Method and apparatus for preparing a magneto-optical trap by switching frequencies of a single laser

Abstract

The present invention provides a method and device for preparing a magneto-optical trap by switching the frequency of a single laser. After locking the laser frequency of a single laser to a preset transition frequency, the laser is frequency-shifted and adjusted to a frequency corresponding to cooling light to obtain cooling light, thereby cooling the preset atoms. Then, after locking the laser frequency of the same laser to another preset transition frequency, the laser is frequency-shifted and adjusted to a frequency corresponding to return pumping light to obtain return pumping light, thereby maintaining the cooling of the preset atoms. By adjusting the frequency of the same laser, cooling light and return pumping light are alternately emitted within a preset period to ensure the cooling effect on the preset atoms.

Description

Technical Field

[0001] The present invention relates to the field of neutral atom quantum computing, and in particular to a method and device for preparing a magneto-optical trap by switching the frequency of a single laser. Background Art

[0002] Neutral atom quantum computing has broad application prospects in numerous fields, including quantum computing, basic scientific research, national defense, and information transmission and storage. A magneto-optical trap (MOT) is a technique for cooling trapped atoms using a magnetic field and several opposing laser beams. To capture atoms in a MOT, cooling light and pumping light of different frequencies are required. Existing technology typically uses multiple lasers to emit cooling light and pumping light separately, but this requires the installation of more lasers in the device, making the system more complex and costly.

[0003] In view of this, overcoming the defects of the prior art is an urgent problem to be solved in this technical field. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to complete the emission of cooling light and return pump light by installing only one laser during the process of capturing atoms in a magneto-optical trap.

[0005] The present invention adopts the following technical solutions:

[0006] In a first aspect, a method for preparing a magneto-optical trap by switching the frequency of a single laser comprises:

[0007] The laser frequency of the laser is locked to the first transition frequency, the laser emits laser light and after frequency shifting, the laser frequency is adjusted to the first preset frequency to obtain cooling light, wherein the cooling light causes energy level transition of the first preset atom, thereby cooling the first preset atom;

[0008] Stabilizing the laser frequency of the same laser to the cross peak of the second transition frequency and the third transition frequency, and after the laser undergoes frequency shifting, adjusting the laser frequency to a second preset frequency to generate back-pumping light. The back-pumping light re-pumps atoms that have exited the cyclic transition due to spontaneous emission back into the cyclic transition, thereby maintaining cooling of the first preset atoms.

[0009] By adjusting the laser frequency of the laser, cooling light and return pump light are emitted alternately within a preset period, thereby maintaining the cooling of the first preset atom.

[0010] Preferably, the laser is subjected to frequency shift, specifically comprising:

[0011] After the laser emits laser light, the laser light is frequency shifted by the AOM crystal.

[0012] Preferably, the preset period is the sum of the first duration of the laser being converted into cooling light after frequency shifting, the second duration of the cooling light, the third duration of the laser being converted into return pumping light after frequency shifting, and the fourth duration of the return pumping light.

[0013] Preferably, by adjusting the ratio between the second time duration and the fourth time duration, the duty ratio of the cooling light and the return pump light in the time sequence is adjusted, thereby adjusting the effect of cooling the trapped atomic clusters.

[0014] Preferably, the step of locking the laser frequency of the laser to the first transition frequency further comprises:

[0015] The laser frequency is adjusted to a third preset frequency to obtain detection light, and the detection light is used to detect the first preset atom.

[0016] Preferably, it also includes:

[0017] The laser emitted from the laser is amplified by a tapered amplifier to amplify the laser power, and then the laser is divided into a first laser beam and a second laser beam by a polarization beam splitter prism, wherein the first laser beam is used to cool and detect the first preset atom, and the second laser beam is used to cool and detect the second preset atom.

[0018] Preferably, the first preset atom is 87 Rb.

[0019] In a second aspect, a single laser switching frequency preparation magneto-optical trap device and a method for preparing a magneto-optical trap using the single laser switching frequency are provided, comprising: a vacuum chamber 3, a first optical path, a second optical path, and a third optical path, wherein:

[0020] The first optical path passes through the vacuum cavity 3 in the vertical direction, and the second optical path and the third optical path pass through the vacuum cavity 3 in the horizontal direction. The first optical path, the second optical path and the third optical path are sequentially provided with an optical fiber output end 1 and a first quarter wave plate 2 on one side of the vacuum cavity 3, and a second quarter wave plate 4 and a reflector 5 are sequentially provided on the other side of the vacuum cavity 3 to convert the cooling light obtained after the frequency shift into a pair of σ + -σ - Cooling light;

[0021] Three pairs of σ + -σ - The cooling light intersects in the vacuum chamber 3 to cool and trap atoms.

[0022] Preferably, the first optical path, the second optical path and the third optical path are sequentially provided with an optical fiber output end 1 and a first quarter wave plate 2 on one side of the vacuum cavity 3, and a second quarter wave plate 4 and a reflector 5 are sequentially provided on the other side of the vacuum cavity 3, for converting the cooling light obtained after the frequency shift into a pair of σ + -σ - Cooling light, specifically including:

[0023] The cooling light or the pumped back light enters the optical path from the optical fiber output end 1, and after passing through the first quarter wave plate 2, the cooling light forms σ + The light enters the vacuum chamber 3 and then passes through the second quarter wave plate 4 and the reflector 5 to form the same σ + σ relative to the light direction - light, thus forming a pair of σ + -σ - Cooling light.

[0024] Preferably, two anti-Helmholtz coils 6 are further provided on the first optical path, wherein one anti-Helmholtz coil 6 is provided between the vacuum cavity 3 and the first quarter wave plate 2, and the other anti-Helmholtz coil 6 is provided between the vacuum cavity 3 and the second quarter wave plate 4, and the two anti-Helmholtz coils 6 provide a four-level magnetic field for trapping atoms.

[0025] The present invention provides a method and device for preparing a magneto-optical trap by switching the frequency of a single laser. After locking the laser frequency of a single laser to a preset transition frequency, the laser is frequency-shifted and adjusted to a frequency corresponding to cooling light to obtain cooling light, thereby cooling the preset atoms. Then, after locking the laser frequency of the same laser to another preset transition frequency, the laser is frequency-shifted and adjusted to a frequency corresponding to return pumping light to obtain return pumping light, thereby maintaining the cooling of the preset atoms. By adjusting the frequency of the same laser, cooling light and return pumping light are alternately emitted within a preset period to ensure the cooling effect on the preset atoms. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] To more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments of the present invention. Obviously, the drawings described below are only some embodiments of the present invention. Those skilled in the art can also derive other drawings based on these drawings without inventive effort.

[0027] Figure 1 This is a flow chart of a method for preparing a magneto-optical trap by switching the frequency of a single laser provided by an embodiment of the present invention;

[0028] Figure 2This is an atomic energy level transition diagram of a method for preparing a magneto-optical trap by switching the frequency of a single laser provided by an embodiment of the present invention;

[0029] Figure 3 This is a frequency shift timing diagram of a method for preparing a magneto-optical trap by switching the frequency of a single laser provided by an embodiment of the present invention;

[0030] Figure 4 This is a duty cycle statistics table of a method for preparing a magneto-optical trap by switching the frequency of a single laser provided by an embodiment of the present invention;

[0031] Figure 5 This is a front view of a first optical path of a single laser frequency switching device for preparing a magneto-optical trap provided by an embodiment of the present invention;

[0032] Figure 6 1 is a top view of a second optical path and a third optical path of a single laser frequency switching device for preparing a magneto-optical trap provided by an embodiment of the present invention;

[0033] Wherein, the reference numerals in the accompanying drawings are as follows:

[0034] Optical fiber output end 1; first quarter wave plate 2; vacuum cavity 3; second quarter wave plate 4; reflector 5; anti-Helmholtz coil 6. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0036] In the description of the present invention, the terms "inside", "outside", "longitudinal", "lateral", "upper", "lower", "top", "bottom", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and do not require that the present invention must be constructed and operated in a specific orientation. Therefore, they should not be understood as limitations on the present invention.

[0037] In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0038] Embodiment 1:

[0039] Embodiment 1 of the present invention provides a method for preparing a magneto-optical trap by switching the frequency of a single laser;

[0040] like Figure 1 and Figure 2 As shown, the method flow is as follows:

[0041] In step 101, lock the laser frequency of the laser to the first transition frequency.

[0042] In this embodiment, the first transition frequency is the resonance transition peak of the energy level transition from |5S 1 / 2 , F = 2> to |5P 3 / 2 , F’ = 3>;

[0043] In this embodiment, the transition frequency refers to the resonance transition peak corresponding to different energy level transitions, including the first transition frequency, the second transition frequency and the third transition frequency in this embodiment.

[0044] In step 102, after the laser emitted by the laser passes through frequency shifting, adjust the laser frequency to the first preset frequency to obtain cooling light, and the cooling light realizes the cooling of the first preset atom through the energy level transition of the first preset atom;

[0045] In this embodiment, the energy level transition in the cooling of the first preset atom through the energy level transition of the first preset atom is from the energy level |5S 1 / 2 , F = 2> to the energy level |5P 3 / 2 , F’ = 3>, and the first preset atom is 87 Rb.

[0046] And in this embodiment, the frequency shifting is all realized through the AOM crystal.

[0047] The magneto-optical trap technology realizes the cooling and capture of atoms through the combined action of the radiation pressure of near-red detuned laser and the quadrupole magnetic field. In this embodiment, it is mainly applied to 87 Rb atoms, and 87 the cooling of Rb atoms is realized through the closed transition from |5S 1 / 2 , F = 2> to |5P 3 / 2 , F’ = 3>. The laser that realizes the above energy level transition is the cooling light. In this embodiment, the frequency of the cooling light is the detuning of -10 MHz from the transition frequency of |5S 1 / 2 , F = 2> to |5P 3 / 2 , F’ = 3>.

[0048] The first preset frequency in this embodiment is detuned by -10 MHz from the transition frequency of |5S 1 / 2 , F = 2> to |5P 3 / 2 , F’ = 3>.

[0049] In this embodiment, the laser frequency of the laser is frequency-shifted to the detuning of -10 MHz from the transition frequency of |5S 1 / 2 , F = 2> to |5P 3 / 2 , F’ = 3> to achieve the effect of cooling light.

[0050] In step 103, the laser of the same one is stabilized at the crossover peak of the second transition frequency and the third transition frequency.

[0051] In this embodiment, the second transition frequency is the resonance transition peak of the energy level transition from |5S 1 / 2 , F = 2> to |5P 3 / 2 , F' = 2>, and the third transition frequency is the resonance transition peak of the energy level transition from |5S 1 / 2 , F = 2> to |5P 3 / 2 , F' = 3>.

[0052] In step 104, after the laser is frequency-shifted, the laser frequency is adjusted to a second preset frequency to obtain a repumping light, and the repumping light repumps the atoms that have exited the cycling transition due to spontaneous emission back into the cycling transition, thereby maintaining the cooling of the first preset atoms.

[0053] Since when 87 Rb atoms are in the |5P 3 / 2 , F' = 3> state, the spontaneously emitted atoms will randomly transition to two ground state hyperfine levels of |5S 1 / 2 , F = 1> and |5S 1 / 2 , F = 2>, resulting in 87 a decrease in the cooling degree of Rb atoms and a decline in the cooling and trapping effects of the atoms. Therefore, a laser resonant with the transition from |5S 1 / 2 , F = 1> to |5P 3 / 2 , F' = 2> needs to be introduced. This laser makes the atoms that have exited the cycling transition due to spontaneous emission return to the cycling transition, thereby maintaining the cooling efficiency of the atoms. This laser is the repumping light.

[0054] The second preset frequency is resonant with the transition frequency from |5S 1 / 2 , F = 2> to |5S 3 / 2 , P' = 2> in this embodiment.

[0055] In this embodiment, the laser of the same laser is frequency-shifted to the transition frequency from |5S 1 / 2 , F = 2> to |5S 3 / 2 , P' = 2> to achieve the effect of the repumping light.

[0056] In step 105, by adjusting the frequency of the same laser, the cooling light and the repumping light are alternately emitted within a preset period, thereby maintaining the cooling of the first preset atoms.

[0057] Since only one laser is used to perform the functions of cooling light and repumping light in this embodiment, when the laser outputs as cooling light for a long time, a large number of atoms will exit the cyclic transition due to spontaneous emission, and the cooling effect gradually weakens as the time increases. When the laser outputs as repumping light for a long time, the atoms cannot be cooled and the operation of atomic capture cannot be performed. Therefore, it is necessary to shift the frequency of the laser alternately within a certain period and switch between cooling light and repumping light to improve the cooling effect on atoms.

[0058] In the prior art, generally multiple lasers are used to emit cooling light and repumping light respectively, but this requires installing more lasers correspondingly in the device, resulting in a more complex system and higher cost.

[0059] This embodiment provides a method for preparing a magneto-optical trap by switching the frequency of a single laser. After locking the laser frequency of a single laser to a preset transition frequency, the frequency of the laser is shifted to adjust to the frequency corresponding to the cooling light, and the cooling light is obtained to cool the preset atoms. Then, after locking the laser frequency of the same laser to another preset transition frequency, the frequency of the laser is shifted to adjust to the frequency corresponding to the repumping light, and the repumping light is obtained to maintain the cooling of the preset atoms. By adjusting the frequency of the same laser, the cooling light and the repumping light are alternately emitted within a preset period to ensure the cooling effect on the preset atoms.

[0060] Generally, in order to obtain cooling light or repumping light with a specific frequency for 87 Rb, the laser needs to be locked on the 87 preset transition spectral line of Rb atoms, and then the frequency of the laser is shifted by an AOM, that is, an acousto-optic modulator, to obtain laser with a specific frequency.

[0061] The laser used in this embodiment is a Vescent laser;

[0062] The laser emitted by the laser is amplified in power by a tapered amplifier, and then the laser is divided into a first laser beam and a second laser beam by a polarization beam splitter prism. The first laser beam is used to cool and detect the first preset atoms, and the second laser beam is used to cool and detect the second preset atoms.

[0063] In this embodiment, the second preset atom is 85 Rb.

[0064] First, lock the laser frequency of the laser to |5S 1 / 2 ,F = 2> to |5P 3 / 2, on the resonance transition peak of F’ = 3>, the laser emitted by the laser is amplified in power by a tapered amplifier. In this embodiment, the amplified output power is about 800 mW. Then the laser is divided into a first laser beam and a second laser beam by a polarization beam splitter prism, where the first laser beam is used for 87 cooling and detecting Rb, and the second laser beam is used for 85 cooling and detecting Rb. In this embodiment, only 87 Rb is discussed.

[0065] The laser emitted by the laser passes through the positive first-order frequency shift of the AOM crystal at 110 ± 0.1 MHz twice, and then passes through the negative first-order frequency shift of the AOM crystal at 115 ± 0.1 MHz twice, shifting the laser frequency to the first preset frequency. The first preset frequency is the same as the frequency detuning of |5S 1 / 2 , F = 2> to |5P 3 / 2 , F’ = 3> transition frequency by -10 MHz to obtain cooling light.

[0066] In this embodiment, the frequency of the cooling light is about 384.22810 THz.

[0067] The laser passes through the negative first-order frequency shift of the AOM crystal at 74 ± 0.1 MHz once, shifting the laser frequency to the second preset frequency. The second preset frequency is resonant with the transition frequency of |5S 1 / 2 , F = 2> to |5P 3 / 2 , F’ = 2> to obtain repumping light.

[0068] In addition to the cooling light and the repumping light, this embodiment also requires a probe light to detect the atomic state. Among them, the probe light uses another laser. However, since the frequency of the probe light in this embodiment is resonant with the transition frequency of |5S 1 / 2 , F = 2> to |5P 3 / 2 , F’ = 3>, the frequency shift of the probe light can share an AOM crystal with the cooling light.

[0069] Locking the laser frequency of the laser to the first transition frequency further includes:

[0070] After the laser emitted by the laser passes through frequency shift, the laser frequency is adjusted to the third preset frequency to obtain a probe light, and the probe light is used to detect the first preset atom. <​​​​,F'=3> transition frequency resonance, the frequency shifting method is: the laser passes through the 110±0.1MHz AOM crystal twice with a positive first-order frequency shift, and then passes through the 110±0.1MHz AOM crystal twice with a negative first-order frequency shift.

[0072] In this embodiment, a single laser is used to obtain the cooling light and the return pump light. By adjusting the laser frequency, the laser is switched back and forth between the cooling light and the return pump light to ensure stable and good cooling efficiency of the atoms. The switching timing is as follows: Figure 3 As shown: First, the laser emits cooling light to capture and cool the atoms. At the same time, a small number of atoms exit the cyclic transition due to spontaneous radiation transition to the ground state. Then a frequency switching is performed to switch the laser frequency to the back pump light frequency, re-exciting the atoms that transitioned to the ground state, thereby increasing the number of excited atoms again. The duty cycle of the cooling light is marked with C.

[0073] like Figure 3 As shown, the horizontal axis is time, the vertical axis is frequency, and the preset period is the sum of the first duration of the laser being converted into cooling light after frequency shifting, the second duration of the cooling light, the third duration of the laser being converted into back-pumping light after frequency shifting, and the fourth duration of the back-pumping light;

[0074] like Figure 3 As shown, the preset period is T cycle , the third duration is T tune , the second duration is CT cycle -T tune , the first duration plus the fourth duration is (1-C)T cycle ; The preset period T in this embodiment cycle <1ms.

[0075] By adjusting the ratio between the second time duration and the fourth time duration, the duty ratio of the cooling light and the return pump light in the time sequence is adjusted, thereby adjusting the effect of cooling the trapped atomic clusters.

[0076] like Figure 3 and Figure 4 As shown, by adjusting the frequency switching timing of the laser, the duty ratio of the two lights in the timing is controlled. The atoms that have completed cooling have fluorescence, and the cooling status of the atoms can be judged by the fluorescent atoms of different sizes and brightness, as shown in Figure 2. Figure 3As shown in the figure, the duty cycle of cooling light and return pumping light corresponds to different brightness of fluorescent atoms; when the cooling light is 0% and the return pumping light is 100%, it means that no atoms are cooled, so no fluorescent atoms can be seen; as the proportion of cooling light increases, the proportion of return pumping light decreases, the number of cooled atoms gradually increases, and the return pumping light is sufficient to pump the atoms that exit the cyclic transition back into the cyclic transition, the number of fluorescent atoms gradually increases, and the brightness of the fluorescent atomic cluster increases; when the cooling light reaches 80% and the return pumping light is about 20%, the return pumping light just maximizes the number of atoms that exit the cyclic transition and pumps them back into the cyclic transition, the most atoms are cooled, and the brightness of the fluorescent atomic cluster is the highest at this time; then as the duty cycle of cooling light increases, the return pumping light duty cycle decreases, and it is not enough to pump the atoms that exit the cyclic transition back into the cyclic transition, the cooling efficiency decreases, the number of cooled atoms gradually decreases, and the brightness of the fluorescent atomic cluster gradually decreases; when the cooling light is 100% and the return pumping light is 0%, only a small number of atoms do not exit the cyclic transition, and they complete a small amount of atomic cooling, so the fluorescent atomic cluster with lower brightness can still be observed.

[0077] In combination with the preset cycle, during the first and second time periods, the return pump light is frequency-shifted to the cooling light, the duty cycle of the return pump light begins to decrease, and the duty cycle of the cooling light begins to increase, and the fluorescence brightness of the atoms is observed. The second time period continues until the atomic fluorescence brightness is brightest, at which time the cooling light duty cycle is 80%, and then the brightness begins to decrease, that is, the cooling light duty cycle is between 80% and 90%. The laser is frequency-shifted to the return pump light, and the third and fourth time periods are started. The atomic fluorescence brightness begins to increase. When the return pump light duty cycle reaches 20%, the atomic fluorescence brightness is brightest, and then the brightness begins to decrease, that is, the return pump light duty cycle is between 20% and 30%. At this time, the fourth time period ends and a new preset cycle is entered, and the return pump light is adjusted to the cooling light. By alternating the frequency shift of the laser in the above preset cycle, the cooling light duty cycle is ensured to be around 80%, and the atomic fluorescence brightness is maintained at a relatively brightest state.

[0078] Example 2:

[0079] Based on Example 1, this embodiment of the present invention provides a single laser frequency switching device for preparing a magneto-optical trap.

[0080] like Figure 5 and Figure 6 As shown, Figure 5 is the front view of the first optical path, Figure 6 The top view of the second optical path and the third optical path includes: a vacuum chamber 3, a first optical path, a second optical path and a third optical path, wherein:

[0081] The first optical path passes through the vacuum cavity 3 in a vertical direction, and the second optical path and the third optical path pass through the vacuum cavity 3 in a horizontal direction. The first optical path, the second optical path and the third optical path are sequentially provided with an optical fiber output end 1 and a first quarter wave plate 2 on one side of the vacuum cavity 3, and a second quarter wave plate 4 and a reflector 5 are sequentially provided on the other side of the vacuum cavity 3 to convert the cooling light obtained after the frequency shift into a pair of σ + -σ - Cooling light;

[0082] Three pairs of σ + -σ - The cooling light intersects in the vacuum chamber 3 to cool and trap atoms.

[0083] The first optical path, the second optical path and the third optical path are all optical channels equipped with a wave plate, a reflector 5 and an optical fiber output end 1, wherein the first optical path, the second optical path and the third optical path intersect in a vacuum cavity 3 in the middle position, and the lasers of the three optical channels intersect in the vacuum cavity 3 to cool and capture atoms.

[0084] Starting from one end of the first optical path, the optical fiber output end 1, the first quarter wave plate 2, the anti-Helmholtz coil 6, the vacuum cavity 3, the anti-Helmholtz coil 6, the second quarter wave plate 4 and the reflector 5 are sequentially mounted on the optical channel;

[0085] Starting from one end of the second optical path, the optical fiber output end 1, the first quarter wave plate 2, the vacuum cavity 3, the second quarter wave plate 4 and the reflector 5 are sequentially mounted on the optical channel;

[0086] Starting from the upper end of the third optical path, the optical fiber output end 1, the first quarter wave plate 2, the vacuum cavity 3, the second quarter wave plate 4 and the reflector 5 are sequentially mounted on the optical channel.

[0087] In this embodiment, three lasers may be provided for the first optical path, the second optical path, and the third optical path. Each laser corresponds to the same frequency shifting process, thereby emitting cooling light or pumping light with synchronized timing and frequency, thereby ensuring that three pairs of identical cooling lights intersect in the vacuum chamber 3 to cool and trap atoms.

[0088] Or in order to reduce the overall complexity of the device and reduce the cost brought by the laser, in this embodiment, only one laser is set to connect with the optical fiber output end 1 of the second optical path or the third optical path. In this embodiment, the laser is set at the optical fiber output end 1 of the second optical path, and two branches are set between the optical fiber output end 1 and the first quarter wave plate 2. One branch is connected to the optical fiber output end 1 of the first optical path in the middle, and the other branch is connected to the optical fiber output end 1 of the third optical path; a PBS is set at each branch to split the laser into two at the branch. One path continues to extend in the second optical path, and the other path enters the corresponding branch path. A half-wave plate is also set on both sides of each PBS, and a half-wave plate is shared between the two PBSs. According to the installation position of each component in the device, when the branch path needs to turn a corner, a reflector 5 with a matching angle is set at the corner to ensure the normal transmission of the laser light path. Finally, the laser light emitted by a single laser is correspondingly introduced into the first optical path, the second optical path and the third optical path to ensure that the lasers of the three optical channels intersect in the vacuum chamber 3 to cool and capture atoms.

[0089] like Figure 5 and Figure 6 As shown, the first optical path, the second optical path and the third optical path are sequentially provided with an optical fiber output end 1 and a first quarter wave plate 2 on one side of the vacuum cavity 3, and a second quarter wave plate 4 and a reflector 5 are sequentially provided on the other side of the vacuum cavity 3 to convert the cooling light obtained after the frequency shift into a pair of σ + -σ - Cooling light, specifically including:

[0090] The cooling light or the pumped back light enters the optical path from the optical fiber output end 1, and after passing through the first quarter wave plate 2, the cooling light forms σ + The light enters the vacuum chamber 3 and then passes through the second quarter wave plate 4 and the reflector 5 to form the same σ + σ relative to the light direction - light, thus forming a pair of σ + -σ - Cooling light.

[0091] Two anti-Helmholtz coils 6 are also provided on the first optical path, respectively arranged between the vacuum cavity 3 and the first quarter wave plate 2, and between the vacuum cavity 3 and the second quarter wave plate 4 on the first optical path. The two anti-Helmholtz coils 6 provide a four-level magnetic field for trapping atoms.

[0092] In this embodiment, the current of the anti-Helmholtz coil 6 is 3A, the magnetic field gradient obtained in the axial direction is 5.01G / cm, and the magnetic field gradient in the radial direction is 9.92G / cm. Since the laboratory also contains experimental equipment, experimental platforms, and energized wires, which are prone to causing stray harmful magnetic fields and geomagnetic fields, which usually cause the center of the magneto-optical trap to shift, in addition to the anti-Helmholtz coil 6, three pairs of compensation coils are usually used to compensate for the stray magnetic field to reduce its impact.

[0093] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a magneto-optical trap by switching the frequency of a single laser, characterized in that: include: The laser frequency of the laser is locked to the first transition frequency, the laser emits laser light and after frequency shifting, the laser frequency is adjusted to the first preset frequency to obtain cooling light, wherein the cooling light causes energy level transition of the first preset atom, thereby cooling the first preset atom; Stabilizing the laser frequency of the same laser to the cross peak of the second transition frequency and the third transition frequency, and after the laser undergoes frequency shifting, adjusting the laser frequency to a second preset frequency to generate back-pumping light. The back-pumping light re-pumps atoms that have exited the cyclic transition due to spontaneous emission back into the cyclic transition, thereby maintaining cooling of the first preset atoms. By adjusting the laser frequency of the laser, cooling light and return pump light are emitted alternately within a preset period, thereby maintaining the cooling of the first preset atom.

2. The method for preparing a magneto-optical trap by switching the frequency of a single laser according to claim 1, characterized in that: The laser is subjected to frequency shift, specifically comprising: After the laser emits laser light, the laser light is frequency shifted by the AOM crystal.

3. The method for preparing a magneto-optical trap by switching the frequency of a single laser according to claim 1, characterized in that: The preset period is the sum of the first duration of the laser being converted into cooling light after frequency shifting, the second duration of the cooling light, the third duration of the laser being converted into return pumping light after frequency shifting, and the fourth duration of the return pumping light.

4. The method for preparing a magneto-optical trap by switching the frequency of a single laser according to claim 3, characterized in that: By adjusting the ratio between the second time duration and the fourth time duration, the duty ratio of the cooling light and the return pump light in the time sequence is adjusted, thereby adjusting the effect of cooling the trapped atomic clusters.

5. The method for preparing a magneto-optical trap by switching the frequency of a single laser according to claim 1, characterized in that: The step of locking the laser frequency of the laser to the first transition frequency further comprises: The laser frequency is adjusted to a third preset frequency to obtain detection light, and the detection light is used to detect the first preset atom.

6. The method for preparing a magneto-optical trap by switching the frequency of a single laser according to claim 1, characterized in that: Also includes: The laser emitted from the laser is amplified by a tapered amplifier to amplify the laser power, and then the laser is divided into a first laser beam and a second laser beam by a polarization beam splitter prism, wherein the first laser beam is used to cool and detect the first preset atom, and the second laser beam is used to cool and detect the second preset atom.

7. The method for preparing a magneto-optical trap by switching the frequency of a single laser according to claim 1, characterized in that: The first preset atom is 87 Rb.

8. A single laser switching frequency preparation magneto-optical trap device, characterized in that: The method for preparing a magneto-optical trap using a single laser switching frequency as claimed in any one of claims 1 to 7 comprises: a vacuum cavity (3), a first optical path, a second optical path and a third optical path, wherein: The first optical path passes through the vacuum cavity (3) in a vertical direction, and the second optical path and the third optical path pass through the vacuum cavity (3) in a horizontal direction. The first optical path, the second optical path, and the third optical path are all provided with an optical fiber output end (1) and a first quarter wave plate (2) on one side of the vacuum cavity (3), and a second quarter wave plate (4) and a reflector (5) are all provided on the other side of the vacuum cavity (3) to convert the cooling light obtained after the frequency shift into a pair of σ + -σ - Cooling light; Three pairs of σ + -σ - The cooling light intersects in the vacuum chamber (3) to cool and trap atoms.

9. The single laser frequency switching magneto-optical trap device according to claim 8, characterized in that: The first optical path, the second optical path, and the third optical path are all provided with an optical fiber output end (1) and a first quarter wave plate (2) on one side of the vacuum cavity (3), and a second quarter wave plate (4) and a reflector (5) are all provided on the other side of the vacuum cavity (3) to convert the cooling light obtained after the frequency shift into a pair of σ + -σ - Cooling light, specifically including: The cooling light or the pumped back light enters the optical path from the optical fiber output end (1), and after passing through the first quarter wave plate (2), the cooling light forms a σ + The light enters the vacuum cavity (3), and then passes through the second quarter wave plate (4) and the reflector (5) to form the same σ + σ relative to the light direction - light, thus forming a pair of σ + -σ - Cooling light.

10. The single laser frequency switching magneto-optical trap device according to claim 8, characterized in that: Two anti-Helmholtz coils (6) are also provided on the first optical path, wherein one anti-Helmholtz coil (6) is provided between the vacuum cavity (3) and the first quarter wave plate (2), and the other anti-Helmholtz coil (6) is provided between the vacuum cavity (3) and the second quarter wave plate (4). The two anti-Helmholtz coils (6) provide a four-level magnetic field for trapping atoms.

Images