Single-photon non-destructive measurement equipment, method and system based on micro-ring resonant cavity

Abstract

The invention discloses single-photon non-destructive measurement equipment based on a micro-ring resonant cavity, and the equipment comprises a signal light input waveguide, a signal light output waveguide, a detection light input waveguide, a detection light output waveguide, a first optical circulator, a second optical circulator, a linear waveguide, the micro-ring resonant cavity, and a three-level quantum emitter. The first ends of the signal light input waveguide, the probe light output waveguide and the linear waveguide are respectively connected to the first optical circulator, the second ends of the signal light output waveguide, the probe light input waveguide and the linear waveguide are respectively connected to the second optical circulator, and the micro-ring resonant cavity is coupled with the linear waveguide. And the three-level quantum emitter is coupled with the micro-ring resonant cavity. The method is high in measurement efficiency and high in measurement precision.

Description

Technical Field

[0001] The present invention relates to single - photon measurement technology, and particularly to a single - photon non - destructive measurement device, method and system based on a micro - ring resonator. Background Art

[0002] Single - photon measurement technology plays a crucial role in basic quantum physics research and the development of quantum information technology. Traditionally, most single - photon measurement methods rely on the absorption of photons by detectors, which inevitably destroys the measured quantum state. Therefore, it is impossible to perform repeated measurements or reuse of individual photons. This destructive measurement method severely limits the further development of quantum information processing, quantum communication and quantum networks. To overcome this problem, Quantum Nondemolition Measurement (QND measurement for short) emerged. This technology can achieve efficient detection of photons without changing the quantum state of the measured photons, enabling individual photons to be reused in subsequent quantum information processing.

[0003] The core idea of quantum non - destructive measurement is that during the measurement process, the eigenstate of the observable of the system to be measured is not destroyed, thereby realizing continuous monitoring of a certain quantum state. In particular, for the electromagnetic field mode, the photon number is an ideal quantum non - destructive observable. Specifically, photon non - destructive measurement is to keep the photon - number eigenstate unchanged while detecting the photon number. This technology relies on the strong interaction between light field and matter, and the most common one is to utilize the cavity - enhanced quantum light - matter interaction effect.

[0004] In recent years, important experimental progress has been made in the research of single - photon non - destructive measurement in the microwave frequency band. One typical method is to utilize the dispersion - displacement effect, and the specific implementation scheme includes coupling microwave photons with a controlled two - level system (such as a superconducting qubit) in a cavity. At this time, the presence or absence of microwave photons is indirectly detected by causing a shift in the resonance frequency of the two - level system. Another scheme is the phase - sensitive ladder - type three - level quantum emitter scheme, which realizes non - destructive measurement of single photons by detecting the nonlinear phase shift induced by the coupling of single photons with the three - level system in the cavity. These methods all ingeniously utilize the phase information of the detection field and successfully achieve high - fidelity non - destructive detection of single photons.

[0005] However, when the above - mentioned technology extends to the optical frequency band, the situation becomes more complex. Implementing single - photon non - destructive measurement in the optical frequency band faces greater challenges, especially the measurement methods based on optical Kerr nonlinearity have significant controversies and difficulties. This is because the nonlinear interaction in the optical frequency band is usually weak and the noise background is higher, resulting in a significant reduction in single - photon detection efficiency and signal fidelity.

[0006] In recent years, a new idea has emerged, such as the dispersion displacement scheme, the ladder-type three-level scheme, or the phase-encoded quantum nonlocal response scheme. All of them indirectly measure the presence of photons by inducing frequency shifts or phase changes in the energy levels of matter by photons, and all rely on the phase change signal of the detection field, effectively enhancing the measurement sensitivity. However, the measurement efficiency and measurement accuracy need to be further improved. Summary of the Invention

[0007] Aiming at the problems existing in the prior art, the purpose of the present invention is to provide a single-photon non-destructive measurement device, method, and system based on a microring resonator with high measurement efficiency and high measurement accuracy.

[0008] In order to achieve the above invention purpose, the present invention provides the following technical solutions:

[0009] A single-photon non-destructive measurement device based on a microring resonator includes a signal light input waveguide, a signal light output waveguide, a probe light input waveguide, a probe light output waveguide, a first optical circulator, a second optical circulator, a linear waveguide, a microring resonator, and a three-level quantum emitter. Among them, the first ends of the signal light input waveguide, the probe light output waveguide, and the linear waveguide are respectively connected to the first optical circulator, and the second ends of the signal light output waveguide, the probe light input waveguide, and the linear waveguide are respectively connected to the second optical circulator. The microring resonator is coupled with the linear waveguide, and the three-level quantum emitter is coupled with the microring resonator.

[0010] Further, the three-level quantum emitter has a ground state, a first excited state, and a second excited state, and has a first transition channel from the ground state to the first excited state and a second transition channel from the ground state to the second excited state.

[0011] Further, the first transition channel of the three-level quantum emitter is coupled with the left-handed circularly polarized evanescent field in the microring resonator, and the second transition channel of the three-level quantum emitter is coupled with the right-handed circularly polarized evanescent field in the microring resonator.

[0012] Further, the signal light input waveguide, the first end of the linear waveguide, and the probe light output waveguide are respectively connected to the first port, the second port, and the third port of the first optical circulator.

[0013] Further, the probe light input waveguide, the second end of the linear waveguide, and the signal light output waveguide are respectively connected to the first port, the second port, and the third port of the second optical circulator.

[0014] A single-photon non-destructive measurement method based on a microring resonator, the method is implemented based on the above measurement device, and the method includes:

[0015] Continuous probe photons are input into the probe light input waveguide, and a single signal photon to be measured is input into the signal light input waveguide;

[0016] A photodetector is used to monitor in real time the probe photons output from the probe light output waveguide;

[0017] The ratio of the number of probe photons input into the probe light input waveguide to the number of probe photons output from the probe light output waveguide is calculated as the transmittance of the probe light field;

[0018] When the transmittance of the probe light field changes and exceeds a preset threshold, it is determined that a single photon has been measured.

[0019] A single-photon non-destructive measurement system based on a microring resonator, the system includes the above measurement device, and further includes:

[0020] A probe light emitter for inputting continuous probe photons into the probe light input waveguide;

[0021] A single-photon generating device to be measured for inputting a single signal photon to be measured into the signal light input waveguide;

[0022] A photodetector for monitoring in real time the probe photons output from the probe light output waveguide;

[0023] A calculation module for calculating the ratio of the number of probe photons input into the probe light input waveguide to the number of probe photons output from the probe light output waveguide as the transmittance of the probe light field; when the transmittance of the probe light field changes and exceeds a preset threshold, it is determined that a single photon has been measured.

[0024] Compared with the prior art, the beneficial effects of the present invention are: The present invention uses the transmittance of the probe field as the detection benchmark, no longer limited to relying on the phase information of the probe field, through the non-linear quantum information contained in the transmittance of the probe field, and using the quantum competition effect of the transmittance of the probe field, significantly improves the measurement efficiency of single-photon non-destructive detection; realizes efficient isolation of the signal and the probe light through an optical circulator, effectively avoids optical interference, and improves the measurement accuracy; the system structure is simple, the control and operation are convenient, and the technical difficulty and cost of realizing high-fidelity single-photon measurement can be greatly reduced. Description of the Drawings

[0025] Figure 1 is a structural diagram of a single-photon non-destructive measurement device based on a microring resonator provided by the present invention;

[0026] Figure 2 is a three-level schematic diagram of a three-level quantum emitter provided by the present invention;

[0027] Figure 3 is a schematic diagram of the change of the transmittance of the probe field of the present invention with the signal field power;

[0028] Figure 4 Schematic diagram of the change in the detected photon stream output by the detection light output waveguide when a single photon passes through. Specific implementation mode

[0029] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention.

[0030] Embodiment 1

[0031] The embodiment of the present invention provides a single-photon non-destructive measurement device based on a microring resonator, as Figure 1 shown, including a signal light input waveguide 1, a signal light output waveguide 2, a detection light input waveguide 3, a detection light output waveguide 4, a first optical circulator 5, a second optical circulator 6, a linear waveguide 7, a microring resonator 8, and a three-level quantum emitter 9. Among them, the signal light input waveguide 1, the first end of the linear waveguide 7, and the detection light output waveguide 4 are respectively connected to the first port, the second port, and the third port of the first optical circulator 5. The detection light input waveguide 3, the second end of the linear waveguide 7, and the signal light output waveguide 2 are respectively connected to the first port, the second port, and the third port of the second optical circulator 6. Because the first optical circulator 5 outputs a signal at the second port when a signal is input at the first port, and outputs a signal at the third port when a signal is input at the second port, when a signal is input from the signal light input waveguide 1, the signal is output from the first end of the linear waveguide 7, and when a signal is input from the first end of the linear waveguide 7, the signal is output from the detection light output waveguide 4. The same applies to the second optical circulator 5. The microring resonator 8 is coupled to the linear waveguide 7, and the three-level quantum emitter 9 is coupled to the microring resonator 8.

[0032] In this embodiment, the signal light input waveguide 1, the signal light output waveguide 2, the detection light input waveguide 3, the detection light output waveguide 4, and the linear waveguide 7 are all linear silicon-based waveguides. The microring resonator 8 is a silicon-based microring resonator with a radius of 100 μm, an effective refractive index of 2, a resonance wavelength designed to be 780.2 nm, and an external attenuation to intrinsic attenuation ratio of 1000:1 to achieve high-quality resonance characteristics.

[0033] The three-level quantum emitter 9 is specifically a rubidium-87 atom D2 line V-type energy level quantum emitter, as Figure 2As shown, it has a ground state |1>, a first excited state |2> and a second excited state |3>, and has a first transition channel from the ground state |1> to the first excited state |2> and a second transition channel from the ground state |1> to the second excited state |3>. The first transition channel of the three-level quantum emitter 9 is coupled to the left-handed circularly polarized evanescent field in the micro-ring resonator, with a coupling strength of g1, and the second transition channel is coupled to the right-handed circularly polarized evanescent field in the micro-ring resonator, with a coupling strength of g2. In the embodiment of the present invention, the ground state selects energy level 5 2 S 1 / 2 , the total angular momentum quantum number F = 1, and the total angular momentum magnetic quantum number m F = 0, the first excited state energy level 5 2 P 3 / 2 , the total angular momentum quantum number F' = 1, and the total angular momentum magnetic quantum number m' F = –1, the second excited state energy level 5 2 P 3 / 2 , the total angular momentum quantum number F' = 1, and the total angular momentum magnetic quantum number m' F = 1, and the wavelengths corresponding to the two transitions are both 780.2 nm. Since the wavelengths of the two transition channels are the same, the coupling strengths to the micro-ring resonator 8 are equal, and the ratio of the coupling strength to the attenuation is about 1:5, ensuring the effectiveness of the quantum transition.

[0034] In other embodiments, the micro-ring resonator 8 can also be fabricated from materials such as silicon oxynitride, polymer, or a photonic crystal-based nanocavity. The three-level quantum emitter 9 can also be a large detuning type V-type quantum emitter, that is, a V-type quantum emitter with a large energy level difference between the two transition channels, so that the two transition channels can both achieve the quantum competition effect and there is no significant interference between them. For example, taking rubidium-87 atoms as an example, the ground state selects energy level 5 2 S 1 / 2 , and the two excited state energy levels 5 2 P 3 / 2 and 5 2 P 1 / 2 , and the wavelengths corresponding to the two transitions are 780.241 nm and 794.978 nm respectively. In this structural configuration, non-destructive measurement of a single signal photon can also be achieved.

[0035] The principle of the present invention will be elaborated in detail below.

[0036] When no signal is input to the signal light input waveguide 1 and only continuous linearly polarized probe photons are input to the probe light input waveguide 3, they are input to the second end of the linear waveguide 7 after passing through the second optical circulator 6, and then propagate along the linear waveguide 7. When approaching the microring resonator 8, the probe photons are coupled into the microring resonator 8 and rotate in the clockwise direction. Due to the transverse optical confinement characteristics of the structures of the linear waveguide 7 and the microring resonator 8, the evanescent field during photon propagation forms a spin-momentum locking effect with its propagation direction, that is, a right-handed circularly polarized evanescent field is generated. When the probe photons reach the three-level quantum emitter 9, because the right-handed circularly polarized evanescent field is coupled to the second transition channel, part of the probe photons will be coupled from the microring resonator 8 to the quantum emitter, and the quantum emitter will transition from the ground state to the second excited state. The remaining probe photons continue to propagate along the microring resonator 8 until they rotate one circle and are then coupled into the linear waveguide 7 again and output from the probe light output waveguide 4. When only the probe light is input, because the coupling strength between the microring resonator and the quantum emitter remains unchanged, the transmittance of the probe light field remains unchanged.

[0037] When a linearly polarized single signal photon is input to the signal light input waveguide 1 and continuous linearly polarized probe photons are input to the probe light input waveguide 3 at the same time, the single signal photon is input to the first end of the linear waveguide 6 through the first optical circulator 5 and then output, and then propagates along the linear waveguide 7. When approaching the microring resonator 8, the single signal photon is coupled into the microring resonator 8 and rotates in the counterclockwise direction. The propagation of the single signal photon generates a left-handed circularly polarized evanescent field. When the single signal photon and the probe photon reach the vicinity of the three-level quantum emitter 9 at the same time, because the left-handed circularly polarized evanescent field generated by the single signal photon is coupled to the first transition channel, and the right-handed circularly polarized evanescent field generated by the probe photon is coupled to the second transition channel, and they share the same ground state, a quantum competition effect of transition probability will be generated, and the competition intensity is closely related to the incident light power. Specifically, under the condition that the power of the probe light field is fixed, as the power of the signal light field increases, the transition probability of the probe light field weakens, the coupling between the probe photon and the second transition channel of the quantum emitter decreases, the number of probe photons coupled to the quantum emitter decreases, and the number of probe photons output from the probe light output waveguide 4 increases, resulting in an increase in the transmittance of the probe light field. The single signal photon is a complete pulse. After being coupled into the quantum emitter 9, it will be released into the microring resonator 8 again and then output from the signal light output waveguide 2 without damage as a whole. As Figure 3 shown, the transmittance of the probe light field increases with the increase of the signal light field power. In the extreme case, when the signal light transition dominates, the transmittance of the probe light field can even reach 100%. In actual single-photon tests, the power of the signal light field does not need to be particularly large, and it can also be achieved when it is less than the probe light field. When no single signal photon (signal photon vacuum state) is input, the transition probability of the probe light field drops back to the initial level, so that the probe photon flux and transmittance both drop back to the initial level, as shown in the appendixFigure 4 As shown. In this embodiment, when there is a single signal photon, the transmittance of the detection optical field remains at 0.15, while when a single signal photon is incident, the transmittance of the detection optical field significantly increases to 0.3. This significant change in transmittance can be used as a sign to achieve non-destructive measurement of a single signal photon.

[0038] Embodiment 2

[0039] This embodiment provides a method for non-destructive measurement of single photons based on a microring resonator. The method is implemented based on the measurement device of Embodiment 1, and the method includes:

[0040] Input continuous linearly polarized detection photons into the detection optical input waveguide, and input the single signal photon to be measured into the signal optical input waveguide;

[0041] Use a photodetector to monitor in real time the detection photons output from the detection optical output waveguide;

[0042] Calculate the ratio of the number of detection photons input into the detection optical input waveguide to the number of detection photons output from the detection optical output waveguide as the transmittance of the detection optical field;

[0043] When the transmittance of the detection optical field changes and exceeds a preset threshold, for example, when it reaches 0.3 from 0.15, it is determined that a single photon has been measured.

[0044] Embodiment 3

[0045] An embodiment of the present invention provides a system for non-destructive measurement of single photons based on a microring resonator. The system includes the measurement device of Embodiment 1, and further includes:

[0046] A detection optical emitter for inputting continuous linearly polarized detection photons into the detection optical input waveguide;

[0047] A single photon generating device to be measured for inputting the single signal photon to be measured into the signal optical input waveguide;

[0048] A photodetector for monitoring in real time the detection photons output from the detection optical output waveguide;

[0049] A calculation module for calculating the ratio of the number of detection photons input into the detection optical input waveguide to the number of detection photons output from the detection optical output waveguide as the transmittance of the detection optical field; when the transmittance of the detection optical field changes and exceeds a preset threshold, it is determined that a single photon has been measured.

[0050] It should be noted that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations.

[0051] It should be understood that the above content describes the principle, system structure and implementation examples of the present invention in combination with the accompanying drawings. However, the present invention is not limited to the above system structure and specific implementation schemes. The implementation schemes in the specification only give specific implementation methods, which are illustrative rather than restrictive. Those skilled in the art can adjust the system structure according to the principle proposed under the inspiration of the present invention, and can select different V-type three-level quantum emitters, micro-ring resonators made of different materials and optical waveguides according to needs. Without violating the V-type three-level quantum emitter chiral coupling micro-ring resonator system proposed by the present invention, various specific implementations can be made, and these all fall within the protection scope of the present invention.

Claims

1. A single-photon non-destructive measurement device based on a microring resonator, characterized in that: It includes a signal light input waveguide, a signal light output waveguide, a probe light input waveguide, a probe light output waveguide, a first optical circulator, a second optical circulator, a linear waveguide, a microring resonator, and a three-level quantum emitter. Among them, the first ends of the signal light input waveguide, the probe light output waveguide, and the linear waveguide are respectively connected to the first optical circulator, and the second ends of the signal light output waveguide, the probe light input waveguide, and the linear waveguide are respectively connected to the second optical circulator. The microring resonator is coupled with the linear waveguide, and the three-level quantum emitter is coupled with the microring resonator.

2. The single-photon non-destructive measurement device based on a microring resonator according to claim 1, characterized in that: The three-level quantum emitter has a ground state, a first excited state, and a second excited state, and has a first transition channel from the ground state to the first excited state and a second transition channel from the ground state to the second excited state.

3. The single-photon non-destructive measurement device based on a microring resonator according to claim 2, wherein: The first transition channel of the three-level quantum emitter is coupled with the left-handed circularly polarized evanescent field in the microring resonator, and the second transition channel is coupled with the right-handed circularly polarized evanescent field in the microring resonator.

4. The single-photon non-destructive measurement device based on a microring resonator according to claim 1, characterized in that: The signal light input waveguide, the first end of the linear waveguide, and the probe light output waveguide are respectively connected to the first port, the second port, and the third port of the first optical circulator.

5. The single-photon non-destructive measurement device based on a microring resonator according to claim 1, characterized in that: The probe light input waveguide, the second end of the linear waveguide, and the signal light output waveguide are respectively connected to the first port, the second port, and the third port of the second optical circulator.

6. The single-photon non-destructive measurement device based on a microring resonator according to claim 1, characterized in that: The three-level quantum emitter is specifically a rubidium-87 atom D2-line V-type energy level quantum emitter or a large-detuning V-type quantum emitter.

7. The single-photon non-destructive measurement device based on a microring resonator according to claim 1, characterized in that: The microring resonator is a microring resonator made of silicon-based, silicon oxynitride, polymer, or a photonic crystal-based nanocavity.

8. A single-photon non-destructive measurement method based on a microring resonator, characterized in that, The method is implemented based on the measuring device described in claim 1, and the method includes: Inputting continuous probe photons into the probe light input waveguide, and inputting a single signal photon to be measured into the signal light input waveguide; Using a photodetector to monitor in real time the probe photons output from the probe light output waveguide; Calculating the ratio of the number of probe photons input into the probe light input waveguide to the number of probe photons output from the probe light output waveguide as the probe light field transmittance; When the probe light field transmittance changes and exceeds a preset threshold, it is determined that a single photon has been measured.

9. The single-photon non-destructive measurement method based on a microring resonator according to claim 8, characterized in that, The probe light is linearly polarized light.

10. A single-photon non-destructive measurement system based on a microring resonator, characterized in that, The system includes the measuring device described in claim 1, and further includes: A probe light emitter for inputting continuous probe photons into the probe light input waveguide; A single photon generating device to be measured for inputting a single signal photon to be measured into the signal light input waveguide; A photodetector for monitoring in real time the probe photons output from the probe light output waveguide; A calculation module for calculating the ratio of the number of probe photons input into the probe light input waveguide to the number of probe photons output from the probe light output waveguide as the probe light field transmittance; when the probe light field transmittance changes and exceeds a preset threshold, it is determined that a single photon has been measured.

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