JP3297682B2 - Quantum operation device and quantum operation device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a quantum operation device used for a quantum computer or the like.

[0002]

2. Description of the Related Art In a quantum computer, it has been proposed to code an atom in a ground state as "0" and code an atom in an excited state as "1". Such one atom is called a quantum bit or a qubit as a minimum element of the arithmetic unit.

As a qubit, an apparatus as shown in FIG. 21 is embodied. JIChirac and Zoller
(P.Zoller) realized a controlled knot with this device. Also, Winland et al
Realized an exclusive OR with this device. This device has a structure in which four electrodes 2a to 2d are arranged in a vacuum vessel. A laser-cooled Wigner crystal is placed in this vacuum vessel, and a high-frequency voltage is applied to each of the electrodes 2a to 2d.
e is held between the electrodes 2a to 2d (called an ion and a wrap). By irradiating the trapped ions 4a to 4e with a laser beam, the excited state is changed to perform the calculation. The calculation is controlled by irradiating the laser with only the ions whose excitation state is to be changed. Thus, a quantum operation can be performed.

[0004]

However, the above apparatus has the following problems.

First, a vacuum vessel, a laser cooling device, and the like are required, and the device is large compared to the number of ions that can be trapped. For this reason, there has been a problem that it has not yet come out of the field of experiments and cannot be said to be a practical quantum calculator.

Second, the trapped ions must be irradiated with a laser beam in a targeted manner. Therefore, there is a problem that precise irradiation control is required and the apparatus becomes complicated.

Third, since the structure is such that ions are held in the space between the electrodes, it is difficult to fix the ions at a fixed position. For this reason, it has been difficult to accurately irradiate specific ions with laser light. In addition, as the number of ions increases, it becomes more difficult to fix ions at a fixed position, so that the number of operation bits is limited.

[0008] It is an object of the present invention to solve the above-mentioned problems and to provide a quantum operator which can be put to practical use.

[0009]

According to a first aspect of the present invention, there is provided a quantum operation device in which a metal atom or a molecule is included in an organic compound, and information is represented by an excited state of pi electrons.

According to a second aspect of the present invention, there is provided a quantum operation device including a plurality of quantum operation devices including a plurality of quantum operation devices including metal atoms or molecules in an organic compound, and an irradiation device for irradiating the quantum operation device group with light having a desired wavelength. Means for selectively determining the wavelength of light that excites pi electrons for each quantum operation element, and performing calculations by selecting the wavelength of light by the irradiation means. .

According to a third aspect of the present invention, the organic compound is a fullerene.

According to a fourth aspect of the present invention, the organic compound is a carbon nanotube.

The quantum operator according to claim 5 is characterized in that the fullerenes or carbon nanotubes are connected by an organic bridging molecule that is not a pi-electron conjugated system, thereby eliminating the quantum mechanical interaction.

The quantum operator according to claim 6 is characterized in that each fullerene or carbon nanotube is linked by a pi-electron conjugated organic bridging molecule to generate a quantum mechanical interaction.

According to a seventh aspect of the present invention, the fullerenes or carbon nanotubes connected by the organic bridging molecules, which are pi-electron conjugated systems, are formed between the fullerenes or carbon nanotubes by the side chains provided in the organic bridging molecules. It is characterized in that it is configured to select the strength of the quantum mechanical interaction.

According to another aspect of the present invention, there is provided a quantum operator having a plurality of quantum operators that can assume a continuous superimposed state from a ground state to an excited state by irradiating a laser beam. It is characterized in that the wavelength of the laser light whose state is to be changed is selectively determined for each arithmetic element, and the operation is performed by irradiating the laser light of the wavelength corresponding to the quantum arithmetic element whose state is to be changed. .

[0017]

According to the quantum operation device of the first aspect, a metal atom or a molecule is included in an organic compound, and information is represented by an excited state of pi electrons. Therefore, it is possible to collectively handle metal atoms (molecules) and organic compounds as one qubit. Further, since the qubit can be physically held at a predetermined position, a device for holding the electrodes and the like is not required.

According to a second aspect of the present invention, the quantum operator selectively determines the wavelength of the light for exciting the pi electrons for each quantum operation element, and performs the operation by selecting the wavelength of the light by the irradiation means. ing. Therefore, it is possible to selectively perform calculations only on necessary elements without changing the irradiation position of light. Further, by changing the wavelength, the content of the calculation can be changed.

According to a third aspect of the present invention, the organic compound is a fullerene. That is, since the fullerene is solid by including metal atoms or molecules in the fullerene, it is not necessary to perform laser cooling.

According to a fourth aspect of the present invention, the organic compound is a carbon nanotube. That is, since the carbon nanotube is solid by including metal atoms or molecules in the carbon nanotube, it is not necessary to perform laser cooling.

According to a seventh aspect of the present invention, the fullerenes or carbon nanotubes connected by the organic bridging molecules which are pi-electron conjugated systems are connected to each other by the side chains provided in the organic bridging molecules. It is configured to select the strength of the quantum mechanical interaction. Therefore, it is possible to easily form a quantum operator that performs an operation based on the quantum mechanical interaction.

According to another aspect of the present invention, there is provided a quantum operation device wherein a wavelength of a laser beam whose state is to be changed is selectively determined for each quantum operation element, and a laser having a wavelength corresponding to the quantum operation element whose state is to be changed is provided. The calculation is performed by irradiating light. Therefore, it is possible to selectively perform calculations only on necessary elements without changing the irradiation position of light.

[0023]

FIG. 1 shows an example of the structure of a qubit (quantum operation element) according to an embodiment of the present invention. The structure is such that lanthanum La is included in a spherical shell-shaped carbon cage. In the example of FIG. 1, since lanthanum La is contained in a cage made of 82 carbon C, La @ C ₈₂
It expresses. Note that @ is a symbol indicating inclusion. The chemical formula of La @ C ₈₂ is shown in FIG. 1A, and the structure is shown in FIG. 1B.

This La @ C ₈₂ has an electronic structure of La ³⁺ @C ₈₂ ^3- . In addition, even if it loses an electron and becomes a cation [La @ C ₈₂ ] ^- , it receives an electron and becomes an anion [La @ C ₈₂ ] ⁺ ,
The charge on the metal is almost the same as the neutral one, and electron transfer occurs on fullerene. In other words, La @ C ₈₂ can be regarded as a superatom in which metal is a positive charge nucleus and pi electrons on fullerene are electrons.

When the metal-encapsulated fullerene La @ C ₈₂ is irradiated with laser light of a predetermined wavelength, the excited state of the superatom pi electrons changes according to the irradiation energy as shown in FIG. That is, a transition between the ground state and the excited state occurs at Sin ² according to the irradiation energy. Therefore, in order to change the ground state to the excited state (or to change the excited state to the ground state), a laser beam (referred to as a π pulse) having an energy corresponding to the π cycle of the square of the sine function is applied. do it.

In order to change the excited state of the metal-encapsulated fullerene La @ C ₈₂ , a laser beam having a specific wavelength must be used. That is, the excitation state does not change with laser light of different wavelengths regardless of the irradiation energy. As described above, the metal-encapsulated fullerene has wavelength selectivity to laser light. The intrinsic wavelength of the metal-encapsulated fullerene (the wavelength of the laser beam that can change the excited state) can be selected by a combination of the type of the included metal, the number of the included metals, the carbon number of the fullerene, and the like.

The metal-encapsulated fullerene is represented by M = C ₆₀ , M = C
a, Ba, Sr, Na, U can be synthesized, and 3 such as Sc and Y
It can also be synthesized by a combination of a group ₈₂ metal element or a rare earth element such as Gd with C82. In addition, Sc ₂ @C ₈₄ , SC ₃ @C ₈₂ , La ₂ @C _80, etc. containing a plurality of metal atoms or molecules can also be synthesized. As described above, many types of metal-encapsulated fullerenes can be manufactured, and each of them has a different intrinsic wavelength. Therefore, it is a preferable element for obtaining a multi-bit quantum operation device.

In the above description, the metal-encapsulated fullerene has been described. However, a metal may be included in a carbon nanotube in which hollow graphite is arranged in the center of the fullerene (see FIG. 1C). If the metal-encapsulated carbon nanotube is used, one having various intrinsic wavelengths can be easily obtained by changing the length of the graphite at the center. The method for producing metal-encapsulated fullerenes and metal-encapsulated carbon nanotubes is described in "Laserevapolation meth
od ", RESmalley, Acc Chem. Res. 25, 98 (1992):" Resi
stance evapolation method ", ASKoch, KCKhemani
& F. Wudl, J. Org. Chem., 56, 4593 (1991): "Plasma induc
tion method ", G. Peters & M. Jansen, 31,223 (1992).

By using a plurality of qubits made of the above-mentioned metal-encapsulated fullerenes and metal-encapsulated carbon nanotubes, a quantum operator can be constructed. In this case, the degree of the quantum mechanical interaction between the qubits can be set by the connection method, the connection distance, and the like. For example, FIG.
As shown in D, when a plurality of metals are included in the carbon nanotube, each qubit corresponding to each metal is connected by a pi-electron conjugate system. Therefore, each qubit is
It will have a quantum mechanical interaction.

As shown in FIG. 20A, a carbon pipe 10 which is a pi-electron conjugated cross-linking molecule is provided between fullerenes 100 and 102 (or carbon nanotubes).
When they are connected by 4th magnitude, they have quantum mechanical interaction.

On the other hand, as shown in FIG. 20B, when fullerenes 100 and 102 (or carbon nanotubes) are connected by a 106 alkyl chain which is not pi-electron conjugate, there is no quantum mechanical interaction.

Furthermore, the strength of the quantum mechanical interaction between the two qubits 100 and 102 in the structure of FIG.
A cross-linking molecule can be provided with a side chain (cl) or the like and adjusted by the number thereof (see FIG. 20C).

Next, a description will be given of a quantum computing device (quantum computer) constituted by using a plurality of the above quantum computing devices. First, a Feynman-type quantum computer having no quantum mechanical interaction between qubits, except for the case where laser light is irradiated, will be described. A quantum computer having a quantum mechanical interaction is described below.

FIG. 3 shows the structure of a Feynman quantum computer. On a substrate 6 (preferably a glass substrate, transparent ceramics or the like), n metal-encapsulated fullerenes (and metal-encapsulated carbon nanotubes) are mounted as qubits 8a to 8n. Around these
The chip is solidified by an organic polymer, a low melting point glass or the like (not shown). Each qubit 8a-8n
Are connected by cylindrical graphite 16 as needed. In FIG. 3, the qubits 8a to 8n are arranged linearly in a line, but they may be arranged two-dimensionally or three-dimensionally. The arrangement may be determined from the relationship with the interaction between qubits and the like.

Above these qubits 8a to 8n, a laser emitting section 12 and a homodyne detection circuit 14 are provided. Further, a control circuit 10 for controlling the laser emitting section 12 and the homodyne detection circuit 14 is provided. FIG. 4 shows a laser light emitting unit 12 and a homodyne detection circuit 1.
4. Details of the control circuit 10 will be described. The laser emitting unit 12
It has m laser emitters 12a to 12m. Each of the laser light emitters 12a to 12m irradiates laser light of a different wavelength to the entire qubit 8a to 8n. The irradiation timing, irradiation time, and the like of each of the light emitters 12a to 12m are controlled by the light emission control circuit 18. The homodyne detection circuit 14 includes the laser emitting unit 1
2 outputs an electric signal corresponding to the phase difference between the light emitted from 2 and the light emitted from the qubits 8a to 8n. The integrated control circuit 22 controls the light emission control circuit 18 to determine which of the light emitters 12a to 12m emit light, and receives the phase difference signal from the homodyne detection circuit 14. Thereby, the integrated control circuit 22 sets the qubit 8
It controls writing, calculation, and reading of information from a to 8n.

The quantum computer calculates the intrinsic wavelength of each of the qubits 8a to 8n, the energy in the ground state and the excited state, the wavelength of the laser light to be irradiated, and the mutual energy between the qubits 8a to 8n when the laser light is irradiated. The operation determines the content of the operation. Next, the setting of the operation content will be described.

First, the case where there is one qubit as shown in FIG. 5A will be described. The excited state is “1”, the energy is E _A ¹ , the ground state is “0”, and the energy is E _A ⁰ . At this time, the Hamiltonian H is represented by the following equation.

[0038]

(Equation 1)

If the spin is not considered, the Hamiltonian H is given by the following equation.

[0040]

(Equation 2)

The energy hυ (π pulse) for changing from the ground state to the excited state (for changing from the excited state to the ground state) is equal to the difference between the two energies.

[0042]

(Equation 3)

Here, υ is the natural frequency of the qubit. Every time a laser beam having an energy of hυ is irradiated, the state changes alternately between a ground state and an excited state.
The energies in the ground state and the excited state are as follows.

[0044]

(Equation 4)

[0045]

(Equation 5)

As described above, when one qubit is irradiated with laser light having a wavelength equal to its natural frequency υ while controlling the time so that the energy becomes hυ (irradiation of π pulse) ), NOT operation can be performed.
Next, as shown in FIG. 5B, two qubits A and B
The case where there is an interaction between the two qubits will be described. Such a state is caused by the qubits 8 connected by cylindrical graphite 16 as shown in FIG.
a and 8b.

The Hamiltonian H in this case is expressed by the following equation.

[0048]

(Equation 6)

Here, V ^AB is energy due to the interaction between the two qubits. Also, where

[0050]

(Equation 7)

Is as follows.

The energy when qubits A and B are both in the ground state is expressed by the following equation.

[0053]

(Equation 8)

Similarly, when the qubit A is in the excited state and the qubit B is in the ground state, the energy is given by the following equation (9).
The energy when the qubit A is in the ground state and the qubit B is in the excited state is given by equation (10), and the energy when both qubits A and B are in the excited state is given by equation (1).
It is represented by 1).

[0055]

(Equation 9)

[0056]

(Equation 10)

[0057]

[Equation 11]

However,

[0059]

(Equation 12)

Therefore, the energy required for the qubits A and B to change from one state to another state is given by the following equation (13).
From equation (17).

[0061]

(Equation 13)

[0062]

[Equation 14]

[0063]

(Equation 15)

[0064]

(Equation 16)

[0065]

[Equation 17]

As is clear from the above equations, the energy (wavelength) required to change from one state to another state is different. However, each change is reversible.

[0067] Here, focusing on the equation (16), using the energy hv _1B when the ([pi pulsed laser beam of frequency upsilon _1B) 6, can be realized Controlled knot shown in Fig. In FIG. 7, AB indicates the state of qubits A and B before laser light irradiation, and A'B 'indicates the state of qubits A and B after laser light irradiation. When AB is “00” (that is, when both qubits are in the ground state), the state changes when any one of the laser beams having the frequencies υ _A , υ _B , and υ _AB is irradiated (Equation (2)). (13) (14) (15)). Therefore, in this case, the state does not change even when irradiated with a laser beam of frequency upsilon _1B. Similarly, AB is "01"
If the state does not change even when irradiated with a laser beam of frequency upsilon _1B.

On the other hand, when AB is "10", the frequency υ
_When the laser beam of _1B is irradiated, the state changes to “11” (see equation (16)). Similarly, when the laser beam having the frequency レ ー ザ_1B is applied when AB is “11”, the state changes to “10” (see equation (16)). Therefore, by using a laser beam having a frequency of 光_1B , an operation as a reversible control knot using the qubit A as a control bit can be performed as shown in FIG.

[0069] Further, if a laser beam of a frequency upsilon _A1,
A control knot operation using the qubit B as a control bit can be performed.

As described above, in the present invention, by changing the frequency, it is possible to change the operation content by the same qubit. Therefore, any logical operation can be performed by increasing the number of qubits. In the following, the controlled knot is described, but all logical operations such as AND and OR can be performed.

Next, as shown in FIG. 5C, there are three qubits A, B, and C, and there is interaction between qubits A and B, between qubits B and C, and between qubits C and A. The case will be described.

The Hamiltonian H in this case is expressed by the following equation.

[0073]

(Equation 18)

Here, V ^AB V ^BC is energy due to interaction between qubits. From this, the following equation is obtained in the same manner as described above (other cases are omitted).

[0075]

[Equation 19]

[0076] Accordingly, by irradiating a laser beam of energy hv _11C, qubit A, B can be performed calculation of Controlled Controlled knots to control bits (see FIG. 8, FIG. 9).

Next, a case where an operation as a half adder is performed using three qubits A, B, and C shown in FIG. 5C will be described. The half adder, as shown in FIG.
This can be achieved with a controlled knot and a controlled knot. The inputs to this half adder are A and B. Note that C is set to “0”.

In order to assign desired values to A, B, and C, the following is performed. First, the qubits A, B, and C are cooled to a ground state (that is, “0”). Next, A,
A laser beam having energy hυ ^ABC _ijk for making B and C desired values is irradiated (see FIG. 11A). Next, the calculation of the controlled knot is performed.
This may be performed by irradiating a laser beam having energy of h 光^C ₁₁₁ as described above. Then, by irradiating a laser beam having an energy of hυ ^B ₁₁₀ + hυ ^B _111, performs Controlled knots. As a result, SU is added to qubit B.
M appears in the qubit C as CARRY. The qubit A shows the content that was initially set as it is. The half adder can obtain an input number from the operation result (reversible) by performing an operation process reverse to the above.

FIG. 12 shows the operation of the half adder for all the numbers of A and B.

Next, the structure for the pre-adder is shown in FIG. Here, four qubits A, B, C, and D interacting with each other are used. Such a structure
For example, as shown in FIG. 14A, qubits A, B, C, and D are arranged on the vertices of a cube, and as shown in FIG. 14B, each qubit A, B, C, and D is placed in a cylindrical graphite 16. It can be realized by connecting with.

The Hamiltonian is represented by the following equation.

[0082]

(Equation 20)

Using the above four qubits, a full adder operation as shown in FIG. 15 can be performed. The inputs of the full adder are A, B, and C, and D is always "0".

If the full adders as shown in FIG. 13 are connected as shown in FIG. 16, an arithmetic unit can be formed.
The Hamiltonian of this is shown in the following equation.

[0085]

(Equation 21)

FIG. 17 shows an operation process when 5 + 3 is executed by this arithmetic unit. “5” is assigned to the qubits A (1), A (2), and A (3). "3"
The qubits C (1) and C (2) are set. Here, by irradiating the energy hυ ^(1,2) , the qubit D
Data is transferred (copied) from (1) to the qubit B (2). The operation result appears in C (1), C (2), C (3), and C (4).

Note that the final reading of the result is a laser beam having the natural frequency of the qubit to be read, and
This is performed by irradiating a laser beam having a pulse area that is half of the π pulse. Thus, if the qubit is in the excited state, the qubit emits laser light having the same phase as the irradiated laser light. In the ground state, the qubit emits laser light having a phase shift of π. Therefore, as shown in FIG. 3, the phase difference can be detected by the homodyne detection circuit 14, and the state of the qubit (that is, information of “0” or “1”) can be known.

In the above embodiment, the information placed in the qubit is two information, the excited state and the ground state.
By irradiating a π pulse (α is an arbitrary real number), an arbitrary superimposed state from the ground state to the excited state may be obtained. Thus, not only digital operation but also analog operation can be performed. In this case, in reading out the final result, the degree of the superposition can be obtained by obtaining the magnitude of the phase difference.

Next, regardless of the presence or absence of laser light irradiation,
A quantum computer having a quantum mechanical interaction between qubits will be described. Such a quantum computer automatically proceeds with the operation by the quantum mechanical interaction between qubits.

For example, as shown in FIG. 18, suppose that there is a maze having one entrance and three exits (details of the maze are omitted). This is effective when calculating which exit of the maze leads to the entrance and which exit has the shortest distance.

A qubit is arranged at each corner and branch point of the maze. Note that at least the qubit A corresponding to the entrance, the qubit X corresponding to the exit α, the qubit Y corresponding to the exit β, the qubit Z corresponding to the exit γ, and other qubit groups have different natural vibrations. It is preferable to have a number. The arranged qubits are connected with an interaction inversely proportional to the distance of the maze. In other words, the shorter the distance,
Increase interaction. Note that corners and branch points that are not directly connected on the maze have no interaction between qubits (see qubits A and F).

After the preparation as described above, all the qubits are cooled to a ground state. Next, laser light is irradiated so that only the qubit A corresponding to the entrance is in an excited state. The excited state of qubit A influences an adjacent qubit by interaction and makes it an excited state. This is repeated, and the excited state is sequentially transmitted. Further, the transmission speed is proportional to the magnitude of the interaction.

Therefore, by observing which of the qubits X, Y, and Z corresponding to the exit changes to the excited state first, the nearest exit can be known. Further, it can be known that the outlet corresponding to the qubit that does not change to the excited state is not connected to the entrance.

[Brief description of the drawings]

FIG. 1 is a diagram showing a structure of a qubit according to an embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between irradiation energy, a ground state, and an excited state.

FIG. 3 is a diagram showing a configuration of a quantum operator according to an embodiment of the present invention.

FIG. 4 is a block diagram of the quantum calculator of FIG. 3;

FIG. 5 is a diagram illustrating a connection example of qubits.

FIG. 6 is a diagram symbolically showing a control to knot.

FIG. 7 is a truth table of a controlled knot.

FIG. 8 is a diagram symbolically showing a control to controlled knot.

FIG. 9 is a truth table of a controlled knot.

FIG. 10 is a diagram showing a half adder symbolized.

FIG. 11 shows the qubit shown in FIG.
FIG. 6 is a diagram showing a laser beam irradiation process for realizing the half adder of FIG.

FIG. 12 corresponds to each laser beam irradiation shown in FIG.
It is a figure showing a state change of a qubit.

FIG. 13 is a diagram illustrating a case in which four qubits are connected to interact with each other;

FIG. 14 is a diagram showing an example of the structure of a qubit for obtaining the configuration shown in FIG.

FIG. 15 is a diagram showing a full adder symbolized.

FIG. 16 shows an arithmetic unit configured by connecting the full adders of FIG. 15;

FIG. 17 is a diagram illustrating an operation process of the arithmetic unit in FIG. 16;

FIG. 18 illustrates a maze with one entrance and three exits.

FIG. 19 is a diagram showing qubits configured to obtain a solution to the maze of FIG. 18;

FIG. 20 is a diagram for explaining selection of a quantum mechanical interaction between qubits.

FIG. 21 is a diagram showing a conventional ion trap type quantum operator.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Koji Ota 1-8-31 Midorioka, Ikeda-shi, Osaka Examiner, Yoshiyuki Kusaka, Osaka Institute of Industrial Technology Research Institute (56) References JP-A-8-114824 ( JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G06E 1/00 G06E 3/00 G02F 3/00

Claims (8)

(57) [Claims] 1. A quantum operation element comprising a metal atom or a molecule contained in an organic compound and expressing information by an excited state of pi electrons. 2. A quantum operation element group having a plurality of quantum operation elements each including a metal atom or a molecule in an organic compound, and irradiation means for irradiating the quantum operation element group with light having a desired wavelength. A quantum arithmetic unit characterized in that it is configured to selectively determine a wavelength of light for exciting pi electrons for each element and to perform an arithmetic operation by selecting a wavelength of light by an irradiation unit. 3. The quantum operation device according to claim 1, wherein the organic compound is fullerene. 4. The quantum operation device according to claim 1, wherein the organic compound is a carbon nanotube. 5. The quantum operator according to claim 3, wherein each fullerene or carbon nanotube is connected by an organic bridging molecule that is not a pi-electron conjugated system to eliminate quantum mechanical interaction. Arithmetic unit. 6. The quantum operator according to claim 3 or 4, wherein each fullerene or carbon nanotube is connected by an organic bridging molecule that is a pi-electron conjugated system to generate a quantum mechanical interaction. Characteristic quantum arithmetic unit. 7. The quantum operator according to claim 6, wherein each fullerene or carbon nanotube is connected to a corresponding one of the fullerenes or carbon nanotubes connected by an organic bridging molecule that is a pi-electron conjugated system. A quantum operator configured to select the strength of a quantum mechanical interaction between the quantum operators. 8. A quantum computing device having a plurality of quantum computing elements capable of continuously superimposing from a ground state to an excited state by irradiation with a laser beam, wherein the state is determined for each quantum computing element. A quantum arithmetic unit, wherein a wavelength of a laser beam to be changed is selectively determined, and a calculation is performed by irradiating a laser beam having a wavelength corresponding to a quantum arithmetic element whose state is to be changed.