Atomic internal and external state control method and device for suppressing carrier transition

Abstract

The invention discloses an atomic internal and external state control method and device for suppressing carrier transition. Firstly, incident light is focused, and a tightly focused light field is generated. Based on spatial parameters of the tightly focused light field, a Rabian frequency with a specific spatial distribution is generated on the ions. The spatial parameters comprise relative positions of ions and the center of the tight focusing light field, and a polarization mode, a spatial mode and an incident direction of incident light. Spatial distribution of the pull ratio frequency is changed by flexibly regulating and controlling spatial parameters, and the quantum gate is constructed according to the changed pull ratio frequency. In order to solve the problems of low control speed and low fidelity of the constructed quantum gate caused by carrier transition in an actual working scene, the method provided by the invention can suppress the carrier transition by changing the pull ratio frequency and reduce the influence of the carrier transition on the construction of the quantum gate, thereby constructing the rapid and high-fidelity quantum gate.

Description

Technical Field

[0001] The present application relates to the field of quantum computing technology, and in particular to a method and device for controlling the internal and external states of an atom to suppress carrier transitions. Background Art

[0002] Sideband transitions refer to transitions that occur when the laser frequency differs from the internal energy level transition frequency of the ion trap system by a vibrational mode frequency. This transition changes the internal energy state (internal state) and external motion state (external state) of the ion. Driving the sideband transitions to couple the internal and external states of the ion can build a quantum gate.

[0003] Existing technologies often control the internal and external states of ions by controlling the frequency and phase of the laser to drive the sideband transition. However, the resulting carrier transition (i.e., the transition that occurs when the laser frequency completely matches the frequency of the ion's internal energy level transition) will destroy the coupling effect between the internal and external states, resulting in low fidelity of the constructed quantum gate. Summary of the invention

[0004] Based on the above problems, the present application provides a method and device for manipulating the internal and external states of atoms by suppressing carrier transitions, so as to construct a high-fidelity quantum gate.

[0005] The present application discloses a method for controlling the internal and external states of an atom to suppress carrier transition, the method comprising: Focusing the incident light to generate a tightly focused light field; Based on the spatial parameters of the tightly focused light field, a Rabi frequency is generated on the ion; the spatial parameters include the relative position of the ion and the center of the tightly focused light field, and the polarization mode, spatial mode and incident direction of the incident light; the Rabi frequency has a preset spatial distribution; By changing the spatial parameter, the spatial distribution of the Rabi frequency is changed; Construct quantum gates based on the altered Rabi frequency.

[0006] Optionally, focusing the incident light to generate a tightly focused light field includes: The incident light is focused on a plane by using an objective lens with a preset numerical aperture, so as to form the tightly focused light field on the plane; the incident light is a unilateral light having the spatial parameters.

[0007] Optionally, changing the spatial distribution of the Rabi frequency to obtain a first spatial distribution and a second spatial distribution of the Rabi frequency, and constructing a quantum gate according to the changed Rabi frequency includes: Based on the first spatial distribution, carrier transition is realized to construct a single-bit quantum gate; Based on the second spatial distribution, sideband transitions that suppress carrier transitions are achieved to construct a multi-bit quantum gate.

[0008] Optionally, changing the spatial distribution of the Rabi frequency by changing the spatial parameter includes: Moving the center to change the relative position; During the movement of the center, when the Rabi frequency is at the maximum point, obtaining the spatial distribution of the Rabi frequency as the first spatial distribution; When the Rabi frequency is at zero, obtaining the spatial distribution of the Rabi frequency as the second spatial distribution.

[0009] Optionally, changing the spatial distribution of the Rabi frequency by changing the spatial parameter includes: When the polarization mode of the incident light is circularly polarized light, and the incident direction is perpendicular to the ion chain direction and parallel to the static magnetic field direction, obtaining the first spatial distribution; When the polarization mode of the incident light is linearly polarized light, and the incident direction is orthogonal to the static magnetic field direction and orthogonal to the ion chain direction, and the polarization direction is perpendicular to the static magnetic field direction, obtaining the second spatial distribution.

[0010] Optionally, changing the spatial distribution of the Rabi frequency by changing the spatial parameter includes: When the polarization mode of the incident light is radially polarized light, obtaining the first spatial distribution; When the polarization mode of the incident light is linearly polarized light, obtaining the second spatial distribution.

[0011] Optionally, changing the spatial distribution of the Rabi frequency by changing the spatial parameter includes: When the spatial mode of the incident light is a Gaussian beam, obtaining the first spatial distribution; When the spatial mode of the incident light is a hollow beam, obtaining the second spatial distribution.

[0012] Optionally, implementing carrier transition based on the first spatial distribution to construct a single-bit quantum gate includes: When the changed Rabi frequency is the first spatial distribution, the spin energy level of the ion undergoes carrier transition and the phonon energy level remains unchanged; Using the carrier transition to construct the single-bit quantum gate.

[0013] Optionally, implementing sideband transition that suppresses carrier transition based on the second spatial distribution to construct a multi-bit quantum gate includes: When the changed Rabi frequency is in the second spatial distribution, the frequency difference between the laser and the energy level transition frequency is set to the negative value of the phonon frequency of the ion, the spin energy level of the ion increases, the phonon energy level decreases, and red sideband transition occurs; When the changed Rabi frequency is in the second spatial distribution, the frequency difference is set to the positive value of the phonon frequency, the spin energy level of the ion decreases, the phonon energy level increases, and blue sideband transition occurs; The multi-bit quantum gate is constructed by using the red sideband transition and the blue sideband transition.

[0014] An apparatus for manipulating the internal and external states of an atom to suppress carrier transition, comprising: a focusing unit, a generating unit, a changing unit, and a constructing unit; The focusing unit is configured to focus the incident light to generate a tightly focused light field; The generating unit is configured to generate a Rabi frequency on the ion based on the spatial parameters of the tightly focused light field; the spatial parameters include the relative position of the ion and the center of the tightly focused light field, as well as the polarization mode, spatial mode, and incident direction of the incident light; the Rabi frequency has a preset spatial distribution; The changing unit is configured to change the spatial distribution of the Rabi frequency by changing the spatial parameters; The constructing unit is configured to construct a quantum gate according to the changed Rabi frequency.

[0015] Optionally, the focusing unit includes: A forming subunit, configured to use an objective lens with a preset numerical aperture to focus the incident light on a plane and form the tightly focused light field on the plane; the incident light is a unilateral light with the spatial parameters.

[0016] Optionally, by changing the spatial distribution of the Rabi frequency, the first spatial distribution and the second spatial distribution of the Rabi frequency are obtained, and the constructing unit includes: A first constructing subunit, configured to implement carrier transition based on the first spatial distribution and construct a single-bit quantum gate; A second constructing subunit, configured to implement sideband transition for suppressing carrier transition based on the second spatial distribution and construct a multi-bit quantum gate.

[0017] Optionally, the changing unit includes: A moving subunit, configured to move the center to change the relative position; A first obtaining subunit, configured to obtain the spatial distribution of the Rabi frequency as the first spatial distribution when the Rabi frequency is at the maximum value point during the movement of the center; A second acquisition subunit, configured to acquire the spatial distribution of the Rabi frequency as the second spatial distribution when the Rabi frequency is at zero.

[0018] Optionally, the change unit includes: A first incident subunit, configured to obtain the first spatial distribution when the polarization mode of the incident light is circularly polarized light, the incident direction is perpendicular to the ion chain direction and parallel to the static magnetic field direction; A second incident subunit, configured to obtain the second spatial distribution when the polarization mode of the incident light is linearly polarized light, the incident direction is orthogonal to the static magnetic field direction and orthogonal to the ion chain direction, and the polarization direction is perpendicular to the static magnetic field direction.

[0019] Optionally, the change unit includes: A first polarization subunit, configured to obtain the first spatial distribution when the polarization mode of the incident light is radially polarized light; A first polarization subunit, configured to obtain the second spatial distribution when the polarization mode of the incident light is linearly polarized light.

[0020] Optionally, the change unit includes: A first light beam subunit, configured to obtain the first spatial distribution when the spatial mode of the incident light is a Gaussian beam; A second light beam subunit, configured to obtain the second spatial distribution when the spatial mode of the incident light is a hollow beam.

[0021] Optionally, the first construction subunit includes: A carrier transition subunit, configured to cause a carrier transition in the spin energy level of the ion and keep the phonon energy level unchanged when the changed Rabi frequency is the first spatial distribution; A first utilization subunit, configured to construct the single-bit quantum gate by using the carrier transition.

[0022] Optionally, the second construction subunit includes: A red sideband transition subunit, configured to set the frequency difference between the laser and the energy level transition frequency to the negative value of the phonon frequency of the ion, increase the spin energy level of the ion, decrease the phonon energy level, and cause a red sideband transition when the changed Rabi frequency is the second spatial distribution; A blue sideband transition subunit, configured to set the frequency difference to the positive value of the phonon frequency, decrease the spin energy level of the ion, increase the phonon energy level, and cause a blue sideband transition when the changed Rabi frequency is the second spatial distribution; A second utilization subunit, configured to construct the multi-bit quantum gate by using the red sideband transition and the blue sideband transition.

[0023] The present application discloses a method and device for manipulating the internal and external states of an atom to suppress carrier transitions. First, the incident light is focused to generate a tightly focused light field. Based on the spatial parameters of the tightly focused light field, a Rabi frequency with a specific spatial distribution is generated on the ion. The spatial parameters include the relative position of the ion to the center of the tightly focused light field, as well as the polarization mode, spatial mode, and incident direction of the incident light. By flexibly adjusting the spatial parameters, the spatial distribution of the Rabi frequency is changed, and a quantum gate is constructed according to the changed Rabi frequency. In an actual working scenario, carrier transitions can cause problems such as slow manipulation speed and low fidelity of the constructed quantum gate. The method of the present application can suppress carrier transitions by changing the Rabi frequency, reduce its influence on the construction of the quantum gate, and thus construct a fast and high-fidelity quantum gate. Description of the Drawings

[0024] To more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only the embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained according to the provided drawings.

[0025] Figure 1a Schematic diagram of the spectral lines of carrier transitions and sideband transitions in the traditional method; Figure 1b Schematic diagram of the spectral lines of carrier transitions and sideband transitions at high laser power Figure 1c Schematic flowchart of a method for manipulating the internal and external states of an atom to suppress carrier transitions disclosed in an embodiment of the present application; Figure 1d Schematic diagram of the spectral lines of carrier transitions and sideband transitions in the method disclosed in an embodiment of the present application Figure 2a Schematic diagram of a method for changing transitions disclosed in an embodiment of the present application; Figure 2b Schematic diagram of another method for changing transitions disclosed in an embodiment of the present application; Figure 2c Schematic diagram of another method for changing transitions disclosed in an embodiment of the present application; Figure 2d Schematic diagram of another method for changing transitions disclosed in an embodiment of the present application; Figure 3a Schematic diagram of the spatial distribution of a Rabi frequency disclosed in an embodiment of the present application; Figure 3b Schematic diagram of the spatial distribution of a Rabi frequency disclosed in an embodiment of the present application; Figure 3cSchematic diagram of the spatial distribution of the Rabi frequency disclosed in the embodiments of the present application; Figure 4 Schematic diagram of the structure of a device for manipulating the internal and external states of an atom to suppress carrier transitions, which is disclosed in the embodiments of the present application. Detailed implementation manners

[0026] To facilitate the understanding of the content related to ion traps, quantum entanglement, etc. in the present application, before introducing the detailed implementation manners, the following is an introduction to the relevant technical background of the present application: In the field of ion traps, the manipulation of the internal and external states of ions is crucial. In order to construct a quantum gate (quantum entanglement gate), it is necessary to couple the internal and external states of ions. This coupling process is mostly realized by using sideband transitions. The traditional sideband transition considers the interaction between a laser and a two-level atom in one-dimensional space. After the rotating wave approximation, the Hamiltonian H1 of this interaction can be expressed as the following formula: (1) In the formula, is the reduced Planck constant, is the Rabi frequency, is the raising operator of the atom, is the lowering operator of the atom. The exponential form represents a wave function, k is the wave vector, is the position operator of the atom, i is the imaginary unit, is the frequency difference between the laser and the energy level transition frequency (i.e., the detuning between the laser and the energy level), t is the time, is the phase of the laser, and H.c represents the complex conjugate.

[0027] Among them, Written in the form of creation-annihilation operators, that is: (2) In the formula, is the size of the ground state wave packet of ion motion, which can be expressed as , m is the mass of the ion, is the ion phonon frequency, a is the annihilation operator, is the creation-annihilation operator.

[0028] It can be seen that the Rabi frequency in the above manipulation method is a constant and has no spatial distribution. The term used for internal and external state coupling, that is, coupling the ion spin energy level and the phonon energy level, is provided by k. When the motion range of the ion is much smaller than the wavelength of the laser, that is, in the Lamb-Dicke region (the internal and external states of the ion can generate entanglement within the Lamb-Dicke region), expand the term and make a first-order approximation to obtain the following formula: (3) In the formula, is the Lamb-Dicke coefficient.

[0029] When is 0, the Hamiltonian is approximated as the following formula: (4) At this time, the spin energy level of the ion transitions with while the phonon energy level remains unchanged, that is, this transition is a carrier transition.

[0030] When is - the Hamiltonian is approximated as the following formula: (5) At this time, as the spin energy level of the ion increases, the phonon energy level decreases, and the transition that the ion undergoes is a red sideband transition.

[0031] When is the Hamiltonian is approximated as the following formula: (6) At this time, as the spin energy level of the ion decreases, the phonon energy level increases, and the transition that the ion undergoes is a blue sideband transition.

[0032] If at the initial moment, the ion is in the ground state of the spin energy level and the ion is driven with a fixed driving time, the ion will be driven to the spin excited state. Scanning the detuning of the laser with the energy level, detecting and recording the probability of the excited state, the spectral line of Figure 1a can be obtained. Among them, the horizontal axis is and the vertical axis is the probability of the spin excited state. The peak corresponding to <0 corresponds to the red sideband transition, the peak corresponding to = 0 corresponds to the carrier transition, and the peak corresponding to > 0 corresponds to the blue sideband transition. As shown in the figure, the spectral lines of different transition types all have a certain broadening, roughly a Lorentzian line shape, where the widths of the red and blue sidebands are

[0033] Due to the effect of the Figure 1bAs shown, when the laser power increases, due to the power broadening effect in the transition spectrum, carrier transitions will still be excited through detuning during the manipulation of sideband transitions. Therefore, it is necessary to limit the laser power, which results in a limited speed of sideband manipulation by traditional methods and further affects the speed of quantum gates.

[0034] The above describes the situation of using single-frequency laser to manipulate ions in traditional methods. When using Raman light composed of beat-frequency lasers (two or more lasers with different frequencies) to manipulate ions, its manipulation principle corresponds to the Hamiltonian in the above method. For example, in the process of two-photon transition, the effective Rabi frequency is , that is, the ratio of the product of the Rabi frequencies of the two lasers to the single-photon detuning. The effective wave vector is , that is, the wave vector difference between the two lasers. Since the amplitudes of the wave vectors of the two lasers are basically equal, if they are in the same direction, the effective wave vector will tend to 0, and coupling cannot be carried out. Therefore, the two lasers in the traditional method cannot be in the same direction, that is, the lasers must be emitted from at least two directions.

[0035] In view of this, the present application provides a new method for ion manipulation, which supports achieving pure carrier transitions or carrier-suppressed sideband transitions, and is also applicable to high-power laser scenarios, effectively avoiding the problems of slow manipulation speed and reduced fidelity caused by carrier transitions in traditional methods. And the manipulation optical path is simple, only requiring a single objective lens and a single multi-frequency laser beam, removing the limitation that traditional methods require lasers propagating from at least two directions.

[0036] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present application.

[0037] Embodiment 1: The present application discloses a method for manipulating the internal and external states of atoms to suppress carrier transitions.

[0038] Specifically, please refer to Figure 1c , a method for manipulating the internal and external states of atoms to suppress carrier transitions disclosed in this embodiment includes the following steps: Step 101: Focus the incident light to generate a tightly focused light field.

[0039] In the method of this embodiment, an objective lens with a preset numerical aperture is used to focus the incident light on a plane, and a tightly focused light field is formed on the plane. Among them, the incident light is a unilateral light with spatial parameters. As an alternative method, parallel light with a specific spatial mode is focused through an objective lens with a preset numerical aperture NA. For example, a linearly polarized Gaussian beam and an objective lens with a high NA (NA>0.1) are used. In this way, a tightly focused light field with spatial parameters can be formed on the focusing plane, and the spatial parameters include the relative position of the ion to the center of the tightly focused light field, as well as the polarization mode, spatial mode, and incident direction of the incident light.

[0040] Step 102: Generate a Rabi frequency on the ion based on the spatial parameters of the tightly focused light field.

[0041] In the method of this embodiment, the Rabi frequency on the ion has a preset spatial distribution. Due to the focusing effect, there is a corresponding relationship between the spatial distribution of the Rabi frequency and the spatial parameters of the tightly focused light field. Compared with the constant-form Rabi frequency in the traditional method, the Rabi frequency in the method of this embodiment is a value representing a change with parameters. . After the rotating-wave approximation, the Hamiltonian of the ion can be expressed as follows: (7) In the formula, represents the position of the ion relative to the center of the tightly focused light field during movement.

[0042] It can be seen from the formula that provides a coupling mechanism between the ion spin energy level and the phonon energy level. For the sake of easy description, let ≈ 1, that is, only the 0th order of this term is retained. In the case of co-directional Raman beams, = 1. Therefore, the final form of the Hamiltonian can be expressed as follows: (8) In the method of this embodiment, since the range of ion movement is on the order of dozens of nm, which is much smaller than the size of the focusing spot of several μm, the Rabi frequency with a preset spatial distribution can be further Taylor-expanded at the equilibrium position of the ion to obtain the following formula: (9) In the formula, is the spatial gradient of the Rabi frequency, is the Rabi frequency at the ion position.

[0043] Step 103: Change the spatial distribution of the Rabi frequency by changing the spatial parameters.

[0044] In the method of this embodiment, by changing the spatial distribution of the Rabi frequency, the Rabi frequency with the first spatial distribution and the Rabi frequency with the second spatial distribution can be obtained. That is, by controlling and in formula (9) of the control step, the type of transition can be flexibly regulated. As an alternative method, the Rabi frequency can be changed in the following ways: ① Move the center of the tightly focused light field to change its relative position with respect to the ion, and change and . That is, during the movement of the center, the Rabi frequency at the maximum point is obtained, and the spatial distribution of this Rabi frequency is used as the first spatial distribution. Correspondingly, during the movement of the center, the Rabi frequency at the zero point is obtained, and the spatial distribution of this Rabi frequency is used as the second spatial distribution.

[0045] ② Change the polarization mode and incident direction of the incident light, and change and . That is, when the polarization mode of the incident light is circularly polarized light, and the incident direction is perpendicular to the ion chain direction and parallel to the static magnetic field direction, the first spatial distribution is obtained. Correspondingly, when the polarization mode of the incident light is linearly polarized light, and the incident direction is orthogonal to the static magnetic field direction and orthogonal to the ion chain direction, and the polarization direction is perpendicular to the static magnetic field direction, the second spatial distribution is obtained.

[0046] ③ Change the polarization mode of the incident light, and change and . That is, when the polarization mode of the incident light is radially polarized light, the first spatial distribution is obtained. Correspondingly, when the polarization mode of the incident light is linearly polarized light, the second spatial distribution is obtained.

[0047] ④ Change the spatial mode of the incident light, and change and . As an alternative method, when the spatial mode of the incident light is a Gaussian beam, the first spatial distribution is obtained. When the spatial mode of the incident light is a hollow beam, the second spatial distribution is obtained.

[0048] Step 104: Construct a quantum gate according to the changed Rabi frequency.

[0049] In the method of this embodiment, based on the first spatial distribution to achieve carrier transition, a single-bit quantum gate can be constructed. Based on the second spatial distribution to achieve sideband transition that suppresses carrier transition, a multi-bit quantum gate can be constructed. Specifically, when the spatial distribution of the changed Rabi frequency is the first spatial distribution, the spin energy level of the ion undergoes carrier transition and the phonon energy level remains unchanged, and a single-bit quantum gate is constructed using the carrier transition. As an alternative method, when ≠0, and When = 0, the coupling effect is eliminated, realizing a pure carrier transition, which can be used to construct a single-bit gate. Specifically, it can be set that ≠0, and = 0, = 0, the Hamiltonian is approximated as: (10) At this time, the spin energy level of the ion undergoes a transition at while the phonon energy level remains unchanged, enabling single-bit operations.

[0050] In the method of this embodiment, when the spatial distribution of the changed Rabi frequency is the second spatial distribution, the frequency difference between the laser and the energy level transition frequency is set to the negative value of the phonon frequency of the ion. The spin energy level of the ion increases, the phonon energy level decreases, and a red sideband transition occurs. When the frequency difference is set to the positive value of the phonon frequency, the spin energy level of the ion decreases, the phonon energy level increases, and a blue sideband transition occurs. The red sideband transition and the blue sideband transition are used to construct a multi-bit quantum gate. As an alternative method, when = 0, and ≠0, the carrier transition term is zero, realizing a carrier-suppressed sideband transition, which can be used to construct a two-bit or multi-bit logic gate. Specifically, it can be set that = 0, and ≠0, the Hamiltonian is approximated as: (11) Rewriting into the form of creation-annihilation operators, the following equation can be obtained: (12) Setting = - , the following equation can be obtained: (13) At this time, as the spin energy level of the ion increases, the phonon energy level decreases, and a red sideband transition occurs.

[0051] Setting = , the following equation can be obtained: (14) At this time, as the spin energy level of the ion decreases, the phonon energy level increases, and a blue sideband transition occurs. The red and blue sideband transitions can be used for two-bit or multi-bit manipulation, thus being used to construct a two-bit or multi-bit quantum gate.

[0052] The method described in this embodiment realizes different transition types and switches between multi-bit and single-bit manipulation modes by adjusting spatial parameters, such as the relative position of ions to the center of the tightly focused optical field, the polarization mode and incident direction of the incident light, and the spatial mode of the incident light. It supports driving sideband transitions with higher laser power and constructing faster quantum gates, thereby improving the gate fidelity. At the same time, by using a single objective lens and a single beam of laser on one side, the optical path is simpler, and an incident window can be left for other ion manipulation light. And the focused spot is generally less than 3um, so it can be used for the individual optical addressing of ions or atoms, and is applicable to multiple fields such as quantum computing, quantum simulation, and quantum optics.

[0053] In the actual scenario, due to the position offset of the ions and the inaccurate regulation method, it is not strictly 0, but still satisfies << the condition. If the ions at the initial moment are in the ground state of the spin energy level, drive the ions with a fixed driving time, scan the laser detuning, and detect the probability of the excited state, then the spectral line as shown in Figure 1d can be obtained. As shown in Figure 1d , compared with the traditional method, the method of this embodiment can suppress the influence of carrier transitions in the inner and outer state coupling processes, thereby constructing a faster and higher-fidelity quantum gate.

[0054] Embodiment 2: The present application discloses a method for changing transitions. The method described in this embodiment details the method for changing the relative position of ions to the center of the tightly focused optical field.

[0055] In the method of this embodiment, taking 171 Yb + ions as an example, its | 2 S 1 / 2 , F = 0, m F = 0〉 state is the quantum state |0〉 state, and | 2 S 1 / 2 , F = 1, m F = 0〉 state is the quantum state |1〉 state. The two-photon Raman transition is used to realize the transition between states, and the energy level difference between the two quantum states is HF = 12.64GHz.

[0056] As an alternative method, as shown in Figure 2a , taking linearly polarized light as the incident light, the direction of the static magnetic field (magnetic field) is perpendicular to the direction of the ion chain, the incident direction of the incident light is orthogonal to the direction of the static magnetic field and also orthogonal to the direction of the ion chain. The polarization direction is perpendicular to the direction of the static magnetic field, and the wavelength of the incident light is 554nm.

[0057] Generate Raman light through devices such as electro-optic modulators, MZ interferometers, and acousto-optic modulators, and vertically incident the Raman light onto the ions through an objective lens with NA = 0.4 to form a tightly focused light field. Move the position of the center of the tightly focused light field and measure the Rabi frequency of the ions to obtain the relationship between the Rabi frequency and the position as shown in Figure 3a shown.

[0058] In the method of this embodiment, when the maximum Rabi frequency is captured during the movement, the Rabi frequency at this time is ≈ , to achieve carrier transition. When the Rabi frequency of the ions is captured as 0 during the movement, the Rabi frequency at this time is ≈ , to achieve sideband transition with carrier suppression.

[0059] Embodiment 3: The present application discloses a method for changing transitions. The method of this embodiment will be introduced in detail for the method of changing the polarization mode and incident direction of the incident light.

[0060] In the method of this embodiment, take the ions, the wavelength of the incident light, and the objective lens in Embodiment 2 as examples. The direction of the static magnetic field is perpendicular to the direction of the ion chain, and the ions are located at the center of the tightly focused light field.

[0061] As an alternative method, as shown in Figure 2b , the incident light is circularly polarized light (the elliptical arrow mark in Figure 2b ), and the incident direction of the incident light is the same as the direction of the static magnetic field. The spatial distribution of the Rabi frequency at this time is as shown in Figure 3b , the ions are located at the maximum value point of the Rabi frequency, and the Rabi frequency is ≈ , and carrier transition can be achieved. When the incident light is linearly polarized light, the incident direction is orthogonal to both the direction of the static magnetic field and the direction of the ion chain, and the polarization direction is perpendicular to the static magnetic field. The spatial distribution of the Rabi frequency at this time is as shown in Figure 3a , the ions are located at the position where the Rabi frequency is 0, and the Rabi frequency is ≈ , and sideband transition with carrier suppression can be achieved.

[0062] Embodiment 4: The present application discloses a method for changing transitions. The method of this embodiment will be introduced in detail for the method of changing the polarization mode of the incident light.

[0063] In the method of this embodiment, take the ions, the wavelength of the incident light, and the objective lens in Embodiment 2 as examples. The direction of the static magnetic field is perpendicular to the direction of the ion chain, the incident direction of the incident light is orthogonal to both the direction of the static magnetic field and the direction of the ion chain, the linear polarization direction is perpendicular to the direction of the static magnetic field, and the ions are located at the center of the tightly focused light field.

[0064] As an alternative method, as shown in Figure 2c , the incident light is radially polarized light, and the spatial distribution of the Rabi frequency at this time is as shown in Figure 3bAs shown, the ion is located at the maximum point of the Rabi frequency, and the Rabi frequency ≈ , and carrier transition can be achieved. The incident light is linearly polarized light. At this time, the spatial distribution of the Rabi frequency is as shown in Figure 3a . The ion is located at the position where the Rabi frequency is 0, and the Rabi frequency ≈ , and sideband transition with carrier suppression can be achieved.

[0065] Example 5: The present application discloses a method for changing transitions. The method in this example will be introduced in detail for the method of changing the spatial mode of the incident light.

[0066] In the method of this example, taking 40 Ca + ion as an example, its | 2 S 1 / 2 , m J = 1 / 2〉 state is the quantum state |0〉 state, and | 2 D 5 / 2 , m J = 1 / 2〉 state is the quantum state |1〉 state. As shown in Figure 2d , taking linearly polarized light with a wavelength of 729 nm as the incident light, vertically incident on the ion, the direction of the static magnetic field is perpendicular to the direction of the ion chain, the polarization direction is parallel to the direction of the static magnetic field, and the ion is located at the center of the tightly focused light field.

[0067] As an alternative method, the incident light is a Gaussian beam (such as LG00 mode). At this time, the spatial distribution of the Rabi frequency is as shown in Figure 3b . The ion is located at the maximum point of the Rabi frequency, and the Rabi frequency ≈ , and carrier transition can be achieved. The incident light is a hollow beam (such as LG01 mode). At this time, the spatial distribution of the Rabi frequency is as shown in Figure 3c . The ion is located at the position where the Rabi frequency is 0, and the Rabi frequency ≈ , and sideband transition with carrier suppression can be achieved.

[0068] Based on the method for manipulating the internal and external states of an atom to suppress carrier transition disclosed in the above embodiments, this embodiment correspondingly discloses a device for manipulating the internal and external states of an atom to suppress carrier transition. Please refer to Figure 4 . The device for manipulating the internal and external states of an atom to suppress carrier transition includes: a focusing unit 401, a generating unit 402, a changing unit 403, and a constructing unit 404; The focusing unit 401 is used to focus the incident light to generate a tightly focused light field; The generating unit 402 is configured to generate a Rabi frequency on the ion based on the spatial parameters of the tightly focused light field; the spatial parameters include the relative position of the ion with respect to the center of the tightly focused light field, as well as the polarization mode, spatial mode, and incident direction of the incident light; the Rabi frequency has a preset spatial distribution; The changing unit 403 is configured to change the spatial distribution of the Rabi frequency by changing the spatial parameters; The constructing unit 404 is configured to construct a quantum gate according to the changed Rabi frequency.

[0069] Optionally, the focusing unit 401 includes: A forming subunit, configured to focus the incident light on a plane by using an objective lens with a preset numerical aperture, and form the tightly focused light field on the plane; the incident light is a unilateral light with the spatial parameters.

[0070] Optionally, by changing the spatial distribution of the Rabi frequency, a first spatial distribution and a second spatial distribution of the Rabi frequency are obtained, and the constructing unit 404 includes: A first constructing subunit, configured to implement carrier transition based on the first spatial distribution and construct a single-bit quantum gate; A second constructing subunit, configured to implement sideband transition that suppresses carrier transition based on the second spatial distribution and construct a multi-bit quantum gate.

[0071] Optionally, the changing unit 403 includes: A moving subunit, configured to move the center to change the relative position; A first obtaining subunit, configured to, during the movement of the center, when the Rabi frequency is at a maximum point, obtain the spatial distribution of the Rabi frequency as the first spatial distribution; A second obtaining subunit, configured to, when the Rabi frequency is at zero, obtain the spatial distribution of the Rabi frequency as the second spatial distribution.

[0072] Optionally, the changing unit 403 includes: A first incident subunit, configured to obtain the first spatial distribution when the polarization mode of the incident light is circularly polarized light, the incident direction is perpendicular to the ion chain direction and parallel to the static magnetic field direction; A second incident subunit, configured to obtain the second spatial distribution when the polarization mode of the incident light is linearly polarized light, the incident direction is orthogonal to the static magnetic field direction and orthogonal to the ion chain direction, and the polarization direction is perpendicular to the static magnetic field direction.

[0073] Optionally, the changing unit 403 includes: The first polarizer unit is configured to obtain the first spatial distribution when the polarization mode of the incident light is radially polarized light. The first polarizer unit is configured to obtain the second spatial distribution when the polarization mode of the incident light is linearly polarized light.

[0074] Optionally, the changing unit 403 includes: The first light beam sub-unit is configured to obtain the first spatial distribution when the spatial mode of the incident light is a Gaussian beam. The second light beam sub-unit is configured to obtain the second spatial distribution when the spatial mode of the incident light is a hollow beam.

[0075] Optionally, the first constructing sub-unit includes: The carrier transition sub-unit is configured to cause the spin energy level of the ion to undergo carrier transition and the phonon energy level to remain unchanged when the changed Rabi frequency is the first spatial distribution. The first utilization sub-unit is configured to construct the single-bit quantum gate by using the carrier transition.

[0076] Optionally, the second constructing sub-unit includes: The red sideband transition sub-unit is configured to set the frequency difference between the laser and the energy level transition frequency to the negative value of the phonon frequency of the ion, cause the spin energy level of the ion to increase and the phonon energy level to decrease, and undergo red sideband transition when the changed Rabi frequency is the second spatial distribution. The blue sideband transition sub-unit is configured to set the frequency difference to the positive value of the phonon frequency, cause the spin energy level of the ion to decrease and the phonon energy level to increase, and undergo blue sideband transition when the changed Rabi frequency is the second spatial distribution. The second utilization sub-unit is configured to construct the multi-bit quantum gate by using the red sideband transition and the blue sideband transition.

[0077] The embodiments in this specification are described in a progressive manner. For the apparatuses disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the descriptions are relatively simple. For the relevant parts, reference may be made to the descriptions in the method section.

[0078] It should also be noted that in this text, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprising", "including" or any other variation thereof are intended to cover non-exclusive inclusion, such that a process, method, article or device comprising a series of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "comprising an..." does not exclude the presence of additional identical elements in the process, method, article or device comprising the element.

[0079] The steps of the methods or algorithms described in connection with the embodiments disclosed herein may be implemented directly in hardware, in a software module executed by a processor, or in a combination of both. The software module may be placed in a random access memory (RAM), memory, read-only memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, registers, hard disk, removable disk, CD-ROM, or any other form of storage medium well known in the art.

[0080] The features described in the embodiments in this specification may be replaced or combined with each other, enabling those skilled in the art to implement or use the present application.

[0081] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but rather to the broadest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for manipulating the internal and external states of an atom to suppress carrier transition, characterized in that, Including: Focusing the incident light to generate a tightly focused light field; Generating a Rabi frequency on the ion based on the spatial parameters of the tightly focused light field; The spatial parameters include the relative position of the ion to the center of the tightly focused light field, as well as the polarization mode, spatial mode, and incident direction of the incident light; the Rabi frequency has a preset spatial distribution; Changing the spatial distribution of the Rabi frequency by changing the spatial parameters; Constructing a quantum gate according to the changed Rabi frequency.

2. The method according to claim 1, wherein The focusing the incident light to generate a tightly focused light field includes: Using an objective lens with a preset numerical aperture to focus the incident light on a plane, and forming the tightly focused light field on the plane; the incident light is a unilateral light with the spatial parameters.

3. The method according to claim 1, characterized in that, Changing the spatial distribution of the Rabi frequency to obtain a first spatial distribution and a second spatial distribution of the Rabi frequency. The constructing a quantum gate according to the changed Rabi frequency includes: Realizing carrier transition based on the first spatial distribution and constructing a single-bit quantum gate; Realizing sideband transition that suppresses carrier transition based on the second spatial distribution and constructing a multi-bit quantum gate.

4. The method according to claim 3, wherein The changing the spatial distribution of the Rabi frequency by changing the spatial parameters includes: Moving the center to change the relative position; During the process of moving the center, when the Rabi frequency is at the maximum point, obtaining the spatial distribution of the Rabi frequency as the first spatial distribution; When the Rabi frequency is at zero, obtaining the spatial distribution of the Rabi frequency as the second spatial distribution.

5. The method according to claim 3, wherein The changing the spatial distribution of the Rabi frequency by changing the spatial parameters includes: When the polarization mode of the incident light is circularly polarized light and the incident direction is perpendicular to the ion chain direction and parallel to the static magnetic field direction, obtaining the first spatial distribution; When the polarization mode of the incident light is linearly polarized light, and the incident direction is orthogonal to the static magnetic field direction and orthogonal to the ion chain direction, and the polarization direction is perpendicular to the static magnetic field direction, obtaining the second spatial distribution.

6. The method according to claim 3, wherein The changing the spatial distribution of the Rabi frequency by changing the spatial parameters includes: When the polarization mode of the incident light is radially polarized light, obtaining the first spatial distribution; When the polarization mode of the incident light is linearly polarized light, obtaining the second spatial distribution.

7. The method according to claim 3, wherein The changing the spatial distribution of the Rabi frequency by changing the spatial parameters includes: When the spatial mode of the incident light is a Gaussian beam, obtaining the first spatial distribution; When the spatial mode of the incident light is a hollow beam, obtaining the second spatial distribution.

8. The method according to claim 3, wherein The realizing carrier transition based on the first spatial distribution and constructing a single-bit quantum gate includes: When the changed Rabi frequency is the first spatial distribution, the spin energy level of the ion undergoes carrier transition and the phonon energy level remains unchanged; Using the carrier transition to construct the single-bit quantum gate.

9. The method according to claim 3, characterized in that, The realizing sideband transition that suppresses carrier transition based on the second spatial distribution and constructing a multi-bit quantum gate includes: When the changed Rabi frequency is in the second spatial distribution, the frequency difference between the laser and the energy level transition frequency is set to the negative value of the phonon frequency of the ion, the spin energy level of the ion increases, the phonon energy level decreases, and red sideband transition occurs; When the changed Rabi frequency is in the second spatial distribution, the frequency difference is set to the positive value of the phonon frequency, the spin energy level of the ion decreases, the phonon energy level increases, and blue sideband transition occurs; The multi-bit quantum gate is constructed by using the red sideband transition and the blue sideband transition.

10. An apparatus for manipulating the internal and external states of an atom to suppress carrier transitions, characterized in that, It includes: a focusing unit, a generating unit, a changing unit, and a constructing unit; The focusing unit is configured to focus the incident light to generate a tightly focused light field; The generating unit is configured to generate a Rabi frequency on the ion based on the spatial parameters of the tightly focused light field; the spatial parameters include the relative position of the ion to the center of the tightly focused light field, as well as the polarization mode, spatial mode, and incident direction of the incident light; the Rabi frequency has a preset spatial distribution; The changing unit is configured to change the spatial distribution of the Rabi frequency by changing the spatial parameters; The constructing unit is configured to construct a quantum gate according to the changed Rabi frequency.

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