CN112924982A - Distributed distance correlation positioning method based on quantum entanglement light correlation characteristic - Google Patents

Abstract

The invention provides a distributed trilateral positioning method based on quantum entanglement light correlation characteristics. Firstly, continuous pump light generates polarized light through a reflector and a polaroid, and the polarized light irradiates to a Periodically polarized potassium titanyl phosphate (PPKTP) crystal to generate idle light and signal light with entanglement characteristics; then, idle light is detected by a local single-photon detector, and signal light is sent to a target to be detected and reflected back to the local for detection by another single-photon detector; secondly, recording the arrival time information of the optical path by using a high-speed acquisition circuit, and generating a time tag sequence; thirdly, obtaining a second-order entangled light correlation characteristic curve through coincidence counting, and finding out the delay corresponding to the peak value of the second-order entangled light correlation characteristic curve, thereby calculating the distance from the local access point to the target to be measured; and finally, deploying 3 local access points with known positions, and calculating the position of the target to be positioned by utilizing a trilateral positioning principle.

Description

Distributed distance correlation positioning method based on quantum entanglement light correlation characteristic

Technical Field

The invention relates to the field of quantum precision measurement, in particular to a method for improving the positioning precision of a distributed distance correlation positioning method by using quantum entanglement photo-correlation characteristics.

Background

With the coming of the internet of things era, position services such as path query, logistics monitoring, navigation positioning and the like have penetrated into the aspects of production and life of people. The common positioning systems comprise a global positioning system, a cellular base station positioning system, an inertial navigation positioning system and a Beidou satellite positioning system, are widely applied to traffic navigation, satellite time service application, emergency command, civil water condition forecasting service and the like, and play a vital role.

Because the positioning system is mostly based on the classical physics which takes Newton mechanics, Maxwell equation set, Shannon information theory and the like as main contents, the positioning precision of the positioning system is limited by the classical shot noise, the positioning system is generally maintained at a meter level, and the positioning system is difficult to further improve. In addition, the positioning systems mostly rely on wireless signals and are very easily interfered by an ionosphere and a troposphere, so that the signals are transmitted in a nonlinear mode, and the interference resistance of the systems is poor. Therefore, the method based on quantum mechanics as a theoretical basis has very considerable research prospect in positioning application due to the characteristics of high positioning precision and high safety.

At present, the trilateral positioning method based on wireless signals is difficult to keep time accurate synchronization between a moving target and a signal access point due to the fact that the signals are susceptible to multipath effects, and is greatly limited in complex practical application. In addition, the signal propagation rate is fast, and even a very small time error can cause a huge positioning error, thereby sharply reducing the positioning performance. Therefore, the requirement for a high-precision clock synchronization technology is more urgent, and the quantum positioning method depends on coincidence counting to measure the time difference, which is proved to provide higher clock synchronization precision compared with the classical method.

Disclosure of Invention

The invention aims to provide a distributed distance correlation positioning method based on quantum entanglement light correlation characteristics. Compared with the traditional distance correlation positioning method based on wireless signals, the scheme based on quantum entangled state does not depend on wireless signals such as electromagnetic waves, and the positioning accuracy is improved by using the second-order correlation characteristic of entangled photons, and can reach the nanometer level theoretically.

The technical scheme adopted by the invention is as follows: a distributed distance correlation positioning method based on quantum entanglement light correlation characteristics specifically comprises the following steps:

generating high-quality pump light by using a semiconductor laser with the wavelength of 405nm, forming a telescope system by using lenses with the focal lengths of 300mm and 75mm respectively, and performing light field compression on the pump light to obtain pure pump light;

irradiating the pure periodic polarized potassium titanyl phosphate (PPKTP) crystal with pumping light to generate a spontaneous parametric down-conversion process, and performing parametric down-conversion on the light beam at a certain probability to obtain entangled light;

thirdly, reflecting the surplus unconverted pump light by the obtained entangled light through a high-pass total reflection mirror with the reflection wavelength of 405nm, and filtering interference light in the environment by using an interference filter to obtain high-quality entangled light;

separating entangled light with the wavelength of 810nm by using a polarization beam splitter to obtain idle light and reference light;

step five, enabling idle light and signal light to pass through a photon coupler respectively, enabling the idle light to be detected by a local single-photon detector 1 directly, and enabling the signal light to be sent to a target to be detected at a distance L and reflected back to be detected by a single-photon detector 2;

step six, in the acquisition time T, the arrival time information of the signals is recorded through a high-speed acquisition circuit, different channel zone bits CH1 and CH2 are set, and the arrival time information of the idle light and the signal light is respectively in a time tag sequence T₁＝{t₁₁,…,t_1i,…,t_1nAnd T₂＝{t₂₁,…,t_2i,…,t_2nStore locally in the form of t_ji(j-1, 2; i-1, …, n) represents the ith time stamp value for the jth channel;

step seven, time sequence label T₁And T₂And (4) performing coincidence counting on the medium label value, and setting different delays tau to obtain a coincidence counting value n (tau). According to the coincidence measurement correlation principle, when the coincidence gate width delta is far smaller than the coherence time tau of the optical field_cI.e. satisfy delta < tau_cWhen the count value n (tau) is matched with the ideal value of twoOrder correlation function g⁽²⁾(τ) satisfies the following relationship:

where T is the total sampling time, δ is the coincidence gate width, R₁And R₂Photon counting rate, gamma, of the single photon detectors 1 and 2, respectively₁And gamma₂Which is the sum of the dark count rate of the single photon detectors 1 and 2, respectively, and the count rate due to ambient noise. From the above formula, g⁽²⁾The expression of (τ) is:

when R is_i＞＞γ_iWhen (i ═ 1,2), the relationship between the normalized second-order correlation function and the coincidence count value can be simplified to obtain:

step eight, the obtained discrete points (tau, g) are subjected to least square fitting algorithm⁽²⁾(τ)) performing curve fitting, and determining the abscissa delay corresponding to the peak of the curve as the time domain measurement result, i.e. the difference between the signal light and the idle light transmission time. At this time, the distance L from the local access point to the target can be expressed as:

wherein c is the speed of light;

ninthly, according to the trilateral positioning principle, by deploying 3 entangled optical transceivers (namely local access points) with known position coordinates, the distances L from the 3 local access points to the target can be obtained according to the method₁、L₂And L₃And calculating the position of the target to be positioned by utilizing a trilateral positioning principle.

The seventh step comprises the following steps:

step seven (one), to T₁Adding delay tau to each label value to obtain T₁'；

Step seven (two), selecting T₂Taking each label value as a reference, taking each time label as a midpoint of a time interval, wherein the length of the time interval is in accordance with the gate width delta;

step seven (three), searching T in each time interval₁If the time tag in' falls within the interval, the coincidence count is increased by 1;

step seven (four), T is searched₁' after all the time tags in the above, the coincidence count value n (τ) delayed by τ is obtained.

The ninth step comprises the following steps:

step nine (one), the physical coordinates of 3 local access points are assumed to be (x) respectively₁,y₁)、(x₂,y₂) And (x)₃,y₃) The distances from the 3 local access points to the target are respectively L₁、L₂And L₃The system of structural equations is as follows:

expanding and simplifying the formula (5) to obtain:

step nine (two), set

And

then there are:

i.e., Y ═ ax, where,

and

step nine (three), using least square relational expression

The coordinates (x) of the target to be positioned can be obtained₀,y₀)。

Drawings

FIG. 1 is a diagram of a quantum entangled light distance path of the present invention;

FIG. 2 is a timing diagram of the operation of the high speed acquisition circuit of the present invention;

FIG. 3 is a flow chart of a coincidence counting algorithm of the present invention;

FIG. 4 is a timing diagram of the operation of the high-speed acquisition circuit according to the count algorithm of the present invention;

fig. 5 is a schematic diagram of trilateral location in accordance with the present invention.

Detailed description of the preferred embodiments

The invention is described in further detail below with reference to the accompanying drawings:

generating high-quality pump light by using a semiconductor laser with the wavelength of 405nm, and performing light field compression on the pump light by using a telescope system consisting of lenses with the focal lengths of 300mm and 75mm respectively to obtain pure pump light;

irradiating the pure pump light to the PPKTP crystal to generate a spontaneous parameter down-conversion process, and performing parameter down-conversion on the light beam at a certain probability to obtain entangled light;

thirdly, reflecting the surplus unconverted pump light by the obtained entangled light through a high-pass total reflection mirror with the reflection wavelength of 405nm, and filtering interference light in the environment by using an interference filter to obtain high-quality entangled light;

step four, separating the entangled light with the wavelength of 810nm by using a polarization beam splitter to obtain signal light and idle light with equal light intensity I, and meeting the following requirements:

wherein the symbol "oc" represents a positive correlation, d is the crystal length, c is the light velocity, and Δ k is the phase mismatch amount, satisfying:

wherein Λ is the polarization period, k_pIs the pumping light wave vector, k_iAs the idle light wave vector, k_sIs the wave vector of the signal light,

is the grating wave vector;

step five, enabling idle light and signal light to pass through a photon coupler respectively, enabling the idle light to be detected by a local single-photon detector 1 directly, and enabling the signal light to be sent to a target to be detected at a distance L and reflected back to be detected by a single-photon detector 2;

setting the acquisition time T to be 30s, recording the arrival time information of the signals through a high-speed acquisition circuit, setting different channel flag bits CH1 and CH2, and respectively setting the arrival time information of the idle light and the signal light in a time tag sequence T₁＝{t₁₁,…,t_1i,…,t_1nAnd T₂＝{t₂₁,…,t_2i,…,t_2nStore locally in the form of t_ji(j-1, 2; i-1, …, n) represents the ith time stamp value for the jth channel;

step seven, time sequence label T₁And T₂And (4) performing coincidence counting on the medium label value, and setting different delays tau to obtain a coincidence counting value n (tau). According to the coincidence measurement correlation principle, when the coincidence gate width delta is far smaller than the coherence time tau of the optical field_cI.e. satisfy delta < tau_cIn time, the count value n (tau) and the ideal second order correlation function g are matched⁽²⁾(τ) satisfiesThe following relationships:

wherein, δ is in accordance with the gate width, R₁And R₂Photon counting rate, gamma, of the single photon detectors 1 and 2, respectively₁And gamma₂Which is the sum of the dark count rate of the single photon detectors 1 and 2, respectively, and the count rate due to ambient noise. From the above formula, g⁽²⁾The expression of (τ) is:

when R is_i＞＞γ_iWhen (i ═ 1,2), the relationship between the normalized second-order correlation function and the coincidence count value can be simplified to obtain:

step eight, the obtained discrete points (tau, g) are subjected to least square fitting algorithm⁽²⁾(τ)) performing curve fitting, and determining the abscissa delay corresponding to the peak of the curve as the time domain measurement result, i.e. the difference between the signal light and the idle light transmission time. At this time, the distance L from the local access point to the target can be expressed as:

wherein c is the speed of light;

ninthly, according to the trilateral positioning principle, by deploying 3 local access points with known position coordinates, the distances L from the 3 local access points to the target can be obtained according to the method₁、L₂And L₃And calculating the position of the target to be positioned by utilizing a trilateral positioning principle.

The seventh step comprises the following steps:

step seven (one), to T₁Adding delay tau to each label value to obtain T₁'；

Step seven (two), selecting T₂Taking each label value as a reference, taking each time label as a midpoint of a time interval, wherein the length of the time interval is in accordance with the gate width delta;

step seven (three), searching T in each time interval₁If the time tag in' falls within the interval, the coincidence count is increased by 1;

step seven (four), T is searched₁' after all the time tags in the above, the coincidence count value n (τ) delayed by τ is obtained.

The ninth step comprises the following steps:

step nine (one), the physical coordinates of 3 local access points are assumed to be (x) respectively₁,y₁)、(x₂,y₂) And (x)₃,y₃) The distances from the 3 local access points to the target are respectively L₁、L₂And L₃The system of structural equations is as follows:

expanding the formula (14), and simplifying to obtain:

step nine (two), set

And

then there are:

i.e., Y ═ ax, where,

and

step nine (three), using least square relational expression

The coordinates (x) of the target to be positioned can be obtained₀,y₀)。

Claims (3)

1. A distributed distance correlation positioning method based on quantum entanglement light correlation characteristics is characterized by comprising the following steps:

generating high-quality pump light by using a semiconductor laser with the wavelength of 405nm, forming a telescope system by using lenses with the focal lengths of 300mm and 75mm respectively, and performing light field compression on the pump light to obtain pure pump light;

irradiating the pure periodic polarized potassium titanyl phosphate (PPKTP) crystal with pumping light to generate a spontaneous parametric down-conversion process, and performing parametric down-conversion on the light beam at a certain probability to obtain entangled light;

thirdly, reflecting the surplus unconverted pump light by the obtained entangled light through a high-pass total reflection mirror with the reflection wavelength of 405nm, and filtering interference light in the environment by using an interference filter to obtain high-quality entangled light;

step four, separating the entangled light with the wavelength of 810nm by using a polarization beam splitter to obtain signal light and idle light with equal light intensity I, and meeting the following requirements:

wherein the symbol "oc" represents a positive correlation, d is the crystal length, c is the light velocity, and Δ k is the phase mismatch amount, satisfying:

wherein Λ is the polarization period, k_pIs the pumping light wave vector, k_iAs the idle light wave vector, k_sIs the wave vector of the signal light,

is the grating wave vector;

step five, enabling idle light and signal light to pass through a photon coupler respectively, enabling the idle light to be detected by a local single-photon detector 1 directly, and enabling the signal light to be sent to a target to be detected at a distance L and reflected back to be detected by a single-photon detector 2;

setting the acquisition time T to be 30s, recording the arrival time information of the signals through a high-speed acquisition circuit, setting different channel flag bits CH1 and CH2, and respectively setting the arrival time information of the idle light and the signal light in a time tag sequence T₁＝{t₁₁,…,t_1i,…,t_1nAnd T₂＝{t₂₁,…,t_2i,…,t_2nStore locally in the form of t_ji(j-1, 2; i-1, …, n) represents the ith time stamp value for the jth channel;

step seven, time sequence label T₁And T₂Performing coincidence counting on the medium label value, and setting different delays tau to obtain a coincidence counting value n (tau); according to the coincidence measurement correlation principle, when the coincidence gate width delta is far smaller than the coherence time tau of the optical field_cI.e. satisfy delta < tau_cIn time, the count value n (tau) and the ideal second order correlation function g are matched⁽²⁾(τ) satisfies the following relationship:

wherein, δ is in accordance with the gate width, R₁And R₂Photon counting rate, gamma, of the single photon detectors 1 and 2, respectively₁And gamma₂Are respectively asThe sum of the dark count rate of the single photon detectors 1 and 2 and the count rate caused by environmental noise can be obtained by the formula⁽²⁾The expression of (τ) is:

when R is_i＞＞γ_iWhen (i ═ 1,2), the relationship between the normalized second-order correlation function and the coincidence count value can be simplified to obtain:

step eight, the obtained discrete points (tau, g) are subjected to least square fitting algorithm⁽²⁾(τ)) performing curve fitting, where the abscissa delay corresponding to the peak of the curve is the time domain measurement result, that is, the difference between the signal light and the idle light transmission time, and at this time, the distance L from the local access point to the target may be represented as:

wherein c is the speed of light;

ninthly, according to the trilateral positioning principle, by deploying 3 local access points with known position coordinates, the distances L from the 3 local access points to the target can be obtained according to the method₁、L₂And L₃And calculating the position of the target to be positioned by utilizing a trilateral positioning principle.

2. The coincidence counting algorithm in the distributed distance correlation positioning method based on the quantum entanglement light correlation characteristic is characterized in that: the seventh step comprises the following steps:

step seven (one), to T₁Adding delay tau to each label value to obtain T₁'；

Step seven (II), selecting T₂Taking each label value as a reference, taking each time label as a midpoint of a time interval, wherein the length of the time interval is in accordance with the gate width delta;

step seven (three), searching T in each time interval₁If the time tag in' falls within the interval, the coincidence count is increased by 1;

step seven (four), T is searched₁' after all the time tags in the above, the coincidence count value n (τ) delayed by τ is obtained.

3. The method for trilateral localization in the distributed distance-dependent localization based on quantum entanglement light correlation property as claimed in, wherein: the ninth step comprises the following steps:

step nine (one), the physical coordinates of 3 local access points are assumed to be (x) respectively₁,y₁)、(x₂,y₂) And (x)₃,y₃) The distances from the 3 local access points to the target are respectively L₁、L₂And L₃The system of structural equations is as follows:

expanding and simplifying the formula (7) to obtain:

step nine (two), set

And

then there are:

i.e., Y ═ ax, where,

and

step nine (three), using least square relational expression

The coordinates (x) of the target to be positioned can be obtained₀,y₀)。

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