JP7636811B2 - Diffuse optical tomography device, backscattered light measurement device, analysis method, analysis device, and program - Google Patents

Description

The present invention relates to an analysis method, an optical emission analysis device, a diffuse optical tomography device, an imaging device, a reflectance measuring device, an analysis device, and a program.

Conventionally, there are known methods for analyzing the characteristics of objects such as molecules and crystals using light. For example, there is a known method for analyzing the characteristics of an object by irradiating one of two pulsed lights onto the object and using the other as a reference.

In addition, although the fields and applications are different, research on the generation and use of quantum entangled photons is also progressing (for example, Patent Documents 1 and 2).

Japanese Patent Publication "JP 2008-216369 (Published on September 18, 2008)" Japanese Patent Publication "Patent Publication No. 2012-522983 (Published on September 27, 2012)"

As mentioned above, the method of analyzing the characteristics of an object using pulsed light has the problem that the analytical equipment tends to be large in size, and there is also the problem that irradiating the object with pulsed light may damage the object. In addition, it is possible to irradiate the object with continuous light in order to reduce damage to the object, but this method has the problem that it is difficult to identify the temporal characteristics of the object.

One aspect of the present invention has been made to solve the above-mentioned problems, and aims to realize a technology that can analyze the characteristics of an object, including temporal characteristics, while reducing damage to the object.

In order to solve the above problems, an analysis method according to one aspect of the present invention includes a generation step of generating a plurality of photons that are in a quantum entangled state with each other, a first detection step of detecting a first photon of the plurality of photons, a second detection step of detecting a third photon obtained by irradiating or making incident a second photon of the plurality of photons on an object, and an analysis step of analyzing characteristics of the object by referring to the difference between the detection timing in the first detection step and the detection timing in the second detection step.

An analysis device according to one aspect of the present invention includes a generation unit that generates a plurality of photons that are in a quantum entangled state with each other, a first detection unit that detects a first photon of the plurality of photons, a second detection unit that detects a third photon obtained by irradiating or making incident a second photon of the plurality of photons on an object, and an analysis unit that analyzes characteristics of the object by referring to the difference between the detection timing by the first detection unit and the detection timing by the second detection unit.

According to one aspect of the present invention, a technology can be realized that can analyze the characteristics of an object, including temporal characteristics, while reducing damage to the object.

1 is a schematic diagram showing a configuration of an analysis device according to a first embodiment of the present invention. 1 is a block diagram showing an analysis unit included in an analysis device according to a first embodiment of the present invention, together with a first detection unit and a second detection unit. FIG. 2 is a diagram showing photon pairs generated in an analysis device according to the first embodiment of the present invention, the photon pairs being generated by spontaneous parametric down-conversion. FIG. 2 is a diagram showing photon pairs generated in an analysis device according to the first embodiment of the present invention, the photon pairs being generated by spontaneous parametric down-conversion. 4 is a flowchart showing a process flow of the analysis device according to the first embodiment of the present invention. FIG. 11 is a block diagram showing the configuration of an optical emission analyzer according to a second embodiment of the present invention. FIG. 11 is a block diagram showing the configuration of a calculation unit of an optical emission analyzer according to a second embodiment of the present invention. 10 is a graph showing an example of a detection result by a detection unit of the issuance analysis device according to the second embodiment of the present invention. 6 is a graph showing an example of a detection result obtained by the emission analyzer according to the second embodiment of the present invention. FIG. 11 is a block diagram showing a configuration of a diffuse optical tomography device according to a third embodiment of the present invention. FIG. 11 is a block diagram showing the configuration of a calculation unit of a diffuse optical tomography device according to a third embodiment of the present invention. FIG. 11 is a block diagram showing a configuration of an imaging device according to a fourth embodiment of the present invention. FIG. 11 is a block diagram showing a configuration of a calculation unit of an imaging device according to a fourth embodiment of the present invention. FIG. 13 is a block diagram showing a configuration of a reflectance measuring device according to a fifth embodiment of the present invention. FIG. 13 is a block diagram showing the configuration of a calculation unit of a reflectance measuring device according to a fifth embodiment of the present invention.

[Embodiment 1]
＜Overview＞
An analysis device according to an embodiment of the present invention will be described below. The analysis device according to this embodiment is a device that analyzes characteristics of an object by using certain photons among a plurality of photons as a reference and using other photons for irradiation or incidence on the object (sometimes called measurement). The analysis device 1 can also be regarded as an example of a device generally called a Time-Correlated Single Photon Counting (TCSPC) device.

Here, the multiple photons according to this embodiment are multiple single photons that are in a quantum entangled state with each other. Here, the multiple single photons that are in a quantum entangled state with each other are synchronized in time with each other. More specifically, the multiple photons according to this embodiment are two single photons that are in a quantum entangled state with each other.

Conventionally, there is known technology that uses pulse waves synchronized in time to analyze the characteristics of an object, but the use of pulse waves has the problem of causing significant damage to the object. In addition, the use of continuous light could be considered to reduce damage to the object, but when continuous light is used in this way, there is the problem that it is difficult to measure the temporal characteristics of the object.

In addition, conventional methods require a device to generate pulse waves, which makes the device configuration complicated. In addition, when there are multiple components in the temporal characteristics of an object (for example, when there are multiple fluorescence lifetime components), measurements must be performed at various modulation frequencies, which makes the measurement and analysis for determining the fluorescence lifetime complicated.

In the analysis device according to this embodiment, a certain photon among multiple photons is used as a reference, and other photons are used for irradiating or being incident on the object, thereby analyzing the characteristics of the object. In the analysis device according to this embodiment, as described below, multiple photons that are in a quantum entangled state with each other are generated at random timing. Therefore, unlike the case where a pulse wave is used, a large number of photons are not irradiated onto the object at the same time, and as a result, the characteristics of the object can be analyzed while minimizing damage to the object.

In addition, according to one example of the configuration of the analysis device according to this embodiment, compared to the case where a pulse wave is used, a device for generating a pulse wave is not required, so there is an advantage that the configuration of the entire device can be simplified. On the other hand, by using the property that the two photons in a pair are synchronized in time, it is possible to directly measure the temporal characteristics of the object as in the case where a pulse wave is used, and even when there are multiple components in the temporal characteristics of the object (for example, when there are multiple fluorescence lifetime components), it is possible to measure with only one continuous light source. Therefore, there is also the advantage that there is no need to perform intensity modulation of the light source each time.

<Configuration example>
Hereinafter, a configuration example of the analysis device according to the present embodiment will be described with reference to the drawings. FIG. 1 is a block diagram showing a configuration example of the analysis device 1 according to the present embodiment. As shown in FIG. 1, the analysis device 1 is configured to include, as an example, a light source 10, a first mirror 21, a first lens 22, a first bandpass filter 23-1, a second bandpass filter 23-2, a second mirror 24, a third mirror 25, a second lens 26, a third lens 27, a longpass filter 28, a fourth lens 29, a fifth lens 30, a first detection unit 50, a second detection unit 60, and an analysis unit 70.

The light source 10 generates a plurality of photons that are in a quantum entangled state with each other in a time-synchronized manner. The light source 10 includes, as an example, a continuous light source 11, a light source lens 12, and a crystalline material 13. The continuous light source 11 is, for example, a laser light source that generates a laser, which is continuous light having a specific wavelength, but this is not a limitation of this embodiment. The continuous light generated by the continuous light source 11 is sometimes called pump light. The light source 10 is also sometimes called a generation unit.

The crystalline material 13 generates a plurality of photons that are in a quantum entangled state with each other in response to the incidence of continuous light from the continuous light source 11. As an example, the crystalline material 13 generates two photons (photon pairs) that are in a quantum entangled state with each other. The crystalline material 13 also generates photon pairs at random timing. An example of the crystalline material 13 is a nonlinear optical crystal, but this is not intended to limit the present embodiment. Specific examples of the crystalline material 13 will be described later.

The first mirror 21 directs a first photon, among the multiple photons supplied from the light source 10, along a first path, and directs a second photon different from the first photon along a second path. The specific configuration of the first mirror 21 does not limit the present embodiment, but it is preferable that the first mirror 21 is configured to appropriately reflect the first photon and the second photon.

The first lens 22 refracts the first and second photons and, as an example, orients the first and second photons so that they propagate parallel to each other, as shown in FIG. 1.

The first bandpass filter 23-1 transmits photons having a first angular frequency among the first photons and blocks photons other than the first angular frequency. The second bandpass filter 23-2 transmits photons having a second angular frequency among the second photons and blocks photons other than the second angular frequency.

The first and second angular frequencies may be appropriately selected according to the characteristics of the light source 10, the object 40, the first detection unit 50, and the second detection unit 60, etc., under the condition that the sum of the two is equal to the angular frequency of the continuous light source 11.

The first photon travels along the first path, passes through the fourth lens 29, is detected by the first detection unit 50, and a detection signal is supplied to the analysis unit 70.

On the other hand, the second photon is reflected by the second mirror 24 and the third mirror 25, and then passes through the second lens 26 arranged on the second path. The second photon that has passed through the second lens 26 is then irradiated or incident on the object 40.

Here, the object 40 emits a third photon in response to being irradiated or incident with the second photon. The third photon may be the same photon as the second photon, or may be a photon different from the second photon, and this does not limit the present embodiment. The third photon may also be a plurality of single photons.

The emitted third photons pass through the third lens 27 and the long-pass filter 28, and then pass through the fifth lens 30. The long-pass filter 28 passes photons of the third photons that have an angular frequency equal to or lower than a specific third angular frequency, and blocks other photons. The third photons that pass through the fifth lens 30 are detected by the second detection unit 60, and a detection signal is supplied to the analysis unit 70.

As an example, a single-photon detector can be used as the first detection unit 50 and the second detection unit 60. More specifically, a one-photon avalanche photodiode can be used, but this is not a limitation of this embodiment.

In the analysis device 1 configured as described above, the first photon reaches and is detected by the first detection unit 50 without being irradiated or incident on the object 40. On the other hand, the second photon is irradiated or incident on the object 40, and the third photon obtained in response reaches and is detected by the second detection unit 60.

In general, after the second photon is irradiated or incident on the object 40, a non-zero response time is required before the third photon is obtained. Therefore, as shown in FIG. 1, the timing at which the third photon is detected by the second detection unit 60 is delayed from the timing at which the first photon is detected by the first detection unit 50. The analysis unit 70 analyzes the characteristics of the object 40 by identifying and referring to this delay time. In other words, the analysis device 1 uses the detection timing of the first photon as a reference for analyzing the characteristics of the object 40.

(Analysis Department)
Next, a configuration example of the analysis unit 70 will be described with reference to Fig. 2. As described above, the analysis unit 70 is configured to analyze characteristics related to the object 40 by referring to the difference between the detection timing of the first photon by the first detection unit 50 and the detection timing of the third photon by the second detection unit 60.

As shown in FIG. 2, the analysis unit 70 is configured to include a first acquisition unit 71, a second acquisition unit 72, a first conversion unit 73, a second conversion unit 74, and a calculation unit 75.

The first acquisition unit 71 acquires the detection signal by the first detection unit 50, performs signal processing, and supplies the signal to the first conversion unit 73. As an example, the first conversion unit 73 amplifies the detection signal by the first detection unit 50 and supplies the amplified signal to the first conversion unit 73.

The second acquisition unit 72 has a configuration similar to that of the first conversion unit 73, but differs in that the detection signal acquired is the detection signal generated by the first detection unit 50.

The first conversion unit 73 converts the signal supplied from the first acquisition unit 71 and supplies the converted signal to the calculation unit 75. As an example, the first conversion unit 73 converts the analog signal supplied from the first acquisition unit 71 into a digital signal and supplies the converted digital signal to the calculation unit 75.

The second conversion unit 74 has a configuration similar to that of the first conversion unit 73, but differs in that the signal it acquires is a signal supplied from the second acquisition unit 72.

The calculation unit 75 analyzes the characteristics of the object 40 by referring to the difference between the detection timing of the first photon by the first detection unit 50 and the detection timing of the third photon by the second detection unit 60. As shown in FIG. 1, the calculation unit 75 includes a time difference determination unit 751 that determines the time difference between the detection timing of the first photon by the first detection unit 50 and the detection timing of the third photon by the second detection unit 60.

According to the analysis device 1 configured as described above, of the multiple photons in a quantum entangled state with each other, the first photon is detected without passing through the object 40, and the third photon obtained by irradiating or being incident on the object 40 with the second photon is detected with a delay time according to the object, as an example. Then, the analysis device 1 analyzes the characteristics of the object 40 by referring to the difference between the detection timing of the first photon and the detection timing of the third photon, so that the characteristics of the object can be suitably analyzed while minimizing damage to the object.

<Generating entangled photons>
The "multiple photons in a quantum entangled state with each other" in this embodiment will be described in more detail below. Note that the following description will be illustratively given of multiple photons generated by spontaneous parametric down-conversion in the crystalline material 13, which is a nonlinear optical crystal, but this is for the sake of explanation only. The "multiple photons in a quantum entangled state with each other" in this embodiment is not limited to those generated using the crystalline material 13, which is a nonlinear optical crystal, and may be generated by various generation methods as described below.

Figure 3 is a schematic diagram for explaining an example of photon pair generation by crystalline material 13. As described above, pump light is supplied to crystalline material 13 from continuous light source 11, and a portion of the pump light is converted into two time-synchronized single photons (one may be called signal light and the other may be called idler light) by spontaneous parametric down-conversion (SPDC) in crystalline material 13. Figure 3 illustrates a type II SPDC in which the polarizations of the two photons are different from each other.

Here, if the (angular frequency, wave vector) of the pump light is denoted as (ω _P , k _p ), and the (angular frequency, wave vector) of the two generated photons are denoted as (ω ₁ , k ₁ ) and (ω ₂ , k ₂ ), respectively, then
ω _P = ω ₁ + ω ₂ ... (Formula 1)
k _p = k ₁ + k ₂ ... (Formula 2)
is satisfied. Equation 1 represents the law of conservation of energy, and Equation 2 represents the law of conservation of momentum. In this specification, the angular frequency may be simply referred to as the frequency.

As shown in Figure 3, the two photons generated by SPDC propagate along paths on two cones that are symmetrically positioned with respect to the pump light, and paths that are symmetrical with respect to the pump light.

3 shows a photon pair A as an example of a plurality of photons in a quantum entangled state with each other, and a photon pair B as another example. In the case of the type II SPDC shown in FIG. 3, the state of the photon pair A including the photon A1 and the photon A2 that take paths on different cones is, for example, as follows:
|Ψ> = |V> ₁ |H> ₂ ... (Formula 3)
Or,
|Ψ> = |H> ₁ |V> ₂ ... (Formula 4)
Here, V and H represent vertical and horizontal polarization, respectively, and the subscripts 1 and 2 of the ket |> are indexes for distinguishing between the two photons. As shown in Equations 3 and 4, photons A1 and A2 included in photon pair A are not entangled with each other in terms of polarization state.

On the other hand, in the case of Type II SPDC, the state of photon pair B including photon B1 and photon B2 along the intersection line of the two cones is, for example,
|Ψ> = (1/√2)|V> ₁ |H> ₂ + (1/√2)|H> ₁ |V> ₂ ... (Formula 5)
In this way, the photon B1 and the photon B2 included in the photon pair B are entangled with each other in terms of the polarization state.

As the multiple photons in a quantum entangled state used in this embodiment, the photon A1 and photon A2 included in the above-mentioned photon pair A may be used, or the photon B1 and photon B2 included in the photon pair B may be used. In other words, the "multiple photons in a quantum entangled state with each other" in this embodiment may or may not be in a polarization entangled relationship with each other as long as they are synchronized in time.
Fig. 4 is a schematic diagram for explaining another example of generation of photon pairs by the crystalline material 13. Fig. 4 illustrates a type I SPDC in which the polarizations of the two photons are equal to each other. In this example, too, when the (angular frequency, wave vector) of the pump light is expressed as ( _ωp , _kp ) and the (angular frequency, wave vector) of the two generated photons are expressed as ( _ω1 , _k1 ) and ( _ω2 , _k2 ), respectively, the above-mentioned formulas 1 and 2 are satisfied, as in the case of Fig. 3.
As shown in FIG. 4, the two photons generated by SPDC propagate along paths on a cone whose axis is the pump light and that are symmetrical with respect to the pump light.
4 shows a photon pair C as an example of a plurality of photons in a quantum entangled state. In the case of the type I SPDC shown in FIG. 4, the state of the photon pair C including the photon C1 and the photon C2 on the path on the cone is, for example, as follows:
|Ψ> = |V> ₁ |V> ₂ ... (Formula 3')
Or,
|Ψ> = |H> ₁ |H> ₂ ... (Formula 4')
Here, as shown in Equations 3' and 4', the photon C1 and the photon C2 included in the photon pair C are not entangled with each other in terms of the polarization state.
As the multiple photons in a quantum entangled state used in this embodiment, the photon C1 and the photon C2 included in the photon pair C described above may be used.

In the following, we will explain in more detail the situation in which a two-photon state |Ψ> containing two photons with frequencies ω ₁ and ω ₂ is generated by SPDC using light with frequency ω _p as pump light, thereby providing a more detailed explanation of the term "multiple photons in a quantum entangled state with each other" in this specification.

と表記し、光子の存在しない真空状態を|0>と表記すると、２光子状態|Ψ>は以下のように表される。

ここで、式８における

はディラックのデルタ関数であり、このデルタ関数の存在により、式９に示すように、式１に示したエネルギー保存則を満たす場合のみを考慮すればよいことが分かる。 First, the creation operators that create two photons are

and the vacuum state where no photons exist is denoted as |0>, then the two-photon state |Ψ> can be expressed as follows:

Here, in Equation 8

is a Dirac delta function, and the presence of this delta function means that, as shown in Equation 9, it is sufficient to consider only the case where the law of conservation of energy shown in Equation 1 is satisfied.

As can be seen from Equation 9, the two-photon state |Ψ> cannot be expressed as a product of a one-photon state having frequency ω ₁ and a one-photon state having frequency ω _2. In this specification, such states are said to be “entangled with each other in frequency (angular frequency).”

を式９に代入し、デルタ関数の関係式

を用いてω₁の積分を先に計算することによって、

を得る。式１４から分かるように、２つの光子は時間的に同期されている。 The above explanation is in the frequency domain, but in the following, we rewrite it in the time domain to investigate the temporal correlation between two photons. First, the Fourier transform

Substituting into Equation 9, the delta function relation

By first calculating the integral of ω ₁ using

As can be seen from Equation 14, the two photons are synchronized in time.

更に、時間積分を和で表現したとすると、

・・・（式１６）
を得る。式１５及び式１６から分かるように、２光子状態|Ψ>は、２つの光子の状態の積として表記することはできない。このような状態を、本明細書では、「時間に関して互いにもつれている」と表現する。 To be more specific, suppose one photon exists on path a and the other photon exists on path b. If we express the state in which one photon exists on path a at time t as |1> _a (t), then equation 14 can be rewritten as follows:

Furthermore, if we express the time integral as a sum,

... (Equation 16)
As can be seen from Equations 15 and 16, the two-photon state |Ψ> cannot be expressed as a product of the states of two photons. In this specification, such a state is expressed as being "entangled with each other in time."

As described above, the "multiple photons in a quantum entangled state" used in this embodiment refers, as an example, to multiple photons that are entangled with each other in terms of frequency (angular frequency) or time.

<Crystalline substances>
The crystalline material 13 according to this embodiment will be described in more detail below. As described above, the light source 10 is not limited to a configuration including the crystalline material 13, but by configuring the light source 10 to include the crystalline material 13, there is an advantage in that the configuration of the analysis device 1 can be made simpler.

As an example, the crystalline material 13 is a nonlinear optical crystal in which the crystal responds nonlinearly to incident light and birefringence exists. However, this is not intended to limit the present embodiment.

Specific examples of the crystalline material 13 include BBO (β-BaB ₂ O ₄ ), KDP (KH ₂ PO ₄ ), ppKTP (periodically polled KTiOPO ₄ ), and ppLN (periodically polled LiNbO ₃ ). However, these specific examples do not limit the present embodiment.

As described above, there are two types of SPDC using nonlinear optical crystals: Type I, which generates two photons with the same polarization direction, and Type II, which generates two photons with different polarization directions. In this embodiment, Type I and Type II SPDC may be used. For example, photon pairs may be generated by Type II SPDC using BBO, or photon pairs may be generated by Type I SPDC using BBO.

Although the frequency of photon pair generation by the crystalline material 13 is not limited to this embodiment, by adjusting the intensity of the pump light, it can be set to, for example, several times to several million times per second.

Another example of the crystalline material 13 may be a material obtained by inverting the spontaneous polarization in a lithium niobate ( _LiNbO3 ) crystal with two different periods. In a material configured in this way, by controlling two different phase matching conditions, it is possible to directly generate a quantum entangled state in which the polarization and frequency of pairs of photons that can be generated in each region are correlated with each other.

The photon pairs generated in this manner can also be used as the "multiple photons in a quantum entangled state with each other" in this embodiment.

<Other light source configuration examples>
The configuration of the light source 10 is not limited to the above-mentioned example. For example, the light source 10 may be configured to include any one of a Mach-Zehnder interferometer, a Michelson interferometer, and a Sagnac interferometer instead of the crystalline material 13, and to generate a plurality of photons in a quantum entangled state with each other by any one of these interferometers.

<Regarding the second and third photons>
As described above, the third photon according to the present embodiment is obtained by irradiating or making the second photon incident on the object 40. Depending on the object 40 and the manner in which the analysis device 1 is applied, the second photon and the third photon may be more appropriately interpreted as being the same photon or may be more appropriately interpreted as being different photons.

For example, if a luminescent (fluorescent, phosphorescent) substance is used as an example of the object 40, the object 40 transitions to an excited state when the second photon is absorbed by the object 40. Then, with the transition from the excited state to a state of lower energy, a third photon is emitted. In such an example, it is appropriate to interpret the third photon as a different photon from the second photon.

As another example, if we consider the case where the second photon is reflected by a mirror or propagates through a fiber as the object 40, during these processes the second photon is simply reflected or transmitted, and therefore it is convenient to interpret the second photon and the third photon as being the same photon.

On the other hand, the third photon travels in a different direction than the second photon, and the time width of the photon wave packet may become wider as it propagates through the fiber. Thus, the physical properties of the second and third photons are generally not completely identical. Therefore, in that sense, it is also valid to interpret the second and third photons as different photons.

In identifying the invention described in this embodiment, whether the second photon and the third photon are the same or different is a matter that involves interpretation depending on how the object 40 and the analytical device 1 are applied, and is not essential.

<Processing flow by the analysis device 1>
Next, the flow of processing by the analysis device 1 according to this embodiment will be described with reference to Fig. 5. Fig. 5 is a flowchart showing the flow of processing by the analysis device 1.

(Step S11)
First, in step S11, the light source 10 generates a plurality of photons that are in a quantum entangled state with each other. Here, the light source 10 may generate photons using the method already described.

(Step S12)
Subsequently, in step S12, the first detection unit 50 detects a first photon that has propagated through a first path, from among the multiple photons in a quantum entangled state generated in step S11.

(Step S13)
Next, in step S13, the second detection unit 60 detects a third photon obtained by irradiating or making the second photon incident on the object 40, among the multiple photons in a quantum entangled state generated in step S11.

(Step S14)
In step S14, the analysis unit 70 analyzes the characteristics of the object 40 by referring to the difference between the detection timing by the first detection unit 50 in step S12 and the detection timing by the second detection unit 60 in step S13.

According to the analysis method including the above steps, of the multiple photons in a quantum entangled state with each other, the first photon is detected without passing through the object 40, and the third photon obtained by irradiating or being incident on the object 40 with the second photon is detected, for example, with a delay time according to the object. The analysis device 1 analyzes the characteristics of the object 40 by referring to the difference between the detection timing of the first photon and the detection timing of the third photon, so that the characteristics of the object can be suitably analyzed while minimizing damage to the object.

In the above description, an example is given in which a first photon is detected in step S12 and then a second photon is detected in step S13, but this does not limit the present embodiment. Depending on how the first and second paths are configured, it may be the case that a second photon is detected in step S13 before a first photon is detected in step S12. Such an example is also included in the present embodiment.

In either case, if one of the first and second photons is detected first, this can cause the wave packet of the other photon to contract.

Interdisciplinary Aspects of the Invention Described Herein
As described above, the analytical method and analytical device described in this specification generate a plurality of photons in a quantum entangled state, and use the generated photons in spectroscopy (molecular spectroscopy as an example). Here, the use of a quantum optical object, namely, a plurality of photons in a quantum entangled state, has been limited to use within the category of quantum optics in the past and has not been applied to spectroscopy. The inventor of the present application was only able to conceive of the invention described in this specification by obtaining a new finding that a quantum optical object, namely, a plurality of photons in a quantum entangled state, is applied to spectroscopy. In this way, the analytical method and analytical device described in this specification have a highly interdisciplinary aspect in that they combine two fields that even a person skilled in the art cannot easily connect.

[Embodiment 2]
A second embodiment of the present invention will be described below. The same reference numerals are used to designate the components already described in the above embodiment, and the description thereof will be omitted.

Figure 6 is a block diagram showing the configuration of the emission analysis device 100 according to this embodiment. As shown in Figure 6, the emission analysis device 100 includes an analysis device 1a. The analysis device 1a includes a calculation unit 75a instead of the calculation unit 75 included in the analysis device 1 described in embodiment 1. The other configuration of the analysis device 1a is similar to that of the analysis device 1 according to embodiment 1.

The emission analysis device 100 is a device that analyzes the characteristics of an object 40 that has luminescence. Here, luminescence includes fluorescence and phosphorescence (phosphorescence). As an example, the emission analysis device 100 determines the luminescence lifetime (e.g., fluorescence lifetime, phosphorescence lifetime) of the object 40.

Figure 7 is a block diagram showing the configuration of the calculation unit 75a provided in the analysis device 1a. As shown in Figure 7, the calculation unit 75a includes a time difference determination unit 751 and a luminescence lifetime determination unit 752. The luminescence lifetime determination unit 752 refers to the detection timing of the first photon and the detection timing of the third photon determined by the time difference determination unit 751, and determines the luminescence lifetime of the object 40.

In relation to Figure 5 described in embodiment 1, in this embodiment, in step S13 of Figure 5, photons associated with the luminescence phenomenon of the object 40 are detected as the third photon.

Figure 8 shows experimental results in which the difference between the detection timing of the first photon and the detection timing of the third photon detected by the emission analysis device 100 is plotted in a situation in which the object 40 is not placed on the second path for comparison.

As shown in Fig. 8, in a situation where the object 40 is not placed on the second path, the difference (detection error) between the detection timing of the first photon and the detection timing of the third photon is suppressed to about 0.23 ns, and it can be seen that high simultaneity of the two photons is achieved. Note that the detection error shown in Fig. 7 is mainly due to the time resolution of the first detection unit 50 and the second detection unit 60, and the light source 10 achieves a higher simultaneity than that shown in Fig. 8.

Figure 9 shows a fluorescence decay curve determined by the luminescence lifetime determination unit 752 when a dye molecule (Rhodamine 6G), which is a fluorescent molecule, is used as the object 40. The fluorescence decay curve shown in Figure 9 is a graph obtained by plotting the time difference determined by the time difference determination unit 751 for each photon pair against a large number of photon pairs by the luminescence lifetime determination unit 752. In the example shown in Figure 9, the luminescence lifetime determination unit 752 determines that the fluorescence lifetime of the object 40 is 4.8 ns.

The emission analysis device 100 of this embodiment can optimally analyze the characteristics related to the emission phenomenon of the object 40 while minimizing damage to the object 40.

In the above example, a molecule is used as the object 40, but this does not limit the present embodiment, and the object 40 may include at least one of an atom, a molecule, a solid, and a crystal.

Even for such objects, the emission analysis device 100 can optimally analyze the characteristics related to the luminescence phenomenon of the object 40 while minimizing damage to the object 40.

[Embodiment 3]
A third embodiment of the present invention will be described below. The same reference numerals are used to designate the same components as those described in the above embodiments, and the description thereof will be omitted.

Figure 10 shows an example configuration of a diffuse optical tomography device 200. As shown in Figure 10, the diffuse optical tomography device 200 includes an analysis device 1b. The analysis device 1b includes a calculation unit 75b instead of the calculation unit 75 included in the analysis device 1 described in embodiment 1. The other configurations of the analysis device 1b are the same as those of the analysis device 1 according to embodiment 1.

The diffuse optical tomography device 200 is a device that generates a tomographic image of a transparent object 40. In this embodiment, the object 40 is a transparent material, but the object 40 is not limited to materials that transmit visible light, and also includes materials that transmit far ultraviolet and far infrared light.

In this embodiment, the second photon is incident on the object, and the first photon is used as a reference. The third photon in this embodiment is a photon obtained as a result of the second photon being repeatedly scattered in the object. It can also be said that the third photon is a photon that has undergone a repeated scattering process in the object.

Figure 11 shows the configuration of the calculation unit 75b provided in the analysis device 1b of the diffuse optical tomography device 200. The calculation unit 75b includes a time difference determination unit 751 and a tomography analysis unit 753. The tomography analysis unit 753 refers to the detection timing of the first photon and the detection timing of the third photon determined by the time difference determination unit 751, and acquires information on how the photons are scattered in the object 40. The tomography analysis unit 753 then analyzes the acquired information to identify the spatial distribution of the substance in the object 40. Then, as an example, a tomography image of the object showing the identified spatial distribution is generated.

In relation to Figure 5 described in embodiment 1, in this embodiment, in step S13 of Figure 5, photons associated with the transmission phenomenon of the object 40 are detected as the third photon.

The diffuse optical tomography device 200 can perform diffuse optical tomography effectively while minimizing damage to the target object. In addition, since there is no need for a device to generate pulsed light as in conventional technology, there is also the advantage that the configuration of the diffuse optical tomography device is simplified.

[Embodiment 4]
A fourth embodiment of the present invention will be described below. The same reference numerals are used to designate the components already described in the above embodiments, and the description thereof will be omitted.

Figure 12 shows an example of the configuration of the imaging device 300. As shown in Figure 12, the imaging device 300 includes an analysis device 1c. The analysis device 1c includes a calculation unit 75c instead of the calculation unit 75 included in the analysis device 1 described in embodiment 1. The other configurations of the analysis device 1c are similar to those of the analysis device 1 according to embodiment 1.

The imaging device 300 is a device that generates imaging information of an imaging range including a reflective object 40.

In this embodiment, the second photon is emitted toward the object, and the first photon is used as a reference. The third photon in this embodiment is a photon obtained by reflecting the second photon by the object.

Figure 13 shows the configuration of the calculation unit 75c provided in the analysis device 1c of the imaging device 300. The calculation unit 75c includes a time difference determination unit 751 and an image generation unit 754. The image generation unit 754 refers to the detection timing of the first photon and the detection timing of the third photon determined by the time difference determination unit 751, and determines the distance to the object 40 as a characteristic of the object 40. Then, based on the characterized distance, it generates imaging information of the imaging range including the object 40, which includes distance information to the object 40.

In relation to Figure 5 described in embodiment 1, in this embodiment, in step S13 of Figure 5, photons associated with the reflection phenomenon of the object 40 are detected as the third photon.

Conventionally, a technology called Lidar (Light Imaging Detection and Ranging) has used pulsed light to measure scattered light in response to laser irradiation and analyze the distance to a target, the properties of the target, etc. However, in this embodiment, multiple single photons that are in a quantum entangled state with each other are used to generate imaging information that includes distance information, so that the distance to a target, the properties of the target, etc. can be analyzed while reducing damage to the target.

Note that the imaging information generated by the image generation unit 754 can be, for example, distance information and a two-dimensional captured image, but this does not limit the present embodiment. The image generation unit 754 may be configured to generate a left-eye image and a right-eye image for stereoscopic vision by referring to the distance information and the two-dimensional captured image.

In this embodiment, a stereoscopic image is generated using multiple single photons that are in a quantum entangled state with each other, so that a stereoscopic image can be generated suitably while reducing damage to the object. In addition, there is also the advantage that the configuration of the imaging device is simplified because there is no need for a device that generates pulsed light as in conventional technology.

[Embodiment 5]
A fifth embodiment of the present invention will be described below. The same reference numerals are used to designate the same components as those described in the above embodiments, and the description thereof will be omitted.

Figure 14 shows an example of the configuration of a reflectance measuring device 400. As shown in Figure 14, the reflectance measuring device 400 includes an analysis device 1d. The analysis device 1d includes a calculation unit 75d instead of the calculation unit 75 included in the analysis device 1 described in embodiment 1. The other configurations of the analysis device 1d are similar to those of the analysis device 1 according to embodiment 1.

The reflectance measuring device 400 is a device for analyzing the characteristics of an object 40 having reflectance.
Here, the object 40 is, for example, an optical fiber.

In this embodiment, the second photon is incident on the object, and the first photon is used as a reference. The third photon in this embodiment is a photon obtained by the second photon passing through or reflecting the object. The third photon may also include backscattered light obtained by the second photon being incident on the object.

Figure 15 shows the configuration of the calculation unit 75d provided in the analysis device 1d of the reflectance measurement device 400. The calculation unit 75d includes a time difference determination unit 751 and a reflectance measurement unit 755. The reflectance measurement unit 755 refers to the detection timing of the first photon and the detection timing of the third photon determined by the time difference determination unit 751, and detects the reflectivity of the object 40.

In relation to Figure 5 described in embodiment 1, in this embodiment, in step S13 of Figure 5, photons associated with the reflection phenomenon of the object 40 are detected as the third photon.

Conventionally, a technology called OTDR (Optical Time Domain Reflectometer) has used pulsed light to perform quality control of optical fibers using backscattered light, but in this embodiment, multiple photons that are in a quantum entangled state with each other are used for quality control, so damage to the target object can be reduced more than when pulsed light is used. In addition, since there is no need for a device that generates pulsed light as in conventional technology, there is also the advantage that the configuration of the reflectance measurement device is simplified.

<Other application examples>
The application examples of the analysis device described above in this specification are not limited to the above examples. As an example, the analysis device described above may be applied to a pump-probe method. More specifically, a configuration may be adopted in which a first photon is used to excite an object 40, and a second photon is used as a probe light to observe the object.

It was previously impossible to perform pump-probe measurements using continuous light as a light source, but by using the analysis device described above, it is possible to perform pump-probe measurements using continuous light as a light source by converting the continuous light into photon pairs in an entangled state.

As a more specific example, the analytical device of this example irradiates a molecular object 40 with a first photon to initiate a photochemical reaction. Then, after a small delay time (on the order of femtoseconds or picoseconds), the analytical device of this example irradiates the object 40 with a second photon as a probe light. This allows the analytical device of this example to measure molecular absorption (infrared light, visible light, and ultraviolet light regions) and Raman scattering. In this way, the analytical device of this example allows the progress of a chemical reaction to be tracked with a time resolution of the order of femtoseconds or picoseconds.

As another example, the above-described analytical device may be applied to a pump-dump-probe method.
Here, the three photons in a quantum entangled state used in the pump-dump-probe technique can be obtained, for example, by the following method.
That is, the analysis device is configured to include two nonlinear optical crystals, and first, continuous light is incident on the first nonlinear optical crystal to generate two photons (called photon 1 and photon 2) that are in a quantum entangled state with each other by SPDC. Then, one of these two photons (for example, photon 1) is irradiated onto the second nonlinear optical crystal, and converted into two photons (called photon 3 and photon 4) by SPDC in the second nonlinear optical crystal.
The three photons obtained in this way (photon 2, photon 3, and photon 4) are in a quantum entangled state with each other and are synchronized in time.
As an example, the analysis device according to this example first excites the object 40, which is a molecule, by irradiating the object 40 with a first photon of three photons in a quantum entangled state. Generally, a molecule in a highly electronically excited state has an equilibrium internuclear distance different from that in the ground state, so that the nuclear wave packet is given momentum and starts to move. Then, the analysis device according to this example irradiates the object 40 with a second photon of the three photons, thereby dumping the wave packet to the ground state. Then, the analysis device according to this example irradiates the object 40 with a third photon of the three photons as a probe light.
By performing the pump-dump-probe method as described above, the analytical device according to this embodiment can, for example, determine the de-excitation efficiency of the target object 40, which is a molecule, and the dependency of the de-excitation efficiency on the timing of dump light irradiation.
It was previously impossible to perform pump-dump-probe measurements using continuous light as a light source. However, by using the above-mentioned analytical device, it is possible to perform pump-dump-probe measurements using continuous light as a light source by converting the light into three photons in an entangled state.

[Software implementation example]
The control blocks of the analysis device 1 (particularly the analysis unit 70, and the calculation units 75, 75a, 75b, 75c, and 75d) may be realized by a logic circuit (hardware) formed in an integrated circuit (IC chip) or the like, or may be realized by software.

In the latter case, the analysis device 1 is equipped with a computer that executes the instructions of a program, which is software that realizes each function. This computer is equipped with, for example, one or more processors, and a computer-readable recording medium that stores the program. The object of the present invention is achieved by the processor reading the program from the recording medium and executing it in the computer. The processor can be, for example, a CPU (Central Processing Unit). The recording medium can be a "non-transient tangible medium", such as a ROM (Read Only Memory), tape, disk, card, semiconductor memory, programmable logic circuit, etc. The device may also be equipped with a RAM (Random Access Memory) that expands the program. The program may be supplied to the computer via any transmission medium (such as a communication network or broadcast waves) that can transmit the program. One aspect of the present invention can also be realized in the form of a data signal embedded in a carrier wave, in which the program is embodied by electronic transmission.

〔summary〕
An analysis method according to one aspect of the present invention includes a generation step of generating a plurality of photons that are in a quantum entangled state with each other, a first detection step of detecting a first photon among the plurality of photons, a second detection step of detecting a third photon obtained by irradiating or making incident a second photon among the plurality of photons on an object, and an analysis step of analyzing characteristics of the object by referring to the difference between the detection timing in the first detection step and the detection timing in the second detection step.

The above analysis method makes it possible to analyze the characteristics of an object, including temporal characteristics, while reducing damage to the object.

In the above analysis method, it is preferable that in the analysis step, the detection timing of the first photon is used as a reference for analyzing characteristics related to the object.

According to the above analysis method, the detection timing of the first photon is used as a reference for the analysis of the characteristics of the object, thereby making it possible to more appropriately analyze the characteristics of the object, including temporal characteristics.

In the above analysis method, it is preferable that in the generation step, the first photon and the second photon are generated using a nonlinear optical crystal.

According to the above analysis method, the characteristics of an object can be detected with a simple configuration.

In the above analysis method, it is preferable that in the first detection step and the second detection step, the first photon and the third photon are detected using a single-photon detector.

According to the above analysis method, the first photon and the third photon are detected using a single-photon detector, so that characteristics of the object, including temporal characteristics, can be suitably detected.

An emission analysis device according to one aspect of the present invention is a emission analysis device that performs the above-mentioned analysis method, and in the second detection step, it is preferable to detect photons associated with the emission phenomenon of the object as the third photons.

The above-mentioned emission analysis device makes it possible to optimally analyze the characteristics of the luminescence phenomenon of an object.

In the emission spectrometer that performs the above analysis method, it is preferable that the object includes at least one of an atom, a molecule, a solid, and a crystal.

The above-mentioned emission spectrometer can effectively analyze the characteristics of the emission phenomena of atoms, molecules, solids, and crystals.

A diffuse optical tomography device according to one aspect of the present invention is a diffuse optical tomography device that performs the above-mentioned analysis method, and in the second detection step, it is preferable to detect transmitted light that has passed through the object as the third photon.

According to the above-mentioned diffuse optical tomography device, the transmitted light that has passed through the object is detected as the third photon, thereby enabling diffuse optical tomography to be performed effectively.

An imaging device according to one aspect of the present invention is an imaging device that performs the above-mentioned analysis method, and in the second detection step, it is preferable that the reflected light reflected by the object is detected as the third photon.

According to the above imaging device, the reflected light reflected by the object is detected as the third photon, so that imaging information that reflects the temporal characteristics of the object can be preferably generated.

A reflectance measuring device according to one aspect of the present invention is a reflectance measuring device that performs the above-mentioned analysis method, and in the second detection step, it is preferable to detect the emitted light from the optical fiber, which is the object, as the third photon.

According to the above reflectance measuring device, the light emitted from the optical fiber is detected as the third photon, so that reflectance measurement can be performed effectively.

An analysis device according to one aspect of the present invention preferably includes a generation unit that generates a plurality of photons that are in a quantum entangled state with each other, a first detection unit that detects a first photon of the plurality of photons, a second detection unit that detects a third photon obtained by irradiating or making incident a second photon of the plurality of photons on an object, and an analysis unit that analyzes characteristics of the object by referring to the difference between the detection timing by the first detection unit and the detection timing by the second detection unit.

The above-mentioned analytical device makes it possible to analyze the characteristics of an object, including temporal characteristics, while reducing damage to the object.

A program according to one aspect of the present invention is a program for causing a computer to function as the above-mentioned analysis device, and preferably causes a computer to function as the above-mentioned analysis unit. The above-mentioned program provides the same effects as the above-mentioned method and device.

[Additional Notes]
The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention.

Reference Signs List 1, 1a, 1b, 1c, 1d Analysis device 10 Light source 11 Continuous light source 12 Light source lens 13 Crystalline substance 40 Object 50 First detection unit 60 Second detection unit 70 Analysis unit 75, 75a, 75b, 75c, 75d Calculation unit 100 Emission analysis device 200 Diffuse optical tomography device 300 Imaging device 400 Reflectance measurement device 751 Time difference determination unit 752 Emission lifetime determination unit 753 Tomography analysis unit 754 Image generation unit 755 Reflectance measurement unit

Claims (5)

A generating step of generating a plurality of single photons in a quantum entangled state with respect to each other;
a first detection step of detecting a first single photon among the plurality of single photons;
a second detection step of detecting a third single photon obtained by irradiating or making an object with a second single photon among the plurality of single photons;
a step of identifying a time difference between a detection timing in the first detection step and a detection timing in the second detection step, and analyzing a temporal characteristic of the object,
A diffuse optical tomography apparatus, characterized in that in the second detection step, transmitted light that has passed through the object is detected as the third single photon. A generating step of generating a plurality of single photons in a quantum entangled state with respect to each other;
a first detection step of detecting a first single photon among the plurality of single photons;
a second detection step of detecting a third single photon obtained by irradiating or making an object with a second single photon among the plurality of single photons;
a backscattered light measurement device that executes an analysis method including an analysis step of identifying a time difference between a detection timing in the first detection step and a detection timing in the second detection step, and analyzing a temporal characteristic of the object,
A backscattered light measuring device, characterized in that in the second detection step, backscattered light from an optical fiber that is the object is detected as the third single photon. A generating step of generating a plurality of single photons in a quantum entangled state with respect to each other;
a first detection step of detecting a first single photon among the plurality of single photons;
a second detection step of detecting a third single photon obtained by irradiating or making an object with a second single photon among the plurality of single photons;
an analysis step of identifying a time difference between a detection timing in the first detection step and a detection timing in the second detection step, and analyzing a temporal characteristic of the object;
Prior to the second detection step,
a first incidence step of irradiating or injecting a fourth single photon of the plurality of single photons in a quantum entangled state with each other onto the object, thereby exciting the object;
and a second incidence step of irradiating or injecting a fifth single photon of the plurality of single photons in a quantum entangled state with one another onto the object, thereby causing the object to be dumped. A generator for generating a plurality of single photons in a quantum entangled state with each other;
a first detector configured to detect a first single photon among the plurality of single photons;
a second detection unit that detects a third single photon obtained by irradiating or making an object with a second single photon among the plurality of single photons;
an analysis unit that specifies a time difference between a detection timing by the first detection unit and a detection timing by the second detection unit and analyzes a temporal characteristic of the object;
Prior to the second single photon being irradiated or incident on the object,
a first incidence unit that excites an object by irradiating or making a fourth single photon of the plurality of single photons in a quantum entangled state with each other onto the object;
and a second incident portion that dumps the object by irradiating or making a fifth single photon of the plurality of single photons that are in a quantum entangled state with each other onto or incident on the object. 5. A program for causing a computer to function as the analysis device according to claim 4 , the program causing a computer to function as the first detection section, the second detection section, and the analysis section.

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