Novel method for trapping light addressing of monatomic quantum bits
By using captivity light (daurus) to address and manipulate single-atom qubits, the complex and coherent time constraints of traditional Raman light technology are solved, and simpler and more efficient quantum computing and simulation are achieved.
Patent Information
- Application Number
- CN202411272545.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-11
- Publication Date
- 2025-02-14
AI Technical Summary
When traditional Raman optical addressing technology implements single-atom qubit addressing, there are complex optical systems and coherent time constraints, making it difficult to support large-scale quantum simulation and calculation.
Using the method of imprisoning light (daurus) to address single-atom qubits, the diaurus is modulated and shifted through the orthogonal two-dimensional acousto-optical modulator AOD and the electro-optical modulator EOM, and the diaurus with sidebands is directly used to perform single-only Atomic manipulation.
The optical system is simplified, the AC-Stark frequency shift caused by Raman light is avoided, the coherence time of single-atom qubits is extended, and more efficient quantum computing and simulation are supported.
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Figure CN119443298A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of quantum computers, and in particular relates to a novel method for trapping light-addressed single-atom quantum bits. Background Art
[0002] Quantum computers have the ability to handle many specific computing problems that classical computers do not have, such as prime factor decomposition or database search. Therefore, the realization of a universal quantum computer will be of epoch-making significance. Information processing technology based on quantum computing will provide strong technical support for research in many fields such as cryptography, big data and machine learning, artificial intelligence, quantum chemistry, and drug synthesis. In view of this, research on quantum computing and quantum information processing is imminent.
[0003] In recent years, researchers have used superconducting circuits, trapped ions, silicon quantum dots, diamond vacancies, topological qubits, neutral atoms and other physical systems as qubit carriers to develop quantum computers and have made significant progress. Neutral atoms trapped in optical dipole traps have many advantages as qubits: the resonance frequency of atoms of the same type is the same, and can be initialized to a specific energy level through the optical pumping process; qubits can be encoded in stable hyperfine magnetic sub-energy levels, such as the clock transition state of cesium (Cs) or rubidium (Rb) atoms; single-bit quantum logic gates can be realized through laser fields or microwave fields; sub-microsecond controlled NOT gates can be realized through the Rydberg blockade mechanism; and the internal state readout of qubits can be realized through state-dependent fluorescence detection technology. It is precisely because of the above basic elements for manufacturing quantum computers that the neutral atom system has become one of the strong candidates for quantum computer carriers.
[0004] More importantly, neutral atom systems show great potential in scalability. Researchers can globally manipulate hundreds or thousands of atoms, and then use atomic rearrangement techniques in dipole trap arrays to prepare defect-free one-dimensional, two-dimensional, or even three-dimensional atomic arrays. These advances fully demonstrate that neutral atom systems have the ability to provide a large number of qubits for quantum computing, which is currently difficult to achieve in other physical systems.
[0005] In the study of atomic arrays, the outstanding problem is the addressing problem of single atomic quantum bits. The traditional method is to add an additional Raman light system to achieve single-atom addressing in the array. At present, although the technology of Raman light addressing single-atom quantum bits in atomic arrays has shown certain applications in the fields of quantum computing and quantum information processing, it also has two significant disadvantages;
[0006] First, complex optical systems: Raman optical addressing technology requires a complex and sophisticated Raman optical system, which requires highly precise laser control and atomic positioning to ensure accurate operation and measurement of single atomic quantum bits; The second is the coherence time limitation: Raman light will cause AC-Stark frequency shift in atoms, seriously affecting the coherence time of the internal state of a single atom, which is not conducive to large-scale quantum simulation and quantum computing. Summary of the invention
[0007] In order to solve the above technical problems, the present invention provides a novel method for trapped light addressing single-atom quantum bits, which solves the problem of complex optical systems in traditional Raman optical system addressing methods.
[0008] The specific plan is as follows: A novel method for trapped light-addressed single-atom quantum bits comprises the following steps: S1): Split the laser light generated by a laser into two beams, one beam is marked as dipole light-1, and the other beam is marked as dipole light-2; S2): The dipole light-1 is frequency-shifted by an orthogonal two-dimensional acousto-optic modulator (AOD) to generate a dipole trap array; S3): setting the frequency of the microwave driving source of the electro-optic modulator EOM according to the frequency shift frequency of each well in the dipole well array, and using the EOM to modulate the laser mode of the dipole-2 to obtain the first-order sideband; S4): The relative frequency of the primary sideband and each well in the dipole well array forms a pair of Raman lights, which can then address and manipulate individual atoms in the atomic array.
[0009] The orthogonal two-dimensional acousto-optic modulator AOD is driven by a microwave radio frequency, and the microwave radio frequency drive is used to generate a frequency shift signal.
[0010] The frequency difference Δf between every two adjacent dipole wells in the dipole well array is a fixed value.
[0011] The method for obtaining the primary sideband in step S3) comprises the following steps: S31): The dipole light-2 is incident into the electro-optic modulator EOM through the optical fiber, and the frequency of the microwave driving source is set to f to drive the electro-optic modulator EOM to work; S32): The electro-optic modulator EOM modulates the incident dipole light-2 and outputs the first-order red and blue sidebands with a bandwidth of 2f from the optical fiber, and filters to remove the first-order red sideband or the first-order blue sideband to obtain the first-order sideband.
[0012] The modulation output end of the electro-optic modulator EOM is also provided with a PBS beam splitter, and the modulated output light is divided into two beams by the PBS beam splitter, one beam is used for laser mode monitoring to determine whether the modulated primary sideband meets the requirements, and the other beam is used to manipulate single atoms.
[0013] The present invention discloses a novel method of addressing single-atom quantum bits with trapped light. Compared with the traditional method of adding an additional Raman light system to achieve single-atom addressing in an array, the present invention proposes a new addressing method, namely, using trapped light (dipole light) to address single-atom quantum bits. The specific implementation method is to modulate the dipole light through a fiber electro-optic modulator (Electro-optic modulator, EOM), and then use the dipole light with sidebands to achieve the addressing of single-atom quantum bits. The advantage of this method is that it is simple to operate and can directly convert the trapped light field into a control method without adding an additional optical path system, thereby laying a solid foundation for the realization of integrated and miniaturized quantum computers; In addition, addressing single-atom quantum bits with trapped light (dipole light) avoids the AC-Stark frequency shift caused by Raman light, greatly extending the coherence time of single-atom quantum bits. BRIEF DESCRIPTION OF THE DRAWINGS
[0014] Figure 1 Schematic diagram of the dipole trap array generated by Dipole Light-1.
[0015] Figure 2 is a schematic diagram of a dipole trap array.
[0016] Figure 3 It is a schematic diagram of electro-optic modulator (EOM) modulating laser.
[0017] Figure 4 This is a schematic diagram of how Dipole-2 modulates different primary red and blue sidebands through an electro-optical modulator (EOM).
[0018] Figure 5 Schematic diagram of the relative frequency of the first-order sideband and each well in the dipole well array forming a pair of Raman lights.
[0019] Figure 6 The circular polarization well measured in the present invention is and Rabi oscillation diagram between states. DETAILED DESCRIPTION
[0020] The following will be combined with the accompanying drawings in the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the implementation of the present invention, not all of the implementations. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.
[0021] A novel method for trapped light-addressed single-atom quantum bits comprises the following steps: S1): Split the laser light generated by a laser into two beams, one is labeled as dipole-1 and the other is labeled as dipole-2; in the field of single atom trapping, the laser used to trap atoms is called dipole light; S2): The dipole light-1 is frequency-shifted by an orthogonal two-dimensional acousto-optic modulator (AOD) to generate a dipole trap array; Figure 1-2 As shown; The orthogonal two-dimensional acousto-optic modulator AOD is driven by a microwave radio frequency, and the microwave radio frequency drive is used to generate a frequency shift signal.
[0022] The number of dipole wells in the dipole well array is related to the frequency shift setting of the orthogonal two-dimensional acousto-optic modulator (AOD).
[0023] In this embodiment, the dipole light-1 is a laser with a wavelength of 830 nm, and the 830 nm dipole light is modulated by a microwave radio frequency driven orthogonal two-dimensional acousto-optic modulator (AOD) to generate a 1×4 dipole well array; The frequency difference Δf between every two adjacent dipole wells in the dipole well array is a fixed value. In this embodiment, the frequency difference between two adjacent dipole wells is 3 MHz, that is, Δf=3 MHz. Figure 2 As shown in the figure, a rubidium-87 atom is trapped in each well, and a 1×4 single atom array is obtained. In quantum computing, it is necessary to address a specific atom in the atomic array and manipulate it.
[0024] The four dipole traps are labeled trap1, trap2, trap3, and trap4; exist Figure 1 In the figure, the carrier frequency is indicated by a black dotted line. In this embodiment, the carrier frequency Carrier is marked as 0 MHz, which is a relative frequency relative to the laser frequency after the frequency shift. The laser frequency of trap1 differs from the carrier frequency before frequency shift by 90 MHz, the laser frequency of trap2 differs from the carrier frequency before frequency shift by 93 MHz, the laser frequency of trap3 differs from the carrier frequency before frequency shift by 96 MHz, and the laser frequency of trap4 differs from the carrier frequency before frequency shift by 99 MHz; S3): The frequency of the microwave driving source of the electro-optic modulator EOM is set according to the frequency shift frequency of each well in the dipole well array, and the EOM is used to modulate the laser mode of the dipole-2 to obtain the first-order sideband; Figure 3-4 As shown; S4): The relative frequency of the primary sideband and each well in the dipole well array constitutes a pair of Raman lights, which can then address and manipulate individual atoms in the atomic array. Figure 5 shown.
[0025] The method for obtaining the primary sideband in step S3) comprises the following steps: S31): The dipole light-2 is incident into the electro-optic modulator EOM through the optical fiber, and the frequency of the microwave driving source is set to f to drive the electro-optic modulator EOM to work; S32): The electro-optic modulator EOM modulates the incident dipole light-2 and outputs the first-order red and blue sidebands with a bandwidth of 2f from the optical fiber, and filters to remove the first-order red sideband or the first-order blue sideband to obtain the first-order sideband.
[0026] The modulation output end of the electro-optic modulator EOM is also provided with a PBS beam splitter, and the modulated output light is divided into two beams by the PBS beam splitter, one beam is used for laser mode monitoring to determine whether the modulated primary sideband meets the requirements, and the other beam is used to manipulate single atoms.
[0027] In this embodiment, the dipole light-2 is a laser with a wavelength of 830 nm. The dipole light-2 is modulated by laser mode. The dipole light is incident on the electro-optic modulator EOM crystal through the optical fiber, and then emitted from the optical fiber after being modulated by the electro-optic modulator EOM crystal. The emitted light is split by the PBS beam splitter, 10% of which is used for laser mode monitoring, and 90% is incident on the single atom manipulation system to manipulate the internal state of the atom.
[0028] The microwave source generates about 3.4 GHz of microwaves to drive the electro-optic modulator EOM crystal. The dipole light passing through the electro-optic modulator EOM crystal is modulated to produce primary red and blue sidebands of ±3417.344 MHz. The microwave driving power of the electro-optic modulator EOM crystal is continuously adjusted until the carrier frequency disappears. The primary red and blue sidebands differ by 6834.688 MHz, which constitutes the two-photon Raman transition of the rubidium-87 atom and can be used to manipulate the internal state of the rubidium-87 atom.
[0029] Any first-order sideband can be filtered out by filtering, and a certain microwave frequency can be set so that the carrier frequency and another first-order sideband form a two-photon Raman transition of a single atom.
[0030] For addressing single atoms in trap1, trap2, trap3, and trap4, the frequencies of the electro-optic modulator EOM microwave driving source are set to 6924.688 MHz, 6927.688 MHz, 6930.688 MHz, and 6933.688 MHz, respectively; red and blue sidebands with bandwidths of ±6924.688 MHz, ±6927.688 MHz, ±6930.688 MHz, and ±6933.688 MHz can be obtained, respectively, as shown in Figure 4 In this embodiment, the model of the microwave driving source is Keysight E8663D.
[0031] To address a specific atom in an atomic array and manipulate it, the traditional method is to image on an electron-multiplying charge coupled device (EMCCD), mark the position of each atom, and then deterministically apply a Raman light system to manipulate the single atom. This addressing method is complex and not conducive to improving integration.
[0032] The design of the present invention eliminates the need for complex Raman optical systems and imaging systems, and accurately controls the microwave frequency setting of the electro-optic modulator EOM drive source, so that the frequency of each well in the dipole trap array formed by the primary blue sideband of dipole light-2 and dipole light-1 can just form a pair of Raman lights, thereby addressing and manipulating a single atom in the atomic array.
[0033] like Figure 5 As shown in (a), addressing a single atom in the 1×4 dipole trap array trap1, trap1 is shifted 90 MHz relative to the carrier frequency, and the microwave frequency of the electro-optic modulator EOM driving source is set to 6924.688 MHz ((6834.688+90) MHz). The first-order blue sideband frequency of dipole light-2 is (6834.688+90) MHz, so the laser frequency of trap1 differs from the first-order blue sideband frequency of dipole light-2 by 6834.688 MHz, which just constitutes the two-photon Raman transition frequency of the atoms in the trap1 trap.
[0034] Similarly, to address a single atom in the 1×4 dipole trap array trap2, it is only necessary to set the microwave frequency of the electro-optic modulator EOM driving source to 6927.688 MHz ((6834.688+93) MHz). The laser frequency of trap2 differs from the first-order blue sideband frequency of dipole light-2 by 6834.688 MHz, which just constitutes the two-photon Raman transition frequency of the atoms in trap2, as shown in Figure 5 (b) as shown; To address a single atom in the 1×4 dipole trap array trap3, we only need to set the microwave frequency of the electro-optic modulator EOM driving source to 6930.688 MHz ((6834.688+96) MHz). The laser frequency of trap3 differs from the first-order blue sideband frequency of dipole light-2 by 6834.688 MHz, which just constitutes the two-photon Raman transition frequency of the atoms in trap3, as shown in Figure 5 (c) as shown; To address a single atom in the 1×4 dipole trap array trap4, we only need to set the microwave frequency of the electro-optic modulator EOM driving source to 6933.688 MHz ((6834.688+99) MHz). The laser frequency of trap4 differs from the first-order blue sideband frequency of dipole light-2 by 6834.688 MHz, which just constitutes the two-photon Raman transition frequency of the atoms in trap4. Figure 5 (d) shown.
[0035] For a single atom trapped in a specific dipole trap, its internal state distribution is random. It is necessary to prepare the atom to a certain magnon energy level through optical pumping to realize the preparation of the initial state of the single-atom quantum bit. The optical pumping process uses special transition selection rules and optical pumping light settings to prevent a certain magnon energy level of the atom from interacting with the optical pumping light, forming a so-called dark state. Atoms at other magnon energy levels will be continuously pumped until all atoms are accumulated in the dark state, ultimately realizing the preparation of the initial state of the single-atom quantum bit.
[0036] After the initial state of the single-atom quantum bit is prepared, a specific method is needed to manipulate the internal state of the single atom. There are currently two commonly used methods: one is the two-photon Raman process, which uses two beams of two-photon transition resonance and single-photon transition large detuned light pulses to act on atoms. By changing the pulse width, the internal state of atoms can be manipulated. The disadvantage is that Raman light will cause AC-Stark frequency shifts to atoms; the second is to use single-photon microwave transitions between the energy levels of hyperfine magnetons in the ground state of neutral atoms to manipulate the internal state of single-atom quantum bits, eliminating the AC-Stark frequency shift caused by Raman light to atoms, and more accurately measuring the energy level interval of the ground state of neutral atoms. The disadvantage is that the intensity of the interaction between microwaves and atoms is related to the position and tilt angle of the microwave horn.
[0037] In the present invention, trapped light is used to address single atoms and manipulate their internal states, thus avoiding the shortcomings of common methods for manipulating the internal states of atoms. For example, for the internal state manipulation of single atoms in trap1, first, the linearly polarized dipole trap is loaded with rubidium-87 atoms; then, the EOM crystal modulation signal of dipole light-2 is turned on, and the frequency is set to 6924.688 MHz, that is, the two-photon Raman transition manipulates the internal state; finally, the EOM crystal modulation signal of dipole light-2 is turned off, and the state of single atoms is detected in the linearly polarized dipole trap. Experimental measurements show that the circularly polarized trap and The Rabi oscillations between states are as follows Figure 3 As shown, the feasibility of the scheme of the present invention is confirmed.
[0038] Rubidium atoms have a rich set of magnetic sub-energy levels. The clock transition state insensitive to magnetic fields in the ground state is selected to encode quantum bits for the storage of quantum information. The specific definition of quantum bits is: ; Among them, 5 is the principal quantum number, 1 / 2 is the angular quantum number, S is the ground state of the fine structure; F is the magnon energy level in the hyperfine structure; mF is the magnetic quantum number in the Zeeman splitting.
[0039] Compared with the traditional Raman light addressing method for single atoms in an array, the present invention discloses a new method for addressing single atoms with trapped light (dipole light) and manipulating their internal states, which is consistent with the principle of manipulating the internal states of single atoms by two-photon Raman transitions. The electro-optic modulator EOM is used to modulate the dipole light, and the dipole light with sidebands is used to manipulate the internal states of single atoms. The advantage is that the operation is simple, and the trapped light field is directly modulated into a control method without adding an additional optical path system, which is more conducive to the miniaturization and integration of the system. The key is to avoid the limitation of the Raman light system on the coherence time of the internal states of single atoms, so that atoms can obtain a sufficiently long coherence time for quantum computing and quantum simulation.
[0040] The technical means disclosed in the scheme of the present invention are not limited to the technical means disclosed in the above-mentioned implementation mode, but also include technical schemes composed of any combination of the above-mentioned technical features. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications are also regarded as the protection scope of the present invention.
Claims
1. A novel method for trapped light-addressed single-atom quantum bits, characterized in that: The steps include: S1): Split the laser light generated by a laser into two beams, one beam is marked as dipole light-1, and the other beam is marked as dipole light-2; S2): The dipole light-1 is frequency-shifted by an orthogonal two-dimensional acousto-optic modulator (AOD) to generate a dipole trap array; S3): setting the frequency of the microwave driving source of the electro-optic modulator EOM according to the frequency shift frequency of each well in the dipole well array, and using the EOM to modulate the laser mode of the dipole-2 to obtain the first-order sideband; S4): The relative frequency of the primary sideband and each well in the dipole well array forms a pair of Raman lights, which can then address and manipulate individual atoms in the atomic array.
2. The novel method for trapped light-addressed single-atom quantum bits according to claim 1, characterized in that: The orthogonal two-dimensional acousto-optic modulator AOD is driven by a microwave radio frequency, and the microwave radio frequency drive is used to generate a frequency shift signal.
3. The novel method for trapped light-addressed single-atom quantum bits according to claim 1, characterized in that: The frequency difference Δf between every two adjacent dipole wells in the dipole well array is a fixed value.
4. The novel method for trapped light-addressed single-atom quantum bits according to claim 1, characterized in that: The method for obtaining the primary sideband in step S3) comprises the following steps: S31): The dipole light-2 is incident into the electro-optic modulator EOM through the optical fiber, and the frequency of the microwave driving source is set to f to drive the electro-optic modulator EOM to work; S32): The electro-optic modulator EOM modulates the incident dipole light-2 and outputs the first-order red and blue sidebands with a bandwidth of 2f from the optical fiber, and filters to remove the first-order red sideband or the first-order blue sideband to obtain the first-order sideband.
5. The novel method for trapped light-addressed single-atom quantum bits according to claim 4, characterized in that: The modulation output end of the electro-optic modulator EOM is also provided with a PBS beam splitter, and the modulated output light is divided into two beams by the PBS beam splitter, one beam is used for laser mode monitoring to determine whether the modulated primary sideband meets the requirements, and the other beam is used to manipulate single atoms.