Environment field mitigation for rydberg atom quantum devices and methods

Abstract

The application provides an environmental electric field neutralization device and method applied to a Rydberg atom quantum device, and belongs to the technical field of atomic physics. The ultra-high vacuum environmental electric field neutralization device comprises a magneto-optical trap and an ionization laser. The magneto-optical trap is configured to capture and cool atoms in an ultra-high vacuum cavity of the Rydberg atom quantum device to form a high-density cold atom group, and the high-density cold atom group is bound in a first spatial region affected by an environmental electric field. The magneto-optical trap comprises a cooling laser configured to emit cooling laser to the first spatial region, and to make part of the atoms in the high-density cold atom group excited to an excited state while capturing and cooling the atoms. The ionization laser is configured to emit ionization laser to the first spatial region to make the atoms in the excited state undergo quantum-enhanced ionization and generate plasma. The charged particles in the plasma move under the action of the environmental electric field and form a compensating charge distribution, thereby neutralizing the environmental electric field.

Description

Technical Field

[0001] This invention relates to the field of atomic physics, and more specifically, to an environmental electric field neutralization device and method for use in the Rydberg atomic quantum device. Background Technology

[0002] Due to their large dipole moments, long-range interactions, and high sensitivity to external fields, Rydberg atoms have shown significant application value in quantum precision measurement and sensing, quantum simulation, quantum computing, and quantum communication in recent years, and have become an important technological route in neutral atom systems.

[0003] However, the ambient electric field has a significant impact on Rydberg atoms. This is because Rydberg atoms have high polarizability and a significant Stark effect, making them extremely sensitive to ambient electric fields. Even a weak residual ambient electric field can cause Rydberg level frequency shifts, spectral line broadening, and deterioration of coherence properties, thereby reducing the stability, controllability, and reproducibility of experimental results. Therefore, how to effectively suppress the residual ambient electric field in the experimental region has always been an important technical problem in this field.

[0004] Currently, the mainstream methods for eliminating and shielding electric fields in Rydberg quantum devices fall into two categories: for electric fields with known sources, attempts are made to address the problem at its source (e.g., photo-induced atom desorption); for electric fields with unknown or complex sources, static shielding (e.g., Faraday cages) or active feedback compensation (e.g., applying a reverse electric field through external electrodes) are employed. However, these methods often suffer from increased system complexity, limited applicability, slow field elimination speed, or insufficient stability under different material systems and experimental configurations. Other general solutions require ionization of vacuum background gas particles, specifically direct ionization from the ground state, which necessitates high laser energy and a laser wavelength less than 200 nm, making them unsuitable for direct application in Rydberg quantum devices operating under ultra-high vacuum conditions. Summary of the Invention

[0005] In view of this, the present invention provides an environmental electric field neutralization device and method for use in a Rydberg atomic quantum device. Unlike existing mainstream technologies, this solution is a quantum-enhanced, measurement-feedback-free active electric field compensation scheme that can reuse existing modules in the Rydberg atomic quantum device to achieve efficient neutralization of environmental electric fields from arbitrary sources in an ultra-high vacuum environment.

[0006] One aspect of the present invention provides an environmental electric field neutralization device for a Rydberg atomic quantum device, comprising a magneto-optical trap and an ionizing laser. The magneto-optical trap is configured to trap and cool atoms within the vacuum cavity of the Rydberg atomic quantum device, forming a high-density cold atom cluster, which is confined within the region of influence of the environmental electric field, i.e., a first spatial region. The magneto-optical trap includes a cooling laser that emits cooling laser light into the first spatial region to induce excited transitions of some atoms in the high-density cold atom cluster to excited states while trapping and cooling the atoms. The ionizing laser is configured to emit ionizing laser light into the first spatial region to induce quantum-enhanced ionization of the excited atoms, generating plasma. Charged particles in the plasma move under the influence of the environmental electric field and form a compensating charge distribution to neutralize the environmental electric field.

[0007] According to an embodiment of the present invention, the vacuum type of the above-mentioned vacuum cavity is a pressure less than 10. -9 Ultra-high vacuum of mbar, with a gas particle density inside the vacuum chamber of less than 2.5 × 10⁻⁶ mbar. 7 cm −3 This is to increase the lifetime of atoms in the trapped structure.

[0008] According to an embodiment of the present invention, the surface of the optical window of the vacuum cavity is coated with an antireflection film, which is configured to reduce the transmission loss of the cooling laser or the ionizing laser passing through the optical window.

[0009] According to an embodiment of the present invention, the material of the optical window of the vacuum cavity includes fused silica, BK7, and high borosilicate. The optical window material has no intrinsic birefringence to reduce the polarization change when the cooling laser or the ionizing laser passes through the optical window.

[0010] According to an embodiment of the present invention, the wavelengths of both the cooling laser and the ionizing laser are greater than 200 nm, and the wavelength of the cooling laser is greater than the wavelength of the ionizing laser.

[0011] According to an embodiment of the present invention, the above-mentioned environmental electric field neutralization device further includes: a focusing module located between the magneto-optical trap and the ionizing laser, configured to change the spot size of the ionizing laser to change the size of the irradiation area of ​​the ionizing laser.

[0012] According to an embodiment of the present invention, the above-mentioned environmental electric field neutralization device further includes: an electric field detection module configured to determine the electric field strength of the environmental electric field by detecting the Stark frequency shift, thereby characterizing the electric field neutralization effect of the charged particles.

[0013] According to an embodiment of the present invention, the ionizing laser is provided by a Rydberg state-excited laser in the aforementioned Rydberg atomic quantum device, and the ionizing laser and the Rydberg state-excited laser share the same laser source.

[0014] According to an embodiment of the present invention, the neutralization process of the above-mentioned environmental electric field is carried out actively and does not depend on the measurement and feedback of the environmental electric field.

[0015] Another aspect of the present invention provides a method for neutralizing the environmental electric field of a Rydberg atomic quantum device. The method, applied to the aforementioned environmental electric field neutralization device, includes: capturing and cooling atoms within the vacuum cavity of the Rydberg atomic quantum device using a magneto-optical trap to form a high-density cold atom cluster, wherein the high-density cold atom cluster is confined within a first spatial region under the influence of the environmental electric field; the cooling laser of the magneto-optical trap, while capturing and cooling the atoms, simultaneously induces some atoms in the high-density cold atom cluster to undergo excited transitions to excited states; ionizing laser light is emitted into the first spatial region to induce quantum-enhanced ionization of the excited-state atoms, generating plasma; charged particles in the plasma move under the influence of the environmental electric field and form a compensating charge distribution to neutralize the environmental electric field. Compared to directly ionizing ground-state atoms, this method significantly increases the ionization cross-section by exciting atoms to the excited state, meaning that a unit intensity of ionizing laser light can ionize more atoms, thereby achieving quantum-enhanced ionization and greatly improving ionization efficiency.

[0016] According to embodiments of the present invention, a high-density cold atom cluster is formed based on a magneto-optical trap and a cooled laser, and some atoms in the high-density cold atom cluster are excited to transition to an excited state. An ionizing laser is then emitted by an ionizing laser to ionize the excited atoms, generating plasma. Finally, the charged particles in the plasma, under the influence of the ambient electric field, neutralize the ambient electric field through a compensating charge distribution. This process is a quantum-enhanced, feedback-independent active electric field neutralization method. It solves the problems of slow electric field cancellation or elimination processes, unstable effects, limited applicability, and difficulty in balancing high efficiency and high stability in existing technologies. It can significantly reduce the ambient electric field within the working area in a short time, achieving rapid compensation and reset of vacuum ambient electric fields from any source within the experimental working area, with high neutralization efficiency. Furthermore, embodiments of the present invention can be implemented using existing modules in the Rydberg atomic quantum device, thus avoiding the introduction of additional compensation components and having no impact on existing experimental structures and optical path layouts. Attached Figure Description

[0017] The above and other objects, features and advantages of the present invention will become clearer from the following description of embodiments of the invention with reference to the accompanying drawings.

[0018] Figure 1A schematic diagram of an environmental electric field neutralization device applied to the Reedburg atomic quantum device according to an embodiment of the present invention is shown.

[0019] Figure 2 A schematic diagram illustrating the photoionization principle of an environmental electric field neutralization device according to an embodiment of the present invention is shown.

[0020] Figure 3 A schematic diagram of the energy levels of a Rydberg atom according to an embodiment of the present invention is shown.

[0021] Figure 4 A schematic diagram illustrating the effect of neutralizing the environmental electric field according to an embodiment of the present invention is shown.

[0022] Figure 5 A schematic diagram illustrating the stability of the environmental electric field neutralization effect according to an embodiment of the present invention is shown.

[0023] Figure 6 A schematic diagram showing the effect of neutralization by an applied electric field according to an embodiment of the present invention is illustrated.

[0024] Figure 7 A schematic diagram showing the relationship between the electric field neutralization rate and the time of each ionization operation according to an embodiment of the present invention is shown.

[0025] Figure 8 A flowchart illustrating a method for neutralizing the environmental electric field applied to a Rydberg atomic quantum device according to an embodiment of the present invention is shown. Detailed Implementation

[0026] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the invention. In the following detailed description, numerous specific details are set forth to provide a thorough understanding of the embodiments of the invention for ease of explanation. However, it will be apparent that one or more embodiments may be practiced without these specific details. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0027] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention. The terms “comprising,” “including,” etc., as used herein indicate the presence of features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0028] All terms used herein (including technical and scientific terms) have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein are to be interpreted in a manner consistent with the context of this specification, and not in an idealized or overly rigid way.

[0029] When using expressions such as "at least one of A, B and C", they should generally be interpreted in accordance with the meaning that is commonly understood by those skilled in the art (e.g., "a system having at least one of A, B and C" should include, but is not limited to, a system having A alone, a system having B alone, a system having C alone, a system having A and B, a system having A and C, a system having B and C, and / or a system having A, B and C, etc.).

[0030] In ultra-high vacuum experimental setups based on Rydberg atoms, the preparation of Rydberg states is necessary, which involves exciting atoms with a laser at a resonance frequency precisely matched to the Rydberg transition. To obtain this resonance frequency, the laser frequency needs to be scanned near the expected frequency to obtain the change in the probability of an atom being excited in a specific quantum state (the lower state of the Rydberg transition) as a function of the laser frequency; this is known as the Rydberg transition resonance line. Ideally, a clear Rydberg transition resonance line should exist near the expected resonance frequency. However, in a specific Sr. 88 Rydberg atom experimental setup, it has been observed that, over a wide frequency range, atoms in the lower Rydberg transition state exhibit a continuous loss independent of the specific frequency under Rydberg laser irradiation, without a clearly visible spectral line. This indicates a large ambient electric field, which needs to be cleared or compensated for.

[0031] Because the sources of the environmental electric field that needs to be removed or compensated are quite complex, the conventional approach is usually to analyze the source of the electric field and treat it accordingly. For example, many papers mention that atoms adsorbed on the inner surface of a vacuum glass cavity generate an electric field, and that using a 365 nm ultraviolet LED (Light Emitting Diode) can desorb atoms from the inner wall; this process is called photo-induced atomic desorption. Following this approach, a 365 nm LED was used to illuminate the vacuum glass cavity in the experimental setup, but the influence of the electric field was still observed. Subsequently, it was speculated that the electric field might originate from the charges carried by insulating devices outside the vacuum glass cavity, so an ion fan was attempted to neutralize these charges, but with little success. Next, multiple layers of aluminum foil were wrapped around several components outside the vacuum glass cavity (magnetic field coil frame, objective lens, etc.) and grounded, making it a Faraday cage to shield the external electric field. After this process, the Rydberg spectrum began to show changes in atomic loss with frequency, but this loss was not stable and changed in each spectral scan.

[0032] As mentioned above, although various conventional methods known in the field were tried, none improved the observed continuous spectrum phenomenon. Further exploration involved reducing the principal quantum number of the Rydberg state. This is because the higher the principal quantum number of a Rydberg state, the farther the outer electrons are from the atomic nucleus. Reducing the principal quantum number lowers the sensitivity of the Rydberg state to external electric fields. For example, reducing the principal quantum number from 61 to 44 reduced the sensitivity of the Rydberg state to electric fields to about one-tenth of its previous level. Initially, clear spectral lines were not observed under lower principal quantum number conditions, and the resonance spectrum exhibited certain spatial distribution characteristics. However, after several days of spectral scanning, the Rydberg spectral lines gradually became clear and distinguishable. After obtaining clean and distinguishable spectral lines, it was further determined which experimental operations affected the resonance frequency. It was subsequently discovered that only by simultaneously loading atoms into a magneto-optical trap and irradiating them with a 365 nm ultraviolet LED could the electric field be reduced; applying only one condition resulted in an increased electric field. Since clearly distinguishable spectral lines are a prerequisite for judging changes in the electric field, the above-mentioned pattern was difficult to discover under the original high principal quantum number condition. Furthermore, whether the electric field decreases depends on whether atoms are loaded in the magneto-optical trap, indicating that this electric field neutralization mechanism is completely different from the photo-induced atom desorption mentioned in other literature. Subsequent studies revealed the reason for the significant reduction in the electric field: the ultraviolet lamp ionizes the atoms in the excited state in the magneto-optical trap, generating plasma. Charged particles in the plasma move under the influence of the ambient electric field and eventually adsorb onto the inner wall of the vacuum glass cavity, thereby compensating for and shielding the original electric field.

[0033] Ionizing atoms in a magneto-optical trap with a UV LED can reduce the electric field, but this process is very slow and fails to completely compensate for the electric field to zero. Subsequently, an attempt was made to multiplex a Rydberg laser as an ionizing laser during the atom loading stage of the magneto-optical trap to irradiate the atoms. It was subsequently observed that under highly focused Rydberg laser irradiation, the number of atoms in the magneto-optical trap decreased rapidly, and the lifetime was significantly shortened. By applying a Rydberg atom ionization process for several hundred milliseconds during each magneto-optical trap loading stage, the electric field was found to be completely compensated after several hours. Under continuous electric field compensation, the Rydberg spectral lines were also stabilized within the range of ±0.1 MHz, exhibiting very good stability.

[0034] Existing approaches to eliminating or compensating for environmental electric fields tend to analyze their sources and address the problem at its root using readily available, mature technologies. For example, given that atoms used in experiments adsorb onto the inner surface of the scientific cavity glass, generating an electric field within the cavity, photodesorption, a well-established technique, is employed. However, the effectiveness of photodesorption depends on the bonding characteristics between the atoms used in the experiment and the inner wall of the vacuum glass window. Furthermore, in actual experimental environments, atoms adsorbed on the inner wall of the cavity, accumulated charges on adjacent dielectric surfaces, surface charging effects of devices, and background fields generated by external electrodes can all contribute to stray electric fields in the atomic working region. These fields may accumulate naturally over experimental cycles or be introduced by the operation of external devices, causing the actual electric field distribution in the atom's region to change over time. Because the sources of the environmental electric field are not singular, photodesorption cannot effectively eliminate the electric field in the Rydberg quantum atomic device.

[0035] When the source of the electric field is complex and difficult to analyze, current approaches tend to shield between the source and the atoms. For example, several layers of aluminum foil are wrapped around the vacuum cavity and grounded to achieve a Faraday cage effect, shielding the electric field outside the foil. In practice, to allow the laser to properly irradiate the atoms, openings need to be made in the aluminum foil, leading to electric field leakage. Furthermore, this method cannot shield the electric field from the charges within the aluminum foil shielding layer. Alternatively, active feedback compensation can be used, for example, by placing multiple electrodes in the vacuum cavity and applying a reverse electric field through the electrodes for compensation. The limitations of these methods are: the electrode structure needs to be designed in advance within the vacuum cavity, adding extra complexity to the system; modifications to existing systems are very difficult; and periodic calibration is required when the ambient electric field changes slowly.

[0036] The aforementioned schemes often suffer from increased system complexity, limited optical path layout, restricted applicability, slow field elimination speed, and insufficient stability under different material systems, different adsorbed particles, and different experimental configurations. Especially when rapid and reproducible experimental conditions are required and high electric field stability is demanded, the above schemes usually cannot simultaneously achieve high efficiency and high stability.

[0037] Breaking away from the path dependence inherent in the mainstream approach of "solving the source when the electric field is known" and "static shielding or active feedback compensation when the electric field is unknown," the technical concept of this invention is to directly perform active electric field compensation without relying on measurement feedback. It establishes a new compensation charge distribution by actively generating plasma and utilizing the migration and surface adsorption behavior of charged particles within it in the electric field. This allows for the handling of stray fields naturally accumulated in a vacuum environment and also for compensation of externally applied electric fields. Compared to solutions that rely on additional compensation electrodes or shielding structures, this approach can fully reuse existing modules in the device, avoiding the introduction of additional compensation components and preventing impact on existing experimental structures and optical path layouts. Furthermore, compared to solutions that require repeated electric field measurements before compensation, this approach reduces the time overhead of additional measurement and adjustment steps, thus improving experimental cycle efficiency and operational stability.

[0038] Furthermore, directly ionizing ground-state background particles or ground-state experimental atoms in a vacuum results in a very small ionization cross-section (a very low ionization probability per unit light intensity). The present invention addresses this by using a cooling laser to first excite atoms in the magneto-optical trap, then ionizing them. Because the ionizing laser energy exceeds the ionization threshold from the excited state, single-photon ionization is possible, resulting in a much larger ionization cross-section for the excited state than for the ground state, significantly improving ionization efficiency. In other words, the present invention achieves improved ionization efficiency through the quantum process of exciting atoms to an excited state; therefore, it is a quantum-enhanced ionization process. The characteristic of exciting atoms in the magneto-optical trap effectively supports the subsequent ionization process.

[0039] Figure 1 A schematic diagram of an environmental electric field neutralization device applied to the Reedburg atomic quantum device according to an embodiment of the present invention is shown.

[0040] like Figure 1 As shown, the environmental electric field neutralization device applied to the Rydberg atomic quantum device includes a magneto-optical trap 101 and an ionizing laser 102. The magneto-optical trap 101 includes a cooled laser 1011.

[0041] The magneto-optical trap 101 is configured to capture and cool atoms within the vacuum cavity of the Rydberg atomic quantum device to form a high-density cold atom cluster, wherein the high-density cold atom cluster is confined in a first spatial region under the influence of an ambient electric field, and the cooling laser 1011 is configured to emit a cooling laser into the first spatial region, thereby causing some atoms of the high-density cold atom cluster to undergo excited transitions to excited states while capturing and cooling atoms.

[0042] The magneto-optical trap 101 is a device for trapping and cooling neutral atoms, combining laser cooling and magnetic field manipulation. In the magneto-optical trap 101, three pairs of cooling lasers propagate in mutually perpendicular directions, each pair containing two cooling laser beams in opposite directions. These lasers form an optical cluster in a first spatial region, cooling the atoms through the Doppler effect and subjecting them to velocity-dependent damping forces. A cooling laser 1011 is used to emit the cooling laser. Simultaneously, a pair of anti-Helmholtz coils generate a non-uniform magnetic field in the first spatial region, with a zero central magnetic field and a constant gradient. Neutral atoms undergo energy level splitting in the non-uniform magnetic field, resulting in Zeeman shifts. When an atom deviates from the trap center, the Zeeman shift caused by the non-uniform magnetic field changes its energy level transition frequency, bringing it closer to the frequency of the cooling laser with a specific polarization direction. This causes it to be scattered towards the center by a scattering force, pushing it back towards the center. The synergistic effect of multiple lasers and magnetic fields allows the atoms to be simultaneously cooled and confined in a tiny region in three-dimensional space, forming a high-density cold atom cluster with a temperature close to absolute zero.

[0043] The cooling laser emitted by the cooling laser 1011 is used not only to slow down and cool atoms, but also to induce stimulated transitions in some atoms within the high-density cold atom cluster. Specifically, in the magneto-optical trap, atoms in the high-density cold atom cluster absorb the energy of laser photons during the cooling process, transitioning from the ground state to an excited state. After the stimulated excitation of atoms and the downward radiation from the excited state reach equilibrium, some atoms are always in the excited state. This process provides the necessary source of excited-state atoms for subsequent operations.

[0044] The ambient electric field refers to the electric field in the working area of ​​the Rydberg quantum atom device, namely the residual electric field, stray electric field, or background electric field in the Rydberg atom ultra-high vacuum experimental device, including but not limited to the stray electric field formed by particles adsorbed on the inner wall of the vacuum cavity, the local electric field formed by the charging of the adjacent medium surface, the background electric field caused by the charging of external vacuum devices, and the controllable electric field applied by electrodes or other external field sources.

[0045] The ionizing laser 102 is configured to emit ionizing laser light into a first spatial region, thereby causing the excited atoms to undergo quantum-enhanced ionization and generate plasma; wherein, the charged particles in the plasma move under the influence of the ambient electric field and form a compensating charge distribution to neutralize the ambient electric field.

[0046] Figure 2 A schematic diagram illustrating the photoionization principle of an environmental electric field neutralization device according to an embodiment of the present invention is shown.

[0047] like Figure 2As shown, the atoms in the vacuum cavity are strontium atoms. When ionizing laser light irradiates the excited-state strontium atoms in the magneto-optical trap, plasma is generated based on photoionization. The plasma contains a large number of electrons and ions, i.e., charged particles. Under the influence of the existing ambient electric field, the charged particles move in the opposite direction and are adsorbed, deposited, or form stable or quasi-stable compensating charge distributions on the inner wall of the vacuum cavity, the surface of the medium, or other boundary locations, thereby compensating for, weakening, or shielding the original ambient electric field. As the compensating charge distribution is established, the equivalent electric field strength in the working area decreases, and the frequency shift, broadening, or coherent degradation of the Rydberg transition is alleviated accordingly.

[0048] Figure 3 A schematic diagram of the energy levels of a Rydberg atom according to an embodiment of the present invention is shown.

[0049] like Figure 3 As shown, the magneto-optical trap of the environmental electric field neutralization device in this embodiment of the invention forms a high-density cold atomic cluster, causing some atoms to undergo excited transitions to the excited state. This allows an ionizing laser to be emitted, causing the excited atoms to couple with a continuous state above the ionization limit, resulting in ionization and the generation of plasma. Finally, the charged particles in the plasma, under the influence of the environmental electric field, neutralize the environmental electric field through a compensating charge distribution. Because the ionizing laser energy is greater than the energy difference between the excited state and the ionization limit, the ionization cross-section is significantly improved compared to direct multiphoton ionization of ground-state atoms. This process is a quantum-enhanced ultra-high vacuum electric field neutralization method. Figure 3 In the embodiment shown, strontium-88 atoms are used as experimental atoms, and the existing Rydberg laser in the Rydberg atom experiment can be directly reused for ionization, thereby avoiding the introduction of additional compensation components and having no impact on the existing experimental structure and optical path layout.

[0050] According to an embodiment of the present invention, the vacuum type of the vacuum cavity is a pressure less than 10. -9 Ultra-high vacuum of mbar, with a gas particle density inside the vacuum chamber of less than 2.5 × 10⁻⁶ mbar. 7 cm −3 This is to increase the lifetime of atoms in the trapped structure.

[0051] The vacuum chamber is the core container in the Rydberg quantum atom device, providing an ultra-high vacuum environment to isolate Rydberg atoms from interference by air molecules. Rydberg atoms are enormous and highly susceptible to disturbance; the ultra-high vacuum environment reduces the impact of background gas collisions on their lifetime. Using vacuum pumps and other pumping systems, the density of air molecules within the chamber can be reduced to extremely low levels, significantly decreasing collisions between atoms and residual gas. However, to maintain the ultra-high vacuum environment, the background gas inside the vacuum chamber is extremely rarefied, lacking sufficient gas particles for direct ionization. To generate a sufficient number of charged particles, the atomic density can be increased within a small region of the ultra-high vacuum. Therefore, a controllable high-concentration cold atomic gas needs to be actively constructed using the magneto-optical trap 101 to increase the atomic density in the first spatial region before efficient ionization using an ionization laser, generating a sufficient number of charged particles to effectively neutralize the ambient electric field.

[0052] According to an embodiment of the present invention, the optical window of the vacuum cavity is coated with an antireflective film, and the selected materials include fused silica, BK7, and high borosilicate silicon. These optical window materials have no intrinsic birefringence. The wavelengths of both the cooling laser and the ionizing laser are greater than 200 nm, and the wavelength of the cooling laser is greater than that of the ionizing laser.

[0053] Since the cooled and ionized lasers are located outside the vacuum cavity, they need to be irradiated into the first spatial region through the optical window of the vacuum cavity. In the Rydberg quantum atomic device, to improve the efficiency of laser manipulation of atomic internal states, an antireflection coating is typically deposited on the optical window of the vacuum cavity. This maximizes the transmittance within the existing laser wavelength range of the Rydberg quantum atomic device, ensuring efficient transfer of laser energy into the vacuum cavity and optimizing the interaction process between the laser and atoms. While meeting the existing requirements, the material selection and film system design of the deposited antireflection coating cannot allow light with wavelengths less than 200 nm to pass through. Meanwhile, the materials used for the optical window include fused silica, BK7, and high borosilicate glass. These materials have no intrinsic birefringence and possess uniform optical properties, which can reduce the polarization change that occurs when the laser passes through the optical window, thereby maintaining polarization consistency during the laser-atom interaction process and ensuring the accuracy and repeatability of experimental results. Furthermore, these materials have low coefficients of thermal expansion and can be baked to temperatures above 150°C, enabling the ultra-high vacuum cavity to achieve the target vacuum level. Furthermore, since the optical window is coated with an antireflective film, and the aforementioned material is chosen for the optical window, the wavelengths of the cooling and ionizing lasers need to be limited. If the wavelength of the cooling or ionizing laser is less than 200 nm, the transmittance of the cooling or ionizing laser relative to the optical window will be significantly reduced, resulting in inefficient laser ionization operations and even irreversible damage to the coated antireflective film, severely affecting subsequent Rydberg atom experiments. In addition, considering the direct ionization of residual gas particles in the vacuum background, vacuum ultraviolet light less than 200 nm is typically required; the aforementioned wavelength limitations of the coating and window directly negate the possibility of such a solution.

[0054] Furthermore, since one of the effects of cooled lasers is to induce excited transitions of atoms from their ground state to excited states, the energy difference between these two levels is relatively small. Therefore, photons from cooled lasers only need to carry lower energy. Ionizing lasers, on the other hand, need to convert excited atoms into ions. This process requires overcoming the remaining binding forces between electrons and the atomic nucleus, and the energy required is typically higher than that of cooled transitions. Therefore, to provide higher energy, ionizing lasers need to have shorter wavelengths than cooled lasers.

[0055] According to an embodiment of the present invention, the ambient electric field neutralization device further includes: a focusing module located between the magneto-optical trap and the ionizing laser, configured to change the spot size of the ionizing laser to change the size of the irradiation area of ​​the ionizing laser.

[0056] The focusing module is used to change the spot size of the incident ionizing laser, thereby adjusting the effective coverage area of ​​the ionizing laser irradiating the first spatial region. Specifically, by focusing or diverging the ionizing laser through the focusing module, the spot diameter of the ionizing laser reaching the location of the cold atom cluster in the magneto-optical trap can be reduced or increased, thus altering the degree of interaction between the ionizing laser and the atoms. When the size of the irradiated area changes, the degree of ionization of the atoms by the ionizing laser also changes. Specifically, when the laser power density varies with the spot area, a smaller irradiated area results in a higher power density, stronger laser-driven effect on the atoms within this area, and a significantly increased probability of photoionization, resulting in the generation of more electrons and ions, i.e., a higher degree of ionization. Conversely, if the irradiated area is enlarged by the focusing module, the laser energy is dispersed over a larger area, the power density decreases, the proportion of atoms ionized decreases accordingly, and the degree of ionization weakens. Therefore, by adjusting the parameters of the focusing module, the number of charged particles generated can be precisely controlled to meet the ionization requirements under different experimental conditions. Meanwhile, changes in the size of the irradiation area will also affect the initial spatial distribution of the generated charged particles to some extent.

[0057] According to an embodiment of the present invention, the environmental electric field neutralization device further includes: an electric field detection module configured to determine the electric field strength of the environmental electric field by detecting the Stark frequency shift, thereby characterizing the electric field neutralization effect of charged particles.

[0058] In embodiments of the present invention, the electric field neutralization effect can be evaluated by monitoring electric field-sensitive characterization parameters of the Rydberg atom-based experimental system. These electric field-sensitive characterization parameters include, but are not limited to, spectral line shift, spectral linewidth, and Rabi oscillation quality.

[0059] According to an embodiment of the present invention, the ionizing laser is provided by a Rydberg state-excited laser in a Rydberg atomic quantum device, and the ionizing laser and the Rydberg state-excited laser share the same laser source.

[0060] Since the Rydberg quantum device is equipped with a laser for exciting the Rydberg state, and the wavelength of the laser is sufficient to ionize the atoms in the excited state, there is no need to introduce an additional independent ionization laser source to carry out the electric field neutralization operation, thus avoiding any impact on the existing experimental structure and optical path layout.

[0061] According to an embodiment of the present invention, the neutralization process of the ambient electric field is carried out actively and does not depend on the measurement and feedback of the ambient electric field.

[0062] In embodiments of the present invention, atoms are excited by cooling laser, and plasma is actively generated using ionizing laser. The charged particles in the plasma, under the influence of the ambient electric field, neutralize the ambient electric field through a compensating charge distribution. Unlike schemes that rely on passive shielding such as Faraday cages, this scheme actively generates plasma to compensate for the electric field. Unlike active feedback compensation schemes that require measuring the electric field before adjusting the applied electrode voltage, this scheme allows the migration and compensation process of charged particles to occur spontaneously after generation. The compensation effect is guaranteed by the physical process itself, eliminating the need for additional measurement and feedback loops, thus simplifying the operation and reducing complexity.

[0063] In embodiments of the present invention, the electric field neutralization rate of charged particles can be adjusted by the duration, repetition period, laser power, irradiation range, and related timing parameters of the ionization laser. After the photoionization parameters are calibrated, subsequent operations can focus solely on the preparation of the atoms to be ionized and the photoionization irradiation steps, achieving rapid compensation of the ambient electric field.

[0064] The environmental electric field neutralization device of this invention can be applied to Rydberg atom-based experimental systems, measurement devices, and quantum information devices, including but not limited to Rydberg atom spectral measurement and coherent manipulation platforms, Rydberg atom microwave electric field measurement devices, neutral atom quantum computing and quantum simulation devices, and other electric field-sensitive devices that experience surface charging, stray field accumulation, or require rapid electric field reset. For systems requiring long-term stable operation, the above steps can be repeated periodically to maintain a low electric field state within the target working area.

[0065] The environmental electric field neutralization device of this invention can compensate for naturally accumulated electric fields. For example, the atoms used in Rydberg experiments and as targets for ionization lasers are strontium-88 atoms. Strontium-88 atoms are placed inside a vacuum cavity. Due to the adsorption of atoms on the inner wall of the vacuum cavity, the adsorbate can form surface dipoles and generate an electric field, thereby gradually forming a naturally accumulated stray electric field within the vacuum cavity. This stray electric field can cause frequency shifts, line broadening, or deterioration of coherence properties in Rydberg transition spectral lines, thus affecting subsequent Rydberg manipulation. Therefore, atoms can first be captured using a 461 nm blue magneto-optical trap, and some atoms can be excited. During this process, a 316.6 nm ionization laser associated with Rydberg transitions is simultaneously irradiated, causing the excited atoms to ionize and generate plasma. Electrons and ions in the plasma migrate in opposite directions under the influence of the original environmental electric field and adhere to the inner wall of the vacuum cavity, forming a compensating charge distribution to reduce the intensity of the environmental electric field within the working area. After ionization for a sufficient duration, typically tens to hundreds of milliseconds, the ionization laser is turned off, and then Rydberg atom experiments can continue as usual, including atom loading, subsequent laser cooling, initial state preparation, Rydberg manipulation, and fluorescence imaging.

[0066] Figure 4 A schematic diagram illustrating the effect of neutralizing the environmental electric field according to an embodiment of the present invention is shown.

[0067] like Figure 4 As shown, by using this ionization scheme, the ambient electric field in the working area gradually decreases to near zero electric field within a few hours.

[0068] For comparison, Table 1 shows the effect of neutralizing the environmental electric field when using ultraviolet lamps for photo-induced atom desorption.

[0069] Table 1: Effect of neutralizing the environmental electric field on photoinduced atom desorption using ultraviolet lamps

[0070]

[0071] As shown in Table 1, in two independent experiments, a photoinduced atom desorption scheme was continuously implemented for a period of time, and the electric field of the working area was measured once before and after the implementation. The results show that the ambient electric field increased after implementation, indicating that the photoinduced atom desorption scheme cannot effectively overcome the natural accumulation of the ambient electric field.

[0072] The comparative results show that the technical solution of the present invention is significantly better than the solution that relies solely on ultraviolet photodesorption in terms of the compensation efficiency of naturally accumulated stray electric fields. This indicates that actively generating plasma by photoionization and using the migration of charged particles therein to form a compensating charge distribution is a more efficient electric field neutralization path.

[0073] Figure 5A schematic diagram illustrating the stability of the environmental electric field neutralization effect according to an embodiment of the present invention is shown.

[0074] like Figure 5 As shown, the relationship between relative frequency and time reveals that the fluctuation of the Rydberg spectral line center frequency measured continuously for more than 12 hours is less than 0.1 MHz, corresponding to an electric field strength of less than 0.1 V / cm. This indicates that the environmental electric field neutralization device of this embodiment can effectively improve the stability of the environmental electric field. The above results demonstrate that the environmental electric field neutralization device of this embodiment can not only achieve a one-time reduction in the environmental electric field strength but also maintain high consistency and repeatability during long-term experimental operation, thereby providing a stable low-electric-field environment for subsequent Rydberg coherent manipulation, precision measurement, and related quantum information processing.

[0075] The environmental electric field neutralization device in this embodiment of the invention can also compensate for the electric field of the external electrodes. For verification, an external electrode can be further introduced based on the Rydberg atomic experiment apparatus to simulate the applied electric field in the actual working environment. To ensure consistency of the initial electric field conditions in each experiment, before setting the electrode voltage of the external electrodes each time, the electrode voltage is first adjusted to 0 V, and the residual electric field is cleared under this condition through photoionization. Then, the electrode voltage is set to the target value. First, the Stark shift of the Rydberg transition is measured under different applied electrode voltage conditions, and a calibration relationship is established between the electrode voltage and the actual electric field strength in the target region. After obtaining the calibration relationship, photoionization compensation is performed under a fixed electrode voltage of 25 V, and a spectral sweep experiment, i.e., an electric field measurement, is conducted after each ionization operation.

[0076] Figure 6 A schematic diagram showing the effect of neutralization by an applied electric field according to an embodiment of the present invention is illustrated.

[0077] like Figure 6As shown, the different shades of purple curves represent different ionization times before each electric field measurement. For example, the darkest purple curve represents an ionization time of 20 s for each laser ionization operation; the lightest purple curve represents an ionization time of 0 s for each laser ionization operation, i.e., no ionization operation. This curve serves as a control for other electric field neutralization operations. The blue curve indicates that before each electric field measurement, atoms are not ionized, but irradiated with a 365 nm ultraviolet lamp for 20 s. It can be seen that as the ionization time increases, the compensation speed of the applied electric field increases accordingly. Under the same conditions, when irradiated with 365 nm ultraviolet light, the electric field reduction effect is close to that of the control group, i.e., there is no significant effect. This indicates that for electric fields introduced by external electrodes, relying solely on ultraviolet photodesorption is insufficient to achieve a compensation effect comparable to the electric field neutralization device of this invention. However, by actively generating plasma through photoionization and utilizing the migration of charged particles within it to form a compensating charge distribution, the neutralization of the applied electric field can be effectively achieved.

[0078] Figure 7 A schematic diagram showing the relationship between the electric field neutralization rate and the time of each ionization operation according to an embodiment of the present invention is shown.

[0079] right Figure 6 The characteristic time can be obtained by exponentially fitting the electric field variation with time of the neutralization electric field curve of ionized atoms, and the neutralization rate can be approximated by the reciprocal of the characteristic time. For example... Figure 7 As shown, the electric field neutralization rate and the duration of each ionization operation are approximately linearly related within the measured time range, indicating that the electric field neutralization device of the present invention does not exhibit a significant saturation effect on the time scale of each ionization operation under investigation, and has good quantitative adjustment capability.

[0080] Through embodiments of the present invention, a high-density cold atom cluster is formed based on a magneto-optical trap. A cooling laser is used to induce excited transitions of some atoms within the high-density cold atom cluster to an excited state. This allows for quantum-enhanced ionization of the excited atoms using an ionizing laser, generating plasma. Finally, the charged particles within the plasma, under the influence of the ambient electric field, neutralize the ambient electric field. This solves the problems of slow electric field cancellation or elimination processes, unstable effects, limited applicability, and difficulty in balancing high efficiency and high stability in existing technologies. It can significantly reduce the ambient electric field within the working area in a short time, achieving rapid compensation and reset of the vacuum environment electric field within the experimental working area, with high neutralization efficiency. Furthermore, embodiments of the present invention can be implemented using existing modules in the Rydberg atomic quantum device, thus avoiding the introduction of additional compensation components and having no impact on existing experimental structures and optical path layouts.

[0081] Figure 8A flowchart illustrating a method for neutralizing the environmental electric field applied to a Rydberg atomic quantum device according to an embodiment of the present invention is shown.

[0082] like Figure 8 As shown, the method for neutralizing the ambient electric field applied to the Rydberg atomic quantum device includes operations S801~S802.

[0083] In operation of S801, a magneto-optical trap is used to capture and cool atoms in the vacuum cavity of the Rydberg atomic quantum device to form a high-density cold atom cluster. The high-density cold atom cluster is confined in the first spatial region under the action of the ambient electric field. While capturing and cooling the atoms, the cooling laser of the magneto-optical trap causes some atoms of the high-density cold atom cluster to undergo excited transitions to excited states.

[0084] In operation S802, an ionizing laser is emitted into the first spatial region to cause the atoms in the excited state to undergo quantum-enhanced ionization, generating plasma. In this plasma, charged particles move under the influence of the ambient electric field and form a compensating charge distribution to neutralize the ambient electric field.

[0085] Those skilled in the art will understand that the features described in the various embodiments of the present invention can be combined and / or combined in various ways, even if such combinations or combinations are not explicitly described in the present invention. In particular, the features described in the various embodiments of the present invention can be combined and / or combined in various ways without departing from the spirit and teachings of the present invention. All such combinations and / or combinations fall within the scope of the present invention.

[0086] The embodiments of the present invention have been described above. However, these embodiments are merely illustrative and not intended to limit the scope of the invention. Although various embodiments have been described above, this does not mean that the measures in the various embodiments cannot be used advantageously in combination. Various substitutions and modifications can be made by those skilled in the art without departing from the scope of the invention, and all such substitutions and modifications should fall within the scope of the invention.

Claims

1. An environmental electric field neutralization device for use in the Rydberg atomic quantum device, characterized in that, include: A magneto-optical trap, configured to trap atoms within a vacuum cavity of a Rydberg atomic quantum device to form a high-density cold atom cluster, wherein the high-density cold atom cluster is confined within a first spatial region under the influence of an ambient electric field; The magneto-optical trap includes a cooling laser configured to emit a cooling laser into the first spatial region, thereby trapping and cooling atoms while simultaneously causing some atoms in the high-density cold atom cluster to undergo excited transitions to excited states. An ionizing laser is configured to emit ionizing laser light into the first spatial region, causing quantum-enhanced ionization of atoms in an excited state to generate plasma; In this process, charged particles in the plasma move under the influence of the ambient electric field and form a compensating charge distribution to neutralize the ambient electric field.

2. The environmental electric field neutralization device according to claim 1, characterized in that, The vacuum type of the vacuum chamber is a pressure less than 10. -9 The ultra-high vacuum is mbar, and the gas particle density inside the vacuum chamber is less than 2.5 × 10⁻⁶ mbar. 7 cm −3 This is to increase the lifetime of atoms in the trapped structure.

3. The environmental electric field neutralization device according to claim 1, characterized in that, The surface of the optical window of the vacuum cavity is coated with an antireflection film, which is configured to reduce the transmission loss of the cooling laser or the ionizing laser through the optical window.

4. The environmental electric field neutralization device according to claim 1, characterized in that, The optical window of the vacuum cavity is made of materials including fused silica, BK7, and high borosilicate. The optical window material has no intrinsic birefringence to reduce the polarization change when the cooling laser or the ionizing laser passes through the optical window.

5. The environmental electric field neutralization device according to claim 1, characterized in that, Both the cooling laser and the ionizing laser have wavelengths greater than 200 nm, and the wavelength of the cooling laser is greater than that of the ionizing laser.

6. The environmental electric field neutralization device according to claim 1, characterized in that, The environmental electric field neutralization device also includes: A focusing module, located between the magneto-optical trap and the ionizing laser, is configured to change the spot size of the ionizing laser to change the size of the irradiation area of ​​the ionizing laser.

7. The environmental electric field neutralization device according to claim 1, characterized in that, The environmental electric field neutralization device also includes: The electric field detection module is configured to determine the electric field strength of the environmental electric field by detecting the Stark frequency shift of Rydberg atoms, thereby characterizing the electric field neutralization effect.

8. The environmental electric field neutralization device according to claim 1, characterized in that, The ionizing laser is provided by a Rydberg state-excited laser in the Rydberg atomic quantum device, and the ionizing laser and the Rydberg state-excited laser share the same laser source.

9. The environmental electric field neutralization device according to claim 1, characterized in that, The neutralization process of the ambient electric field is active and does not depend on the measurement and feedback of the ambient electric field.

10. A method for neutralizing the environmental electric field in a Rydberg atomic quantum device, applied to the environmental electric field neutralization device as described in any one of claims 1 to 9, characterized in that, The environmental electric field neutralization method includes: Atoms are captured and cooled in the vacuum cavity of the Rydberg atomic quantum device using a magneto-optical trap to form a high-density cold atom cluster. The high-density cold atom cluster is confined in a first spatial region under the influence of an ambient electric field. The cooling laser of the magneto-optical trap, while capturing and cooling the atoms, causes some atoms of the high-density cold atom cluster to undergo excited transitions to excited states. An ionizing laser is emitted into the first spatial region to cause quantum-enhanced ionization of atoms in the excited state, generating plasma; In this process, charged particles in the plasma move under the influence of the ambient electric field and form a compensating charge distribution to neutralize the ambient electric field.

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