Measurement device, measurement method, and program

Abstract

To provide a measuring apparatus which eliminates an influence on safety caused by an effect of a finite reference light and is capable of satisfying all the conditions required for certification of safety.SOLUTION: The measuring apparatus comprises: a phase modulator which impresses a phase to a signal light; a first beam splitter which two-branches a reference light; a second beam splitter which branches one of the phase-impressed signal light and the two-branched reference lights, superposes, outputs and two-branches them; a first photodetector which observes the intensity of a first light coming from the second splitter; a second photodetector which observes the intensity of a second light coming from the second splitter; a third photodetector which observes the intensity of the other of the two-branched reference lights; and a calculation unit which calculates a measurement value on the basis of an observed value obtained from the first photodetector, an observed value obtained from the second photodetector, and an observed value obtained from the third photodetector.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to homodyne and dual-homodyne measurements. [Background technology]

[0002] Homodyne measurement and double homodyne measurement are important technologies for realizing information communication. Measurement devices that implement these technologies are used not only in conventional communication but also in quantum communication. For example, continuous quantum cryptography, which observes the quadrature phase amplitude, a continuous physical quantity, can generate a shared key that guarantees security (privacy) by using a homodyne measurement device or a double homodyne measurement device. However, security cannot be guaranteed unless homodyne measurement and double homodyne measurement are ideally realized. Homodyne measurement and double homodyne measurement use reference light (the argument of a complex number is expressed as (argβ) and the complex amplitude is expressed as β) that serves as a phase reference, and the measurement becomes ideal when this reference light is a coherent light of infinitely large intensity.

[0003] Fig. 1(a) is a diagram showing the configuration of a homodyne measurement device. As shown in Fig. 1(a), the homodyne measurement device includes a phase modulator 1a that applies a phase (θ) to a measurement light, a beam splitter 2a with a transmittance of 1 / 2 that splits, superimposes, and outputs the measurement light and reference light to which the phase has been applied, and an output splitter 2b with an intensity x 1 and x 2 and photodetectors 3a and 4a for observing the light beams, respectively.

[0004] Fig. 1(b) is a diagram showing the configuration of the double homodyne measurement device. As shown in Fig. 1(b), the double homodyne measurement device includes a beam splitter 2g with a transmittance of 1 / 2 that splits the measurement light into two, a beam splitter 2g with a transmittance of 1 / 2 that splits the reference light into two, a beam splitter 2b with a transmittance of 1 / 2 that splits one of the two split measurement light and one of the two split reference light, superimposes them, and outputs them. The two output lights from the beam splitter 2b have intensities y 1 and y2 The phase modulator 1c applies a phase (π / 2) to the other of the two split measurement lights, the phase-applied measurement light and the other of the two split reference lights are split into two, superimposed, and output by a beam splitter 2c with a transmittance of 1 / 2. The intensity of the two output lights from the beam splitter 2c is y 3 and y 4 1(b) also shows a mirror 5b that reflects one of the measurement beams split between the beam splitter 2g and the beam splitter 2b, and a mirror 5c that reflects the other of the reference beams split between the beam splitter 2h and the beam splitter 2c.

[0005] The units of the observed values ​​at the photodetectors 3a, 3b, 3c, 4a, 4b, and 4c of the homodyne measurement device of Fig. 1(a) and the double homodyne measurement device of Fig. 1(b) are configured so that one photon is 1. The units of the complex amplitude β of the reference light are configured so that the square of the absolute value is the number of photons. The measured value α in the double homodyne measurement device of Fig. 1(b) is the observed value y 1 ,y 2 ,y 3 , and y 4 , and the known complex amplitude β of the reference light, α={(y 1 -y 2 ,)+(y 3 -y 4 )i} / |β|, where α is a dimensionless complex number representing the magnitude of the phase and amplitude. When α is a sufficiently large classical light, the square of the absolute value of α approximately corresponds to the number of photons and represents the intensity of the light. The phase of α represents the phase of that light. A computer (not shown) that calculates the measured value α may be provided in the double homodyne measurement device of FIG. 1(b) or may be separate from the double homodyne measurement device. Also, the measured value p θ is the observation value x at the photodetectors 3a and 4a. 1 and x 2 Using p θ =(x 1-x 2 ) / 2|β|. The measured value p θ A calculator (not shown) for calculating may be provided in the homodyne measurement device of FIG. 1(a) or may be separate from the homodyne measurement device.

[0006] The homodyne measurement device in FIG. 1(a) or the double homodyne measurement device in FIG. 1(b) can easily obtain the measurement value p of an ideal homodyne measurement device even in a situation where a reference light satisfying the conditions is not available. θ This provides a means for providing statistics (covariance matrix) related to α or statistics (covariance matrix) related to the measurement value α of the double homodyne measurement device. As a result, it provides a simple means for implementing continuous quantum cryptography that ensures security even in a situation where an ideal reference light cannot be used as a phase reference. When homodyne measurement is used in quantum cryptography, the measurement value p required for the homodyne measurement device in Figure 1(a) to ensure security is θ In addition, when double homodyne measurement is used in quantum cryptography, the double homodyne measurement device in FIG. 1(b) can easily provide the measurement value α required to ensure security to the relevant parties.

[0007] When using homodyne or double-homodyne measurements in communications, it is necessary to synchronize the phase of the reference light used in the measurement with the phase that is the reference for generating the signal. To achieve this synchronization, light synchronized with the signal light (usually used when generating the signal light) is sent as a reference light from the sender to the receiver along the same path as the signal light, and the transmitted reference light is often used directly as the reference light for the homodyne or double-homodyne measurement. In fact, in many current implementations of continuous quantum cryptography, synchronization is achieved by this means.

[0008] FIG. 2 shows a typical configuration of a communication system that implements continuous quantum cryptography, and is a diagram showing the configuration of a communication system that utilizes homodyne measurement or double homodyne measurement. The device on the sender side includes a light source 6a, beam splitters 2p and 2q with a transmittance of 1 / 2, and a phase / amplitude modulator 11 between the beam splitters 2p and 2q. Here, the transmittance of the beam splitter 2p is defined as T p The transmittance of the beam splitter 2q is T q In general, T p ×Tq<<(1-T p )(1-T q ) can be satisfied. The beam splitter 2p splits the light from the light source 6a into two. One of the two split lights is used as a reference light, and the other is used to generate a signal light. The signal light and the reference light are each incident on the beam splitter 2q and output to the communication path 7. FIG. 2 also shows mirrors 5p and 5q between the beam splitter 2p and the beam splitter 2q. One of the lights (reference light) split by the beam splitter 2p has an optical path length increased by the amount of light reflected by the mirrors 5p and 5q and incident on the beam splitter 2q. The other light split by the beam splitter 2p has a phase applied thereto and its intensity attenuated by the phase / amplitude modulator 11 to become a signal light. The product T of the transmittances of the beam splitters 2p and 2q is p ×T q satisfies the above condition, the intensity modulation in the phase / amplitude modulator 11 does not have to significantly reduce the intensity of the input light, but rather it is sufficient that the intensity of the light is changed in accordance with the information to be transmitted.

[0009] The receiver's device is a device that performs homodyne measurement or double homodyne measurement using a reference light transmitted from the sender through the same communication path 7 as the signal light. The receiver's device includes an optical switch 8 that separates the signal light and the reference light transmitted from the sender's device through the same communication path 7, and a homodyne measurement device or double homodyne measurement device arranged after the optical switch 8. The homodyne measurement device can be configured as described above with reference to FIG. 1(a), and the double homodyne measurement device can be configured as described above with reference to FIG. 1(b). FIG. 2 also shows mirrors 5r and 5s between the optical switch 8 and the homodyne measurement device or double homodyne measurement device. The signal light separated by the optical switch 8 has an optical path length that is increased by the amount of light reflected by the mirrors 5r and 5s and incident on the homodyne measurement device or double homodyne measurement device.

[0010] The positional relationship between the reference light and the signal light is not limited to the positional relationship shown in Fig. 2. The arrangement of the elements of the transmitter and receiver devices can be changed so that the positional relationship between the reference light and the signal light is reversed. Also, the arrangement of the elements of the transmitter and receiver devices can be changed so that one reference light is used for multiple signal lights.

[0011] However, this implementation method can only guarantee theoretical security when the eavesdropper's attacks are greatly restricted. Because, when the reference light is sent along the same path as the signal light, it is reasonable to consider the possibility that the eavesdropper may also tamper with the reference light. However, in such a situation, it is necessary to use the possibly tampered reference light as the reference light, and therefore it is not possible to guarantee that the implemented measurement device is an ideal homodyne measurement device or a double homodyne measurement device. In all currently known security proofs of continuous quantum cryptography, it is assumed that the homodyne measurement or the double homodyne measurement is performed ideally, so that the prerequisites of the theory for guaranteeing security against eavesdroppers who also attack the reference light cannot be met. Therefore, in the conventional implementation method, security against eavesdroppers that can be naively assumed cannot be guaranteed.

[0012] The following method has been proposed to solve the problem of limited situations in which safety is guaranteed (see Non-Patent Documents 1 and 2). In this proposed method, instead of performing homodyne measurement or double-homodyne measurement using the transmitted reference light as a direct reference light, double-homodyne measurement is performed on both the reference light and signal light transmitted from the sender's device, using a reference light locally generated by the receiver's device that is not synchronized with the reference light from the sender's device. More specifically, one measurement value is derived using two double-homodyne measurements as follows. First, α obtained by double-homodyne measurement using a locally generated reference light for the reference light is 1 Furthermore, the measured value α 2 At this time, the phase of the reference light argα 1 The result after subtracting α 2 e -iargα1 is the measurement value obtained by using two double homodyne measurements. This makes it possible to obtain a measurement value obtained by performing an ideal double homodyne measurement based on the phase indicated by the reference light relative to the signal light, and security is guaranteed even in the case where an eavesdropper has access to the reference light according to the conventional theory of security proof.

[0013] FIG. 3 is a diagram showing the configuration of a communication system implementing the above proposed method. The configuration of the sender's device is the same as that described with reference to FIG. 2. The receiver's device is configured to perform double-homodyne measurement on each of the signal light and reference light transmitted from the sender through the communication path 7. The receiver's device includes an optical switch 8 that separates the signal light and the reference light transmitted from the sender's device through the same communication path 7, and two double-homodyne measurement devices arranged after the optical switch 8. The double-homodyne measurement devices can be configured as described above with reference to FIG. 1(b).

[0014] As shown in FIG. 3, the transmitter device includes a light source 6c for generating a local reference light and a beam splitter 2r with a transmittance of 1 / 2 that splits the reference light into two. The reference light split into two by the beam splitter 2r is set as reference light 2 and reference light 3, respectively. The equalization ratio of the beam splitter 2r is not limited to 1 / 2 as long as it is not extremely large (small) and is known. The signal light separated by the optical switch 8 is reflected by a mirror 5t and input as measurement light in the double homodyne measurement of the signal light. The reference light 2 is reflected by mirrors 5u and 5v and input as reference light in the double homodyne measurement of the signal light. The reference light separated by the optical switch 8 is input as reference light 1 and as measurement light in the double homodyne measurement of the reference light. The reference light 3 is reflected by a mirror 5w and input as reference light in the double homodyne measurement of the reference light. The device on the sender side may be configured to use one double-homodyne measurement device to perform double-homodyne measurements on each of the signal light and reference light separated by the optical switch 8. In this case, the measurement light and reference light are configured to be input so that the double-homodyne measurement on the signal light and the double-homodyne measurement on the reference light are performed with a time difference between them. [Prior art documents] [Non-patent literature]

[0015] [Non-Patent Document 1] Bing Qi, et al., "Generating the Local Oscillator "Locally" in Continuous-Variable Quantum Key Distribution Based on Coherent Detection", Phys. Rev. X 5, 041009, October 2015 [Non-Patent Document 2] Daniel BS Soh, et al. "Self-Referenced Continuous-Variable Quantum Key Distribution Protocol", Phys. Rev. X 5, 041010, October 2015 Summary of the Invention [Problem to be solved by the invention]

[0016] However, although the above proposed method can eliminate deviations from the ideal in homodyne and double-homodyne measurements caused by an eavesdropper's access to the reference light, the intensity of the reference light must be finite. Therefore, even if the above proposed method is used, the homodyne and double-homodyne measurements cannot be ideal, and their influence remains. However, there is no theory that takes into account the impact of this influence on the security proof, and there is a problem in that there is no guarantee that it is secure.

[0017] In addition, the above proposed method requires that the signal light be measured by double homodyne measurement, and cannot be applied to continuous quantum cryptography protocols that use homodyne measurement. Furthermore, since it is necessary to measure the reference light in addition to the signal light, in order to achieve this, it is necessary to prepare twice as many photodetectors, or to halve the measurement frequency, which reduces communication efficiency. In addition, a stable light source is required on the receiver side, which requires extra equipment.

[0018] The present invention has been made in consideration of these problems, and its object is to provide a measurement device that eliminates the impact on safety caused by the effect of the finite reference light, and is capable of satisfying all of the conditions required for safety certification. [Means for solving the problem]

[0019] In order to achieve this object, one embodiment of the present invention is a measurement device comprising: a phase modulator that applies a phase to an input signal light; a first beam splitter that splits an input reference light into two; a second splitter that superimposes the signal light to which the phase has been applied and one of the split reference light to split into two; a first photodetector that observes the intensity of the first light from the second splitter; a second photodetector that observes the intensity of the second light from the second splitter; a third photodetector that observes the intensity of the other of the split reference light; and a calculation unit that calculates a measurement value based on the observation values ​​from the first photodetector, the second photodetector, and the third photodetector. Moreover, one embodiment of the present invention is a measurement device including a first beam splitter that splits an input signal light into two, a second beam splitter that splits an input reference light into two, a third beam splitter that splits the split reference light into two, a fourth beam splitter that superimposes one of the split signal lights and one of the split reference lights by the third beam splitter to split the light into two, a first photodetector that observes the intensity of a first light from the fourth beam splitter, a second photodetector that observes the intensity of a second light from the fourth beam splitter, and a third photodetector that observes the intensity of the other of the split lights. Signal light a fifth beam splitter that splits the signal light to which the phase has been applied and the other reference light split by the third beam splitter into two by superimposing them together; a third photodetector that observes the intensity of the third light from the fifth beam splitter; a fourth photodetector that observes the intensity of the fourth light from the fifth beam splitter; a fifth photodetector that observes the intensity of the other of the split reference light; and a calculation unit that calculates a measurement value based on the observation values ​​from the first photodetector, the second photodetector, the third photodetector, the fourth photodetector, and the fifth photodetector. Effect of the Invention

[0020] As described above, according to the homodyne measurement device and double homodyne measurement device of one embodiment of the present invention, the effect of the finite reference light eliminates the impact on safety, and it is possible to meet all of the conditions required for safety certification. [Brief description of the drawings]

[0021] [Figure 1] FIG. 2A is a diagram for explaining the configuration of a homodyne measurement device, and FIG. 2B is a diagram for explaining the configuration of a double homodyne measurement device. [Diagram 2] FIG. 1 is a diagram illustrating a typical configuration of a communication system that implements continuous quantum cryptography. [Diagram 3] FIG. 1 is a diagram illustrating the configuration of a communication system that performs double homodyne measurement using reference light locally generated by a receiver device. [Figure 4] FIG. 1A is a diagram for explaining the configuration of a homodyne measurement device according to one embodiment, and FIG. 1B is a diagram for explaining the configuration of a dual-homodyne measurement device according to one embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. The same or similar reference numerals denote the same or similar elements, and repeated description may be omitted.

[0023] There are several protocols called continuous quantum cryptography, and they are divided into direct reconciliation and reverse reconciliation, depending on whether the sender or receiver publishes the error correction information of the bit string obtained from the measurement value of homodyne or double homodyne measurement. Continuous quantum cryptography protocols generally aim to share a bit string with a correlation of 1. The sender and receiver share a bit string that has some degree of correlation as a result of sending and receiving error correction information. Then, to obtain a perfect correlation, the difference in this bit string is corrected (adjusted) based on this bit string that has some degree of correlation. The solution method shown here can be applied to continuous quantum cryptography classified as direct reconciliation. This is because, in the case of direct reconciliation, the only measurement information required to evaluate its security is the covariance matrix, which is a statistic for the measurement value of ideal homodyne or double homodyne measurement, and each measurement value does not necessarily have to be for ideal homodyne or double homodyne measurement. In fact, the impact of deviation from ideal measurement only affects the generation efficiency of the generated common key, and does not affect security. Therefore, security can be guaranteed as long as the covariance matrix of the measurement values ​​of an ideal homodyne or dual-homodyne measurement is obtained.

[0024]

number

[0025] This embodiment is a communication system that uses a measurement device with two-mode input. Here, the measurement device with two-mode input is a measurement device that has two input modes, namely, a mode for receiving reference light and a mode for receiving measurement light. FIG. 4 is a diagram showing the configuration of the device on the receiver side of the communication system of this embodiment. The configuration of the device on the transmitter side of the communication system of this embodiment is the same as the configuration described with reference to FIG. 2. FIG. 4(a) is a diagram showing the configuration of a homodyne measurement device with two-mode input, and FIG. 4(b) is a diagram showing the configuration of a double homodyne measurement device with two-mode input. The configuration of the device on the transmitter side is the same as the configuration described with reference to FIG. 2. The homodyne measurement device shown in FIG. 4(a) can be used by replacing it with the homodyne measurement device shown in FIG. 1(a), and the double homodyne measurement device shown in FIG. 4(b) can be used by replacing it with the double homodyne measurement device shown in FIG. 1(b).

[0026] As shown in FIG. 4(a), the homodyne measurement device of this embodiment includes a phase modulator 1d, a beam splitter 9d with a transmittance T (where 0 < T < 1), a beam splitter 2d with a transmittance of 1 / 2, and photodetectors 3d, 4d, and 10d. The functions of the phase modulator 1d, the beam splitter 2d, and the photodetectors 3d and 4d are the same as the functions of the phase modulator 1a, the beam splitter 2a, and the photodetectors 3a and 4a described with reference to FIG. 1(a).

[0027] The phase modulator 1d applies a phase (θ) to the measurement light and outputs it. The beam splitter 9d splits the reference light into two branches and outputs it toward the beam splitter 2d and the photodetector 10d. The beam splitter 2d splits one of the measurement light with the applied phase and one of the two-branched reference lights, overlaps them, and outputs them toward the photodetectors 3d and 4d. The photodetector 10d observes the other x' of the reference light branched by the beam splitter 9d 0 of. The photodetectors 3d and 4d respectively observe the intensities x' 1 and x' 2 of the two output lights from the beam splitter 2d.

[0028] Also, as shown in Fig. 4(b), the dual homodyne measurement apparatus of the present embodiment includes a beam splitter 2i with a transmittance of 1 / 2 that splits the measurement light into two branches, a beam splitter 9g with a transmittance of T (where 0 < T < 1) that splits the reference light into two branches, and a beam splitter 2j with a transmittance of 1 / 2 that splits the split reference light into two branches. Further, the dual homodyne measurement apparatus of the present embodiment includes a beam splitter 2e with a transmittance of 1 / 2 that splits one of the split measurement lights and one of the reference lights split by the beam splitter 2j, superimposes them, and outputs the result. The intensities y' 1 and y' 2 are respectively observed by photodetectors 3e and 4e. Furthermore, the dual homodyne measurement apparatus of the present embodiment includes a phase modulator 1f that applies a phase (π / 2) to the other measurement light split by the beam splitter 2i, and a beam splitter 2f with a transmittance of 1 / 2 that splits the measurement light with the applied phase and the other reference light split by the beam splitter 2j, superimposes them, and outputs the result. The intensities y' 3 and y' 4 are respectively observed by photodetectors 3f and 4f. Fig. 4(b) also shows a mirror 5e that reflects one of the split measurement lights between the beam splitter 2i and the beam splitter 2e, and a mirror 5f that reflects the other reference light between the beam splitter 2j and the beam splitter 2f. The functions of the beam splitter 2e, the photodetectors 3e and 4e, the phase modulator 1f, the beam splitter 2f, and the photodetectors 3f and 4f are the same as the functions of the beam splitter 2c, the photodetectors 3c and 4c, the phase modulator 1c, the beam splitter 2c, and the photodetectors 3c and 4c described with reference to Fig. 1(b).

[0029] The units of the observation values ​​at photodetectors 3d, 3e, 3f, 4d, 4e, 4f, 10d, and 10g of the homodyne measurement device of Fig. 4(a) and the double homodyne measurement device of Fig. 4(b) are configured so that one photon is 1. The units of the complex amplitude β of the reference light input to beam splitters 9d and 9g are configured so that the square of the absolute value is the number of photons. The measurement value α' in the double homodyne measurement device of Fig. 4(b) is the observation value y' at photodetectors 3e, 4e, 3f, 4f, and 10g. 1 ,y' 2 ,y' 3 ,y' 4 , and y' 0、 Using the known transmittance T of the reference light, α' = {(y' 1 -y' 2 ,)+(y' 3 -y' 4 )i} / √{(1-T)(y' 0 +y' 1 +y' 2 +y' 3 +y' 4 +1}. A calculator (not shown) for calculating the measured value α' may be provided in the double-homodyne measurement device of FIG. 4(b) or may be separate from the double-homodyne measurement device. Also, the measured value p' in the homodyne measurement device of FIG. 4(a) may be calculated as follows: θ are the observation values ​​x at photodetectors 3d, 4d and 10d. 1 , x 2 , and x 0 Using p' θ =(x 1 -x 2 ) / √{(1-T)(x' 0 +x' 1 +x' 2 +1}. The measured value p' θ A calculator (not shown) for calculating may be provided in the homodyne measurement device of FIG. 4(a) or may be separate from the homodyne measurement device.

[0030] In the communication system of this embodiment, the measurement value p' of the homodyne measurement device of FIG. θAlternatively, the measurement value α′ of the double-homodyne measurement device in FIG. 4(b) is regarded as the measurement value of a homodyne measurement or a double-homodyne measurement.

[0031]

number

[0032] Furthermore, in the communication system of this embodiment, different statistics of the measurement results of the homodyne measurement device and the double-homodyne measurement device provide a theoretical upper limit for the difference between the approximation value and the ideal value. More precisely, in the communication system of this embodiment, the upper limit for the mean and variance errors between the measurement values ​​of the homodyne measurement device and the double-homodyne measurement device and the measurement values ​​of the ideal homodyne and double-homodyne measurements are given by different statistics of the measurement results of the devices.

[0033]

number

[0034] Due to the above properties, the communication system of this embodiment uses the homodyne measurement device and double homodyne measurement device shown in FIG. 4 to implement the continuous quantum cryptography by direct adjustment, instead of using the homodyne measurement device and double homodyne measurement device shown in FIG. 1. Furthermore, when the covariance matrix of the homodyne measurement device and double homodyne measurement device shown in FIG. 4 is used to evaluate the security of the communication system of this embodiment, the evaluation is performed by taking into account the upper limit of the difference shown above in addition to the actual statistical error as the error. According to this embodiment, security can be guaranteed even if any attack is made on the light passing through the communication path, whereas in the conventional implementation method, it was necessary to assume that no attack was made on the reference light. The calculation of the covariance matrix, the error of the covariance matrix, the actual statistical error, and the upper limit of the difference shown above in the homodyne measurement device and double homodyne measurement device is performed by a computer associated with the homodyne measurement device and double homodyne measurement device. The computer typically includes a processor, and a memory and a storage device coupled to the processor. The storage device stores a program for controlling application of a phase by the phase modulator and observation of light intensity by the photodetector. The storage device also stores a program for causing the processor to calculate the covariance matrix, the error of the covariance matrix, the actual statistical error, and the upper limit of the difference shown above. The processor loads the program stored in the storage device into the memory and executes it.

[0035] The homodyne measurement device and heterodyne measurement device of this embodiment make it possible to estimate the covariance matrix for the measurement results of ideal homodyne and heterodyne measurements, thereby eliminating the impact on safety due to the effect of finite reference light, and satisfying all of the conditions required for safety certification.

[0036] In addition, the homodyne measurement device and the heterodyne measurement device of the present embodiment can be realized by simply adding one photodetector to the homodyne measurement and the double homodyne measurement configurations, respectively. Therefore, unlike the conventional technology, ideal security can be achieved without sacrificing the simplicity that is an advantage of continuous quantum cryptography.

[0037] Furthermore, while the conventional technology was only applicable to protocols that utilize double-homodyne measurements, the homodyne measurement device and heterodyne measurement device of the present embodiment can be applied to protocols that use either homodyne measurements or double-homodyne measurements. [Explanation of symbols]

[0038] 1a, 1c, 1d, 1f Phase Modulators 2a, 2b, 2c, 2d, 2e, 2f, 2g, 2h, 2i, 2j, 2p, 2q, 2r Beam splitters 3a, 3b, 3c, 3d, 3e, 3f, 4a, 4b, 4c, 4d, 4e, 4f, 10d, 10g photodetector 5b, 5c, 5e, 5f, 5p, 5q, 5r, 5s, 5t, 5u, 5v, 5w mirror 6a, 6c light source 7 Communication Channel 8. Optical Switch 9d, 9g Beam splitter 11 Phase / amplitude modulator

Claims

1. a phase modulator that applies a phase to an input signal light; a first beam splitter that splits the input reference light into two beams; a second splitter which superimposes the signal light to which the phase has been applied and one of the two branched reference lights and branches the light into two; a first photodetector for observing an intensity of the first light from the second splitter; a second photodetector for monitoring the intensity of the second light from the second splitter; and a third photodetector for observing the intensity of the other of the two branched reference lights; a calculation unit that calculates a measurement value based on an observation value from the first photodetector, an observation value from the second photodetector, and an observation value from the third photodetector; A measuring device comprising:

2. a first beam splitter for splitting an input signal light into two beams; a second beam splitter that splits the input reference light into two beams; a third beam splitter that splits the two-branched reference light beams into two beams; a fourth beam splitter that superimposes one of the two branched signal lights and one of the two branched reference lights by the third beam splitter and branches the light into two beams; a first photodetector for observing an intensity of the first light from the fourth beam splitter; a second photodetector for observing an intensity of the second light from the fourth beam splitter; and a phase modulator that applies a phase to the other of the two branched signal lights; a fifth beam splitter that superimposes the signal light to which the phase has been applied and the other reference light split by the third beam splitter and splits the signal light into two beams; a third photodetector for observing an intensity of the third light from the fifth beam splitter; and a fourth photodetector for observing an intensity of the fourth light from the fifth beam splitter; and a fifth photodetector for observing the intensity of the other of the two branched reference lights; a calculation unit that calculates a measurement value based on an observation value from the first photodetector, an observation value from the second photodetector, an observation value from the third photodetector, an observation value from the fourth photodetector, and an observation value from the fifth photodetector; A measuring device comprising:

3. applying a phase to the input signal light by a phase modulator; A first beam splitter splits the input reference light into two beams; a second splitter superimposing the signal light to which the phase has been applied and one of the two branched reference lights to branch into two; observing with a first photodetector an intensity of the first light from the second splitter; observing with a second photodetector an intensity of the second light from the second splitter; Observing the intensity of the other of the two branched reference lights with a third photodetector; a calculation unit calculating a measurement value based on the observation value from the first photodetector, the observation value from the second photodetector, and the observation value from the third photodetector; A measurement method including:

4. A first beam splitter splits an input signal light into two beams; A second beam splitter splits the input reference light into two beams; a third beam splitter splits the reference light into two beams; a fourth beam splitter superimposing one of the two branched signal lights and one of the two branched reference lights by the third beam splitter into two beams, and branching the two beams into two beams; observing with a first photodetector an intensity of the first light from the fourth beam splitter; observing with a second photodetector an intensity of the second light from the fourth beam splitter; applying a phase to the other of the two branched signal lights by a phase modulator; a fifth beam splitter superimposing the signal light to which the phase has been applied and the other reference light split by the third beam splitter into two beams, and splitting the signal light into two beams; observing with a third photodetector an intensity of the third light from the fifth beam splitter; and observing with a fourth photodetector an intensity of the fourth light from the fifth beam splitter; and observing the intensity of the other of the two branched reference lights with a fifth photodetector; a calculation unit calculating a measurement value based on the observation value from the first photodetector, the observation value from the second photodetector, the observation value from the third photodetector, the observation value from the fourth photodetector, and the observation value from the fifth photodetector; A measurement method including:

5. 2. A program for performing measurement with the measurement device according to claim 1, wherein the measurement device includes a processor, and the program causes the processor to: applying a phase to the input signal light by the phase modulator; Observing an intensity of the first light with the first photodetector; Observing an intensity of the second light with the second photodetector; a third photodetector is used to observe the intensity of the other of the two branched reference lights; a program that causes the calculation unit to calculate a measurement value based on an observation value from the first photodetector, an observation value from the second photodetector, and an observation value from the third photodetector.

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