A system for implementing a rydberg atom based on modulation transfer spectroscopy between different quantum transitions of a single quantum system

Abstract

The application provides a Rydberg atom implementation system based on modulation transfer spectrum between different quantum transitions of a single quantum system, laser frequency stabilization and Rydberg atom preparation are performed by using the modulation transfer spectrum between different quantum transitions of the single quantum system, since the modulation transfer spectrum between different quantum transitions of the single quantum system shares an atomic cell and an optical optical path system with probe light and coupling light in the Rydberg atom preparation system, an additional atomic system required by a traditional system is not needed for locking of related lasers, and the volume of the system is significantly reduced. Since the modulation transfer spectrum between different quantum transitions of the single quantum system has the characteristics of high sensitivity and high signal-to-noise ratio, system noise is suppressed by high-speed modulation and high-speed feedback, the signal-to-noise ratio of the detection of the AT splitting is significantly increased, and the detection sensitivity of the EIT enhanced signal caused by a weak microwave signal is increased.

Description

Technical Field

[0001] This invention belongs to the field of Rydberg atom technology, specifically relating to a system for realizing Rydberg atoms based on the modulation transfer spectrum between different quantum transitions in a single quantum system. Background Technology

[0002] Rydberg atoms are atoms in a highly excited state (with a very large principal quantum number n), whose electrons are far from the nucleus and possess a series of unique properties (such as a very large atomic radius, strong polarization, and long lifetime). They have shown significant application potential in many cutting-edge fields such as precision measurement, sensing, quantum information and quantum computing, and quantum communication.

[0003] Rydberg atom preparation generally employs three methods: single-photon absorption excitation, two-photon absorption excitation, and three-photon absorption excitation. Two-photon absorption excitation typically uses a fixed-frequency laser (probe light) to excite the atom from its ground state nS (e.g., 5S¹ / ² in rubidium) to an intermediate state nP (e.g., 5P³ / ²). Then, a second tunable laser (coupling light) excites the atom from the intermediate state to the target Rydberg state nS or nD. By precisely adjusting the wavelength of the tunable laser, a specific principal quantum number n can be selected. Through two-photon absorption, the ground-state atom is excited to the target Rydberg state, completing the preparation of the Rydberg atom. However, current two-photon absorption excitation methods use two lasers, each requiring an additional atomic gas chamber and a corresponding optical path for laser frequency stabilization, which often results in a large preparation system. Furthermore, the coupling light generated by scanning the Rydberg atoms induces an electromagnetically induced transparency (EIT) line in the absorption spectrum of the probe light (the principle being that when the two beams resonate, the system enters a quantum coherent state—the "dark state"). At this point, the medium becomes transparent to the probe light, even though it strongly absorbs it during single-photon resonance. A narrow transparency window (EIT window) appears in the probe light transmission spectrum. If an external microwave field is applied near the Rydberg state, the EIT spectrum splits into two by controlling the microwave field; this is called the Atmospheric Transmission (AT) effect. By analyzing the spectral shift, the splitting interval, or the change in transmittance, combined with the theoretical model of the Rydberg atom (whose polarizability is known), the intensity and frequency of this microwave field can be calculated. Since the degree of splitting of EIT spectral lines is determined by the applied microwave field, the split EIT spectral lines are highly susceptible to the influence of the external environment. Traditional EIT spectral testing is inaccurate, difficult, and time-consuming, and it is difficult to capture rapidly changing transient fields. Therefore, it is necessary to improve the signal-to-noise ratio of the AT effect error signal and improve the accuracy of external microwave field testing based on traditional EIT spectral testing.

[0004] Therefore, in order to reduce the size of the Rydberg atom preparation system and improve the accuracy of Rydberg atom testing, it is necessary to use a multi-wavelength laser system to share the atomic gas cell and the supporting optical path system. At the same time, it is necessary to improve the signal-to-noise ratio of the error signal corresponding to the AT effect split spectral line and realize accurate measurement of the external microwave field. Summary of the Invention

[0005] The purpose of this invention is to overcome the aforementioned technical deficiencies and provide a smaller, simpler system for realizing Rydberg atoms, while improving the accuracy of applied microwave field detection and reducing detection difficulty. This invention aims to realize a system and method for preparing Rydberg atoms using the modulation transfer spectrum between different quantum transitions in a single quantum system. It eliminates the need for an additional atomic gas chamber to stabilize the probe and coupling light, and simultaneously improves the signal-to-noise ratio of Rydberg atom detection by employing a high-speed heterodyne method for signal detection at high frequencies.

[0006] The core idea of ​​this invention is to enable the probe light and coupling light in the Rydberg atom preparation system to share a single atomic gas cell and optical path system, thereby reducing the system size. On the other hand, modulation-transfer spectroscopy is applied to the Rydberg atom detection system. By modulating and transferring the spectral lines split by the Atlas effect (AT) through modulation-transfer demodulation, an error signal corresponding to the AT effect is generated. The intensity of the microwave field under test is obtained by modeling and analyzing the error signal, thus improving the signal-to-noise ratio of the error signal and achieving more accurate measurement of the external microwave field intensity. For weak microwave field detection, since the signal from the electromagnetic induction transparency enhancement effect is mainly limited by the noise of the coupling light and the probe light field, modulation-transfer spectral locking between different quantum transitions in a single quantum system can significantly suppress the phase and intensity noise of the light field, increasing the detection sensitivity.

[0007] Based on this, the present invention provides a Rydberg atom realization system based on the modulation transfer spectrum between different quantum transitions in a single quantum system. The system is characterized in that it includes a first wavelength laser 1 and a first polarizing beam splitter 3 disposed on the output light path of the first wavelength laser 1. An electro-optic modulator 6 and a second polarizing beam splitter 7 are disposed on the reflected light path of the first polarizing beam splitter 3. A dichroic mirror 13 and a gas cell 12 are disposed on the reflected light path of the second polarizing beam splitter 7, and the gas cell 12 is located on the transmitted light path of the first polarizing beam splitter 3. A first electro-optic detector 8 is disposed on the output light path of the second polarizing beam splitter 7. The system also includes a signal source 9, a first mixer 10 and a first wavelength servo feedback circuit 11.

[0008] The output laser of the first wavelength laser 1 transmits and reflects light through the first polarizing beam splitter 3. The transmitted light serves as the first probe light, and the reflected light serves as the first pump light. These light enters the electro-optic modulator 6 for modulation, resulting in pump light with a main frequency and a modulation signal (i.e., two modulation sidebands). The pump light is reflected by the second polarizing beam splitter 7 and the dichroic mirror 13 into the atomic gas chamber 12, where it undergoes a four-wave mixing process with the probe light of the first wavelength laser 1 under the nonlinear effect of atoms. The modulation signal is transferred to the probe light and, after passing through the second polarizing beam splitter 7, is converted into an electrical signal by the first photodetector 8. The first mixer 10 beats the frequency generated by the signal source 9 with the electrical signal, and then feeds it back to the first wavelength laser 1 through the first wavelength servo feedback circuit 11, thus stabilizing the frequency of the first wavelength laser 1. At this time, the frequency of the first wavelength laser 1 is the resonant frequency of the ground state and the first excited state energy levels.

[0009] The system further includes a second wavelength laser 18, with the first polarizing beam splitter 3 located in the output light path of the second wavelength laser 18. The system also includes a third polarizing beam splitter 14, a second photodetector 15, a second mixer 16, and a second wavelength servo feedback circuit 17. The first pump light of the frequency-stabilized first wavelength laser 18 serves as the second pump light, and the output light of the second wavelength laser 18 serves as the second probe light. After passing through the first polarizing beam splitter 3, the light enters the atomic gas chamber 12, passes through the dichroic filter 13, and then passes through the third polarizing beam splitter 14 to obtain two beams. One beam enters the second photodetector 15 to obtain a high signal-to-noise ratio spectral line. The second mixer 16 beats the obtained spectral line with the signal source 9, and the resulting output signal is fed back to the second wavelength laser 18 via the second wavelength servo feedback circuit 17, thereby stabilizing the frequency of the second wavelength laser 18. At this time, the frequency of the second wavelength laser 18 is the resonance frequency between the first excited state and the Rydberg state, thus realizing the Rydberg atom.

[0010] In a preferred embodiment, the system further includes a microwave field 19 and a data processing module 20. The second beam of light obtained by the third polarizing beam splitter 14 is subjected to the microwave field 19 to form an electromagnetically induced transparent spectral detection optical path, generating an electromagnetically induced transparent enhancement effect and an AT effect. The data is input to the data processing module 20 to perform model analysis on the transmission signal of the electromagnetically induced transparent enhancement effect or the error signal corresponding to the AT effect. By comparing it with the theoretical model, the signal intensity of the microwave field 19 to be measured can be obtained.

[0011] Preferably, in this invention, the system further includes a first half-wave plate 2 disposed between the first wavelength laser 1 and the first polarizing beam splitter 3, and a first reflecting mirror 4 and a second half-wave plate 5 disposed between the first polarizing beam splitter 3 and the electro-optic modulator 6.

[0012] In this invention, the resonant frequency of the electro-optic modulator 6 ensures both the resonant frequency of the first wavelength laser 1 itself and the resonant frequency of modulation transfer between different wavelengths.

[0013] In a particularly preferred embodiment, the error signal obtained from the beat frequency is fed back to the first wavelength laser 1 through the first wavelength servo feedback circuit 11 to obtain the modulation transfer spectrum signal through the PID algorithm.

[0014] The dichroic mirror 13 of the present invention has the spectral reflection characteristics of a first wavelength laser 1 and the transmission characteristics of a second wavelength laser 18.

[0015] The frequency of the first wavelength laser 1 after frequency stabilization depends on the selected atoms in the alkali metal atom gas cell 12, and the resonance frequency between the ground state and the first excited state.

[0016] The frequency of the second wavelength laser 18 after stabilization depends on the selected atoms in the alkali metal atom gas chamber 12, as well as the resonance frequency between the first excited state and the Rydberg state.

[0017] In this invention, the atomic gas chamber 12 is filled with rubidium atoms, cesium atoms, or other atoms known to those skilled in the art. The structure of the atomic gas chamber 12 can be a single-layer atomic gas chamber, a double-layer atomic gas chamber, or other structures known to those skilled in the art; the atomic gas chamber may or may not be filled with buffer gas, etc.

[0018] According to a preferred embodiment, the Rydberg atom fabrication laser based on modulation transfer spectra of different wavelengths can be an external cavity semiconductor laser, a distributed feedback laser, or a vertical cavity surface-emitting laser, etc.

[0019] As a particularly preferred embodiment, the electro-optic modulator 6 may be a lithium niobate thin-film electro-optic modulator 6 or other electro-optic modulators known to those skilled in the art.

[0020] This invention proposes a Rydberg atom realization system based on the modulation transfer spectrum between different quantum transitions in a single quantum system. It innovatively utilizes the modulation transfer spectrum between different quantum transitions in a single quantum system for laser frequency stabilization and Rydberg atom fabrication. By using modulation transfer processes at different wavelengths, high signal-to-noise ratio (SNR) electromagnetic induction transparency enhancement (EIT) and AT effect splitting spectral lines are obtained based on the traditional EIT spectrum. Model analysis of the transmission signals or error signals corresponding to the EIT and AT effects is performed, and compared with the theoretical model, the signal intensity of the microwave field to be measured can be obtained. Since the modulation transfer spectrum between different quantum transitions in a single quantum system shares a single atomic gas cell and optical path system for both the probe and coupling beams in the Rydberg atom fabrication system, the additional atomic system required for laser locking in traditional systems is eliminated, significantly reducing the system size. Due to the high sensitivity and high SNR characteristics of the modulation transfer spectrum between different quantum transitions in a single quantum system, high-speed modulation and high-speed feedback suppress system noise, significantly increasing the detection SNR of the AT splitting and the detection sensitivity of the EIT enhancement signal caused by weak microwave signals. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the system structure of the present invention;

[0022] The components are: 1. First wavelength laser, 2. First half-wave plate, 3. First polarizing beam splitter, 4. First reflector, 5. Second half-wave plate, 6. Electro-optic modulator, 7. Second polarizing beam splitter, 8. First electro-optic detector, 9. Signal source, 10. First mixer, 11. First wavelength servo feedback circuit, 12. Gas cell, 13. Dichroic mirror, 14. Third polarizing beam splitter, 15. Second photodetector, 16. Second mixer, 17. Second wavelength servo feedback circuit, 18. Second wavelength laser, 19. Microwave field, 20. Data processing module. Detailed Implementation

[0023] The following examples are used to explain the technical solutions of the present invention in a non-limiting manner.

[0024] Example 1

[0025] like Figure 1The Rydberg atom realization system shown includes a laser 1 with a frequency / wavelength corresponding to the first excited state transition of rubidium (or cesium) atoms at 780nm (852nm for cesium atoms), and a first half-wave plate 2, a first polarizing beam splitter 3, and an atomic gas cell 12 sequentially arranged in the direction of the emitted light from the first wavelength laser 1. A first reflecting mirror 4, a second half-wave plate 5, an electro-optic modulator 6, and a second polarizing beam splitter 7 are arranged in the reflected light path of the first polarizing beam splitter 3. A dichroic mirror 13 is arranged in the reflected light path of the second polarizing beam splitter 7, and the dichroic mirror 13 is also located in the emitted light path of the gas cell 12. Furthermore, a first electro-optic detector 8 is arranged in the output light path of the second polarizing beam splitter 7. The system also includes a signal source 9, a first mixer 10, and a first wavelength servo feedback circuit 11.

[0026] On the other hand, the system also includes a second wavelength laser 18 (or 510 nm corresponding to cesium atoms) that can excite rubidium atoms (or cesium atoms) to the Rydberg state at a wavelength of 480 nm, a third polarizing beam splitter 14, a second photodetector 15, a second mixer 16, and a second wavelength servo feedback circuit 17.

[0027] The 780nm spectrum emitted by the first wavelength laser 1 (or the corresponding 852nm for cesium atoms) is split into two beams after passing through the first half-wave plate 2 and the first polarizing beam splitter 3. The transmitted beam is used as the first probe beam, and the reflected beam is used as the first pump beam. The intensity of the first probe beam and the first pump beam can be adjusted by rotating the first half-wave plate 2.

[0028] The first pump light, after passing through the first reflector 4 and the second half-wave plate 5, is modulated by the electro-optic modulator 6, generating two modulation sidebands. The frequency of the electro-optic modulator 6 is on the order of MHz.

[0029] The first pump light, carrying a main frequency and two modulation sidebands, is reflected by the second polarizing beam splitter prism 7 and the dichroic mirror 13 and enters the rubidium atom (or cesium atom) gas chamber 12. There, it undergoes a four-wave mixing process with the first probe light under the nonlinear effect of the atoms. The modulation signal (i.e., the two modulation sidebands) loaded onto the first pump light is transferred to the unmodulated first probe light carrying a saturated absorption spectrum signal. The first probe light with the modulation signal passes through the second polarizing beam splitter 7, and is converted from an optical signal to an electrical signal by the first photodetector 8. This signal beats the main frequency emitted by the signal source 9. After passing through the mixer 11, the first wavelength servo feedback circuit 11 uses a PID algorithm to obtain the modulation transfer spectrum signal from the beat frequency error signal, which is then fed back to the first wavelength laser 1, thus stabilizing the frequency of the first wavelength laser 1. At this time, the frequency of the first wavelength laser 1 is the resonance frequency of the ground state and the first excited state, i.e., the 5S ohm of rubidium atoms. 1 / 2 →5P 3 / 2 Transition (or corresponding to cesium atom 6S) 1 / 2 →6P3 / 2 (Leap).

[0030] On the other hand, the spectrum emitted by the second-wavelength laser 18 with a wavelength of 480nm (or corresponding to 510nm for cesium atoms) is reflected by the first polarizing beam splitter 3, and then mixed with the pump light emitted by the first-wavelength laser 1, which has been modulated by the first electro-optic modulator 6 and then reflected by the second polarizing beam splitter 7 and the dichroic mirror 13 into the gas chamber 12, again generating a four-wave mixing process. The dichroic mirror can reflect the laser light from the first laser 1 while transmitting the laser light from the second laser 18, that is, reflect 780nm and transmit 480nm (or reflect 852nm and transmit 510nm for cesium atoms).

[0031] Subsequently, the second probe light from the second-wavelength laser 18, carrying modulation information, is transmitted through the dichroic mirror 13 and reflected again by the third polarizing beam splitter 14, splitting into two beams. One beam reflected by the third polarizing beam splitter 14 is converted into an electrical signal by the second photodetector 15 and beats the main frequency emitted by the signal source 9 (which is in the MHz range and the same as the frequency of the first electro-optic modulator 6). After mixing by the second mixer 16, the second-wavelength servo feedback circuit 17 uses a PID algorithm to obtain the modulation transfer spectrum signal from the error signal and feeds it back to the second-wavelength laser 18, thereby achieving frequency stabilization of the second-wavelength laser 18. At this time, the frequency of the second-wavelength laser 18 is the resonance frequency of the first excited state and the Rydberg state, i.e., the 5P rubidium atom. 3 / 2 → nS / nD transition or corresponding cesium atom 6P 3 / 2 →nS / nD transition). That is, the preparation of Rydberg atoms is realized.

[0032] On the other hand, the transmission spectrum after passing through the third polarizing beam splitter 14 exhibits the EIT effect, which can be generated by an external microwave source 19 to produce the AT effect. Then, the data processing module 20 performs model analysis on the error signal corresponding to the AT effect to obtain the signal intensity of the microwave field 19 to be measured. The electromagnetic induction transparency enhancement effect and the AT effect are generated. The data processing module 20 performs model analysis on the electromagnetic induction transparency enhancement transmission signal or the error signal corresponding to the AT effect, and compares this with the theoretical model to obtain the signal intensity of the microwave field 19 to be measured.

[0033] In summary, this invention realizes a small-volume Rydberg atom preparation system, improves the signal-to-noise ratio of the error signal corresponding to the AT effect splitting spectral line, and accurately measures the applied microwave field, thus achieving the goal of precise measurement of the Rydberg atom system. It solves the technical problems faced by Rydberg atoms in quantum precision measurement technology and is expected to be applied to key fields such as precision measurement, sensing, quantum information and quantum computing, and quantum communication.

Claims

1. A Rydberg atom realization system based on the modulation transfer spectrum between different quantum transitions in a single quantum system, characterized in that... The system includes a first wavelength laser (1) and a first polarizing beam splitter (3) disposed on the output light path of the first wavelength laser (1). An electro-optic modulator (6) and a second polarizing beam splitter (7) are disposed on the reflected light path of the first polarizing beam splitter (3). A dichroic mirror (13) and a gas cell (12) are disposed on the reflected light path of the second polarizing beam splitter (7), and the gas cell (12) is located on the transmitted light path of the first polarizing beam splitter (3). A first electro-optic detector (8) is disposed on the output light path of the second polarizing beam splitter (7). The system also includes a signal source (9), a first mixer (10), and a first wavelength servo feedback circuit (11). The output laser of the first wavelength laser (1) obtains transmitted and reflected light through the first polarizing beam splitter (3). The transmitted light serves as the first probe light, and the reflected light serves as the first pump light. It enters the electro-optic modulator (6) for modulation to obtain a pump light with a main frequency and a modulation signal. The pump light is reflected by the second polarizing beam splitter (7) and the dichroic mirror (13) into the atomic gas cell (12). It generates a four-wave mixing process with the probe light of the first wavelength laser (1) under the nonlinear effect of the atom. The modulation signal is transferred to the probe light and converted into an electrical signal by the first photodetector (8) after passing through the second polarizing beam splitter (7). The first mixer (10) beats the frequency generated by the signal source (9) with the electrical signal and then feeds it back to the first wavelength laser (1) through the first wavelength servo feedback circuit (11) to achieve frequency stabilization of the first wavelength laser (1). At this time, the frequency of the first wavelength laser (1) is the resonance frequency of the ground state and the first excited state. The system also includes a second wavelength laser (18) and the first polarizing beam splitter (3) is located in the output light path of the second wavelength laser (18). The system also includes a third polarizing beam splitter (14), a second photodetector (15), a second mixer (16), and a second wavelength servo feedback circuit (17). The first pump light of the frequency-stabilized first wavelength laser (1) is used as the second pump light, and the output light of the second wavelength laser (18) is used as the second probe light and enters the atomic gas cell (12) through the first polarizing beam splitter (3). Two beams of light are obtained after passing through a dichroic filter (13) and a third polarizing beam splitter (14). One beam enters the second photodetector (15) to obtain a high signal-to-noise ratio spectral line. The second mixer (16) beats the obtained spectral line with the signal source (9). The obtained output signal is fed back to the second wavelength laser (18) through the second wavelength servo feedback circuit (17) to achieve frequency stabilization of the second wavelength laser (18). At this time, the frequency of the second wavelength laser (18) is the resonance frequency between the first excited state and the Rydberg state, realizing the Rydberg atom.

2. The system according to claim 1, characterized in that... The system also includes a microwave field (19) and a data processing module (20). The second beam of light obtained by the third polarizing beam splitter (14) is input to the data processing module (20) after being acted upon by the microwave field (19).

3. The system according to claim 1, characterized in that... The system also includes a first half-wave plate (2) disposed between the first wavelength laser (1) and the first polarizing beam splitter (3), a first reflector (4) disposed between the first polarizing beam splitter (3) and the electro-optic modulator (6), and a second half-wave plate (5).

4. The system according to claim 1, characterized in that... The resonant frequency of the electro-optic modulator (6) ensures both the resonant frequency of the first wavelength laser (1) itself and the resonant frequency of the modulation transfer between different wavelengths.

5. The system according to claim 1, characterized in that... The error signal obtained by the beat frequency is fed back to the first wavelength laser (1) through the first wavelength servo feedback circuit (11) to obtain the modulation transfer spectrum signal through the PID algorithm.

6. The system according to claim 1, characterized in that... The dichroic mirror (13) has the characteristics of spectral reflection of the first wavelength laser (1) and transmission of the second wavelength laser (18).

7. The system according to claim 1, characterized in that... The atomic gas chamber (12) is filled with rubidium atoms and cesium atoms.

8. The system according to claim 1, characterized in that... The laser is an external cavity semiconductor laser, a distributed feedback laser, or a vertical cavity surface-emitting laser.

9. The system according to claim 1, characterized in that... The electro-optic modulator (6) is a lithium niobate thin-film electro-optic modulator (6).

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