Quantum dense metering device based on nonlinear interferometer and feedback optimization

Abstract

The invention relates to a quantum dense metering device based on a nonlinear interferometer and feedback optimization. The method mainly solves the technical problem of coupling loss in the existing quantum dense measurement. According to the technical scheme, the device comprises a dual-wavelength laser, a non-degenerate optical parameter amplifier, a half-wave plate, a polarization beam splitter, a lossy sample, a first optical beam splitter, two measuring systems and a feedback system. A probe optical signal aS and a pump optical signal aP output by the dual-wavelength laser are respectively connected with two input ends of the non-degenerate optical parameter amplifier, an output end of the non-degenerate optical parameter amplifier is connected with an input end of the half-wave plate, and an output end of the half-wave plate is connected with an input end of the polarization beam splitter. The two output ends of the polarization beam splitter are respectively connected with the lossy sample and the input end of the first optical beam splitter, the output end of the lossy sample is connected with the first input end of the first optical beam splitter, and the two output ends of the first optical beam splitter are respectively connected with the input ends of the two measurement systems.

Description

Technical Field

[0001] The present invention belongs to the technical field of quantum precision measurement, and particularly relates to a quantum dense metrology device based on a non-linear interferometer and feedback optimization. Background Art

[0002] In precision measurement, an interferometer is an important measurement tool and is widely used in various fields, including gravitational wave detection, displacement sensing, biosensing, etc. However, the measurement sensitivity of the interferometer is limited by the standard quantum limit determined by the vacuum fluctuations of the electromagnetic field. By using quantum means to construct a quantum interferometer, the measurement sensitivity can be effectively improved, and quantum precision measurement beyond the standard quantum limit can be achieved.

[0003] In addition to improving the measurement sensitivity of a single physical quantity, in practical applications, it is also necessary to simultaneously measure multiple non-commuting quantities. When simultaneously measuring two non-commuting quantities, the measurement sensitivity is restricted by the Heisenberg uncertainty principle, while quantum dense metrology can achieve the simultaneous measurement of two non-commuting quantities by using quantum entanglement. In 2013, the Leibniz University of Hannover and the Max Planck Institute in Germany achieved quantum dense metrology in a Michelson interferometer, distinguishing two non-commuting quantities, amplitude and phase, and published a paper titled "Quantum-dense metrology" in Nature Photonics 7, 626 (2013).

[0004] The above research work has solved the problem of simultaneously measuring two non-commuting quantities in quantum dense metrology and breaking through the standard quantum limit. However, inevitable losses in actual samples will greatly affect or even destroy the quantum enhancement effect, restricting the practical application of quantum dense metrology in precision measurement. Summary of the Invention

[0005] The object of the present invention is to solve the above-mentioned technical problems existing in the prior art, and provide a quantum dense metrology device based on a non-linear interferometer and feedback optimization. This device is easy to construct and operate and has no coupling loss, can simultaneously measure lossy non-commuting observables, and can be applied to the measurement of biological samples.

[0006] To solve the above technical problems, the technical solution adopted by the present invention is:

[0007] A quantum dense metrology device based on a non-linear interferometer and feedback optimization, which includes a dual-wavelength laser (1), a non-degenerate optical parametric amplifier (2), a half-wave plate (3), a polarization beam splitter (4), a lossy sample (5), a first optical beam splitter (6), a first measurement system (7), a second measurement system (8), and a feedback system (9); the probe optical signal a output by the dual-wavelength laser (1) Sis connected to the first input end of the non-degenerate optical parametric amplifier (2), and the pump optical signal a output by the dual-wavelength laser (1) P is connected to the second input end of the non-degenerate optical parametric amplifier (2). The output end of the non-degenerate optical parametric amplifier (2) is connected to the first input end of the half-wave plate (3). The output end of the half-wave plate (3) is connected to the input end of the polarization beam splitter (4). The phase-sensitive optical field at the first output end of the polarization beam splitter (4) is connected to the input end of the lossy sample (5). The output end of the lossy sample (5) is connected to the first input end of the first optical beam splitter (6). The phase-sensitive optical field at the second output end of the polarization beam splitter (4) is connected to the second input end of the first optical beam splitter (6). The first output end of the first optical beam splitter (6) is connected to the first input end of the first measurement system (7). The second output end of the first optical beam splitter (6) is connected to the first input end of the second measurement system (8). The first local oscillator optical signal a output by the dual-wavelength laser (1) L1 is connected to the second input end of the first measurement system (7), and the second local oscillator optical signal a output by the dual-wavelength laser (1) L2 is connected to the second input end of the second measurement system (8). The output end of the first measurement system (7) is connected to the input end of the feedback system (9). The output end of the feedback system (9) is connected to the second input end of the half-wave plate (3); the dual-wavelength laser (1) is used to output the probe optical signal a S and the pump optical signal a P and the first local oscillator optical signal L1 and the second local oscillator optical signal L2 .

[0008] Furthermore, the feedback system (9) includes an FPGA having a mapping function of the loss of the lossy sample (5) and the optimized angle of the half-wave plate (3).

[0009] The working principle of the present invention is as follows: Two coherent optical fields are injected into a non-degenerate optical parametric amplifier. The generated entangled optical field is split into two optical fields after passing through a half-wave plate and a polarization beam splitter, serving as the phase-sensitive optical fields of an interferometer; after one of the phase-sensitive optical fields interacts with a lossy sample, the two phase-sensitive optical fields interfere again on an optical beam splitter; a simplified non-linear interferometer is constructed, and finally the quadrature amplitude components and quadrature phase components of the two interferometric output optical fields are measured by two sets of balanced homodyne measurement systems. At the same time, according to the magnitude of the sample loss, the entanglement distribution is optimized through the feedback system, further improving the sensitivity and system robustness.

[0010] The beneficial effects of the present invention are as follows:

[0011] 1. The present invention utilizes the correlation characteristics of the entangled optical field output by a non-degenerate optical parametric amplifier to construct a simplified non-linear interferometer composed of a single non-degenerate optical parametric amplifier and an optical beam splitter, which has the advantages of simple structure and easy operation. By coupling and interfering two entangled sub-modes on the optical beam splitter to cancel each other out, the quantum correlation noise is compressed, coupling loss is avoided, and quantum dense metrology that breaks through the standard quantum limit is achieved. At the same time, the entanglement distribution is optimized through a feedback system to protect limited quantum resources, reduce the influence of sample loss, optimize sensitivity, and improve the robustness of the system.

[0012] 2. The present invention provides a quantum dense metrology device with high sensitivity and good robustness, solving the practical application problem that strong light irradiation is likely to cause optical damage.

[0013] 3. Since two non-commuting quantities, namely the absorption coefficient and the refractive index, need to be measured in biosensing, and these two non-commuting quantities can correspond to the amplitude change and phase change of the optical field, the amplitude information and phase information of the sample can be obtained by measuring the quadrature amplitude component and quadrature phase component of the two output ports of the optical beam splitter with two sets of balanced homodyne detection systems respectively, and the absorption coefficient and refractive index information of the sample can be obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 is a schematic structural diagram of the present invention;

[0015] Figure 2 is a schematic structural diagram of the non-degenerate optical parametric amplifier in the present invention;

[0016] Figure 3 is a schematic structural diagram of the first measurement system in the present invention;

[0017] In the figure: 1 - dual-wavelength laser, 2 - non-degenerate optical parametric amplifier, 2a - non-linear crystal, 2b - concave mirror, 2c - piezoelectric ceramic, 2d - temperature control system, 3 - half-wave plate, 4 - polarization beam splitter, 5 - lossy sample, 6 - first optical beam splitter, 7 - first measurement system, 7a - second optical beam splitter, 7b - first balanced homodyne detector, 7c - second balanced homodyne detector, 7d - power subtractor, 7e - spectrum analyzer, 8 - second measurement system, 9 - feedback system. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0018] The present invention will be described in detail below with reference to the drawings and embodiments.

[0019] As Figure 1As shown, a quantum dense metrology device based on a non - linear interferometer and feedback optimization in this embodiment includes a dual - wavelength laser 1, a non - degenerate optical parametric amplifier 2, a half - wave plate 3, a polarization beam splitter 4, a lossy sample 5, a first optical beam splitter 6, a first measurement system 7, a second measurement system 8, and a feedback system 9; the probe optical signal a output by the dual - wavelength laser 1 S is connected to the first input end of the non - degenerate optical parametric amplifier 2, and the pump optical signal a output by the dual - wavelength laser 1 P is connected to the second input end of the non - degenerate optical parametric amplifier 2. The output end of the non - degenerate optical parametric amplifier 2 is connected to the first input end of the half - wave plate 3. The output end of the half - wave plate 3 is connected to the input end of the polarization beam splitter 4. The phase - sensitive optical field at the first output end of the polarization beam splitter 4 is connected to the input end of the lossy sample 5. The output end of the lossy sample 5 is connected to the first input end of the first optical beam splitter 6. The phase - sensitive optical field at the second output end of the polarization beam splitter 4 is connected to the second input end of the first optical beam splitter 6. The first output end of the first optical beam splitter 6 is connected to the first input end of the first measurement system 7. The second output end of the first optical beam splitter 6 is connected to the first input end of the second measurement system 8. The first local oscillator optical signal a output by the dual - wavelength laser 1 L1 is connected to the second input end of the first measurement system 7. The second local oscillator optical signal a output by the dual - wavelength laser 1 L2 is connected to the second input end of the second measurement system 8. The output end of the first measurement system 7 is connected to the input end of the feedback system 9. The output end of the feedback system 9 is connected to the second input end of the half - wave plate 3. The dual - wavelength laser 1 is used to output the probe optical signal a S , the pump optical signal a P , the first local oscillator optical signal a L1 , and the second local oscillator optical signal a L2 . The feedback system 9 includes an FPGA with a mapping function of the loss of the lossy sample 5 and the optimized angle of the half - wave plate 3. The FPGA can use the STEMlab 125 - 14 digital board of the model Red Pitaya. The dual - wavelength laser 1 uses a fully solid - state dual - wavelength output tunable intracavity frequency - doubled Nd:YAP / LBO laser to output lasers with wavelengths of 540 nm and 1080 nm.

[0020] As Figure 2 shown, the non - degenerate optical parametric amplifier 2 includes a 1° wedge - angle cut KTP nonlinear crystal 2a, a concave mirror 2b, a piezoelectric ceramic 2c, and a temperature control system 2d. The KTP nonlinear crystal 2a is arranged on the concave side of the concave mirror 2b. The piezoelectric ceramic 2c is arranged on the plane of the concave mirror 2b. The probe optical signal a output by the dual - wavelength laser 1 S and the pump optical signal aP It sequentially passes through the nonlinear crystal 2a and the concave mirror 2b and exits from the concave mirror 2b. A high-reflection film for the probe light field is coated on the front surface of the nonlinear crystal 2a, and the transmittance of the pump light field is 18%. An antireflection film for both the probe light field and the pump light field is coated on the rear surface of the nonlinear crystal 2a, and it has a 1° wedge angle. The transmittance of the concave mirror 2b for the probe light field is 12.5%, and it is highly reflective for the pump light field. The temperature control system 2d includes a copper furnace and a temperature control instrument. The KTP nonlinear crystal 2a is placed in the copper furnace of the temperature control system 2d for precise temperature control of the nonlinear crystal.

[0021] As Figure 3 shown, the first measurement system 7 includes a second optical beam splitter 7a, a first balanced homodyne detector 7b, a second balanced homodyne detector 7c, a power subtractor 7d, and a spectrum analyzer 7e. The first output end of the first optical beam splitter 6 and the local oscillation optical signal a output by the dual-wavelength laser 1 L1 are respectively connected to the first and second input ends of the second optical beam splitter 7a. The first and second output ends of the second optical beam splitter 7a are respectively connected to the input ends of the first balanced homodyne detector 7b and the second balanced homodyne detector 7c. The first output end of the first balanced homodyne detector 7b and the output end of the second balanced homodyne detector 7c are respectively connected to the first input end and the second input end of the power subtractor 7d. The second output end of the first balanced homodyne detector 7b serves as the output end of the first measurement system 7 and is connected to the input end of the feedback system 9. The output end of the power subtractor 7d is connected to the spectrum analyzer 7e. The spectrum analyzer 7e is used to measure and analyze the quantum noise of the quadrature amplitude component of the optical signal at the first output end of the first optical beam splitter 6, and then obtain the amplitude information.

[0022] In addition, in this embodiment, the second measurement system 8 has the same structure as the first measurement system 7. However, the spectrum analyzer in the second measurement system 8 is used to measure and analyze the quantum noise of the quadrature phase component of the optical signal at the second output end of the first optical beam splitter 6, and then obtain the phase information. And the output end of the second measurement system 8 is not connected to any device.

Claims

1. A quantum dense metrology device based on nonlinear interferometer and feedback optimization, characterized in that: The invention comprises a dual-wavelength laser (1), a non-degenerate optical parametric amplifier (2), a half-wave plate (3), a polarization beam splitter (4), a lossy sample (5), a first optical beam splitter (6), a first measurement system (7), a second measurement system (8) and a feedback system (9); the probe optical signal a output by the dual-wavelength laser (1) is S connected to the first input end of the non-degenerate optical parametric amplifier (2), the pump light signal a output by the dual-wavelength laser (1) P The optical signal is connected to the second input end of the non-degenerate optical parametric amplifier (2), the output end of the non-degenerate optical parametric amplifier (2) is connected to the first input end of the half-wave plate (3), the output end of the half-wave plate (3) is connected to the input end of the polarization beam splitter (4), the phase-sensitive light field at the first output end of the polarization beam splitter (4) is connected to the input end of the lossy sample (5), the output end of the lossy sample (5) is connected to the first input end of the first optical beam splitter (6), the phase-sensitive light field at the second output end of the polarization beam splitter (4) is connected to the second input end of the first optical beam splitter (6), the first output end of the first optical beam splitter (6) is connected to the first input end of the first measurement system (7), the second output end of the first optical beam splitter (6) is connected to the first input end of the second measurement system (8), and the first local oscillator light a outputted by the dual-wavelength laser (1) is connected to the first input end of the first measurement system (7). L1 is connected to the second input end of the first measurement system (7), and the second local oscillator light a output by the dual-wavelength laser (1) L2 The dual-wavelength laser (1) is used to output the probe optical signal a. S , pump light signal a P , the first local oscillator optical signal a L1 and the second local oscillator optical signal a L2 .

2. A quantum dense metrology device based on nonlinear interferometer and feedback optimization according to claim 1, characterized in that: The feedback system (9) comprises an FPGA having a mapping function between the loss of the lossy sample (5) and the optimized angle of the half-wave plate (3).

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