A method and device for controlling atomic internal and external states by suppressing carrier transition

Abstract

The present application discloses a method and device for manipulating the internal and external states of atoms by suppressing 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 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 spatial distribution of the Rabi frequency is changed by flexibly regulating the spatial parameters, and a quantum gate is constructed based on the changed Rabi frequency. In actual working scenarios, carrier transitions can cause the constructed quantum gate to have slow control speed and low fidelity. The method of the present application can suppress carrier transitions by changing the Rabi frequency, reduce its impact on the construction of the quantum gate, and thus construct a fast, 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 manipulating the internal and external states of an atom to suppress carrier transitions. Background Art

[0002] Sideband transitions occur when the laser frequency differs from the internal energy level transition frequency of the ion trap system by a single vibrational mode frequency. These transitions alter the ion's internal energy state (internal state) and external motion state (external state). Driving sideband transitions to couple the internal and external states of the ion allows for the construction of quantum gates.

[0003] Existing technologies often manipulate the internal and external states of ions by controlling the frequency and phase of laser light to drive sideband transitions. However, the resulting carrier transitions (i.e., transitions that occur when the laser frequency perfectly matches the frequency of the ion's internal energy level transitions) can disrupt the coupling 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 to suppress carrier transitions, so as to construct a high-fidelity quantum gate.

[0005] The present application discloses a method for manipulating the internal and external states of an atom to suppress carrier transitions, the method comprising:

[0006] Focus the incident light to generate a tightly focused light field;

[0007] generating a Rabi frequency on the ion based on spatial parameters of the tightly focused light field; the spatial parameters including the relative position of the ion to the center of the tightly focused light field, and the polarization mode, spatial mode, and incident direction of the incident light; the Rabi frequency having a preset spatial distribution;

[0008] By changing the spatial parameter, the spatial distribution of the Rabi frequency is changed;

[0009] Construct quantum gates based on the altered Rabi frequency.

[0010] Optionally, focusing the incident light to generate a tightly focused light field includes:

[0011] 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 unilateral light with the spatial parameters.

[0012] 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:

[0013] Implementing carrier transition based on the first spatial distribution to construct a single-bit quantum gate;

[0014] Based on the second spatial distribution, sideband transitions that suppress carrier transitions are achieved to construct a multi-bit quantum gate.

[0015] Optionally, changing the spatial distribution of the Rabi frequency by changing the spatial parameter includes:

[0016] moving the center to change the relative position;

[0017] During the center movement process, when the Rabi frequency is at a maximum value point, obtaining the spatial distribution of the Rabi frequency as the first spatial distribution;

[0018] When the Rabi frequency is at zero, the spatial distribution of the Rabi frequency is obtained as the second spatial distribution.

[0019] Optionally, changing the spatial distribution of the Rabi frequency by changing the spatial parameter includes:

[0020] 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;

[0021] When the polarization mode of the incident light is linearly polarized light, the incident direction is orthogonal to the direction of the static magnetic field and the direction of the ion chain, and the polarization direction is perpendicular to the direction of the static magnetic field, the second spatial distribution is obtained.

[0022] Optionally, changing the spatial distribution of the Rabi frequency by changing the spatial parameter includes:

[0023] When the polarization mode of the incident light is radially polarized light, the first spatial distribution is obtained;

[0024] When the polarization mode of the incident light is linearly polarized light, the second spatial distribution is obtained.

[0025] Optionally, changing the spatial distribution of the Rabi frequency by changing the spatial parameter includes:

[0026] When the spatial mode of the incident light is a Gaussian beam, the first spatial distribution is obtained;

[0027] When the spatial mode of the incident light is a hollow beam, the second spatial distribution is obtained.

[0028] Optionally, implementing carrier transition based on the first spatial distribution to construct a single-bit quantum gate includes:

[0029] When the Rabi frequency after the change is the first spatial distribution, the spin energy level of the ion undergoes a carrier transition and the phonon energy level remains unchanged;

[0030] The single-bit quantum gate is constructed using the carrier transition.

[0031] Optionally, the step of achieving sideband transitions that suppress carrier transitions based on the second spatial distribution to construct a multi-bit quantum gate includes:

[0032] When 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 is increased, the phonon energy level is decreased, and a red sideband transition occurs;

[0033] When the changed Rabi frequency is the second spatial distribution, the frequency difference is set to a positive value of the phonon frequency, the spin energy level of the ion is reduced, the phonon energy level is increased, and a blue sideband transition occurs;

[0034] The multi-bit quantum gate is constructed using the red sideband transition and the blue sideband transition.

[0035] A device for manipulating atomic internal and external states to suppress carrier transitions, characterized by comprising: a focusing unit, a generating unit, a changing unit, and a constructing unit;

[0036] The focusing unit is used to focus the incident light to generate a tightly focused light field;

[0037] The generating unit is configured to generate a Rabi frequency on the ion based on spatial parameters of the tightly focused light field; the spatial parameters include a relative position of the ion and a center of the tightly focused light field, and a polarization mode, a spatial mode, and an incident direction of the incident light; the Rabi frequency has a preset spatial distribution;

[0038] The changing unit is configured to change the spatial distribution of the Rabi frequency by changing the spatial parameter;

[0039] The construction unit is used to construct a quantum gate according to the changed Rabi frequency.

[0040] Optionally, the focusing unit includes:

[0041] A subunit is formed, which is used to focus the incident light on a plane 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 with the spatial parameters.

[0042] Optionally, the spatial distribution of the Rabi frequency is changed to obtain a first spatial distribution and a second spatial distribution of the Rabi frequency, and the construction unit includes:

[0043] A first construction subunit, configured to implement carrier transition based on the first spatial distribution to construct a single-bit quantum gate;

[0044] The second construction subunit is used to realize sideband transition that suppresses carrier transition based on the second spatial distribution, and construct a multi-bit quantum gate.

[0045] Optionally, the changing unit includes:

[0046] a moving subunit, configured to move the center to change the relative position;

[0047] a first acquiring subunit, configured to acquire, when the Rabi frequency is at a maximum value during movement of the center, a spatial distribution of the Rabi frequency as the first spatial distribution;

[0048] The second acquiring subunit is configured to acquire the spatial distribution of the Rabi frequency as the second spatial distribution when the Rabi frequency is at zero.

[0049] Optionally, the changing unit includes:

[0050] A first incident subunit, configured to obtain the first spatial distribution 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;

[0051] The second incident subunit is used 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 the ion chain direction, and the polarization direction is perpendicular to the static magnetic field direction.

[0052] Optionally, the changing unit includes:

[0053] a first polarization subunit, configured to obtain the first spatial distribution when the polarization mode of the incident light is radial polarization;

[0054] The first polarization subunit is configured to obtain the second spatial distribution when the polarization mode of the incident light is linearly polarized light.

[0055] Optionally, the changing unit includes:

[0056] a first beam subunit, configured to obtain the first spatial distribution when the spatial mode of the incident light is a Gaussian beam;

[0057] The second beam subunit is configured to obtain the second spatial distribution when the spatial mode of the incident light is a hollow beam.

[0058] Optionally, the first construction subunit includes:

[0059] a carrier transition subunit, configured to cause the spin energy level of the ion to undergo carrier transition while the phonon energy level remains unchanged when the changed Rabi frequency is the first spatial distribution;

[0060] The first utilizing subunit is configured to utilize the carrier transition to construct the single-bit quantum gate.

[0061] Optionally, the second construction subunit includes:

[0062] A red sideband transition subunit 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 when the changed Rabi frequency is the second spatial distribution, so that the spin energy level of the ion increases and the phonon energy level decreases, resulting in a red sideband transition;

[0063] a blue sideband transition subunit, configured to set the frequency difference to a positive value of the phonon frequency when the changed Rabi frequency is the second spatial distribution, thereby reducing the spin energy level of the ion and increasing the phonon energy level, and causing a blue sideband transition;

[0064] The second utilizing subunit is configured to utilize the red sideband transition and the blue sideband transition to construct the multi-bit quantum gate.

[0065] The present application discloses a method and device for manipulating the internal and external states of atoms by suppressing 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 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 spatial distribution of the Rabi frequency is changed by flexibly regulating the spatial parameters, and a quantum gate is constructed based on the changed Rabi frequency. In actual working scenarios, carrier transitions can cause the constructed quantum gate to have slow control speed and low fidelity. The method of the present application can suppress carrier transitions by changing the Rabi frequency, reduce its impact on the construction of the quantum gate, and thus construct a fast, high-fidelity quantum gate. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are merely embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without any creative work.

[0067] Figure 1a Schematic diagram of the spectrum lines of carrier transition and sideband transition in the traditional method;

[0068] Figure 1b Schematic diagram of the spectrum of the wavelet transition and sideband transition at high laser power

[0069] Figure 1c A flow chart 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;

[0070] Figure 1d Schematic diagram of the spectrum lines of carrier transition and sideband transition in the method disclosed in the embodiment of this application

[0071] Figure 2a A schematic diagram of a method for changing transition disclosed in an embodiment of the present application;

[0072] Figure 2b A schematic diagram of another method for changing transitions disclosed in an embodiment of the present application;

[0073] Figure 2c A schematic diagram of another method for changing transitions disclosed in an embodiment of the present application;

[0074] Figure 2d A schematic diagram of another method for changing transitions disclosed in an embodiment of the present application;

[0075] Figure 3a A schematic diagram of the spatial distribution of Rabi frequency disclosed in an embodiment of the present application;

[0076] Figure 3b A schematic diagram of the spatial distribution of Rabi frequency disclosed in an embodiment of the present application;

[0077] Figure 3c A schematic diagram of the spatial distribution of Rabi frequency disclosed in an embodiment of the present application;

[0078] Figure 4 This is a structural diagram of a device for manipulating the internal and external states of an atom to suppress carrier transitions disclosed in an embodiment of the present application. DETAILED DESCRIPTION

[0079] To facilitate understanding of the contents of the present application, such as ion traps and quantum entanglement, the following technical background related to the present application is introduced before introducing the specific implementation methods:

[0080] In the field of ion traps, manipulating the internal and external states of ions is crucial. To construct quantum gates (quantum entanglement gates), the internal and external states of ions need to be coupled. This coupling process is often achieved using sideband transitions. Traditional sideband transitions consider the interaction between lasers and two-level atoms in one-dimensional space. Using the spin wave approximation, the Hamiltonian H1 of this interaction can be expressed as follows:

[0081] (1)

[0082] Where, is the reduced Planck constant, is the Rabi frequency, is the atomic raising operator, is the atomic reduction operator, the e exponential form represents a wave function, k is the wave vector, is the symbol for the atomic position, 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 Hc represents the complex conjugate.

[0083] in, Written in the form of a creation-annihilation operator, that is:

[0084] (2)

[0085] Where, 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, To generate the annihilation operator.

[0086] It can be seen that the Rabi frequency in the above manipulation method is constant and has no spatial distribution. The term used for coupling between the internal and external states, that is, coupling the ion spin energy level and the phonon energy level, is , is provided by k. When the range of motion of the ion is much smaller than the wavelength of the laser, that is, in the Lamb-Dicke region (the ion can only be entangled in the Lamb-Dicke region when its internal and external states are entangled), Term, and make a first-order approximation, we get the following formula:

[0087] (3)

[0088] Where, is the Lamb-Dicke coefficient.

[0089] when When is 0, the Hamiltonian is approximately as follows:

[0090] (4)

[0091] At this time, the spin energy level of the ion is A transition occurs while the phonon energy level remains unchanged, that is, the transition is a carrier transition.

[0092] when for- When , the Hamiltonian is approximately as follows:

[0093] (5)

[0094] At this time, as the ion spin energy level increases, the phonon energy level decreases, and the transition that occurs in the ion is a red-edge band transition.

[0095] when for When , the Hamiltonian is approximately as follows:

[0096] (6)

[0097] At this time, as the ion spin energy level decreases, the phonon energy level increases, and the transition that occurs in the ion is a blue-edge band transition.

[0098] If the ion is in the ground state of the spin energy level at the initial moment, driving the ion with a fixed driving time will drive the ion to the spin excited state. , detect and record the excited state probability, we can get Figure 1a The horizontal axis is , the vertical axis is the probability of spin excited state. The peaks <0 correspond to red sideband transitions, = 0 corresponds to the carrier transition, The peaks with a value >0 correspond to blue sideband transitions. As shown in the figure, the spectral lines of different transition types have a certain degree of broadening, which is roughly a Lorentz line shape, where the width of the red and blue sidebands is ,because The effect of the coefficient results in a narrower peak width (i.e., weaker coupling). The width of the carrier transition is , which is much larger than the coupling between the red and blue sidebands.

[0099] Therefore, in order to couple the spin energy level of the ion with the phonon energy level, the truly effective transition type is the red and blue sideband transition. Carrier transition will destroy the coupling effect between the spin energy level and the phonon energy level, resulting in a decrease in the fidelity of the quantum gate. In experiments, although the influence of the carrier term can be suppressed by laser modulation, filtering, etc., Figure 1b As shown in Figure 1, when the laser power increases, due to the power broadening effect in the transition spectrum, the carrier transition will still be excited by detuning when manipulating the sideband transition. Therefore, the laser power must be limited, which limits the speed of traditional sideband manipulation methods and thus affects the speed of quantum gates.

[0100] The above describes the traditional method of manipulating ions using a single-frequency laser. When using a beat-frequency laser (two or more lasers with different frequencies) to manipulate ions, the manipulation principle corresponds to the Hamiltonian in the above method. For example, in the two-photon transition process, the effective Rabi frequency is , which is the ratio of the product of the Rabi frequencies of the two lasers to the single-photon detuning. The effective wave vector is , which is the difference in the wave vectors of the two lasers. Since the wave vector amplitudes of the two lasers are essentially equal, if they were oriented in the same direction, the effective wave vector would approach zero, and coupling would be impossible. Therefore, in traditional methods, the two lasers cannot be oriented in the same direction, meaning they must be emitted from at least two different directions.

[0101] In light of this, this application provides a novel ion manipulation method that supports either pure carrier transitions or carrier-suppressed sideband transitions. It is also applicable to high-power laser scenarios, effectively avoiding the slow manipulation speed and reduced fidelity caused by carrier transitions in traditional methods. Furthermore, the manipulation optical path is simple, requiring only a single objective lens and a single multi-frequency laser beam, eliminating the limitation of traditional methods that require lasers propagating in at least two directions.

[0102] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0103] Example 1: This application discloses a method for manipulating the internal and external states of an atom to suppress carrier transitions.

[0104] For details, please refer to Figure 1c The present embodiment discloses a method for controlling the internal and external states of an atom to suppress carrier transitions, comprising the following steps:

[0105] Step 101: Focus the incident light to generate a tightly focused light field.

[0106] In the method of this embodiment, an objective lens with a preset numerical aperture is used to focus the incident light onto a plane, forming a tightly focused light field on the plane. The incident light is unilateral light with spatial parameters. As an optional method, parallel light with a specific spatial pattern is focused through an objective lens with a preset numerical aperture NA, for example, using a Gaussian beam with linear polarization and an objective lens with a high NA (NA>0.1). This can form a tightly focused light field with spatial parameters on the focusing plane, where the spatial parameters include the relative position of the ions and the center of the tightly focused light field, as well as the polarization mode, spatial pattern, and incident direction of the incident light.

[0107] Step 102: Generate a Rabi frequency on the ions based on the spatial parameters of the tightly focused light field.

[0108] In the method of this embodiment, the Rabi frequency on the ion has a preset spatial distribution. Due to the focusing effect, the spatial distribution of the Rabi frequency corresponds to the spatial parameters of the tightly focused light field. Compared with the constant Rabi frequency in the traditional method, the Rabi frequency in the method of this embodiment is a value that varies with the parameter. After the rotation wave approximation, the Hamiltonian of the ion can be expressed as follows:

[0109] (7)

[0110] Where, Indicates the position of an ion relative to the center of a tightly focused light field.

[0111] It can be seen from the formula that The coupling mechanism between ion spin energy level and phonon energy level is provided. For the convenience of description, let ≈1, that is, the term is only retained to the 0th order. In the case of the same-direction Raman beam, =1, so the final Hamiltonian can be expressed as follows:

[0112] (8)

[0113] In the method of this embodiment, since the range of ion movement is in the order of tens of nm, which is much smaller than the size of the focused light spot of several um, the Rabi frequency of the preset spatial distribution can be Further Taylor expansion is performed at the equilibrium position of the ion to obtain the following formula:

[0114] (9)

[0115] Where, is the spatial gradient of the Rabi frequency, is the Rabi frequency at the ion position.

[0116] Step 103: Changing the spatial distribution of the Rabi frequency by changing the spatial parameters.

[0117] In the method of this embodiment, the spatial distribution of the Rabi frequency can be changed to obtain the Rabi frequency of the first spatial distribution and the Rabi frequency of the second spatial distribution. That is, the control step formula (9) and , you can flexibly control the type of transition. As an optional method, you can change the Rabi frequency in the following ways:

[0118] ① Move the center of the tightly focused light field to change its relative position to the ions, changing and That is, during the center movement process, the Rabi frequency at the maximum point is obtained, and the spatial distribution of the Rabi frequency is used as the first spatial distribution. Correspondingly, during the center movement process, the Rabi frequency at the zero point is obtained, and the spatial distribution of the Rabi frequency is used as the second spatial distribution.

[0119] ②Change the polarization mode and incident direction of the incident light, change and That is, when the polarization mode of the incident light is circularly polarized, 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, and the incident direction is orthogonal to the static magnetic field direction and the ion chain direction, and the polarization direction is perpendicular to the static magnetic field direction, the second spatial distribution is obtained.

[0120] ③Change the polarization mode of the incident light, change and That is, when the polarization mode of the incident light is radial polarization, the first spatial distribution is obtained. Correspondingly, when the polarization mode of the incident light is linear polarization, the second spatial distribution is obtained.

[0121] ④Change the spatial pattern of incident light, change and As an optional method, when the spatial mode of the incident light is a Gaussian beam, a first spatial distribution is obtained. When the spatial mode of the incident light is a hollow beam, a second spatial distribution is obtained.

[0122] Step 104: Construct a quantum gate according to the changed Rabi frequency.

[0123] In the method of this embodiment, a single-bit quantum gate can be constructed by implementing carrier transition based on the first spatial distribution. A multi-bit quantum gate can be constructed by implementing sideband transition that suppresses carrier transition based on the second spatial distribution. 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, the phonon energy level remains unchanged, and a single-bit quantum gate is constructed using carrier transition. As an optional method, when ≠0, and = 0, the coupling effect is eliminated, achieving a pure carrier transition, which can be used to construct a single-bit gate. Specifically, we can set ≠0, and =0, = 0, the Hamiltonian is approximately:

[0124] (10)

[0125] At this time, the spin energy level of the ion is When a transition occurs, the phonon energy level remains unchanged and single-bit operations can be performed.

[0126] 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 ion's phonon frequency, the ion's spin energy level increases, the phonon energy level decreases, and a red sideband transition occurs. When the frequency difference is set to a positive value of the phonon frequency, the ion's spin energy level decreases, the phonon energy level increases, and a blue sideband transition occurs. A multi-bit quantum gate is constructed using red sideband transitions and blue sideband transitions. As an optional method, when =0, and ≠0, the carrier transition term is zero, achieving carrier-suppressed sideband transition, which can be used to construct two-bit or multi-bit logic gates. Specifically, we can set =0, and ≠0, the Hamiltonian is approximately:

[0127] (11)

[0128] Will Rewriting it in the form of a creation-annihilation operator, we get the following:

[0129] (12)

[0130] set up =- , we can get the following formula:

[0131] (13)

[0132] At this time, as the ion spin energy level increases, the phonon energy level decreases, and a red-edge transition occurs.

[0133] set up = , we can get the following formula:

[0134] (14)

[0135] At this point, as the ion spin energy level decreases, the phonon energy level increases, resulting in a blue-sideband transition. Using red and blue-sideband transitions, two-bit or multi-bit manipulation can be achieved, allowing the construction of two-bit or multi-bit quantum gates.

[0136] The method described in this embodiment achieves different types of transitions and switches between multi-bit and single-bit control modes by adjusting spatial parameters, such as the relative position of ions and the center of the tightly focused light 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 greater laser power and constructing faster quantum gates, thereby improving gate fidelity. At the same time, a single objective lens and a single laser beam on a single side are used, which simplifies the optical path while leaving an incident window for other ion control lights. The focused spot is generally less than 3um, so it can be used for individual optical addressing solutions for ions or atoms, and is suitable for multiple fields such as quantum computing, quantum simulation, and quantum optics.

[0137] In actual scenarios, due to the positional offset of ions and inaccurate control methods, Not strictly 0, but still satisfies << If the ion is in the ground state of the spin energy level at the initial moment, the ion is driven with a fixed driving time, the laser is detuned, and the excited state probability is detected, the following can be obtained: Figure 1d The spectral lines shown. Figure 1d As shown, compared with the traditional method, the method of this embodiment can suppress the influence of carrier transition in the coupling process between the inner and outer states, thereby constructing a quantum gate with higher speed and higher fidelity.

[0138] Example 2: This application discloses a method for changing transitions. The method described in this example provides a detailed introduction to a method for changing the relative position of ions and the center of a tightly focused light field.

[0139] In the method of this embodiment, 171 Yb + ion, for example, its | 2 S 1 / 2 ,F=0,m F =0〉state is the quantum state|0〉state,| 2 S 1 / 2 ,F=1,m F =0〉state is the quantum state|1〉state. The transition between the states is realized by two-photon Raman transition, and the energy level difference between the two quantum states is HF =12.64GHz.

[0140] As an alternative method, Figure 2a As shown, linearly polarized light is used as the incident light. The static magnetic field (magnetic field) is perpendicular to the ion chain direction. The incident light's direction is orthogonal to the static magnetic field and the ion chain direction. The polarization direction is perpendicular to the static magnetic field direction, and the wavelength of the incident light is 554nm.

[0141] Raman light is generated by devices such as electro-optic modulators, MZ interferometers, and acousto-optic modulators. The Raman light is incident vertically on the ions through an objective lens with NA = 0.4 to form a tightly focused light field. The center of the tightly focused light field is moved and the Rabi frequency of the ions is measured. The relationship between the Rabi frequency and position is obtained as follows: Figure 3a shown.

[0142] In the method of this embodiment, when the Rabi frequency is the highest during the movement, the Rabi frequency at this time is ≈ , to achieve carrier transition. When the Rabi frequency of the captured ion is 0 during the movement, the Rabi frequency at this time is ≈ , realizing sideband transition of carrier suppression.

[0143] Example 3: This application discloses a method for changing transitions. The method described in this embodiment provides a detailed introduction to a method for changing the polarization mode and incident direction of incident light.

[0144] In the method of this embodiment, taking the ions, wavelength of incident light and objective lens of embodiment 2 as an example, 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.

[0145] As an alternative method, Figure 2b As shown, the incident light is circularly polarized light ( Figure 2b The elliptical arrow in the figure shows the incident light direction is the same as the static magnetic field direction. The spatial distribution of the Rabi frequency at this time is as follows: Figure 3b As shown, the ion is located at the maximum Rabi frequency point, Rabi frequency ≈ , carrier transition can be achieved. The incident light is linearly polarized light, the incident direction is orthogonal to the static magnetic field direction and the ion chain direction, and the polarization direction is perpendicular to the static magnetic field. The spatial distribution of the Rabi frequency at this time is as follows Figure 3a As shown, the ion is located at a Rabi frequency of 0, and the Rabi frequency ≈ , which can realize the sideband transition of carrier suppression.

[0146] Example 4: This application discloses a method for changing transitions. The method described in this embodiment provides a detailed introduction to a method for changing the polarization mode of incident light.

[0147] In the method of this embodiment, taking the ions, wavelength of incident light and objective lens of Example 2 as an example, 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 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.

[0148] As an alternative method, Figure 2c As shown, the incident light is radially polarized light, and the spatial distribution of the Rabi frequency is as follows: Figure 3bAs shown, the ion is located at the maximum Rabi frequency point, Rabi frequency ≈ , carrier transition can be achieved. The incident light is linearly polarized light, and the spatial distribution of the Rabi frequency is as follows Figure 3a As shown, the ion is located at a Rabi frequency of 0, and the Rabi frequency ≈ , which can realize the sideband transition of carrier suppression.

[0149] Example 5: This application discloses a method for changing transitions. The method described in this embodiment provides a detailed introduction to a method for changing the spatial pattern of incident light.

[0150] In the method of this embodiment, 40 Ca + ion, for example, its | 2 S 1 / 2 , m J =1 / 2〉state is the quantum state |0〉state, | 2 D 5 / 2 , m J =1 / 2〉state is the quantum state|1〉state. Figure 2d As shown, linearly polarized light with a wavelength of 729 nm is used as the incident light, which is incident vertically 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.

[0151] As an optional method, the incident light is a Gaussian beam (such as LG00 mode), in which case the spatial distribution of the Rabi frequency is as follows: Figure 3b As shown, the ion is located at the maximum Rabi frequency point, Rabi frequency ≈ , which can realize carrier transition. The incident light is a hollow beam (such as LG01 mode), and the frequency space distribution of Rabi is as follows Figure 3c As shown, the ion is located at a Rabi frequency of 0, and the Rabi frequency ≈ , which can realize the sideband transition of carrier suppression.

[0152] Based on the method for controlling the internal and external states of an atom to suppress carrier transition disclosed in the above embodiment, this embodiment correspondingly discloses a device for controlling the internal and external states of an atom to suppress carrier transition. Figure 4 , the device for manipulating the internal and external states of an atom for suppressing carrier transition comprises: a focusing unit 401, a generating unit 402, a changing unit 403 and a constructing unit 404;

[0153] The focusing unit 401 is used to focus the incident light to generate a tightly focused light field;

[0154] The generating unit 402 is configured to generate a Rabi frequency on the ion based on spatial parameters of the tightly focused light field; the spatial parameters include a relative position of the ion and a center of the tightly focused light field, and a polarization mode, a spatial mode, and an incident direction of the incident light; the Rabi frequency has a preset spatial distribution;

[0155] The changing unit 403 is configured to change the spatial distribution of the Rabi frequency by changing the spatial parameter;

[0156] The construction unit 404 is configured to construct a quantum gate according to the changed Rabi frequency.

[0157] Optionally, the focusing unit 401 includes:

[0158] A subunit is formed, which is used to focus the incident light on a plane 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 with the spatial parameters.

[0159] Optionally, the spatial distribution of the Rabi frequency is changed to obtain the first spatial distribution and the second spatial distribution of the Rabi frequency, and the constructing unit 404 includes:

[0160] A first construction subunit, configured to implement carrier transition based on the first spatial distribution to construct a single-bit quantum gate;

[0161] The second construction subunit is used to realize sideband transition that suppresses carrier transition based on the second spatial distribution, and construct a multi-bit quantum gate.

[0162] Optionally, the changing unit 403 includes:

[0163] a moving subunit, configured to move the center to change the relative position;

[0164] a first acquiring subunit, configured to acquire, when the Rabi frequency is at a maximum value during movement of the center, a spatial distribution of the Rabi frequency as the first spatial distribution;

[0165] The second acquiring subunit is configured to acquire the spatial distribution of the Rabi frequency as the second spatial distribution when the Rabi frequency is at zero.

[0166] Optionally, the changing unit 403 includes:

[0167] A first incident subunit, configured to obtain the first spatial distribution 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;

[0168] The second incident subunit is used 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 the ion chain direction, and the polarization direction is perpendicular to the static magnetic field direction.

[0169] Optionally, the changing unit 403 includes:

[0170] a first polarization subunit, configured to obtain the first spatial distribution when the polarization mode of the incident light is radial polarization;

[0171] The first polarization subunit is configured to obtain the second spatial distribution when the polarization mode of the incident light is linearly polarized light.

[0172] Optionally, the changing unit 403 includes:

[0173] a first beam subunit, configured to obtain the first spatial distribution when the spatial mode of the incident light is a Gaussian beam;

[0174] The second beam subunit is configured to obtain the second spatial distribution when the spatial mode of the incident light is a hollow beam.

[0175] Optionally, the first construction subunit includes:

[0176] a carrier transition subunit, configured to cause the spin energy level of the ion to undergo carrier transition while the phonon energy level remains unchanged when the changed Rabi frequency is the first spatial distribution;

[0177] The first utilizing subunit is configured to utilize the carrier transition to construct the single-bit quantum gate.

[0178] Optionally, the second construction subunit includes:

[0179] A red sideband transition subunit 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 when the changed Rabi frequency is the second spatial distribution, so that the spin energy level of the ion increases and the phonon energy level decreases, resulting in a red sideband transition;

[0180] a blue sideband transition subunit, configured to set the frequency difference to a positive value of the phonon frequency when the changed Rabi frequency is the second spatial distribution, thereby reducing the spin energy level of the ion and increasing the phonon energy level, and causing a blue sideband transition;

[0181] The second utilizing subunit is configured to utilize the red sideband transition and the blue sideband transition to construct the multi-bit quantum gate.

[0182] The embodiments in this specification are described in a progressive manner. As for the devices disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple, and the relevant parts can be referred to the description of the methods.

[0183] It should also be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations 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 explicitly listed, or elements inherent to such process, method, article, or device. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of additional identical elements in the process, method, article, or device comprising the element.

[0184] The steps of the methods or algorithms described in conjunction with the embodiments disclosed herein may be implemented directly using hardware, a software module executed by a processor, or a combination of the two. The software module may be placed in random access memory (RAM), internal memory, read-only memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, registers, a hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art.

[0185] The features described in the embodiments of this specification can be replaced with each other or combined to enable professional and technical personnel in this field to implement or use this application.

[0186] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present application. Various modifications to these embodiments will be readily apparent to one 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 is not limited to the embodiments shown herein, but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for controlling the internal and external states of an atom by suppressing carrier transitions, characterized in that: include: Focus the incident light to generate a tightly focused light field; generating a Rabi frequency on the ions based on spatial parameters of the tightly focused optical field; The spatial parameters include the relative position of the ions 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 parameters, the spatial distribution of the Rabi frequency is changed to obtain a first spatial distribution and a second spatial distribution of the Rabi frequency; Construct quantum gates based on the altered Rabi frequency; Changing the spatial distribution of the Rabi frequency by changing the spatial parameter comprises: moving the center to change the relative position; During the center movement process, when the Rabi frequency is at a maximum value point, obtaining the spatial distribution of the Rabi frequency as the first spatial distribution; When the Rabi frequency is at zero, the spatial distribution of the Rabi frequency is obtained as the second spatial distribution.

2. The method according to claim 1, characterized in that The step of 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 unilateral light with the spatial parameters.

3. The method according to claim 1, characterized in that The step of constructing a quantum gate according to the changed Rabi frequency includes: Implementing carrier transition based on the first spatial distribution 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.

4. The method according to claim 1, wherein Changing the spatial distribution of the Rabi frequency by changing the spatial parameter comprises: 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; When the polarization mode of the incident light is linearly polarized light, the incident direction is orthogonal to the direction of the static magnetic field and the direction of the ion chain, and the polarization direction is perpendicular to the direction of the static magnetic field, the second spatial distribution is obtained.

5. The method according to claim 1, wherein Changing the spatial distribution of the Rabi frequency by changing the spatial parameter comprises: When the polarization mode of the incident light is radially polarized light, the first spatial distribution is obtained; When the polarization mode of the incident light is linearly polarized light, the second spatial distribution is obtained.

6. The method according to claim 1, wherein Changing the spatial distribution of the Rabi frequency by changing the spatial parameter comprises: 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.

7. The method according to claim 3, characterized in that The method of realizing carrier transition based on the first spatial distribution and constructing a single-bit quantum gate includes: When the Rabi frequency after the change is the first spatial distribution, the spin energy level of the ion undergoes a carrier transition and the phonon energy level remains unchanged; The single-bit quantum gate is constructed using the carrier transition.

8. The method according to claim 3, characterized in that The method of achieving sideband transitions that suppress carrier transitions based on the second spatial distribution and constructing a multi-bit quantum gate includes: When 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 is increased, the phonon energy level is decreased, and a red sideband transition occurs; When the changed Rabi frequency is the second spatial distribution, the frequency difference is set to a positive value of the phonon frequency, the spin energy level of the ion is reduced, the phonon energy level is increased, and a blue sideband transition occurs; The multi-bit quantum gate is constructed using the red sideband transition and the blue sideband transition.

9. A device for controlling the internal and external states of atoms by suppressing carrier transitions, characterized in that: include: Focusing units, generating units, changing units, and building units; The focusing unit is used 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 spatial parameters of the tightly focused light field; the spatial parameters include a relative position of the ion and a center of the tightly focused light field, and a polarization mode, a spatial mode, and an 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 parameter to obtain a first spatial distribution and a second spatial distribution of the Rabi frequency; The construction unit is used to construct a quantum gate according to the changed Rabi frequency; The changing unit includes: a moving subunit, configured to move the center to change the relative position; a first acquiring subunit, configured to acquire, when the Rabi frequency is at a maximum value during movement of the center, a spatial distribution of the Rabi frequency as the first spatial distribution; The second acquiring subunit is configured to acquire the spatial distribution of the Rabi frequency as the second spatial distribution when the Rabi frequency is at zero.

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