A method for measuring the anomalous moment of a quantum light field

Abstract

This invention discloses a method for measuring the anomalous moment of a quantum optical field, relating to the field of quantum optics technology, including: light source preparation; coherent excitation; signal acquisition; parameter extraction; and anomalous moment inversion. This invention utilizes an attosecond time-resolved interference process to achieve phase-resolved measurement of the anomalous moment of the optical field, with a sensitivity reaching tens of attoseconds, far exceeding traditional optical measurement methods. Unlike traditional optical zero-difference measurements, this invention does not require an optical local oscillator. Instead, it achieves quantum optical field characterization through photoelectron interference, avoiding the additional noise and system complexity introduced by the local oscillator. This invention is applicable to strong optical field conditions and can be applied to the measurement of strong quantum optical fields, overcoming the problems of decreased signal-to-noise ratio and loss of phase information under high-intensity conditions found in traditional methods. This invention is highly scalable, applicable to various non-classical optical fields (squeezed states, entangled states, etc.), and can be extended to the measurement of higher-order correlation functions.

Description

Technical Field

[0001] This invention relates to the field of quantum optics technology, and more specifically to a method for measuring the anomalous moment of a quantum optical field. Background Technology

[0002] High-power laser technology plays a crucial role in numerous cutting-edge scientific and applied fields, encompassing fundamental physics, materials science, and biomedicine. For example, in the medical field, high-power lasers are widely used in precision surgery, photodynamic therapy, and imaging diagnostics. However, traditional high-power laser sources typically operate in classical coherent states, and their quantum statistical properties are not fully utilized.

[0003] In recent years, with the cross-integration of quantum optics and strong-field physics, researchers have discovered that preparing strong lasers in non-classical states (such as squeezed states and entangled states) can significantly enhance their performance in nonlinear optical processes, precision measurements, and information processing. This type of "quantum strong light" possesses unique advantages over classical light fields, such as lower quantum noise, higher signal-to-noise ratio, and stronger nonlinear effects, demonstrating significant application prospects.

[0004] Therefore, developing measurement methods capable of accurately characterizing the quantum statistical properties of strong quantum light fields has become a key technological requirement in the current intersection of quantum optics and strong field physics. In existing technologies, the characterization of quantum light fields mainly relies on optical null tomography or second-order correlation function measurements. While these methods can extract some quantum information of the light field, they fall short in measuring higher-order anomalous moments (such as...). , It suffers from problems such as insufficient sensitivity and lack of phase information, making it particularly difficult to apply to high-precision measurements under strong light field conditions.

[0005] Attosecond photoelectron interferometry, particularly the RABBIT technique based on two-photon transition interferometry, possesses extremely high time resolution and phase sensitivity, and has been widely applied in the study of ultrafast electron dynamics in atoms, molecules, and solids. If the statistical information of the quantum light field can be encoded into the photoelectron signal using the attosecond interferometry process, it is expected to achieve highly sensitive, phase-resolved measurement of higher-order anomalous moments of high-intensity quantum light fields, thereby filling the gap in the characterization of strong quantum light using existing techniques.

[0006] In response, this application proposes a method for measuring the anomalous moment of a quantum optical field to solve the above-mentioned problems. Summary of the Invention

[0007] The purpose of this invention is to provide a method for measuring the anomalous moment of a quantum optical field, in order to solve the problem that traditional high-power laser sources usually operate in classical coherent states and their quantum statistical properties are not fully utilized.

[0008] To achieve the above objectives, the present invention provides the following technical solution:

[0009] A method for measuring the anomalous moment of a quantum optical field includes:

[0010] Light source preparation: Prepare an extreme ultraviolet attosecond pulse sequence as excitation light, and prepare an infrared light field of the substate to be measured as probe light;

[0011] Coherent excitation: The extreme ultraviolet attosecond pulse sequence and the infrared light field of the quantized substate are applied collinearly to the target atom or molecule with a variable time delay to induce two-photon or multi-photon transitions and generate sideband photoelectron signals;

[0012] Signal acquisition: The interference pattern of the photoelectron energy spectrum as a function of the time delay is recorded using an electron energy spectrum analyzer;

[0013] Parameter extraction: Extract the time delay of the sideband oscillation and the interference contrast from the interference pattern;

[0014] Anomalous Moment Inversion: Based on the time delay and interference contrast, the anomalous moments of the light field under test are inverted to obtain the anomalous moments. , where n is the order, n≥2.

[0015] Furthermore, the infrared light field of the sub-state to be measured is at least one of the following: displacement compressed vacuum state, compressed vacuum state, coherent state, thermal state, or entangled state.

[0016] Furthermore, the anomalous moment is a second-order anomalous moment. or fourth-order anomalous moment .

[0017] Furthermore, the extreme ultraviolet attosecond pulse sequence is generated by high-order harmonics, with a center frequency of With the center frequency of the infrared light field Satisfy one of the following relationships:

[0018] For the standard RABBIT scheme ,in It is an integer;

[0019] For the three-sideband RABBIT scheme ,in It is an integer.

[0020] Furthermore, the scanning range of the time delay between the extreme ultraviolet attosecond pulse sequence and the infrared light field is 0 to 2 optical cycles, and the scanning step size is less than 1 / 20 of an optical cycle.

[0021] Furthermore, the intensity of the infrared light field is to ;

[0022] The infrared light field is in a displacement-compressed vacuum state, and the expression for the anomalous moment is:

[0023]

[0024] in, For displacement parameters, For compressive strength, It is the compression angle.

[0025] Furthermore, the time delay is used to invert the phase information of the second-order anomalous moment of the optical field under test;

[0026] The time delay The functional relationship between the anomalous moment and the non-probable moment is expressed as follows:

[0027]

[0028] in, The center frequency of the infrared light field.

[0029] Furthermore, when the three-sideband RABBIT scheme is adopted, the time delay is used to invert the phase information of the fourth-order anomalous moment of the optical field under test;

[0030] When the three-sided RABBIT scheme is adopted, the anomalous moment is The obtained time delay The expression is:

[0031]

[0032] in, The ratio of the intensity of vacuum fluctuations to that of the coherent component is given. This is the relative compression angle.

[0033] Furthermore, the interference contrast is used to characterize the modulation effect of the quantum light field on the visibility of the interference. By comparing the interference contrast under the quantum light field and the coherent light field, the modulus information of the second-order anomalous moment of the light field under test is obtained by inversion.

[0034] Furthermore, when the three-sideband RABBIT scheme is adopted, the interference contrast is used to characterize the modulation effect of the quantum light field on the interference visibility. By comparing the interference contrast under the quantum light field and the coherent light field, the modulus information of the fourth-order anomalous moment of the light field under test is obtained by inversion.

[0035] Compared with existing technologies, this invention provides a method for measuring the anomalous moment of a quantum optical field. This invention possesses high sensitivity, utilizing an attosecond time-resolved interference process to achieve phase-resolved measurement of the anomalous moment of the optical field, with a sensitivity reaching tens of attoseconds, far exceeding traditional optical measurement methods. Unlike traditional optical zero-difference measurements, this invention does not require an optical local oscillator. It achieves quantum optical field characterization through photoelectron interference, avoiding the additional noise and system complexity introduced by the local oscillator. This invention is applicable to strong optical field conditions. The method can be applied to the measurement of strong quantum optical fields, overcoming the problems of decreased signal-to-noise ratio and loss of phase information under high-intensity conditions found in traditional methods. This invention has strong scalability, applicable to various non-classical optical fields (squeezed states, entangled states, etc.), and can be extended to the measurement of higher-order correlation functions, providing a new path for the complete state tomography of quantum optical fields. This invention employs a quantum-attosecond interface, combining attosecond photoelectron interference with quantum optical field measurement for the first time, providing a new interdisciplinary research method for quantum optics and attosecond science, and is expected to promote the application of quantum strong light in precision measurement, quantum information processing, and other fields. Attached Figure Description

[0036] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this invention. For those skilled in the art, other drawings can be obtained based on these drawings.

[0037] Figure 1 This is a schematic diagram of the method provided in an embodiment of the present invention, illustrating the process of generating photoelectron interference signals by the interaction of an extreme ultraviolet attosecond pulse train (XUV-APT) and a quantum state infrared light field with an atomic target. (a) is a schematic diagram of the infrared light field and the quantum light field, and a schematic diagram of the principle of attosecond photoelectron interference. (b) shows the change of photoelectron energy spectrum with the time delay of the infrared and extreme ultraviolet attosecond pulse trains. (c) shows the change of photoelectron yield corresponding to the 24th sideband (SB24) with the time delay. (d) shows the change of time delay extracted by different quantum light fields with photoelectron energy;

[0038] Figure 2 A comparison of numerical experimental results and theoretical results of the oscillation time delay of the 24th-order sideband (SB24) with the compression angle under different quantum state infrared light fields provided for embodiments of the present invention;

[0039] Figure 3The three-sideband RABBIT scheme provided in this embodiment of the invention. (a) Schematic diagram of the attosecond photoelectron interference path in the three-sideband RABBIT scheme. (b) Change of photoelectron energy spectrum with time delay of infrared and extreme ultraviolet attosecond pulse trains. (c) Change of photoelectron yield corresponding to the 12th sideband (SB12) with time delay. (d) Figure showing the change of time delay extracted by different quantum light fields with photoelectron energy. Detailed Implementation

[0040] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings.

[0041] As attached Figure 1 To be continued Figure 3 As shown:

[0042] Example 1:

[0043] A method for measuring the anomalous moment of a quantum optical field includes:

[0044] S1. Light source preparation: Prepare an extreme ultraviolet attosecond pulse sequence as excitation light and prepare an infrared light field of the substate to be measured as probe light;

[0045] Specifically, the infrared light field of the sub-state to be measured is at least one of the following: displacement-compressed vacuum state, compressed vacuum state, coherent state, thermal state, or entangled state.

[0046] S2. Coherent excitation: The extreme ultraviolet attosecond pulse sequence and the infrared light field of the quantized substate are applied collinearly to the target atom or molecule with a variable time delay to induce two-photon or multi-photon transitions and generate sideband photoelectron signals.

[0047] Specifically, the extreme ultraviolet attosecond pulse sequence is generated by high-order harmonics, and its center frequency is... With the center frequency of the infrared light field Satisfy one of the following relationships:

[0048] For the standard RABBIT scheme ,in It is an integer;

[0049] For the three-sideband RABBIT scheme ,in It is an integer;

[0050] The scanning range of the time delay between the extreme ultraviolet attosecond pulse sequence and the infrared light field is 0 to 2 optical cycles, and the scanning step size is less than 1 / 20 of an optical cycle.

[0051] The intensity of the infrared light field is to ;

[0052] The infrared light field is in a displacement-compressed vacuum state, and the expression for the anomalous moment is:

[0053]

[0054] in, For displacement parameters, For compressive strength, It is the compression angle;

[0055] S3. Signal acquisition: Record the interference pattern of photoelectron energy spectrum changes with the time delay using an electron energy spectrum analyzer;

[0056] S4. Parameter extraction: Extract the time delay of the sideband oscillation and the interference contrast from the interference pattern;

[0057] S5. Anomalous Moment Inversion: Based on the time delay and interference contrast, the anomalous moments of the light field under test are inverted to obtain the anomalous moments. , where n is the order, n≥2;

[0058] Specifically, the anomalous moment is a second-order anomalous moment. or fourth-order anomalous moment ;

[0059] The time delay is used to retrieve the phase information of the second-order anomalous moment of the optical field under test;

[0060] The time delay The functional relationship between the anomalous moment and the non-probable moment is expressed as follows:

[0061]

[0062] in, The center frequency of the infrared light field;

[0063] The interference contrast is used to characterize the modulation effect of the quantum light field on the visibility of interference. By comparing the interference contrast under the quantum light field and the coherent light field, the modulus information of the second-order anomalous moment of the light field under test is obtained by inversion.

[0064] The expression for calculating the modulus of the second-order anomalous moment is as follows:

[0065]

[0066] When the three-sideband RABBIT scheme is used, the time delay is used to invert the phase information of the fourth-order anomalous moment of the optical field under test;

[0067] When the three-sided RABBIT scheme is adopted, the anomalous moment is The obtained time delay The expression is:

[0068]

[0069] in, The ratio of the intensity of vacuum fluctuations to that of the coherent component is given. It is the relative compression angle;

[0070] When the three-sideband RABBIT scheme is adopted, the interference contrast is used to characterize the modulation effect of the quantum light field on the interference visibility. By comparing the interference contrast under the quantum light field and the coherent light field, the modulus information of the fourth-order anomalous moment of the light field under test is obtained by inversion.

[0071] The expression for calculating the modulus of the fourth-order anomalous moment is as follows:

[0072]

[0073] Used to characterize the modulation effect of quantum light fields on the visibility of interference.

[0074] As can be seen from the above, the present invention has high sensitivity. By using an attosecond time-resolved interference process, it can achieve phase-resolved measurement of the anomalous moment of the optical field with a sensitivity of tens of attoseconds, which is far higher than that of traditional optical measurement methods.

[0075] This invention does not require optical local oscillator light. Unlike traditional optical zero-difference measurement, this invention achieves quantum optical field characterization through photoelectron interference, avoiding the additional noise and system complexity introduced by local oscillator light.

[0076] This invention is applicable to strong light field conditions, and the method of this invention can be applied to the measurement of strong quantum light fields, overcoming the problems of reduced signal-to-noise ratio and loss of phase information under high intensity conditions in traditional methods.

[0077] Example 2:

[0078] This embodiment is specifically applied to the measurement of the second anomalous moment of infrared light in a compressed vacuum state:

[0079] like Figure 1 As shown, the device setup is as follows: A measurement device as described in the invention is constructed. The light source is an 800nm ​​Ti:sapphire laser. The APT generation module generates an attosecond pulse sequence based on higher harmonics. The quantum light field preparation module prepares a beam of displacement-compressed vacuum state (DSV) infrared light with a center wavelength of 800nm ​​through optical parametric downconversion, whose compression parameters are... And the relative compression angle ζ is adjustable, such as Figure 1 As shown in (a).

[0080] Parameter settings: Set the compression intensity of the DSV light to... =0.10 (i.e., the vacuum fluctuation intensity is 10% of the coherent part), and the compression angles are set to 0, π, and ±0.5π respectively. The target material is a rare gas atom (such as neon atom).

[0081] Data collection: such as Figure 1 As shown in (b), the time delay between the APT and IR light is scanned by the delay adjustment module, and the photoelectron energy spectrum at each delay point is recorded by the photoelectron detection and analysis module (such as a time-of-flight mass spectrometer), resulting in the RABBIT energy spectrum shown. Figure 1 As shown in (d).

[0082] Data processing:

[0083] First, the photoelectron yield of the 24th sideband (SB24) is extracted as a function of time delay, as follows: Figure 1 As shown in (c). Using the function Fit it to obtain the time delay. .

[0084] Then, the different compression angles ζ were measured. Reference time delay measured with a classical coherent light field (with the compression function of the quantum light field preparation module turned off) By comparison, the time delay shift caused by photon statistics is obtained. .

[0085] Finally, we get It exhibits a sinusoidal relationship with the relative compression angle ζ, such as Figure 2 As shown. Based on the theoretical formula... From this, the compression intensity χ and compression angle ζ can be deduced, thus determining the second-order anomalous moment of the DSV light. The modulus and phase.

[0086] Example 3:

[0087] This embodiment is specifically applied to the measurement of the fourth anomalous moment of infrared light in a compressed vacuum state:

[0088] like Figure 3 As shown, compared to Embodiment 2, the parameter adjustment in this embodiment is as follows: the adjustment device makes the infrared field wavelength 1600nm, and the extreme ultraviolet attosecond pulse train center frequency corresponds to the fundamental frequency light 26ω, so as to realize the three-photon RABBIT (3-SB RABBIT) process. At this time, the sideband oscillation frequency is 4ω, as shown. Figure 3 (a), Figure 3 As shown in (b).

[0089] Data Acquisition and Processing: Repeat the steps in Example 2 to extract the oscillation curve of the center sideband SBc12, as follows: Figure 3 As shown in (c). Using the function Fitting .

[0090] like Figure 3 As shown in (d), the final result is: Calculating the delay offset. For DSV light with χ=0.10, The maximum value can reach approximately 60 attoseconds, far exceeding the 20 attoseconds of a single-photon process. This delay shift directly corresponds to the fourth-order anomalous moment. Phase information, obtained through theoretical formulas:

[0091]

[0092] It can be parsed .

[0093] As can be seen from the above, this invention has strong scalability, is applicable to a variety of non-classical optical fields (squeezed states, entangled states, etc.), and can be extended to the measurement of higher-order correlation functions, providing a new path for the complete state tomography of quantum optical fields.

[0094] By employing a quantum-attosecond interface, attosecond photoelectron interference and quantum optical field measurement are combined for the first time, providing a new interdisciplinary research method for quantum optics and attosecond science, and is expected to promote the application of quantum high intensity light in precision measurement, quantum information processing and other fields.

[0095] The foregoing has only described certain exemplary embodiments of the present invention by way of illustration. Undoubtedly, those skilled in the art can modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the foregoing drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.

Claims

1. A method for measuring the anomalous moment of a quantum optical field, characterized in that, include: Light source preparation: Prepare an extreme ultraviolet attosecond pulse sequence as excitation light, and prepare an infrared light field of the substate to be measured as probe light; Coherent excitation: The extreme ultraviolet attosecond pulse sequence and the infrared light field of the quantized substate are applied collinearly to the target atom or molecule with a variable time delay to induce two-photon or multi-photon transitions and generate sideband photoelectron signals; Signal acquisition: The interference pattern of the photoelectron energy spectrum as a function of the time delay is recorded using an electron energy spectrum analyzer; Parameter extraction: Extract the time delay of the sideband oscillation and the interference contrast from the interference pattern; Anomalous Moment Inversion: Based on the time delay and interference contrast, the anomalous moments of the light field under test are inverted to obtain the anomalous moments. , where n is the order, n≥2.

2. The method for measuring the anomalous moment of a quantum optical field according to claim 1, characterized in that, The infrared light field of the sub-state to be measured is at least one of the following: displacement-compressed vacuum state, compressed vacuum state, coherent state, thermal state, or entangled state.

3. The method for measuring the anomalous moment of a quantum optical field according to claim 1, characterized in that, The anomalous moment is a second-order anomalous moment. or fourth-order anomalous moment .

4. The method for measuring the anomalous moment of a quantum optical field according to claim 1, characterized in that, The extreme ultraviolet attosecond pulse sequence is generated by high-order harmonics, with the center frequency of the high-order harmonics being... With the center frequency of the infrared light field Satisfy one of the following relationships: For the standard RABBIT scheme ,in It is an integer; For the three-sideband RABBIT scheme ,in It is an integer.

5. The method for measuring the anomalous moment of a quantum optical field according to claim 1, characterized in that, The scanning range of the time delay between the extreme ultraviolet attosecond pulse sequence and the infrared light field is 0 to 2 optical cycles, and the scanning step size is less than 1 / 20 of an optical cycle.

6. The method for measuring the anomalous moment of a quantum optical field according to claim 1, characterized in that, The intensity of the infrared light field is to ; The infrared light field is in a displacement-compressed vacuum state, and its anomalous moment expression is: in, For displacement parameters, For compressive strength, It is the compression angle.

7. The method for measuring the anomalous moment of a quantum optical field according to claim 1, characterized in that, The time delay is used to retrieve the phase information of the second-order anomalous moment of the optical field under test; The time delay The functional relationship between the anomalous moment and the non-probable moment is expressed as follows: in, The center frequency of the infrared light field.

8. The method for measuring the anomalous moment of a quantum optical field according to claim 1, characterized in that, When the three-sideband RABBIT scheme is used, the time delay is used to invert the phase information of the fourth-order anomalous moment of the optical field under test; When the three-sided RABBIT scheme is adopted, the anomalous moment is The obtained time delay The expression is: in, The ratio of the intensity of vacuum fluctuations to that of the coherent component. This is the relative compression angle.

9. The method for measuring the anomalous moment of a quantum optical field according to claim 1, characterized in that, The interference contrast is used to characterize the modulation effect of the quantum light field on the visibility of interference. By comparing the interference contrast under the quantum light field and the coherent light field, the modulus information of the second-order anomalous moment of the light field under test is obtained by inversion.

10. The method for measuring the anomalous moment of a quantum optical field according to claim 8, characterized in that, When the three-sideband RABBIT scheme is adopted, the interference contrast is used to characterize the modulation effect of the quantum light field on the interference visibility. By comparing the interference contrast under the quantum light field and the coherent light field, the modulus information of the fourth-order anomalous moment of the light field under test is obtained by inversion.

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