Optical calculation device and optical calculation method

Abstract

The optical arithmetic device includes a plurality of stages having one or more Mach-Zehnder interference type optical switches, inputs input light whose phase has been changed by a predetermined phase amount in advance in accordance with a position of the input light in an input stage of the input light, and transmits the input light in accordance with a control electrical signal.

Description

Technical Field

[0001] The present invention relates to a method for mounting a memory using an optical circuit used in optical communication, optical computing infrastructure, etc., and a computing technology using the method for mounting the memory. Background Art

[0002] In recent years, the development of nanophotonics technology has made it possible to install small optical circuits, and the technology of installing optical circuits and computing methods is developing. As optical computing elements for performing operations based on optical circuits, there are Ψ gates and Mach-Zehnder interference optical switches (MZI optical switches).

[0003] In conventional optical computing circuits, MZI optical switches are used to perform table operations (nonlinear operations of cryptography (S-box operations)) by selecting and outputting an arbitrary optical signal from a plurality of optical signals (Non-Patent Document 1). This operation can select a specific value from a certain memory value, so it is the same operation as the installation of a memory.

[0004] The technology disclosed in non-patent document 1 shows a method of selecting a path of an MZI optical switch from a group of 256 optical inputs formed by a table according to an input value based on an electrical signal, and finally selecting a value (1 bit) to calculate 1 bit of the table. According to this method, the nonlinear operation part of the Advanced Encryption Standard (AES) encryption operation, namely the S-box, can be operated.

[0005] Non-patent document 1: "Cryptographic circuit technology composed of optical logic gates", Junko Takahashi, Hiroshi Chida, Kohiro Yamakoshi, Shota Kita, Akihiko Shinke, NTT Technology Journal 2021.11, pp. 59-63. Summary of the invention

[0006] <Problems to be Solved by the Invention>

[0007] When using an MZI optical switch, light may travel straight (through) or cross (crossing) depending on the nature of the optical switch, and the phase of the input light and the output light may change depending on the position of the MZI phase shifter. Furthermore, when the MZI optical switch is set to multiple stages for operation, the phase of the output result may change depending on the input value (control electrical signal) of the MZI optical switch due to the influence of the phase change caused by the multiple MZI optical switches.

[0008] In conventional technologies such as non-patent document 1, the phase change of light after passing through the MZI optical switch is not considered, and the phase of the output light changes according to the input value (control electrical signal). Therefore, when the amplitude of the optical signal or the phase difference between the two signals is used to represent the bit, there is a problem that the phase of the output light needs to be consistent with the input light (the phase difference between the input light and the output light is 0) through photoelectric conversion processing when the output result selected from the memory is used as the input of the next operation.

[0009] For example, in non-patent document 1, when calculating the linear operation of AES, namely MixColumns, a bit judgment (a judgment of whether the bit is "1" or "0") is performed based on the amplitude of the light (or the intensity of the light (which is proportional to the square of the amplitude)). Since it is assumed that there is no phase difference in the input light for the operation, there is a problem that if the phase changes according to the input value, the operation result will also change.

[0010] The present invention has been made in view of the above-mentioned situation, and an object of the present invention is to provide a technology for eliminating the phase difference between input light and output light in an optical computing device.

[0011] <Methods used to solve the problem>

[0012] According to the technology of the present disclosure, there is provided an optical computing device including a plurality of stages having one or more Mach-Zehnder interference type optical switches,

[0013] Input light whose phase is changed by a predetermined phase amount according to the position of the input light in the input stage of the input light is input, and the input light is transmitted according to the control electric signal.

[0014] <Effects of the Invention>

[0015] According to the disclosed technology, a technology for eliminating the phase difference between input light and output light in an optical computing device is provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a diagram showing an example of the overall configuration of an optical computing system.

[0017] Figure 2 : is a diagram showing an example of an MZI optical switch.

[0018] Figure 3 It is a diagram for explaining the phase shift of the MZI optical switch.

[0019] Figure 4 : is a diagram showing an example of an MZI optical switch.

[0020] Figure 5 2 is a diagram showing a configuration example of the light output device 200 .

[0021] Figure 6 2 is a diagram showing a configuration example of the control device 300 .

[0022] Figure 7 1 is a diagram showing a configuration including a plurality of optical computation devices 100 .

[0023] Figure 8 1 is a diagram showing a configuration including a plurality of optical computation devices 100 .

[0024] Fig. 9 1 is a diagram showing the structure of the optical computing device 100 in the first embodiment.

[0025] Fig.10 3 is a diagram showing the amount of prior change in the phase of input light in Example 1.

[0026] Fig.11 1 is a diagram showing the structure of an optical computing device 100 in the second embodiment.

[0027] Fig.12 This is a diagram showing the amount of prior change in the phase of input light in Example 2. DETAILED DESCRIPTION

[0028] Hereinafter, an embodiment of the present invention (this embodiment) will be described with reference to the drawings. The embodiment described below is merely an example, and the embodiment to which the present invention is applied is not limited to the following embodiment.

[0029] (Overview of Embodiments)

[0030] In this embodiment, in the optical computing device, the phase change (phase difference) of the output result corresponding to the path through which the light passes is calculated in advance based on the input value (control electrical signal) to the MZI optical switch, and the phase of the input light is set by taking the phase difference change into consideration, thereby making the phase difference of the input / output light 0 for any input value of the MZI optical switch.

[0031] This eliminates the need to change the phase of the output of the MZI optical switch by photoelectric conversion, and reduces delay and power consumption caused by photoelectric conversion. The technology of this embodiment can be applied to general memory operations that can extract and read arbitrary values ​​by looking up a table, for example.

[0032] (System configuration example)

[0033] Figure 1 FIG. 2 shows an example of the overall structure of the optical computing system of this embodiment. Figure 1 As shown, the optical computing system includes an optical computing device 100 , an optical output device 200 and a control device 300 .

[0034] The optical computing device 100 and the optical output device 200 are connected via a waveguide or an optical fiber. The control device 300 and the optical computing device 100 are connected via a wire or a network capable of transmitting electrical signals. Alternatively, the control device 300 and the optical output device 200 may be connected via a network or the like.

[0035] The light output device 200 inputs an optical signal to the optical computing device 100. The control device 300 inputs an electrical signal for controlling the optical computing device 100. The control device 300 can be realized in a typical computer having a CPU and a memory.

[0036] <About MZI Optical Switch>

[0037] The optical computing device 100 includes a multi-stage MZI optical switch. The connection structure of the MZI optical switch is described in the embodiment. Figure 2 An example of the structure of an MZI optical switch is shown.

[0038] like Figure 2 As shown, the MZI optical switch includes two optical couplers and a phase shifter. The phase shifter is arranged on one of the two paths (arms) connecting the two optical couplers. Figure 2 In the example of FIG. 1 , the phase shifter is provided on the lower path of the two paths.

[0039] In an MZI optical switch, the path of input light can be switched by turning on / off a voltage (control electric signal) applied to the path where the phase shifter is embedded. In this case, the control electric signal is "1" when the voltage is on, and "0" when the voltage is off.

[0040] like Figure 3 As shown, for example, when an optical signal is input to the upper path, when the control electric signal = 1, the optical signal is output from the straight path (upper side), and when the control electric signal = 0, the optical signal is output from the crossing path (lower side).

[0041] Similarly, when input light is input from the lower path, when the control electric signal = 1, the light signal is output from the straight path, and when the control electric signal = 0, the light signal is output from the crossing path.

[0042] In addition, if Figure 4 As shown, even when the phase shifter is provided in the upper path, similarly to the above, when the control electric signal = 1, the optical signal is output from the straight path, and when the control electric signal = 0, the optical signal is output from the crossing path.

[0043] It is known that when the input light crosses, the phase of the output light is shifted by π / 2 relative to the phase of the input light, regardless of the position of the phase shifter or the connection method of the multi-stage MZI optical switch (reference: Christi K. Madsen, Jian H. Zhao, "Optical Filter Design and Analysis: A Signal Processing Approach", Wiley, ISBN: 978-0-471-18373-0, June 1999, page 432). Figure 3 In the example on the lower side, the phase of the input light become And output (here, assume that the light is delayed by π / 2.) In addition, when the phase of the input light is And when it moves in a straight line, no phase difference occurs.

[0044] That is, the phase of the output light remains

[0045] <About Light Output Device 200 >

[0046] Figure 5 FIG. 2 shows a structural example of the light output device 200. Figure 5 As shown, the light output device 200 includes a phase quantity setting unit 210, a light source 220, and a phase adjustment unit 230 (eg, a phase modulator).

[0047] The number of light sources 220 may correspond to the number of lights input to the optical computing device 100 , or the light from one light source 220 may be divided into the number of lights corresponding to the number of lights input to the optical computing device 100 .

[0048] Furthermore, the number of phase adjustment units 230 may correspond to the number of input lights to the optical computation device 100 , or one phase adjustment unit 230 may be provided for a plurality of input lights so that the phases of the plurality of input lights are adjusted by the one phase adjustment unit 230 .

[0049] The phase amount setting unit 210 holds the phase amount changed with respect to the input light for each input position of the optical computing device 100, and notifies the phase amount to the phase adjustment unit 230. The phase adjustment unit 230 changes the phase amount of the input light for each input light based on the phase amount, and outputs the optical signal after the phase amount change to the optical computing device 100.

[0050] It should be noted that the phase quantity setting unit 210 in the light output device 200 may be provided in the control device 300. In this case, the configuration example of the control device 300 is as follows: Figure 6 As shown in Figure 6As shown, control device 300 includes phase amount setting unit 210 and optical computing device control unit 310. Optical computing device control unit 310 outputs a control electrical signal to optical computing device 100. Phase amount setting unit 210 notifies optical output device 200 of the phase amount to be changed for each input light.

[0051] In addition, a device including "optical computing device 100 and optical output device 200" may be referred to as an optical computing device. A device including "optical computing device 100 and phase quantity setting unit 210" may be referred to as an optical computing device. A device including "optical computing device 100 and phase adjustment unit 230" may be referred to as an optical computing device.

[0052] For example, the phase amount setting section 210 in the light output device 200 / control device 300 can be realized by causing a computer having a CPU and a memory to execute a program. The program can be stored in a non-temporary storage medium such as a portable memory.

[0053] <Multi-stage Structure of Optical Computing Device 100>

[0054] like Figure 7 As shown in FIG. 1 , the optical computing system may be configured to include a plurality of optical computing devices 100 in parallel. Figure 8 As shown, the optical computing system may be configured by connecting a plurality of stages in series and including a plurality of optical computing devices 100 in parallel.

[0055] The following, as Figure 1 The first and second embodiments are described as specific examples of the structure and operation of the optical computing device 100 in the system structure. The first and second embodiments are both examples of 4-bit table conversion, in which for a 4-bit input, from 2 4 Select 1 bit from among (=16) bits.

[0056] Table conversion means that the output value corresponding to the input value is set in the form of a table, and the output value corresponding to the input value is obtained from the table. n When any one of the input values ​​is input, the output value corresponding to the specified input value is obtained.

[0057] (Example 1)

[0058] In Example 1, reference Figure 2 In the MZI optical switch described above, the phase shifter is located on the lower side of the arm. In the first embodiment, the upper arm of the output path of each MZI optical switch included in the optical computing device 100 is connected to the input path of the next MZI optical switch.

[0059] Fig. 9 FIG. 2 shows the structure of the optical computing device 100 in Embodiment 1. Fig. 9 As shown, by connecting the MZI optical switches in four stages, a 4-bit table conversion operation is performed.

[0060] That is, the light path is selected according to the input value (control electric signal) {(x3, x2, x1, x0)} converted from the table. 4 Only one light is selected from the input lights for output (here, x0 is set as the least significant bit).

[0061] like Fig. 9 As shown, there are A class, B class, C class, and D class corresponding to the 4 bits of the input value of the table conversion. A class corresponds to x0, B class corresponds to x1, C class corresponds to x2, and D class corresponds to x3.

[0062] Class A has 8 MZI optical switches, and input light is input to each of the two input paths of each MZI optical switch. 16 input lights correspond to 16 bits of information, for example, input light means bit value = 1, and no input light means bit value = 0.

[0063] The upper arm on the output side of each MZI optical switch of the A class is connected to the arm (input path) on the input side of the B class. Fig. 9 As shown, the upper arm on the output side of the A-class MZI optical switch is connected to the upper arm on the input side of the B-class, the lower arm, and so on. The connection between the B-class and the C-class, and the connection between the C-class and the D-class are similar.

[0064] At this time, by presetting 4 The value in the table corresponding to the input light can be selected according to the value in the table. For example, when (x3,x2,x1,x0) = (1,1,1,1), it is equivalent to Fig. 9 The top input light "1" becomes the output light. That is, by presetting 4 The bit value corresponding to each of the values ​​(control electrical signals) is used as the input light, and the 2 4 The bit value corresponding to the value specified in the value (control electrical signal) is used as the output light (presence or absence).

[0065] As mentioned above, in an MZI optical switch, when light travels in a straight line, the phase does not change, but when light crosses, the phase changes by π / 2. That is, the phase of the output light changes according to the path that the input light travels. For example, when the phase of the input light is When the phase of the output light is relative to the uppermost input light ( Fig. 9 (1st)) remains unchanged (remains ).

[0066] On the other hand, when (x3, x2, x1, x0) = (1, 1, 1, 0), the second input light from the top is output ( Fig. 9 (No. 2)), but the phase of the output light is This is because the light crosses through the MZI optical switch only in the A-stage.

[0067] Therefore, in the technology according to the present embodiment, the phase of the input light is adjusted in advance according to the input position of the input light to the optical computing device 100. By changing the phase of the output light, the phase of the output light is kept constant regardless of the input light. It should be noted that it is assumed here that the phase of each input light before the change is

[0068] Specifically, in the case of 4-bit table conversion, the phase shift of the output light is (π / 2)×(4-HW(X)), so the phase shift of the input light is set by 2π-((π / 2)×(4-HW(X))). Here, HW represents the Hamming weight, showing X=(x3,x2,x1,x0). It should be noted that the Hamming weight is the number of 1s in the bit string. For example, when X=(1,1,1,1), HW(X)=4 and (π / 2)×(4-HW(X))=0. Therefore, the phase of the input light is In the case of performing an n-bit table conversion, that is, when switching from 2 n When outputting one input light from among the input lights, the phase of the input light to be output may be shifted by 2π-((π / 2)×(n-HW(X))).

[0069] Fig.10 The previous change amount of the phase of the input light according to the Hamming weight in the case of performing 4-bit table conversion is shown. For example, (x3, x2, x1, x0) = (0, 0, 0, 1) corresponds to Fig.10 The input light number in is 15. At this time, 2π-((π / 2)×(4-HW(X)))=2π-(3π / 2)=π / 2, so the phase of the input light is That is, the phase of the input light is maintained at In the case of Therefore, if the phase of the input light is The phase of the output light is As shown.

[0070] The method of changing the phase amount of the input light in advance can be to use 16 light sources to change the phase one by one, or to change the phase of the light divided into 16 parts from one light source by a phase modulator. In addition, the MZI optical switch can also be used to distribute the bits "1" and "0" from one light source, but in this case, the phase shift of the MZI optical switch based on the bit distribution needs to be considered.

[0071] For example, when using Figure 5 In the case of the light output device 200 shown in FIG. 1 , the phase quantity setting unit 210 holds in advance Fig.10 The phase adjustment unit 230 outputs the input light whose phase is changed by the notified phase amount to the corresponding input position in the optical computing device 100.

[0072] In the first embodiment, the phase shifter is located on the lower path of the MZI optical switch, and the upper path on the output side of each MZI optical switch is connected to the next stage, but this is only an example.

[0073] When the phase shifter is located on the path below the MZI optical switch and the path below the output side of each MZI optical switch is connected to the next stage, Fig.10 The number and phase amount of the input light are reversed. For example, when the number of the input light is 1, the phase amount to be changed is 0, when the number is 2, the phase amount to be changed is π / 2, and when the number is 3, the phase amount to be changed is π / 2. In addition, when the number of the input light is 14, the phase amount to be changed is π. When the number of the input light is 15, the phase amount to be changed is 3π / 2.

[0074] (Example 2)

[0075] Next, Example 2 is described. The following mainly describes the differences from Example 1. In Example 2, Figure 4 The phase shifters shown are located on the upper side of the arms of the MZI optical switch.

[0076] Fig.11 FIG. 2 shows the structure of the optical computing device 100 in Embodiment 2. Fig.11 As shown, in the second embodiment, in each stage of the optical computing device 100, the lower arm on the output side of the MZI optical switch is connected to the upper arm on the input side of the MZI optical switch of the next stage, and the upper arm on the output side of the MZI optical switch below it is connected to the lower arm on the input side of the MZI optical switch of the next stage. This connection structure is repeated sequentially from the top for the two MZI optical switches of each stage.

[0077] Fig.12 Shown according to Fig.11The Hamming weight in the structure shown is the amount of prior change in the phase of the input light. Fig.12 As shown, in Example 2, when the Hamming weight of the control electric signal is an odd number, the phase of the input light is shifted in advance. For example, when (x3, x2, x1, x0) = (1, 1, 1, 1) (corresponding to the 11th input light), the phase difference between the input and output lights is 0, so there is no need to shift the phase of the input light.

[0078] On the other hand, when (x3, x2, x1, x0) = (1, 1, 1, 0) (corresponding to the 12th input light), the phase difference between the input and output lights is π / 2. Therefore, the input light is shifted in advance. The method of changing the phase amount of the input light in advance is the same as that of the first embodiment.

[0079] (Summary of Examples, Effects)

[0080] As described above, regardless of the position of the phase shifter or the connection method of multiple MZI optical switches, by changing the phase of the input light in advance, the phase difference between the input and output lights can be made 0 (the phases of the input and output lights are made in phase). Although the case of 4-bit table conversion is shown in each embodiment, the same method can be used to perform calculations in the case of n-bit table conversion.

[0081] In addition, the above-mentioned installation method can be applied to S-box operation as a nonlinear operation of the encryption method. For example, according to the technology of this embodiment, it is possible to perform 8-bit S-box operation as a nonlinear operation of the encryption method AES and 4-bit S-box operation of the encryption method PRESENT. As a result, since the phase of the optical signal after the S-box operation does not change, the subsequent operation can be performed correctly.

[0082] That is, according to the technology of this embodiment, the phase difference of input / output light can be eliminated, so the operation after selecting an arbitrary value from the memory and the S-box operation of the encryption operation can be performed correctly. In addition, since no photoelectric conversion processing is required after the operation, the operation delay and power consumption can be reduced.

[0083] (Note)

[0084] This specification discloses an optical computing device and an optical computing method of at least the following items.

[0085] (Note 1)

[0086] An optical computing device, wherein:

[0087] The optical computing device comprises a plurality of stages having one or more Mach-Zehnder interference optical switches,

[0088] According to the position of the input light in the input stage of the input light, the input light whose phase is changed in advance by a predetermined phase amount is input, and the input light is transmitted according to the control electric signal.

[0089] (Note 2)

[0090] The optical computing device according to note 1, wherein:

[0091] The phase is changed in advance so that the phase difference between the input light and the output light output from the optical computation device becomes zero.

[0092] (Note 3)

[0093] An optical computing device according to Note 1 or 2, wherein:

[0094] The optical computing device has a plurality of stages corresponding to a plurality of bits constituting the control electrical signal.

[0095] The plurality of stages are connected so that, according to the control electrical signal, one input light from among the plurality of input lights in the input stage is selected and output as output light.

[0096] (Note 4)

[0097] An optical computing device according to any one of Notes 1 to 3, wherein:

[0098] The optical computing device further includes a phase adjustment unit configured to change a phase of the input light by a predetermined phase amount.

[0099] (Note 5)

[0100] An optical computing method is performed by an optical computing device including a plurality of stages having one or more Mach-Zehnder interference optical switches, wherein:

[0101] According to the position of the input light in the input stage of the input light, the input light whose phase is changed in advance by a predetermined phase amount is input, and the input light is transmitted according to the control electric signal.

[0102] As mentioned above, although this embodiment was described, this invention is not limited to this specific embodiment, Various deformation|transformation and change are possible within the range of the summary of this invention described in a claim.

[0103] Description of Reference Numerals

[0104] 100 Optical computing device

[0105] 200 Light output device

[0106] 210 Phase quantity setting unit

[0107] 220 Light Source

[0108] 230 Phase adjustment unit

[0109] 300 Control Device

[0110] 310: optical computing device control unit.

Claims

1. An optical computing device, wherein: The optical computing device comprises a plurality of stages having one or more Mach-Zehnder interference optical switches, According to the position of the input light in the input stage of the input light, the input light whose phase is changed in advance by a predetermined phase amount is input, and the input light is transmitted according to the control electric signal.

2. The optical computing device according to claim 1, wherein: The phase is changed in advance so that the phase difference between the input light and the output light output from the optical computation device becomes zero.

3. The optical computing device according to claim 1, wherein: The optical computing device has a plurality of stages corresponding to a plurality of bits constituting the control electrical signal. The plurality of stages are connected so that, according to the control electrical signal, one input light from among the plurality of input lights in the input stage is selected and output as output light.

4. The optical computing device according to claim 1, wherein: The optical computing device further includes a phase adjustment unit configured to change a phase of the input light by a predetermined phase amount.

5. An optical computing method, performed by an optical computing device comprising a plurality of stages having one or more Mach-Zehnder interference optical switches, wherein: According to the position of the input light in the input stage of the input light, the input light whose phase is changed in advance by a predetermined phase amount is input, and the input light is transmitted according to the control electric signal.

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