KR20220037090A - Apparatus for distace measurement and method thereof - Google Patents

Abstract

Provided are a method and device for measuring a distance from a target. The method includes the steps of: recording a first arrival time, which is a time taken for a photon pair emitted by a quantum light source to directly reach a first detector, during a predetermined time period; recording a second arrival time, which is a time required for a photon pair emitted by the quantum light source to be transmitted or reflected by a target and reach a second detector, during the predetermined time period; determining a non-classical correlation of the photon pair based on a difference between a plurality of first times of arrival and a plurality of second times of arrival; and calculating a distance from the target according to a measurement result. Accordingly, it is possible to measure a distance from a distant target.

Description

DISTANCE MEASUREMENT AND METHOD THEREOF

The present disclosure relates to an apparatus and method for measuring a distance to a target using a non-classical correlation of a photon pair.

Time correlated single photon counting (TCSPC) measurement is mainly used to calculate the fluorescence lifetime in the field of time-resolved spectroscopy, and measures the time difference between excitation and emission for each photon. This means a method of obtaining the distribution of photons emitted with time. By using TCSPC, it is possible to check the non-classical properties of photons, the properties of single photons, and the quantum interference properties of independent photons. Among them, the property of the temporal correlation of photon pairs is utilized as an important index for confirming the properties of photons in quantum optics.

The temporal correlation of the photon pairs may be performed based on information about the arrival time of the detected photon pairs when the photon pairs are detected by the photon detector. If a photon pair has a non-classical strong correlation, it exhibits a higher signal-to-noise ratio (SNR) than a photon pair with a classical correlation, even in a noisy environment. A relatively strong signal can be obtained.

Meanwhile, as the distance from the target increases, a signal transmitted or reflected by the target and received may include more noise. Therefore, if a photon pair with a non-classical strong correlation is used for a quantum radar that measures distance, the measurement accuracy can be improved by using a high SNR signal. Accordingly, research on a distance measuring device using the non-classical correlation of photon pairs is in progress.

The problem to be solved by this embodiment is to find a non-classical correlation of a photon pair based on the arrival time, which is the time it takes for the photon pair to reach a photon detector, and to use it to find a method and apparatus for measuring the distance to a target is to provide

The technical problems to be achieved by the present embodiment are not limited to the technical problems described above, and other technical problems may be inferred from the following embodiments.

According to a first embodiment, a method for measuring a distance from a target records a first arrival time, which is a time taken for a photon pair emitted by a quantum light source to directly reach a first detector, for a predetermined time range. recording a second arrival time, which is a time required for a photon pair emitted by the quantum light source to be transmitted or reflected by a target to reach a second detector, for the predetermined time range, a plurality of first arrival times and measuring a non-classical correlation of the photon pair based on differences in a plurality of second arrival times, and calculating a distance to the target according to the measurement result.

According to a second embodiment, an apparatus for measuring a distance to a target includes a quantum light source that emits a quantum photon pair, a first detector that detects the photon pair directly from the quantum light source for a predetermined time range, the target A second detector, which detects the photon pair transmitted or reflected by the , during the predetermined time range, and a first arrival time, which is a time required for the photon pair to reach the first detector, are recorded for a predetermined time range, and the A second arrival time, which is the time taken for the photon pair to reach the second detector, is recorded for a predetermined time range, and the non-classical time of arrival of the photon pair is based on the difference between the plurality of first arrival times and the plurality of second arrival times. It may include a control unit that measures the correlation and calculates the distance to the target according to the measurement result.

According to the third embodiment, the computer-readable recording medium is a computer-readable non-transitory recording medium in which a program for executing a method for measuring a distance from a target is recorded in a computer, and the distance from the target is The method for measuring comprises recording a first arrival time, which is the time taken for a photon pair emitted by a quantum light source to directly reach a first detector, for a predetermined time range, wherein the photon pair emitted by the quantum light source is recording a second arrival time, which is a time taken for transmission or reflection from a target to reach a second detector, for the predetermined time range, based on a difference between a plurality of first arrival times and a plurality of second arrival times The method may include measuring a non-classical correlation of the photon pair and calculating a distance to the target according to the measurement result.

Specific details of other embodiments are included in the detailed description and drawings.

Since the distance measuring method and apparatus according to the present disclosure use a photon pair having a non-classical strong correlation, a distance to a target may be measured using an SNR signal higher than a classical limit.

In addition, the distance measuring method and apparatus according to the present disclosure update the arrival time by subtracting a time offset from the arrival time required for the photon pair to reach the detector, and detect a non-classical correlation of the photon pair based on the update result. , it is possible to detect the non-classical correlation of photon pairs even when the difference in the time that the photon pairs arrive at each detector is large. Accordingly, it is possible to measure the distance to a distant target.

Effects of the invention are not limited to the effects mentioned above, and other effects not mentioned will be clearly understood by those skilled in the art from the description of the claims.

1 is a flowchart illustrating a method of measuring a photon pair correlation based on a time-correlated single photon count (TCSPC).
FIG. 2 is a diagram for explaining a plurality of first arrival times and a plurality of second arrival times recorded by the disclosed method of FIG. 1 .
3 is a graph for explaining a TCSPC measurement result obtained by performing the method disclosed in FIG. 1 .
4 is a flowchart illustrating a method of measuring a distance according to an exemplary embodiment.
5 is a flowchart illustrating a method of measuring a distance according to another exemplary embodiment.
6 and 7 are diagrams for explaining a method for a controller to update a second arrival time, according to an embodiment.
8 is a diagram for comparing photon pair correlations when a second arrival time is updated using different time offsets, according to an embodiment.
9 is a block diagram illustrating an apparatus for measuring a distance according to an exemplary embodiment.
10 is a block diagram illustrating an apparatus for measuring a distance according to another exemplary embodiment.
11 is a block diagram illustrating a distance measuring device simulated to verify the performance of the distance measuring device according to an embodiment.
12 is a diagram for explaining the performance of a distance measuring apparatus according to an exemplary embodiment.

Terms used in the embodiments are selected as currently widely used general terms as possible while considering functions in the present disclosure, but may vary according to intentions or precedents of those of ordinary skill in the art, emergence of new technologies, and the like. In addition, in a specific case, there is a term arbitrarily selected by the applicant, and in this case, the meaning will be described in detail in the corresponding description. Therefore, the terms used in the present disclosure should be defined based on the meaning of the term and the contents of the present disclosure, rather than the simple name of the term.

In the entire specification, when a part "includes" a certain element, this means that other elements may be further included, rather than excluding other elements, unless otherwise stated.

The expression "at least one of a, b, and c" described throughout the specification means 'a alone', 'b alone', 'c alone', 'a and b', 'a and c', 'b and c ', or 'all of a, b, and c'.

Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings so that those of ordinary skill in the art to which the present disclosure pertains can easily implement them. However, the present disclosure may be implemented in several different forms and is not limited to the embodiments described herein.

Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings.

1 is a flowchart illustrating a method of measuring a photon pair correlation based on a time-correlated single photon count (TCSPC).

Referring to FIG. 1 , in step S110, the photon pair correlation measurement method calculates a first arrival time, which is a time required for a photon pair emitted by a quantum light source to reach a first detector, for a predetermined time range. can be recorded Here, the quantum light source refers to a component that emits photon pairs using spontaneous parametric down conversion or spontaneous four-wave mixing.

In step S120, the second detector may record a second arrival time, which is a time required for the photon pair emitted by the quantum light source to reach the second detector, for a predetermined time range. Here, the first detector and the second detector are photon detectors, and refer to components that detect a pair of photons emitted from a quantum light source.

In step S130, a non-classical correlation of the emitted photon pairs may be measured based on differences between the plurality of first arrival times and the plurality of second arrival times recorded over a predetermined time range. Specifically, a method of measuring the photon pair correlation using the plurality of first arrival times and the plurality of second arrival times will be described with reference to FIGS. 2 and 3 .

FIG. 2 is a diagram for explaining a plurality of first arrival times and a plurality of second arrival times recorded by the disclosed method of FIG. 1 .

When a time list is generated by arranging a plurality of first arrival times and second arrival times recorded by the method of FIG. 1 in chronological order, the generated time list may be the same as that of FIG. 2 . In the case of 210 of FIG. 2 , the arrival time t ₁ means the arrival time detected by the first detector ch1 .

Referring to FIG. 2 , the plurality of first arrival times, that is, the arrival times of the photon pairs detected by the first detector ch1 are {t ₁ , t ₂ , t ₄ , t ₆ , t ₁₀ , t ₁₂ , t _N } can be In addition, the plurality of second arrival times, that is, the arrival times of the photon pairs detected by the second detector ch2 may be {t ₃ , t ₅ , t ₇ , t ₈ , t ₉ , t ₁₁ }.

Meanwhile, the photon pair correlation measuring method may extract a case in which the second arrival time is detected after the first arrival time. For example, in the case of 220 in FIG. 2 , since the second arrival time t ₃ exists after the first arrival time t ₂ , the photon pair correlation measurement method can extract t ₂ and t ₃ values of 220 there is. Cases that can be extracted by the photon pair correlation measurement method other than 220 of FIG. 2 may include 230 to 250.

Meanwhile, a TCSPC measurement result obtained based on the extracted time data will be described with reference to FIG. 3 .

3 is a graph for explaining a TCSPC measurement result obtained by performing the method disclosed in FIG. 1 .

The photon pair correlation measurement method may be performed using time data extracted from the time list of FIG. 2 . Specifically, as shown in FIG. 3 , the difference (t _ch2 -t _ch1 ) between the first arrival time and the second arrival time of the extracted time may be histogramd to measure the correlation between the photon pairs.

In the graph of FIG. 3 , the x-axis means the difference (t _ch2 -t _ch1 ) between the second arrival time and the first arrival time, and the y-axis means a normalized coincidence count. In this case, each y value may be a TCSPC measurement result corresponding to the variable x, and may be proportional to a value obtained by normalizing the frequency of the variable x.

Meanwhile, in some cases, if the photon pair detected by the first detector and the photon pair detected by the second detector have a strong correlation with each other, a peak signal such as the first section 310 may be measured. Specifically, when the photon pair has a strong correlation, a point t _peak at which the y value exceeds the first threshold value may exist. Here, the first threshold may mean a classical limit.

If the TCSPC measurement result shows that the time domain (Δt) exceeding the classical limit value exists, the photon pair can be determined to have a non-classical strong correlation, indicating that the signal has a high signal to noise ratio (SNR) value. Able to know.

Also, referring to FIG. 3 , in a region other than the first section 310 , the y value is less than or equal to the first threshold value. Regions other than the first section 310 are temporal data regarding photon pairs that are not correlated with each other, and it can be confirmed that they have a random correlation. The y value of the region having a random correlation may be defined as a background signal. If the background signals are normalized to “1”, the correlation value that can be classically generated cannot exceed “2”, the classical limit value. Here, the normalized value of the background signals may be defined as the second threshold, and the classical threshold may be defined as the first threshold.

Meanwhile, although the first threshold value of FIG. 3 is illustrated as being twice the second threshold value, the present invention is not limited thereto. In other words, the first threshold value may be another value that is greater than or equal to the second threshold value and equal to or less than twice the second threshold value, and the relationship between the first threshold value and the second threshold value may vary depending on the implementation of the distance measuring device .

On the other hand, when a photon pair has a non-classical strong correlation, it has a high SNR, so a strong signal that is easy to distinguish from external noise can be measured by using the photon pair. When measuring the distance to a far-off target, since the influence of external noise is large, the above-described quantum technique can be utilized for long-distance measurement. Accordingly, the present disclosure proposes a method and apparatus for measuring a distance to a target using the correlation of photon pairs.

4 is a flowchart illustrating a method of measuring a distance according to an exemplary embodiment.

In step S410, the first arrival time, which is the time required for the photon pair emitted by the quantum light source to directly reach the first detector, may be recorded for a predetermined time range.

In step S420, the second arrival time, which is the time required for the photon pair emitted by the quantum light source to be transmitted or reflected by the target to reach the second detector, may be recorded for a predetermined time range.

In operation S430 , a non-classical correlation of the photon pair may be measured based on differences between the plurality of first arrival times and the plurality of second arrival times.

In step S440, a distance to the target may be calculated based on the measurement result.

Specific embodiments of steps S430 and S440 will be described with reference to FIG. 5 .

5 is a flowchart illustrating a method of measuring a non-classical correlation of a photon pair according to an embodiment.

In step S510, the method of the present disclosure may generate a time list by arranging the plurality of first arrival times and the plurality of second arrival times in chronological order. 2 may be an example of a time list generated through step S510.

In step S520, a case in which the second arrival time exists after the first arrival time may be extracted from the time list. 220 to 250 of FIG. 2 may be an example of extraction through step S520.

In step S530, the difference between the second arrival time and the first arrival time in the case extracted in step S520 may be histogrammed. 3 may be an example of a histogram result obtained through step S530.

Comparing the histogram result and the first threshold in step S540 may include. According to an embodiment, the first threshold value may correspond to the above-described classical threshold value. If the histogram result exceeds the first threshold, the method of the present disclosure may determine that the photon pair has a non-classical strong correlation in step S560, and may perform step S440 of FIG. 4 . In this case, step S440 may be a step of calculating the distance to the target based on the difference between the second arrival time and the first arrival time of the photon pair having a non-classical strong correlation. In this case, the distance to the target l _target may be calculated using Equation 1.

[Equation 1]

Here, A is a variable that changes depending on the movement path of the photon pair that has reached the first arrival time and the movement path of the photon pair that has reached the second arrival time, and C represents the speed of light. And the variable t _peak means the x value (t _peak in FIG. 3 ) of the peak shape located within the measurable time range (Δt in FIG. 3 ).

On the other hand, the first threshold value means a classical threshold value, and is a value equal to or greater than the second threshold value (N _noise ) and equal to or less than twice the second threshold value (N _noise ), and may vary depending on the type of quantum light source. The second threshold (N _noise ) is a standardized value of background signals, and may be a criterion for determining whether a signal related to a detected photon pair is a background signal. The second threshold value N _noise may be calculated using Equation (2).

[Equation 2]

Here, N _D1 means the number of single photons per second measured by the first detector, and N _D2 means the number of single photons per second measured by the second detector. Δt denotes a resolution of a time bin applied when measuring TCSPC, and T denotes a predetermined time range in which a plurality of first arrival times and a plurality of second arrival times are measured.

On the other hand, when the distance from the target increases, a delay occurs in the time when the photon pair is transmitted or reflected by the target and arrives at the detector, so that the difference between the first arrival time and the second arrival time may increase. Accordingly, a difference between the first arrival time and the second arrival time may be out of a measurable time range of the distance measuring device. In this case, it may be difficult to measure the correlation between photon pairs.

In general, since the TCSPC measuring apparatus has a fixed number of time bins, a possible measurable time range can be determined by adjusting the time resolution. For example, in the case of PicoHarp300 of PicoQuant, the number of time bins is approximately 65,000 and the time resolution is 4ps to 512ps, so the possible measurement time range can be 260ns to 33us. Therefore, if the PicoHarp300 is used, it may be difficult to measure the distance of a target in which the difference between the second arrival time and the first arrival time of the photon pair exceeds 33 us.

Even if the number of time bins can be increased to extend the measurable time range, it may be difficult to measure long distances because the quantum light source has a limited rate of photon pairs per second.

Two pairs of photons emitted at the same time from a quantum light source have a strong correlation with each other. Therefore, the difference between the first arrival time, which is the time at which a photon pair directly reaches the first detector from the quantum light source, and the second arrival time, which is the time at which the photon pair reaches the second detector after being transmitted or reflected by the target, corresponds to the photon pair generation rate per second larger than the time domain, only random correlations can be measured. In this case, all histogram results may be equal to or less than the first threshold value.

Accordingly, the distance measuring method and apparatus according to another embodiment may perform step S560 when the histogram result is equal to or less than the first threshold value. Specifically, the method of the present disclosure may update the plurality of second arrival times by subtracting a time offset from the plurality of second arrival times in step S560.

After step S560, the method of the present disclosure includes updating the time list by rearranging the plurality of first arrival times and the updated plurality of second arrival times in chronological order, the second updated time list after the first arrival time in the updated time list The method may further include extracting the case where the arrival time exists and rehistograming the difference between the updated second arrival time and the first arrival time in the extracted case.

A method of updating the plurality of second arrival times and time lists will be described with reference to FIGS. 6 and 7 .

6 and 7 are diagrams for explaining a method for a controller to update a second arrival time, according to an embodiment.

FIG. 6A shows a time list in which a plurality of first arrival times and a plurality of second arrival times are arranged in chronological order before updating the plurality of second arrival times. If the histogram result is equal to or less than the first threshold in step S540 of FIG. 5 , the method of the present disclosure may classify time data on the time list as shown in FIG. 6B .

Referring to (b) of FIG. 6 , time data may be classified according to a detector that has detected the corresponding photon pair, ch1 means the arrival time of the photon pair detected by the first detector, and ch2 is the second detector means the arrival time of the photon pair detected by .

Thereafter, as shown in FIG. 7A , the plurality of second arrival times may be updated. Specifically, each of the plurality of updated second arrival times 710 is equal to the original value minus the time offset t _offset '. Here, the time offset (t _offset ') may be defined as in Equation (3).

[Equation 3]

Here, t _offset means a time offset interval, and n means the number of times the plurality of second arrival times are updated. Meanwhile, the time offset interval t _offset may be shorter than the reciprocal of the number of photon pairs per second generated by the quantum light source.

When a plurality of second arrival times are updated as shown in FIG. 7A , the plurality of first arrival times and the plurality of updated second arrival times may be rearranged in chronological order. 7 (b) is an example of a rearranged time list.

Meanwhile, when the plurality of second arrival times are updated, the distance to the target may be calculated using Equation (4).

[Equation 4]

Here, l _target , A, C and t _peak correspond to l _target , A, C and t _peak of Equation 1, respectively, and t _offset ' means a time offset derived using Equation 3 .

8 is a diagram for comparing photon pair correlations when a second arrival time is updated using different time offsets, according to an embodiment.

Meanwhile, when the second arrival time t _ch2 is updated m times, the updated second arrival time t _ch2 ′ may be defined as in Equation 5.

[Equation 5]

Here, m×t _offset means a total time offset (t _offset' ) when updated m times.

If m is a natural number value less than n, and n is the number of times the plurality of second arrival times are updated until the non-classical correlation of the photon pair is measured, the plurality of second arrival times are respectively m and The histogram result when updated n times may be as shown in FIG. 8 .

Referring to FIG. 8A , all histogram results corresponding to differences between the plurality of updated second arrival times and the plurality of first arrival times are equal to or less than the first threshold value. In this case, the method and apparatus of the present disclosure determine that the non-classical correlation of the photon pair cannot be measured with the corresponding time offset (m×t _offset ), and increase the time offset (t _offset ') to reach a plurality of second You can update the time again. For example, the method and apparatus of the present disclosure may increase the time offset t _offset ′ while increasing m by one.

Meanwhile, in the histogram result of FIG. 8B , a peak signal exceeding the first threshold value exists. The method and apparatus of the present disclosure may update the plurality of second arrival times while increasing the time offset t _offset ' until the histogram result has a peak signal as shown in FIG. 8B .

9 is a block diagram illustrating an apparatus for measuring a distance according to an exemplary embodiment.

The distance measuring apparatus 900 according to an embodiment may include a quantum light source 910 , a first detector 920 , a second detector 930 , and a controller 940 .

The quantum light source 910 may emit a pair of quantum photons. The quantum light source 910 may generate and emit photon pairs based on spontaneous parametric down conversion or spontaneous four-wave mixing in a nonlinear medium. The method used to create the pair is not limited thereto.

The first detector 920 may detect the photon pair directly from the quantum light source 910 for a predetermined time range.

The second detector 930 may detect a photon pair transmitted or reflected by the target for a predetermined time range after being emitted by the quantum light source 910 .

The control unit 940 records the first arrival time, which is the time required for the photon pair to reach the first detector 920 , for a predetermined time range, and the second, which is the time required for the photon pair to reach the second detector 930 . The arrival time is recorded for a predetermined time range, the non-classical correlation of the photon pair is measured based on the difference between the plurality of first arrival times and the plurality of second arrival times, and the distance to the target is calculated according to the measurement result. can

Meanwhile, when measuring the non-classical correlation of the photon pair, the control unit 940 generates a time list by arranging the plurality of first arrival times and the plurality of second arrival times in chronological order, and the first arrival time in the time list A case in which the second arrival time exists after a time may be extracted, the difference between the second arrival time and the first arrival time may be histogrammed in the extracted case, and the histogram result may be compared with the first threshold value.

If the histogram result exceeds the first threshold, the control unit 940 determines that the photon pair has a non-classical strong correlation, and the second arrival time and the first arrival time of the photon pair having the non-classical strong correlation The distance to the target may be calculated based on the time difference.

Here, the first threshold value is equal to or greater than the second threshold value and equal to or less than twice the second threshold value, and may be a value that varies depending on the light source. In addition, the second threshold is at least one of the number of single photons per second measured by the first detector 920, the number of single photons per second measured by the second detector 930, the resolution of the time bin, and a predetermined time range. can be determined based on

If the histogram result is equal to or less than the first threshold value, the controller 940 updates the plurality of second arrival times by subtracting time offsets from the plurality of second arrival times, and updates the plurality of first arrival times and the updated plurality of times of arrival. Update the time list by rearranging the second arrival time in chronological order, extract the case where the updated second arrival time exists after the first arrival time from the updated time list, and the updated second arrival time from the extracted case and the difference of the first arrival time can be rehistogrammed. Also, until the rehistogram result exceeds the first threshold value, the controller 940 may increase the time offset and update the plurality of second arrival times with the increased time offset.

Here, the time offset is a multiple of the time offset interval, and the time offset interval may be a value less than the reciprocal of the number of photon pairs per second generated by the quantum light source 910 .

10 is a block diagram illustrating an apparatus for measuring a distance according to another exemplary embodiment.

By utilizing the non-classical nature of quantum light sources and data processing methods for measuring long-range targets, it can be extended to quantum technologies such as quantum radar. The distance measuring apparatus 1000 according to an embodiment of the present disclosure includes a transmitter 1050 and a receiver 1060 in addition to the quantum light source 1010 , the first detector 1020 , the second detector 1030 , and the controller 1040 . may include more.

Meanwhile, since the first detector 1020 and the controller 1040 correspond to the first detector 920 and the controller 940 of FIG. 9 , respectively, a detailed description thereof will be omitted. In addition, in the case of the quantum light source 1010 and the second detector 1030 , descriptions overlapping those of the quantum light source 910 and the second detector 930 of FIG. 9 will be omitted.

The transmitter 1050 may be connected to the quantum light source 1010 to emit a photon pair received from the quantum light source 1010 to the target 1070 . In this case, the quantum light source 1010 may transmit the photon pair to the transmitter 1050 instead of directly emitting the photon pair to the target 1070 .

The receiver 1060 may be connected to the second detector 1030 to receive a photon pair transmitted or reflected by the target 1070 and arrives therein. In this case, the second detector 1030 may receive the photon pair from the receiver 1060 instead of directly receiving the photon pair from the target 1070 .

In the case of the distance measuring apparatus 1000 including the transmitter 1050 and the receiver 1060 as shown in FIG. 10 and the transmitter 1050 and the receiver 1060 are positioned side by side at the same location, A in Equations 1 and 4 may be 0.5, but the value of A is not limited thereto.

The distance measuring apparatuses 900 and 1000 according to the present disclosure have an effect of increasing a photon pair generation probability and extending a measurable distance range.

11 is a block diagram illustrating a distance measuring device simulated to verify the performance of the distance measuring device according to an embodiment.

In order to verify the performance of the distance measuring device of the present disclosure, as shown in FIG. 11 , the simulated distance measuring device 1100 may be utilized. On the other hand, the quantum light source 1110, the first detector 1120, and the controller 1140 of the simulated distance measuring device 1100 are the quantum light source 910, the first detector 920 and the controller 940 of FIG. Since each corresponds to each other, a detailed description will be omitted.

In a simulated environment, it is difficult to measure the distance to an actual target. Accordingly, the simulated distance measuring apparatus 1100 may include an electrical delay unit 1150 instead of the second detector 1130 detecting a photon pair transmitted or reflected by the target. The electrical delay unit 1150 means a component capable of delaying transmission of the photon pair from the second detector 1130 to the control unit 1140, and a cable may be used, but the electrical delay unit 1150 is limited thereto. It is not possible, and any component capable of delaying the photon pair from reaching the control unit 1140 is possible.

12 is a diagram for explaining the performance of a distance measuring apparatus according to an exemplary embodiment.

The experimental result of FIG. 12 assumes that the difference between the second arrival time and the first arrival time that can be measured by the simulated distance measuring apparatus 1100 is 0 to 20 ns. On the other hand, "no delay" shown in FIGS. 12 (a) and (b) means a case in which the photon pair detected by the second detection 1130 without the electrical delay unit 1150 is transmitted to the control unit 1140, and , “6 ns delay” and “12 ns delay” indicate results when delays of 6 ns and 12 ns are generated using the electrical delay unit 1150 , respectively. And “35 ns delay” indicates a result of generating a delay of 35 ns through the electrical delay unit 1150 .

If the simulated distance measuring device 1100 does not perform the process of updating the second arrival time, the same result as in (a) of FIG. 12 can be obtained, and if the process of updating the second arrival time is performed, the result shown in FIG. The same result as (b) can be obtained.

Specifically, when the photon pair detected by the second detector 1130 is received by the controller 1140 without delay, the difference between the second arrival time and the first arrival time may be close to zero. Therefore, as shown in (a) and (b) of FIG. 12 , a peak appears at a position close to zero on the x-axis.

On the other hand, when "6ns delay" and "18ns delay" are simulated, the difference between the second arrival time and the first arrival time may be close to 6ns and 18ns, respectively. Therefore, as shown in (a) and (b) of FIG. 12 , peaks appear at positions close to 6ns and 18ns, respectively, on the x-axis.

When the “35 ns delay” is simulated, since the maximum value of the difference between the second arrival time and the first arrival time that the simulated distance measuring device 1100 can measure exceeds 20 ns, the second time offset is used to If the arrival time is not updated, a peak cannot be found as shown in FIG. 12(a).

However, according to an embodiment of the present disclosure, when the second arrival time is updated, the difference between the updated second arrival time and the first arrival time is within 20 ns, and a peak can be found as shown in (b) of FIG. 12 . . According to an embodiment, the simulated distance measuring apparatus 1100 may measure the peak as shown in FIG. 12( b ) when the time offset interval t _offset is 10 ns and n is 2 .

The control unit according to the above-described embodiments includes a processor, a memory for storing and executing program data, a permanent storage such as a disk drive, a communication port for communicating with an external device, a touch panel, a key, a button, etc. user interface devices, and the like. Methods implemented as software modules or algorithms may be stored on a computer-readable recording medium as computer-readable codes or program instructions executable on the processor. Here, the computer-readable recording medium includes a magnetic storage medium (eg, read-only memory (ROM), random-access memory (RAM), floppy disk, hard disk, etc.) and an optically readable medium (eg, CD-ROM). ), and DVD (Digital Versatile Disc)). The computer-readable recording medium may be distributed among network-connected computer systems, so that the computer-readable code may be stored and executed in a distributed manner. The medium may be readable by a computer, stored in a memory, and executed on a processor.

This embodiment may be represented by functional block configurations and various processing steps. These functional blocks may be implemented in any number of hardware and/or software configurations that perform specific functions. For example, an embodiment may be an integrated circuit configuration, such as memory, processing, logic, look-up table, etc., capable of executing various functions by means of the control of one or more microprocessors or other control devices. can be hired Similar to how components may be implemented as software programming or software components, this embodiment includes various algorithms implemented in a combination of data structures, processes, routines, or other programming constructs, including C, C++, Java ( It can be implemented in a programming or scripting language such as Java), assembler, or the like. Functional aspects may be implemented in an algorithm running on one or more processors. In addition, the present embodiment may employ the prior art for electronic environment setting, signal processing, and/or data processing. Terms such as “mechanism”, “element”, “means” and “configuration” may be used broadly and are not limited to mechanical and physical configurations. The term may include the meaning of a series of routines of software in association with a processor or the like.

The above-described embodiments are merely examples, and other embodiments may be implemented within the scope of the claims to be described later.

Claims (10)

A method for measuring a distance to a target, comprising:
recording a first arrival time, which is a time taken for a photon pair emitted by a quantum light source to directly reach a first detector, for a predetermined time span;
recording a second arrival time, which is a time required for a photon pair emitted by the quantum light source to be transmitted or reflected by a target to reach a second detector, during the predetermined time range;
determining a non-classical correlation of the photon pair based on a difference between a plurality of first times of arrival and a plurality of second times of arrival; and
Comprising the step of calculating a distance to the target according to the measurement result, the distance measuring method. According to claim 1,
Measuring the non-classical correlation of the photon pair comprises:
generating a time list by arranging the plurality of first arrival times and the plurality of second arrival times in chronological order;
extracting a case in which a second arrival time exists after the first arrival time from the time list;
histogram the difference between the second arrival time and the first arrival time in the extracted case; and
Comprising the step of comparing the histogram result with a first threshold value, the distance measuring method. 3. The method of claim 2,
If the histogram result exceeds the first threshold, further comprising the step of determining that the photon pair has a non-classical strong correlation,
Calculating the distance to the target according to the measurement result comprises:
calculating a distance to the target based on a difference between the second arrival time and the first arrival time of the non-classically strongly correlated photon pair. 3. The method of claim 2,
The first threshold is
A value that is greater than or equal to the second threshold and less than or equal to twice the second threshold, which is a value that varies depending on the light source,
The second threshold is
a distance determined based on at least one of a number of single photons per second measured by the first detector, a number of single photons per second measured by the second detector, a resolution in a time bin, and the predetermined time span measurement method. 3. The method of claim 2,
When the histogram result is less than or equal to the first threshold,
updating a plurality of second arrival times by subtracting a time offset from the plurality of second arrival times;
updating the time list by rearranging the plurality of first arrival times and the plurality of updated second arrival times in chronological order;
extracting a case in which an updated second arrival time exists after the first arrival time from the updated time list; and
The method of claim 1, further comprising rehistograms the difference between the updated second arrival time and the first arrival time in the extracted case. 6. The method of claim 5,
until the rehistogram result exceeds the first threshold,
incrementing the time offset and updating the plurality of second arrival times with the increased time offset. 6. The method of claim 5,
the time offset is a multiple of the time offset interval,
wherein the time offset interval is a value less than the reciprocal of the number of photon pairs per second generated by the quantum light source. In the device for measuring the distance to the target,
a quantum light source that emits a pair of quantum photons;
a first detector for detecting the photon pair directly from the quantum light source for a predetermined time range;
a second detector for detecting the photon pair transmitted or reflected by the target for the predetermined time range; and
The first arrival time, which is the time taken for the photon pair to reach the first detector, is recorded for a predetermined time range, and the second arrival time, which is the time taken for the photon pair to reach the second detector, is recorded for the predetermined time range. and a control unit configured to record a non-classical correlation of the photon pair based on differences between a plurality of first arrival times and a plurality of second arrival times, and to calculate a distance to the target according to the measurement result. which is a distance measuring device. 9. The method of claim 8,
a transmitter coupled to the quantum light source to emit a photon pair received from the quantum light source to the target; and
Further comprising a receiver connected to the second detector to receive a photon pair transmitted or reflected to reach the target, the distance measuring device. As a computer-readable non-transitory recording medium in which a program for executing a method for measuring a distance with a target is recorded on a computer,
A method for measuring the distance to the target,
recording a first arrival time, which is a time taken for a photon pair emitted by the quantum light source to directly reach a first detector, for a predetermined time range;
recording a second arrival time, which is a time required for a photon pair emitted by the quantum light source to be transmitted or reflected by a target and reach a second detector, during the predetermined time range;
determining a non-classical correlation of the photon pair based on a difference between a plurality of first times of arrival and a plurality of second times of arrival; and
and calculating a distance to the target according to the measurement result.

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