cooling laser system (13) and the 313nm pumping laser system to + The ions undergo Doppler cooling; Step S3: The highly ionized ion source (2) generates a pulse beam of nickel highly ionized ions, and the FPGA control system (12) turns on the ion beam line system (3) to screen out Ni 12+ The pulsed beam of ions is collimated and decelerated and then output to the low temperature ion trap system (1), which traps Ni 12+ ions, Ni 12+ ions are Be + Ion cooperative cooling; Step S4, the FPGA control system (12) turns on the 313nm Raman sideband cooling laser system (15) to cool the Be after Doppler cooling. + ions undergo Raman sideband cooling, Ni 12+ ions are Be + The ions are cooperatively cooled to a vibrational quantum ground state; Step S5, the FPGA control system (12) turns on the 498nm narrow linewidth laser generated by the 498nm narrow linewidth laser (7) system and performs frequency shifting through the first acousto-optic modulator (6). The frequency-shifted 498nm narrow linewidth laser acts on the Ni in the vibration quantum ground state. 12+ ions, Ni 12+ ions are excited to the first excited state, Ni 12+ Ions transmit external state information to Be + ion, Be + The ions emit a 313 nm fluorescence signal; Step S6, the FPGA control system (12) turns on the ultraviolet fluorescence collection system (4) to detect and collect Be + The 313 nm fluorescence signal emitted by the ions is output to the servo feedback circuit (5); Step S7, the FPGA control system (12) controls the first acousto-optic modulator (6) to sweep the 498nm narrow linewidth laser, the first acousto-optic modulator (6) outputs the swept laser to the low-temperature ion trap system (1), and the ultraviolet fluorescence collection system (4) synchronously detects and collects Be + The 313nm fluorescence signal emitted by the ion was obtained by Ni 12+ The spectral line shape of the ion's 498 nm transition; Step S8, the ultraviolet fluorescence collection system (4) collects Ni 12+ The spectral line shape of the ion's 498nm transition is transmitted to the servo feedback circuit (5), which calculates Ni 12+ The servo feedback circuit (5) calculates the deviation of the 313nm fluorescence signal from Ni based on the 313nm fluorescence signal of step S5. 12+ The size of the spectral line center value of the 498nm transition of the ion is fed back to the first acousto-optic modulator (6), and the acousto-optic modulator shifts the frequency of the 498nm narrow linewidth laser according to the error signal, and locks the laser frequency of the 498nm narrow linewidth laser to Ni 12+ The center value of the ion's 498nm transition line; Step S9: The first acousto-optic modulator (6) outputs the 498nm narrow linewidth laser light after the laser frequency is locked to the optical frequency comb (10) for beat frequency, measures the laser frequency value of the 498nm narrow linewidth laser light after the laser frequency is locked, and outputs it to the FPGA control system (12); the FPGA control system (12) outputs the first clock signal (16) to the clock signal output system (11); and the clock signal output system (11) outputs the first clock signal (16); Step S10, setting an initial clock reference, the FPGA control system (12) controls the optical clock system according to the initial clock reference to cycle steps S2 to S9 ten times in a set period; Step S11: The FPGA control system (12) switches the 498 nm narrow linewidth laser (7) system to the 511 nm narrow linewidth laser (9) system, switches the first acousto-optic modulator (6) to the second acousto-optic modulator (8), the 511 nm narrow linewidth laser (9) system generates 511 nm narrow linewidth laser light, and the second acousto-optic modulator (8) performs frequency shifting and frequency sweeping on the 511 nm narrow linewidth laser light, and steps S1 to S10 are repeated; Step S12, repeating steps S1 to S11, the clock signal output system (11) alternately outputs the first clock signal (16) and the second clock signal (17), and the first clock signal (16) and the second clock signal (17) are mutually verified.

6. The method for realizing a nickel highly ionized ion optical clock according to claim 5, characterized in that: The step S11 specifically includes the following process: the FPGA control system (12) switches the 498nm narrow linewidth laser (7) system to the 511nm narrow linewidth laser (9) system, switches the first acousto-optic modulator (6) to the second acousto-optic modulator (8), the 511nm narrow linewidth laser (9) system generates 511nm narrow linewidth laser, and the second acousto-optic modulator (8) performs frequency shifting and frequency sweeping on the 511nm narrow linewidth laser, repeats steps S1 to S5, and Ni 12+ The ion is excited to the second excited state; steps S6 and S7 are repeated, and the ultraviolet fluorescence collection system (4) obtains Ni 12+ Repeat step S7, the servo feedback circuit (5) calculates Ni 12+ The acousto-optic modulator locks the laser frequency of the 511 nm narrow linewidth laser to the center value of the 511 nm transition of Ni 12+ The spectral line center value of the 511nm transition of the ion; repeating steps S8 and S9, the FPGA control system (12) outputs the second clock signal (17) to the clock signal output system (11), and the clock signal output system (11) outputs the second clock signal (17); repeating step S10, the FPGA control system (12) uses the first clock signal (16) as a clock reference to control the optical clock system to set the cycle for ten times.

7. The method for realizing a nickel highly ionized ion optical clock according to claim 6, characterized in that: When step S10 is executed for the first time, the FPGA control system (12) outputs a first clock signal (16) using the initial clock reference as the clock reference, and each subsequent output of the clock signal uses the previously output clock signal as the clock reference.

8. The method for realizing a nickel highly ionized ion optical clock according to claim 7, characterized in that: In step S11, the first clock signal (16) and the second clock signal (17) are mutually verified in the following manner: The FPGA control system (12) records the laser frequency value f1 of the locked 498nm narrow linewidth laser and the laser frequency value f2 of the locked 511nm narrow linewidth laser respectively, and obtains the initial ratio R0 of f1 and f2 based on the laser frequency value f1 and the laser frequency value f2 recorded for the first time. After that, the ratio R of the new f1 and the new f2 is calculated each time a new f2 is recorded, and checks whether R is equal to R0. If R is equal to R0, the verification is normal; if R is not equal to R0, the verification is faulty.

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