A quantum interferometer for simultaneously amplifying a signal and reducing noise

Abstract

The application discloses a quantum interferometer for simultaneously amplifying signals and reducing noises, comprising a light source, a first non-degenerate optical parametric amplifier, a second non-degenerate optical parametric amplifier, a first degenerate optical parametric amplifier, a second degenerate optical parametric amplifier, a phase sensor and a measurement system; two polarized lights with perpendicular polarization directions are injected into the interferometer by the first non-degenerate optical parametric amplifier and have quantum correlation characteristics; the two light fields are respectively passed through the first and second degenerate optical parametric amplifiers to further improve the quantum characteristics, and one of the two light fields is phase-shifted by a physical quantity to be measured and then interfered in the second non-degenerate optical parametric amplifier, and the orthogonal components of the output light field contain the relative phase difference signal introduced by the physical quantity to be measured. The application simultaneously realizes the deterministic amplification of the measured signal in the interferometer and the noise reduction of the detection light field by using the cascade of the non-degenerate and degenerate optical parametric amplifiers, can realize the phase measurement with super-high sensitivity, and has important application value.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of quantum precision measurement, and particularly relates to a quantum interferometer for simultaneously amplifying a signal and reducing noise. BACKGROUND

[0002] Metrology is the basis of quantitative science, which helps humans to detect materials more accurately, obtain more comprehensive unknown information, and deepen the understanding of space-time. Optical interferometer is one of the important measurement tools due to its comprehensive detection information, high precision, long-distance detection, and the fact that the phase is very sensitive to many physical quantities (biological tissue, gravitational wave, displacement, etc.) that can affect the optical path. However, the ultimate sensitivity of the interferometer is limited by the shot noise limit determined by the vacuum fluctuation of the electromagnetic field. The sensitive measurement of weak signals submerged in the shot noise limit is one of the current research hotspots and is extremely challenging.

[0003] Quantum interferometer can improve the sensitivity of the interferometer in measuring phase by using quantum resources, and can overcome the influence of the shot noise limit, and even achieve the measurement of weak phase changes beyond the standard quantum noise limit. Filling the idle port of the interferometer with quantum states can make the detection noise break through the shot noise limit. Expanding the configuration of the interferometer by using quantum devices can improve the phase measurement sensitivity of the interferometer and achieve higher precision detection. A series of researches on new structure quantum interferometer have been carried out. In 2020, Peng Kunzhi's research group of Shanxi University expanded the configuration of Mach-Zehnder interferometer by using optical parametric amplifier, realized the phase measurement beyond the shot noise limit, and published a journal paper entitled "Quantum Interferometer Combining Squeezing and Parametric Amplification" in Physical Review Letters 124, 173602.

[0004] The above research work realizes the quantum interferometer based on optical parametric amplifier, solves the problem of breaking the standard quantum limit of optical interferometer, but does not realize the amplification of the measured signal. Therefore, when the sensitivity is improved by increasing the injection power, the radiation pressure on the transmission mirror will increase the reaction force noise, which will reduce the detection sensitivity. SUMMARY

[0005] In view of this, in order to solve the problem that the prior art cannot amplify the measured signal while making the noise lower than the shot noise limit, the present application provides a quantum interferometer for simultaneously amplifying signals and reducing noise, which uses non-degenerate and degenerate optical parametric amplifier cascades to simultaneously achieve deterministic amplification of the measured signal in the interferometer and reduction of the phase-sensitive light field noise of the detection, and can realize ultra-high sensitivity phase measurement.

[0006] The present application solves the above problems by the following technical means:

[0007] The present application provides a quantum interferometer for simultaneously amplifying signals and reducing noise, comprising a light source, a first optical frequency doubler, a second optical frequency doubler, a first non-degenerate optical parametric amplifier, a second non-degenerate optical parametric amplifier, a first degenerate optical parametric amplifier, a second degenerate optical parametric amplifier, a phase sensor, and a measurement system.

[0008] The light source outputs three probe light fields a S1 , a S2 , a S3 and a local oscillation light field a L ; the probe light fields a S1 , a S3 output by the light source are one-to-one connected with the input ends of the first optical frequency doubler and the second optical frequency doubler; and the probe light field a S2 output by the light source is connected with the input end of the first non-degenerate optical parametric amplifier.

[0009] The output end of the first non-degenerate optical parametric amplifier is connected with the signal light field input ends of the first degenerate optical parametric amplifier and the second degenerate optical parametric amplifier; the phase-sensitive light field output by the second degenerate optical parametric amplifier is connected with the input end of the phase sensor; the phase sensor is used for phase-shifting the phase-sensitive light field output by the second degenerate optical parametric amplifier according to the physical quantity to be measured; and the phase-sensitive light field output by the second degenerate optical parametric amplifier after passing through the phase sensor is injected into the input end of the second non-degenerate optical parametric amplifier together with the output light field of the first degenerate optical parametric amplifier, and interference is carried out in the second non-degenerate optical parametric amplifier; and the output light field of the second non-degenerate optical parametric amplifier is injected into the input end of the measurement system together with the local oscillation light field a L of the light source.

[0010] The pump light fields a P1 and a P2 output by the first optical frequency doubler are one-to-one connected with the pump light field input ends of the first non-degenerate optical parametric amplifier and the first degenerate optical parametric amplifier; the pump light fields a P3 and a P4 output by the second optical frequency doubler are one-to-one connected with the pump light field input ends of the second non-degenerate optical parametric amplifier and the second degenerate optical parametric amplifier.The pump light field input ends of the second degenerate optical parametric amplifier and the second non-degenerate optical parametric amplifier are connected with the probe light field input end of the first optical frequency doubler and the pump light field output end of the first optical frequency doubler respectively, so as to provide pump light fields for the two optical parametric amplifiers.

[0011] Preferably, the first non-degenerate optical parametric amplifier and the second non-degenerate optical parametric amplifier have the same structure; the first degenerate optical parametric amplifier and the second degenerate optical parametric amplifier have the same structure.

[0012] Preferably, the first non-degenerate optical parametric amplifier comprises a first optical resonant cavity, a wedge-shaped nonlinear crystal and a temperature control displacement system.

[0013] The first optical resonant cavity comprises a first plano-concave mirror, a second plano-concave mirror and a first piezoelectric ceramic; the first plano-concave mirror and the second plano-concave mirror form a two-mirror cavity structure; and the first piezoelectric ceramic is fixed on the second plano-concave mirror.

[0014] The probe light field as2 of the light source and the pump light field ap1 output by the first optical frequency doubler are both input into the first non-degenerate optical parametric amplifier from the first plano-concave mirror, but the probe light field is emitted from the second plano-concave mirror after passing through the wedge-shaped nonlinear crystal, and the pump light field is emitted from the first plano-concave mirror after being reflected by the second plano-concave mirror after passing through the wedge-shaped nonlinear crystal.

[0015] The first plano-concave mirror serves as an input mirror, is coated with a high-reflection film for the probe light field and has a transmittance for the pump light field; the second plano-concave mirror has a transmittance for the probe light field and is coated with a high-reflection film for the pump light field, so that the pump light field and the probe light field are both resonated in the cavity.

[0016] The temperature control displacement system is used for heating and precisely controlling the temperature of the wedge-shaped nonlinear crystal and making the wedge-shaped nonlinear crystal translate along a direction perpendicular to the light propagation direction, so that the pump light field and the probe light field are precisely matched.

[0017] Preferably, the transmittance of the first plano-concave mirror for the pump light field is 10%; and the transmittance of the second plano-concave mirror for the probe light field is 5%.

[0018] Preferably, the temperature control displacement system comprises a first copper furnace, a first temperature control instrument and a two-dimensional micro translation stage; the first copper furnace is used for heating the wedge-shaped nonlinear crystal; the first temperature control instrument is used for precise temperature control; and the two-dimensional micro translation stage is used for making the wedge-shaped nonlinear crystal translate along a direction perpendicular to the light propagation direction.

[0019] Preferably, the first degenerate optical parametric amplifier comprises a second optical resonant cavity, a nonlinear crystal and a temperature control system.

[0020] The second optical resonant cavity comprises a third plano-concave mirror, a fourth plano-concave mirror, a first plane mirror, a second plane mirror and a second piezoelectric ceramic, wherein the third plano-concave mirror, the fourth plano-concave mirror, the first plane mirror and the second plane mirror form a four-mirror eight-diagram ring cavity structure; the second piezoelectric ceramic is fixed on the fourth plano-concave mirror;

[0021] The output light field of the first non-degenerate optical parametric amplifier is input from the first plane mirror to the first degenerate optical parametric amplifier, and is sequentially output from the first plane mirror after passing through the second plane mirror, the third plano-concave mirror, the nonlinear crystal and the fourth plano-concave mirror; the pump light field ap2 output by the first optical frequency doubler is output from the fourth plano-concave mirror after passing through the third plano-concave mirror and the nonlinear crystal;

[0022] The first plane mirror serves as an input-output coupling mirror and has a transmittance to the probe light field; the second plane mirror is coated with a high-reflection film to the probe light field; the third plano-concave mirror and the fourth plano-concave mirror are both coated with a high-reflection film to the probe light field and a low-reflection film to the pump light field;

[0023] The temperature control system is used for heating and precisely controlling the temperature of the nonlinear crystal.

[0024] Preferably, the transmittance of the first plane mirror to the probe light field is 5%.

[0025] Preferably, the temperature control system comprises a second copper furnace and a second temperature control instrument, wherein the second copper furnace is used for heating the nonlinear crystal, and the second temperature control instrument is used for precisely controlling the temperature.

[0026] Preferably, the phase sensor comprises a third piezoelectric ceramic, a high-reflection mirror and a high-frequency signal source; and the third piezoelectric ceramic is fixed on the back of the high-reflection mirror.

[0027] The output light field of the second degenerate optical parametric amplifier is input to the high-reflection mirror, and is driven by the high-frequency signal source through the third piezoelectric ceramic to produce a slight displacement through an electrical path, so as to achieve the purpose of phase-shifting the phase-sensitive light field output by the second degenerate optical parametric amplifier; the output light field of the high-reflection mirror is input to the second non-degenerate optical parametric amplifier together with the output light field of the first degenerate optical parametric amplifier.

[0028] Preferably, the measurement system comprises an optical beam splitter, a first photodetector, a second photodetector, a power subtractor and a spectrum analyzer.

[0029] The local oscillation light field a LThe output light signals of the first and second non-degeneration optical parametric amplifiers interfere on an optical beam splitter, and the interference signals are respectively injected into input ends of first and second photodetectors, output ends of the first and second photodetectors are connected with input ends of a power subtractor, and an output end of the power subtractor is connected with a spectrum analyzer, the spectrum analyzer is used for measuring and analyzing signal power and noise power of the quadrature component of the output light signal of the second non-degeneration optical parametric amplifier, and then a phase signal is obtained.

[0030] Compared with the prior art, the present application has at least the following beneficial effects:

[0031] 1、The first non-degeneration optical parametric amplifier (NOPA) of the present application is placed in front of a half-wave plate, which injects two mutually perpendicular polarized light fields into an interferometer, and generates quantum entangled light fields after the first non-degeneration optical parametric amplifier; after the two light beams are separated by the half-wave plate and a polarization beam splitter prism PBS, they are injected into the first and second degeneration optical parametric amplifiers (DOPA) respectively, so as to further improve the quantum characteristics of the two light fields, and the two light fields are used as phase-sensitive light fields acting on the measured signal inside the interferometer; the phase sensor converts the physical quantity to be measured into the relative phase difference of the two phase-sensitive light fields; then, the two phase-sensitive light fields interfere in the second non-degeneration optical parametric amplifier, and the quadrature component of the output light field contains the relative phase difference signal introduced by the physical quantity to be measured; finally, the balanced homodyne measurement system is used for detection, and the quadrature component of the output light field can be obtained. Since the degeneration and non-degeneration optical parametric amplifiers are cascaded, not only the measured signal is amplified, but also the quantum noise of the phase-sensitive light field is reduced, so that the phase measurement sensitivity of the interferometer can be improved without increasing the intensity of the phase-sensitive light field, and a weak signal submerged in the shot noise limit can be detected, so that the sensitivity of the interferometer is significantly improved.

[0032] 2、The present application cascades the degeneration and non-degeneration optical parametric amplifiers to construct a new type of interferometer, realizes precise phase measurement with higher sensitivity which breaks through the standard quantum limit, and the phase measurement sensitivity is improved by times compared with the previous invention patent "Quantum interferometer device based on optical parametric amplifier" (ZL 202010067366.6). times compared with the SNL.

[0033] 3, The application utilizes the different advantages of different types of optical parametric amplifiers in the interferometer, cascades degenerate and non-degenerate optical parametric amplifiers to construct a new type of interferometer, and realizes the determination of the amplified signal of the interferometer and the reduction of quantum noise. Only the non-degenerate optical parametric amplifier is used to expand the configuration of the interferometer, the obtained interferometer can maintain the noise at the SNL level, only amplify the signal, realize the improvement of the sensitivity, but cannot detect the weak signal submerged in the shot noise limit. The combination of degenerate and non-degenerate optical parametric amplifiers not only has a higher improvement of the sensitivity, but also can detect the weak signal submerged in the shot noise limit, greatly enhances the use rate of the interferometer under different measurement conditions.

[0034] 4, The application also has the advantages of the previous "quantum interferometer device based on optical parametric amplifier" (ZL202010067366.6). In the presence of interferometer loss and other noises, precise phase measurement beyond the standard quantum limit can also be achieved unconditionally. The sensitivity of the interferometer can be improved by reducing the quantum noise of the interferometer phase-sensitive light field, and the main factor affecting the measurement sensitivity, the quantum noise of the interferometer phase-sensitive light field, is solved. On the other hand, the intensity of the interferometer phase-sensitive light field is one of the main factors affecting the measurement sensitivity; improving the intensity of the interferometer phase-sensitive light field can improve the sensitivity of the interferometer, but high phase-sensitive light field intensity will increase the radiation pressure on the mirror, causing reaction force noise. The cascading of non-degenerate and degenerate optical parametric amplifiers in the application makes the signal carried by the phase-sensitive light field amplified times, which is not limited by the intensity of the phase-sensitive light field, so that the sensitivity of the interferometer can be improved. BRIEF DESCRIPTION OF DRAWINGS

[0035] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0036] Figure 1 The structure schematic diagram of the quantum interferometer for simultaneously amplifying signal and reducing noise provided in the embodiment of the present application is shown in the figure;

[0037] Figure 2 The structure schematic diagram of the non-degenerate optical parametric amplifier in the embodiment of the present application is shown in the figure;

[0038] Figure 3 The structure schematic diagram of the degenerate optical parametric amplifier in the embodiment of the present application is shown in the figure;

[0039] Figure 4 The schematic diagram of the phase sensor in the embodiment of the present application is shown in the figure;

[0040] Figure 5 The structural schematic diagram of the measuring system in the embodiment of the present application;

[0041] Figure 6 The result diagram of the device of the present application, wherein 6(a) is the result of the phase measurement sensitivity of the interferometer, 6(b) is the local enlarged diagram of the phase measurement sensitivity of the interferometer, 6(c) is the result of the interferometer reducing the intensity noise of the phase-sensitive light field, and 6(d) is the result of the interferometer amplifying the measured signal;

[0042] In the figure, 11 is a light source, 12 is a first optical frequency doubler, 13 is a second optical frequency doubler; 21 is a first non-degenerate optical parametric amplifier, 22 is a second non-degenerate optical parametric amplifier, 2a is a first plano-concave mirror, 2b is a second plano-concave mirror, 2c is a wedge-shaped nonlinear crystal, 2d is a first piezoelectric ceramic; 31 is a first degenerate optical parametric amplifier, 32 is a second degenerate optical parametric amplifier, 3a is a third plano-concave mirror, 3b is a fourth plano-concave mirror, 3c is a first plane mirror, 3d is a second plane mirror, 3e is a second piezoelectric ceramic, 3f is a nonlinear crystal; 4 is a phase sensor; 4a is a signal generator, 4b is a third piezoelectric ceramic, 4c is a high-reflectivity mirror; 5 is a measuring system, 5a is a 50:50 optical beam splitter, 5b is a first photodetector, 5c is a second photodetector, 5d is a power subtractor, 5e is a spectrum analyzer. DETAILED DESCRIPTION

[0043] In order to make the above objectives, characteristics and advantages of the present application more obvious and easy to understand, the technical solutions of the present application will be described in detail below with reference to the drawings and specific embodiments. It should be pointed out that the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0044] The terms "first", "second", "third" are only used for description purpose, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined with "first", "second", "third" can explicitly or implicitly include one or more of the features. In the description of the present application, unless otherwise specified, the meaning of "a group" is two or more.

[0045] As Figure 1As shown, this embodiment of the invention provides a quantum interferometer that simultaneously amplifies signals and reduces noise, including a light source 11, a first optical frequency multiplier 12, a second optical frequency multiplier 13, a first non-degenerate optical parametric amplifier 21, a second non-degenerate optical parametric amplifier 22, a first degenerate optical parametric amplifier 31, a second degenerate optical parametric amplifier 32, a phase sensor 4, and a measurement system 5.

[0046] The light source 11 is used to output three probe light fields a respectively. S1 a S2 a S3 and local oscillating light field a L ; probe light field a output by light source 11 S1 a S3 Each of these is connected to the input terminals of the first optical frequency multiplier 12 and the second optical frequency multiplier 13 respectively; the output terminal of the first optical frequency multiplier 12 outputs the pump light field a. P1 and a P2 The output of the second optical frequency multiplier 13 outputs the pump light field a. P3 and a P4 ; probe light field a output by light source 11 S2 The first non-degenerate optical parametric amplifier 21 is connected to its input terminal. The output terminal of the first non-degenerate optical parametric amplifier 21 is connected to the signal light field input terminals of the first degenerate optical parametric amplifier 31 and the second degenerate optical parametric amplifier 32, respectively. The phase-sensitive light field output by the second degenerate optical parametric amplifier 32 is connected to the input terminal of the phase sensor 4. The phase sensor 4 is used to phase-shift the phase-sensitive light field output by the second degenerate optical parametric amplifier 32 according to the measured physical quantity. After passing through the phase sensor 4, the phase-sensitive light field output by the second degenerate optical parametric amplifier 32, together with the output light field of the first degenerate optical parametric amplifier 31, is injected into the input terminal of the second non-degenerate optical parametric amplifier 22, where interference occurs. The output light field of the second non-degenerate optical parametric amplifier 22 interacts with the local oscillation light field a of the light source 11. L They are injected together into the input terminal of measurement system 5.

[0047] The pump light field a output by the first optical frequency multiplier 12 P1 and pump light field a P2 The pump field a output by the second optical frequency multiplier 13 is connected to the pump field input terminals of the first non-degenerate optical parametric amplifier 21 and the first degenerate optical parametric amplifier 31 respectively. P3 and pump light field a P4 Each of these circuits is connected to the pump field input terminals of the second degenerate optical parametric amplifier 32 and the second non-degenerate optical parametric amplifier 22, respectively, to provide them with pump fields.

[0048] The phase sensor 4 is a device for converting a physical quantity to be measured into a relative phase difference of two phase-sensitive light fields, for example, a piezoelectric ceramic can be used as the phase sensor to convert displacement into phase.

[0049] As shown in Figure 2 In the embodiment, the first non-degenerate optical parametric amplifier 21 comprises a first optical resonant cavity, a wedge-shaped nonlinear crystal 2c and a temperature control displacement system.

[0050] The first optical resonant cavity comprises two plano-concave mirrors, a first plano-concave mirror 2a and a second plano-concave mirror 2b, and a first piezoelectric ceramic 2d, wherein the first plano-concave mirror 2a and the second plano-concave mirror 2b form a two-mirror cavity structure, and the first piezoelectric ceramic 2d is fixed on the second plano-concave mirror 2b.

[0051] The probe light field as2 of the light source 11 and the pump light field ap1 output by the first optical frequency doubler 12 are both input from the first plano-concave mirror 2a to the first non-degenerate optical parametric amplifier 21, except that the probe light field is emitted from the second plano-concave mirror 2b after passing through the wedge-shaped nonlinear crystal 2c, and the pump light field is emitted from the first plano-concave mirror 2a after being reflected by the second plano-concave mirror 2b after passing through the wedge-shaped nonlinear crystal 2c.

[0052] The first plano-concave mirror 2a serves as an input mirror, and a high-reflection film is coated on the first plano-concave mirror 2a for the probe light field, and the transmittance of the first plano-concave mirror 2a for the pump light field is 10%; the transmittance of the second plano-concave mirror 2b for the probe light field is 5%, and a high-reflection film is coated on the second plano-concave mirror 2b for the pump light field, so that the pump light field and the probe light field are both resonated in the cavity.

[0053] The temperature control displacement system is used for heating and precisely controlling the temperature of the wedge-shaped nonlinear crystal 2c, and can make the wedge-shaped nonlinear crystal 2c translate along a direction perpendicular to the light propagation direction to make the pump light field and the probe light field precisely match.

[0054] Specifically, the temperature control displacement system comprises a first copper furnace, a first temperature control instrument and a two-dimensional micro translation stage, the first copper furnace is used for heating the wedge-shaped nonlinear crystal 2c, the first temperature control instrument is used for precise temperature control, and the two-dimensional micro translation stage is used for translating the wedge-shaped nonlinear crystal 2c along a direction perpendicular to the light propagation direction.

[0055] In addition, in the embodiment, the structure of the second non-degenerate optical parametric amplifier 22 is the same as that of the first non-degenerate optical parametric amplifier 21.

[0056] As shown in Figure 3 The first degenerate optical parametric amplifier 31 comprises a second optical resonant cavity, a nonlinear crystal 3f and a temperature control system.

[0057] The second optical resonant cavity comprises two plano-concave mirrors, a third plano-concave mirror 3a and a fourth plano-concave mirror 3b, two plane mirrors, a first plane mirror 3c and a second plane mirror 3d, and a second piezoelectric ceramic 3e, wherein the third plano-concave mirror 3a, the fourth plano-concave mirror 3b, the first plane mirror 3c and the second plane mirror 3d form a four-mirror astigmatism ring cavity structure; and the second piezoelectric ceramic 3e is fixed on the fourth plano-concave mirror 3b.

[0058] The output light field of the first non-degenerate optical parametric amplifier 21 is input into the first degenerate optical parametric amplifier 31 from the first plane mirror 3c, sequentially passes through the second plane mirror 3d, the third plano-concave mirror 3a, the nonlinear crystal 3f and the fourth plano-concave mirror 3b, and is emitted from the first plane mirror 3c; and the pump light field ap2 output by the optical frequency doubler 12 is emitted from the fourth plano-concave mirror 3b via the third plano-concave mirror 3a and the nonlinear crystal 3f.

[0059] The first plane mirror 3c serves as an input-output coupling mirror, and has a transmittance of 5% for the probe light field; the second plane mirror 3d is coated with a high-reflection film for the probe light field; and the third plano-concave mirror 3a and the fourth plano-concave mirror 3b are both coated with a high-reflection film for the probe light field and a low-reflection film for the pump light field.

[0060] The temperature control system is used for heating and precisely controlling the temperature of the nonlinear crystal 3f.

[0061] Specifically, the temperature control system comprises a second copper furnace used for heating the nonlinear crystal 3f and a second temperature control instrument used for precisely controlling the temperature.

[0062] In addition, in the embodiment, the first degenerate optical parametric amplifier 32 has the same structure as the second degenerate optical parametric amplifier 31.

[0063] As shown in Figure 4 In the embodiment, the phase sensor 4 comprises a third piezoelectric ceramic 4b, a high-reflection mirror 4c and a high-frequency signal source 4a; and the third piezoelectric ceramic 4b is fixed on the back of the high-reflection mirror 4c.

[0064] The output light field of the second degenerate optical parametric amplifier 32 is injected into the high-reflection mirror 4c, and is driven by the high-frequency signal source 4a via an electrical path to make the third piezoelectric ceramic 4b produce a slight displacement, so as to achieve the purpose of phase-shifting the phase-sensitive light field output by the second degenerate optical parametric amplifier 32; and the output light field of the high-reflection mirror 4c is injected into the second non-degenerate optical parametric amplifier 22 together with the output light field of the first degenerate optical parametric amplifier 31.

[0065] As shown in Figure 5 In the embodiment, the measurement system 5 comprises a 50:50 optical beam splitter 5a, a first photodetector 5b, a second photodetector 5c, a power subtractor 5d and a spectrum analyzer 5e.

[0066] The local oscillation light field a output by the light source 11 L The output light signals of the non-degenerate optical parametric amplifier 22 interfere on the 50:50 optical beam splitter 5a, and the interference signals are respectively injected into the input ends of the first photodetector 5b and the second photodetector 5c. The output ends of the first photodetector 5b and the second photodetector 5c are connected with the input end of the power subtractor 5d, and the output end of the power subtractor 5d is connected with the spectrum analyzer 5e. The spectrum analyzer 5e is used for measuring and analyzing the signal power and noise power of the quadrature components of the output light signals of the non-degenerate optical parametric amplifier 22, and then obtaining the phase signal.

[0067] The working principle of the present application is as follows: a half-wave plate is placed in front of the first non-degenerate optical parametric amplifier to inject two mutually perpendicular polarized light fields into the interferometer. After passing through the first non-degenerate optical parametric amplifier, quantum entangled light fields are generated. After the two light fields are separated by a half-wave plate and a polarization beam splitter prism PBS, they are injected into the first and second degenerate optical parametric amplifiers, respectively, to further improve the quantum characteristics of the two light fields, and they are used as phase-sensitive light fields acting on the measured signal inside the interferometer. The phase sensor converts the physical quantity to be measured into the relative phase difference of the two phase-sensitive light fields. Next, the two phase-sensitive light fields interfere in the second non-degenerate optical parametric amplifier, and the quadrature components of the output light field contain the relative phase difference signal introduced by the physical quantity to be measured. Finally, the output light field quadrature components can be obtained by detecting through the balanced homodyne measurement system. Since the degenerate and non-degenerate optical parametric amplifiers are cascaded, not only the measured signal is amplified, but also the quantum noise of the phase-sensitive light field is reduced. In the case of not improving the intensity of the phase-sensitive light field, the phase measurement sensitivity of the interferometer can be improved, and the weak signal submerged in the shot noise limit can be detected. Therefore, the present application significantly improves the sensitivity of the interferometer.

[0068] As Figure 6As shown, in this embodiment, as shown in 6(a), 6(b) solid line, under the same phase-sensitive light field intensity, the phase measurement sensitivity of the interferometer exceeds "a quantum interferometer device based on optical parametric amplifier" (ZL202010067366.6), and can approach the quantum Cramer-Rao bound (QCRB) and has good phase measurement capability; as shown in 6(c) solid line, under the same phase-sensitive light field intensity, by adjusting the gain factor of the non-degenerate optical parametric amplifier to be much larger than that of the degenerate optical parametric amplifier, the noise level of the interferometer is lower than that of "a quantum interferometer device based on optical parametric amplifier" (ZL202010067366.6); as shown in 6(d) solid line, under the same phase-sensitive light field intensity, the signal level of the interferometer is higher than that of "a quantum interferometer device based on optical parametric amplifier" (ZL202010067366.6), and the present embodiment is successful and effective.

[0069] The present application cascades degenerate and non-degenerate optical parametric amplifiers to construct a new type of interferometer, realizes precise phase measurement with higher sensitivity beyond the standard quantum limit, and the phase measurement sensitivity is improved by times compared with the previous invention patent "a quantum interferometer device based on optical parametric amplifier" (ZL202010067366.6) times compared with SNL.

[0070] The present application utilizes the different advantages of different types of optical parametric amplifiers in the interferometer, cascades degenerate and non-degenerate optical parametric amplifiers to construct a new type of interferometer, and realizes the reduction of quantum noise while amplifying the measured signal of the interferometer in a deterministic manner. Only non-degenerate optical parametric amplifiers are used to expand the configuration of the interferometer, and the obtained interferometer can maintain the noise at the SNL level, only amplify the signal, realize the improvement of sensitivity, but cannot detect the weak signal submerged in the shot noise limit. The combination of degenerate and non-degenerate optical parametric amplifiers not only has a higher improvement in sensitivity, but also can detect the weak signal submerged in the shot noise limit, greatly enhancing the use rate of the interferometer under different measurement conditions.

[0071] The present application also has the advantages of the previous "quantum interferometer device based on optical parametric amplifier" (ZL202010067366.6). In the presence of interferometer loss and other noise, precise phase measurement that breaks through the standard quantum limit can be achieved unconditionally. By reducing the quantum noise of the interferometer phase-sensitive light field, the sensitivity of the interferometer can be improved, and the main factor affecting the measurement sensitivity, the quantum noise of the phase-sensitive light field inside the interferometer, can be solved. On the other hand, the intensity of the interferometer phase-sensitive light field is one of the main factors affecting the measurement sensitivity; improving the intensity of the interferometer phase-sensitive light field can improve the sensitivity of the interferometer, but high phase-sensitive light field intensity will increase the radiation pressure on the mirror, causing reaction force noise. The present application uses non-degenerate and degenerate optical parametric amplifier cascades to amplify the signal carried by the phase-sensitive light field times, which is not limited by the intensity of the phase-sensitive light field, so that the sensitivity of the interferometer can be improved.

[0072] The above-described embodiments only express several embodiments of the present application, which are described in detail and specifically, but should not be understood as a limitation on the scope of the patent of the present application. It should be noted that for ordinary skilled persons in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are within the scope of protection of the present application. Therefore, the scope of protection of the patent of the present application should be subject to the appended claims.

Claims

1. A quantum interference device that simultaneously amplifies signals and reduces noise, characterized in that: It includes a light source (11), a first optical frequency multiplier (12), a second optical frequency multiplier (13), a first non-degenerate optical parametric amplifier (21), a second non-degenerate optical parametric amplifier (22), a first degenerate optical parametric amplifier (31), a second degenerate optical parametric amplifier (32), a phase sensor (4), and a measurement system (5); The light source (11) outputs three probe light fields a respectively. S1 a S2 a S3 and local oscillating light field a L ; probe light field a output by light source (11) S1 a S3 Each of these is connected to the input terminals of the first optical frequency multiplier (12) and the second optical frequency multiplier (13) respectively; the probe light field a output by the light source (11) S2 Connected to the input terminal of the first non-degenerate optical parametric amplifier (21); The output of the first non-degenerate optical parametric amplifier (21) is connected to the signal light field input of the first degenerate optical parametric amplifier (31) and the second degenerate optical parametric amplifier (32), respectively. The phase-sensitive light field output by the second degenerate optical parametric amplifier (32) is connected to the input of the phase sensor (4). The phase sensor (4) is used to phase-shift the phase-sensitive light field output by the second degenerate optical parametric amplifier (32) according to the physical quantity to be measured. After passing through the phase sensor (4), the phase-sensitive light field output by the second degenerate optical parametric amplifier (32) is injected into the input of the second non-degenerate optical parametric amplifier (22) together with the output light field of the first degenerate optical parametric amplifier (31) and interferes therewith. The output light field of the second non-degenerate optical parametric amplifier (22) and the local oscillation light field a of the light source (11) are interfering with each other. L Inject together into the input terminal of the measurement system (5); The pump field a output by the first optical frequency multiplier (12) P1 and pump light field a P2 The pump field a output by the second optical frequency multiplier (13) is connected to the pump field input terminals of the first non-degenerate optical parametric amplifier (21) and the first degenerate optical parametric amplifier (31) respectively. P3 and pump light field a P4 Each of these circuits is connected to the pump field input terminals of the second degenerate optical parametric amplifier (32) and the second non-degenerate optical parametric amplifier (22) respectively, to provide them with pump fields.

2. The quantum interference device for simultaneously amplifying signals and reducing noise according to claim 1, characterized in that: The first non-degenerate optical parametric amplifier (21) and the second non-degenerate optical parametric amplifier (22) have the same structure; the first degenerate optical parametric amplifier (31) and the second degenerate optical parametric amplifier (32) have the same structure.

3. The quantum interference device for simultaneously amplifying signals and reducing noise according to claim 1, characterized in that: The first non-degenerate optical parametric amplifier (21) includes a first optical resonant cavity, a wedge-shaped nonlinear crystal (2c), and a temperature-controlled displacement system; The first optical resonant cavity includes a first plano-concave mirror (2a), a second plano-concave mirror (2b), and a first piezoelectric ceramic (2d); wherein the first plano-concave mirror (2a) and the second plano-concave mirror (2b) form a two-mirror cavity structure; the first piezoelectric ceramic (2d) is fixed on the second plano-concave mirror (2b); The probe light field as2 of the light source (11) and the pump light field ap1 output by the first optical frequency multiplier (12) are both input from the first plano-concave mirror (2a) to the first non-degenerate optical parametric amplifier (21). The difference is that the probe light field is emitted from the second plano-concave mirror (2b) after passing through the wedge-shaped nonlinear crystal (2c), and the pump light field is reflected by the second plano-concave mirror (2b) after passing through the wedge-shaped nonlinear crystal (2c) and then emitted from the first plano-concave mirror (2a). The first plano-concave mirror (2a) serves as the input mirror, coated with a high-reflectivity film for the probe light field and has transmittance for the pump light field; the second plano-concave mirror (2b) has transmittance for the probe light field and is coated with a high-reflectivity film for the pump light field, so that both the pump light field and the probe light field resonate within the cavity. The temperature-controlled displacement system is used to precisely control the temperature of the wedge-shaped nonlinear crystal (2c) and to translate the wedge-shaped nonlinear crystal (2c) along a direction perpendicular to the light propagation direction so that the pump light field and the probe light field are precisely matched.

4. The quantum interference device for simultaneously amplifying signals and reducing noise according to claim 3, characterized in that: The first plano-concave mirror (2a) has a transmittance of 10% for the pump light field; the second plano-concave mirror (2b) has a transmittance of 5% for the probe light field.

5. The quantum interference device for simultaneously amplifying signals and reducing noise according to claim 3, characterized in that: The temperature-controlled displacement system includes a first copper furnace, a first temperature control instrument, and a two-dimensional micro translation stage. The first copper furnace is used to heat the wedge-shaped nonlinear crystal (2c), the first temperature control instrument is used for precise temperature control, and the two-dimensional micro translation stage is used to translate the wedge-shaped nonlinear crystal (2c) along a direction perpendicular to the light propagation direction.

6. The quantum interference device for simultaneously amplifying signals and reducing noise according to claim 1, characterized in that: The first degenerate optical parametric amplifier (31) includes a second optical resonant cavity, a nonlinear crystal (3f), and a temperature control system; The second optical resonant cavity includes a third plano-concave mirror (3a), a fourth plano-concave mirror (3b), a first plane mirror (3c), a second plane mirror (3d), and a second piezoelectric ceramic (3e). The third plano-concave mirror (3a), the fourth plano-concave mirror (3b), the first plane mirror (3c), and the second plane mirror (3d) form a four-mirror figure-eight annular cavity structure. The second piezoelectric ceramic (3e) is fixed on the fourth plano-concave mirror (3b). The output light field of the first non-degenerate optical parametric amplifier (21) is input into the first degenerate optical parametric amplifier (31) through the first plane mirror (3c), and then exits from the first plane mirror (3c) after passing through the second plane mirror (3d), the third plano-concave mirror (3a), the nonlinear crystal (3f), and the fourth plano-concave mirror (3b); the pump light field ap2 output by the first optical frequency multiplier (12) is exited from the fourth plano-concave mirror (3b) after passing through the third plano-concave mirror (3a) and the nonlinear crystal (3f). The first plane mirror (3c) serves as an input-output coupling mirror and has transmittance to the probe light field. The second plane mirror (3d) is coated with a high-reflection film to the probe light field. The third plano-concave mirror (3a) and the fourth plano-concave mirror (3b) are both coated with a high-reflection film to the probe light field and an anti-reflection film to the pump light field. The temperature control system is used to heat and precisely control the temperature of the nonlinear crystal (3f).

7. The quantum interference device for simultaneously amplifying signals and reducing noise according to claim 6, characterized in that: The first plane mirror (3c) has a transmittance of 5% for the probe light field.

8. The quantum interference device for simultaneously amplifying signals and reducing noise according to claim 6, characterized in that: The temperature control system includes a second copper furnace and a second temperature control instrument. The second copper furnace is used to heat the nonlinear crystal (3f), and the second temperature control instrument is used for precise temperature control.

9. The quantum interference device for simultaneously amplifying signals and reducing noise according to claim 1, characterized in that: The phase sensor (4) includes a third piezoelectric ceramic (4b), a high-reflection mirror (4c), and a high-frequency signal source (4a); and the third piezoelectric ceramic (4b) is fixed to the back of the high-reflection mirror (4c); The output light field of the second degenerate optical parametric amplifier (32) is injected into the high-reflection mirror (4c), and after passing through the third piezoelectric ceramic (4b), it is driven by the high-frequency signal source (4a) through the electrical path to produce a small displacement, thereby achieving the purpose of phase shifting the phase-sensitive light field output by the second degenerate optical parametric amplifier (32). The output light field of the high-reflection mirror (4c) and the output light field of the first degenerate optical parametric amplifier (31) are injected together into the second non-degenerate optical parametric amplifier (22).

10. The quantum interference device for simultaneously amplifying signals and reducing noise according to claim 1, characterized in that: The measurement system (5) includes an optical beam splitter (5a), a first photodetector (5b), a second photodetector (5c), a power subtractor (5d), and a spectrum analyzer (5e); The local oscillating light field a output by the light source (11) L The output optical signal of the second non-degenerate optical parametric amplifier (22) interferes on the optical beam splitter (5a). The interference signal is injected into the input terminals of the first photodetector (5b) and the second photodetector (5c). The output terminals of the first photodetector (5b) and the second photodetector (5c) are connected to the input terminal of the power subtractor (5d). The output terminal of the power subtractor (5d) is connected to the spectrum analyzer (5e). The spectrum analyzer (5e) is used to measure and analyze the signal power and noise power of the quadrature components of the output optical signal of the second non-degenerate optical parametric amplifier (22) to obtain the phase signal.

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