JP4845375B2 - Quantum device, control method thereof, and manufacturing method thereof - Google Patents

Description

  The present invention relates to a quantum device including quantum qubits, a control method thereof, and a manufacturing method thereof.

Various methods for forming quantum qubits (bits) constituting a quantum computer have been studied. Nuclear spins are preferred as quantum qubit candidates. This is because the decoherence time is as long as 10 ⁻² seconds to 10 ⁸ seconds. Therefore, verification has been conducted on a nuclear spin qubit in a liquid state (Patent Document 1). This document describes the operation of a nuclear spin quantum computer in a solvent in which a molecule containing a large amount of atoms having a nuclear spin of 1/2 (eg, ¹ H, ¹³ C, ¹⁹ F, ¹⁵ N and ³¹ P) is dissolved. Is described as causing nuclear magnetic resonance (NMR). Each atom having a 1/2 nuclear spin operates as a qubit. Further, in the molecule, since the resonance frequencies are different between atoms located at different sites, each qubit can be operated independently. According to such a technique, it is possible to perform quantum Fourier transform and factorization of small prime numbers. However, it is difficult to reduce the size of the device in a liquid state.

Therefore, there is a need for solid state nuclear spin qubits. For example, Non-Patent Document 2 proposes a nuclear spin quantum computer using Si as a main material. In this quantum computer, ³¹ P atoms having a nuclear spin of 1/2 in ²⁸ Si are used as qubits, and rotation of nuclear spins is performed by a combination of electrostatic field application and resonance radio frequency (rf). It has been broken. Further, a quantum gate composed of two qubits is performed by a combination of an electrostatic gate of adjacent ³¹ P atoms and a resonance radio frequency.

  However, in such a quantum computer, it is very difficult to accurately operate an electron cloud using an electrostatic gate. It is also extremely difficult to accurately place nuclear spin atoms one by one in each qubit.

JP 2003-338618 A I. L. Chuang et al., Nature 393, 143 (1998) B. E. Kane, Nature 393, 133 (1998)

  An object of the present invention is to provide a quantum device that can be easily controlled even in a solid state, a control method thereof, and a manufacturing method thereof.

  As a result of intensive studies to solve the above problems, the present inventor has come up with various aspects of the invention described below.

The quantum device according to the present invention has quantum qubits. The quantum qubit includes a quantum ring, a nuclear spin composed of a single impurity atom surrounded by the quantum ring, and a quantum dot adjacent to the quantum ring.

The quantum device control method according to the present invention includes a quantum ring, a nuclear spin composed of a single impurity atom surrounded by the quantum ring, a quantum dot adjacent to the quantum ring, and a quantum qubit including a quantum qubit. Intended for a method of controlling a device. Then, electrons existing in the quantum ring are moved into the quantum dots by optical excitation.

  In the first method for producing a quantum device according to the present invention, in a water-containing atmosphere, a probe of an atomic force microscope to which a negative bias is applied is brought into contact with the surface of the semiconductor substrate, so that the surface of the semiconductor substrate is After forming the annular oxide film and the dot-like oxide film adjacent to each other, the annular oxide film and the dot-like oxide film are removed, so that an annular groove and a dot-like film are formed on the surface of the semiconductor substrate. A depression is formed. Next, a quantum film and a quantum dot are formed by growing a semiconductor film in the groove and the recess. However, before the step of forming the groove and the depression, a single impurity atom is attached to the center of the annular oxide film.

In the second method for manufacturing a quantum device according to the present invention, after introducing a single impurity atom at a position where a quantum ring is to be formed on the surface of the semiconductor substrate, a negative bias is applied in an atmosphere containing water. An applied atomic force microscope probe is brought into contact with the surface of the semiconductor substrate, and an annular oxide film and a dotted oxide film are formed adjacent to each other on the surface of the semiconductor substrate. Next, the periphery of the annular oxide film and the dotted oxide film is oxidized. Next, the annular oxide film and the dotted oxide film are removed, and the oxidized portion around the annular oxide film is removed, thereby forming an annular groove and a dotted depression on the surface of the semiconductor substrate. And a quantum ring and a quantum dot are formed by growing a semiconductor film in the said groove | channel and a hollow.

  According to the present invention, even in a solid state quantum device, the quantum ring and the quantum dot are adjacent to each other, so that the nuclear spin can be easily controlled. For example, if an electron is in a quantum ring, a hyperfine interaction between a nuclear spin and an electron spin works. In addition, if the electrons are moved to the quantum dots, the hyperfine interaction can be disabled. And since the rotation of the nuclear spin can be controlled based on, for example, the NMR frequency, the control is easy. Furthermore, since movement of electrons can be controlled by optical pulses, decoherence can be made difficult to occur. Furthermore, such a structure can be easily formed using an AFM probe or the like.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a schematic diagram illustrating a quantum device according to an embodiment of the present invention.

In the quantum device according to the present embodiment, a plurality of quantum rings 1 are arranged in one direction on a semiconductor substrate. In addition, one ³¹ P atom 2 exists in the center of each quantum ring 1. Further, one quantum dot 3 is formed adjacent to each quantum ring 1. The semiconductor substrate is obtained, for example, by growing a Si _1-x Ge _x epitaxial layer having a thickness of about 100 nm on a Si substrate. The quantum ring 1 is composed of, for example, a ring-shaped Si or Si _1-x Ge _x film (where x is smaller than that of the epitaxial layer). The quantum dots 3 are composed of, for example, dotted Si or Si _1-x Ge _x (where x is smaller than that of the epitaxial layer). ³¹ P atom 2 is introduced, for example, in the formation process of quantum ring 1. The quantum ring 1 has a diameter of about 50 nm or less, preferably about 10 nm. The quantum dots 3 have a diameter of about 40 nm or less, preferably about 10 nm. In addition, it is preferable to use what does not have a nuclear spin as Si and Ge which comprise these.

In this embodiment, a quantum qubit 5 is composed of the quantum ring 1, ³¹ P atom 2 and the quantum dot 3, and the quantum qubit 5 inevitably has electrons 4 due to the presence of ³¹ P atom 2. It is included. The electrons 4 are confined in the quantum ring 1 or the quantum dots 3.

  In the quantum device configured as described above, an effective hyperfine interaction works between the electron spin and the nuclear spin. For this reason, the spin state can be controlled by applying an optical pulse, rather than applying an electric field from an external electrostatic gate or the like as in the prior art to manipulate electrons. Further, the electrons 4 are not affected by the voltage applied from the outside. For this reason, operational stability is improved.

Here, an example of the operation of the quantum device will be described. In the state after manufacture, the electrons 4 exist in the quantum ring 1. When a predetermined optical pulse is applied to each quantum qubit 5 in this state, the electrons 4 are excited and move from the quantum ring 1 to the quantum dots 3 as shown in FIG. As a result, the nuclear spin of ³¹ P atom 2 is released from the interaction with the spin of electron 4. This state is maintained for the time that the coherent state is maintained.

Then, as shown in FIG. 1, for example, in an NMR apparatus, nuclear spins can be aligned by applying an rf pulse of frequency ν to all quantum qubits 5 and applying a magnetic field. This is because the resonance radio frequencies of all the quantum qubits 5 are equal to each other. Here, the frequency ν is represented by “ν = 2 g _n μ _n B / h”. Where B is the strength of the applied magnetic field, μ _n is the nuclear magneton, g _n is the nuclear g factor, and h is the Planck's constant. This state is a standby state in this embodiment.

For example, by applying an optical pulse to one quantum qubit 5, the electrons 4 existing in the quantum dots 3 in the quantum qubit 5 can be returned into the quantum ring 1. At this time, the optical pulse may be applied to another quantum qubit 5 adjacent to the quantum qubit 5 to be manipulated, but by appropriately adjusting the wavelength, Incorrect operation can be avoided. As shown in FIG. 3, when the electron 4 returns to the quantum ring 1, a hyperfine interaction starts to work between the spin of the electron 4 and the nuclear spin of the ³¹ P atom 2. As a result, the NMR frequency in the quantum qubit 5 changes. The resonance frequency ν _A after the change is obtained from “hν _A = 2g _n μ _n B + 2A + 2A ² / μ _B B”. Where A is the hyperfine interaction energy and μ _B is the Bohr magneton. Note that the hyperfine interaction energy A depends on the wave function of electrons overlapping the nucleus.

Such operation of a single quantum qubit 5 makes it possible to selectively rotate one nuclear spin as shown in FIG. That is, by applying an NMR pulse having a resonance frequency ν _A , a single nuclear spin can be rotated without rotating the nuclear spins in the remaining quantum qubits 5. Such nuclear spin rotation is completed by the movement of the electrons 4 and the end of the NMR pulse.

Further, for example, by applying an optical pulse to two adjacent quantum qubits 5, the electrons 4 existing in the quantum dots 3 in these two quantum qubits 5 are returned to the quantum ring 1. Can do. When such an operation is performed, exchange coupling between two quantum qubits 5 can be used. As described above, in these quantum qubits 5, a hyperfine interaction acts between the spin of the electron 4 and the nuclear spin. Further, since the quantum rings 1 are close to each other between these two quantum qubits 5, as shown in FIG. 4, the spins of the two electrons 4 are coupled to each other by exchange interaction. For this reason, when an appropriate magnetic field is applied, the nuclear spins in the two adjacent quantum qubits 5 are also coupled to each other by the exchange interaction of electron spins and the hyperfine interaction between electron spins and nuclear spins. Can be made. That is, the nuclear spin of two ³¹ P atoms can be rotated. An appropriate magnetic field can be obtained based on, for example, the exchange energy of electrons.

  Then, after performing the operation as described above, by applying the optical pulse again and returning the electrons 4 into the quantum dots 3, it is possible to cut the coupling and return to the standby state.

  According to the present embodiment, an appropriate nuclear spin operation can be easily performed in a solid state quantum device.

  Next, a method for manufacturing the quantum device as described above will be described. FIG. 5 is a schematic view showing a method of forming an oxide film using AFM in the order of steps. FIG. 6 is a cross-sectional view showing the method of forming an oxide film in the order of steps.

As shown in FIG. 5, in the atmosphere, a negative bias is applied to the probe 22 of an atomic force microscope (AFM), and a positive bias is applied to the semiconductor substrate 10 such as a SiGe substrate. When the probe 22 is brought close to the semiconductor substrate 10 until the distance between them becomes about 5 nm, the surface of the semiconductor substrate 10 is partially oxidized, and the spherical or ellipsoidal oxide film 11 is formed. This is because water (H ₂ O) in the atmosphere is decomposed near the probe 22 and OH ⁻ acts as an oxidizing agent. That is, as shown in FIG. 6A, after a minute ellipsoidal oxide film 11 is generated, the oxide film 11 grows as shown in FIG. 6B.

  Further, when the probe 22 is brought closer to the semiconductor substrate 10, for example, when the interval is set to about 2 nm, first, the growth is performed until the oxide film 12 comes into contact with the probe 22 as shown in FIG. To do. Thereafter, the oxide film 12 cannot be grown in the vertical direction as it is, but starts to grow outward, and the oxide film 12 surrounds the probe 22 as shown in FIG. To grow.

  When the probe 22 is brought into contact with the semiconductor substrate 10, a donut-shaped oxide film 13 is generated from the beginning as shown in FIG. 8A, and this is shown in FIG. 8B. It grows in a donut shape. Note that the oxide film 13 does not grow in the portion where the probe 22 is in contact.

  Therefore, as shown in FIGS. 8A and 8B, if the semiconductor substrate 10 is oxidized while the probe 22 is in contact with the semiconductor substrate 10, the size is almost the same as that of the oxide film 11 shown in FIG. A ring-shaped oxide film 13 can be obtained.

Note that the oxidation reaction of the surface of the semiconductor substrate 10 is not limited to the amount of H ₂ O but the strength of the external electric field while the oxide film is growing in an ellipsoidal shape. When it starts to grow into a donut shape, the amount of H ₂ O becomes the rate-limiting factor.

  The formation of quantum dots and quantum rings can be performed based on the formation of the oxide film as described above. 9A to 9D are cross-sectional views illustrating a method for manufacturing a quantum device according to an embodiment of the present invention in the order of steps. However, FIGS. 9A to 9D show only the quantum ring portion. FIG. 11 is a plan view corresponding to FIG. 9C, and FIG. 9C shows a cross section taken along the line II in FIG.

In this method, first, as shown in FIG. 9A, the AFM probe 22 is brought into contact with the surface of the semiconductor substrate 10a, a negative bias is applied to the probe 22, and a positive bias is applied to the semiconductor substrate 10a. By applying, a donut-shaped oxide film 13 is formed in a region where the quantum ring 1 is to be formed. However, in this embodiment, before forming the oxide film 13, metal atoms used as a dopant are attached to the tip of the probe 22. An example of such a metal atom is ³¹ P atom. Such a metal atom is released when a positive bias is applied to the probe 22, but the bias applied to the probe 22 during formation of the oxide film 13 is negative, so that the metal atom falls off. There is no. Further, the probe 22 itself may contain a metal atom used as a dopant.

  Further, before or after the oxide film 13 is formed, a dot-shaped oxide film (not shown) is formed in the region where the quantum dots 3 are to be formed.

  Next, as shown in FIG. 9A, after the probe 22 is separated from the surface of the semiconductor substrate 10a, a positive bias is applied to the probe 22 to convert the positive dopant 55 into a ring-shaped oxidation. It is made to adhere to the center of the film 13, that is, the part where the oxide film 13 is not formed. At this time, by adjusting the applied voltage and the applied time, the adhering dopant 55 can be made to be only one atom.

  Note that the oxide film 13 may be formed after the dopant 55 is deposited. In consideration of the adhesion stability of the dopant 55, it is preferable that the dopant 55 is adhered and further annealed before the oxide film 13 is formed.

As the semiconductor substrate 10a, a substrate obtained by growing a Si _1-x Ge _x epitaxial layer having a thickness of about 100 nm on a Si substrate is preferably used. This is because even if there is strain in the Si substrate, the strain on the substrate surface can be relaxed by growing the Si _1-x Ge _x epitaxial layer.

Next, as shown in FIG. 9B, the oxide film 13 is removed. As a result, a ring-shaped groove 27 is formed and a dot-shaped depression (not shown) is formed. However, it is necessary to remove the oxide film 13 under the condition that the dopant 55 does not fall off. In order to prevent the dopant 55 from falling off, the dopant 55 may be diffused into the semiconductor substrate 10a having the Si _1-x Ge _x layer by performing a heat treatment before the oxide film 13 is removed. Good. The oxide film 13 can be removed by, for example, chemical etching, ultrasonic cleaning using water, or treatment using atomic hydrogen in a vacuum.

  Thereafter, as shown in FIGS. 9C and 11, the semiconductor film 36 (for example, Si film) is epitaxially grown in the groove 27 and in the dot-like depression.

Then, as shown in FIG. 10D, a quantum film is completed by forming a cap film 50 covering the semiconductor film 36 and the semiconductor substrate 10a. As the cap film 50, for example, a Si _1-x Ge _x film is formed. The cap film 50 can be formed, for example, by molecular beam epitaxy (MBE) or metal-organic chemical vapor deposition (MOCVD).

  According to such a manufacturing method, a paramagnetic or ferromagnetic quantum ring 1 can be obtained. If such a quantum ring 1 is used, a nano-level device exhibiting the Aharanov-Bohm effect can be obtained.

  In addition, the quantum ring 1 having a diameter of about 50 nm or less and the same size as the quantum dot 3 can be obtained with high accuracy. For example, even if a commonly used AFM probe is used, the diameter can be reduced to about 20 nm. Furthermore, if a particularly fine probe made of carbon nanotubes or the like is used, the diameter can be reduced to about 10 nm. Further, the size variation can be less than about 5%.

  And in this manufacturing method, the quantum ring 1 and the quantum dot 3 can be formed in the desired position of the semiconductor substrate 10a by controlling the position of the probe 22. The size and shape of the oxide film 13 change according to the humidity in the atmosphere, the potential difference between the probe 22 and the semiconductor substrate 10a, and the growth time. These three elements can be easily controlled. In addition, the thickness of the semiconductor film 36 can be easily controlled. Therefore, not only the quantum dot 3 but also the size of the quantum ring 1 can be easily controlled.

  The quantum device can also be manufactured by the following method. FIGS. 10A to 10D are cross-sectional views illustrating another method for manufacturing a quantum device in the order of steps.

In this method, first, as shown in FIG. 10A, a small amount of dopant 56, for example, ³¹ P atoms is implanted into the surface of the semiconductor substrate 10a. At this time, the doping conditions are adjusted so that only one atom of the dopant 56 exists at the position where the quantum ring 1 is to be formed. Next, an epitaxial layer 57 such as a SiGe layer is formed with a thickness of about 1 to 2 nm. Thereafter, as shown in FIG. 10A, an oxide film 13 is formed in the same manner as described above.

  Further, before or after the oxide film 13 is formed, a dot-shaped oxide film (not shown) is formed in the region where the quantum dots 3 are to be formed.

Next, the probe 22 is separated from the semiconductor substrate 10a, and the oxide film 19 is formed around the oxide film 13 as shown in FIG. That is, the oxide film 19 is formed on the entire surface excluding the center of the oxide film 13. The formation of the oxide film 19 is performed by an oxidation reaction accompanying the decomposition of H ₂ O in the atmosphere, like the oxide film 13. The oxide film 19 is thicker than the epitaxial layer 57. However, a sufficient distance from the bottom of the oxide film 13 to the lower surface of the oxide film 19 is also ensured. In FIG. 10B, for the sake of simplification, the remaining epitaxial layer 57 is shown as being integrated with the semiconductor substrate 10a.

  Thereafter, as shown in FIG. 10C, the oxide films 13 and 19 are removed in the same manner as described above, thereby forming grooves 27 and dot-like depressions (not shown). As a result, the dopant 56 is removed except for those present in the central portion of the groove 27.

  Subsequently, as shown in FIG. 10D, a semiconductor film 36a (for example, a Si film) is epitaxially grown in the groove 27 and the dot-like depression.

  Then, a quantum film is completed by forming a cap film (not shown in FIG. 10) in the same manner as described above.

  Also by such a method, the same effect as the above method can be obtained.

  Note that a weak interaction of the electrons 4 may occur between the quantum dots 3 of two adjacent quantum qubits 5. In such a case, the operability is reduced. For this reason, when there is such a concern, as shown in FIGS. 12A to 12C, the quantum ring 1 is located between the adjacent quantum qubits 5 where the quantum dots 3 are arranged. It is preferable that the line is on the opposite side with respect to the line. 12A shows a standby state, FIG. 12B shows a state where an operation is performed on a single quantum qubit 5, and FIG. 12C shows two adjacent quantum cues. This shows a state in which an operation for bit 5 is being performed.

  Hereinafter, various aspects of the present invention will be collectively described as supplementary notes.

(Appendix 1)
With quantum rings,
A single nuclear spin surrounded by the quantum ring;
Quantum dots adjacent to the quantum ring;
A quantum device comprising a quantum qubit including the quantum device.

(Appendix 2)
The quantum device according to appendix 1, wherein the quantum qubit contains SiGe.

(Appendix 3)
The quantum device according to appendix 1 or 2, wherein the nuclear spin is of ³¹ P atoms.

(Appendix 4)
The operation on the quantum qubit is performed based on a hyperfine interaction between an electron spin in the quantum ring and the nuclear spin. Quantum device.

(Appendix 5)
A plurality of the quantum qubits;
The quantum device according to any one of appendices 1 to 4, wherein the quantum rings of the plurality of quantum qubits are arranged side by side on one line.

(Appendix 6)
The quantum device according to appendix 5, wherein the quantum rings of the plurality of quantum qubits are arranged side by side on one straight line.

(Appendix 7)
The quantum device according to appendix 5 or 6, wherein each quantum dot of the plurality of quantum qubits is arranged on the same side with respect to the one line.

(Appendix 8)
The quantum device according to appendix 5 or 6, wherein each quantum dot of the plurality of quantum qubits is arranged on the opposite side between adjacent quantum qubits with the one line as a reference.

(Appendix 9)
Any one of appendices 5 to 8, wherein an operation on two adjacent ones of the plurality of quantum qubits is performed based on an exchange interaction between spins of two electrons in the quantum ring. A quantum device according to claim 1.

(Appendix 10)
A method for controlling a quantum device comprising a quantum ring, a single nuclear spin surrounded by the quantum ring, a quantum dot adjacent to the quantum ring, and a quantum qubit comprising:
A method for controlling a quantum device, comprising: a step of moving electrons existing in the quantum ring into the quantum dot by optical excitation.

(Appendix 11)
The quantum device control method according to appendix 10, wherein the quantum qubit contains SiGe.

(Appendix 12)
12. The quantum device control method according to appendix 10 or 11, wherein the nuclear spin is of ³¹ P atoms.

(Appendix 13)
Returning the electrons in the quantum dots back into the quantum ring;
Rotating the nuclear spin by exerting a hyperfine interaction between the spin of electrons in the quantum ring and the nuclear spin;
The method for controlling a quantum device according to any one of appendices 10 to 12, wherein:

(Appendix 14)
14. The quantum device control method according to appendix 13, wherein the step of rotating the nuclear spin includes a step of applying a pulse having a resonance frequency to the quantum qubit.

(Appendix 15)
The quantum device has a plurality of the quantum qubits,
Each quantum ring of the plurality of quantum qubits is arranged side by side on one line,
For two adjacent quantum qubits,
Returning the electrons in the quantum dots back into the quantum ring;
Rotating the nuclear spin by exerting an exchange interaction between spins of two electrons in the quantum ring;
15. The quantum device control method according to any one of appendices 10 to 14, wherein the quantum device control method includes:

(Appendix 16)
16. The quantum device control method according to appendix 15, wherein the step of rotating the nuclear spin includes a step of applying a magnetic field to the two quantum qubits.

(Appendix 17)
In an atmosphere containing water, an atomic force microscope probe to which a negative bias is applied is brought into contact with the surface of the semiconductor substrate, and an annular oxide film and a dotted oxide film are adjacent to each other on the surface of the semiconductor substrate. And forming the process,
Removing the annular oxide film and the dotted oxide film to form an annular groove and a dotted recess on the surface of the semiconductor substrate;
Forming quantum rings and quantum dots by growing a semiconductor film in the grooves and depressions;
Have
The method for manufacturing a quantum device further includes a step of attaching a single impurity atom to the center of the annular oxide film before the step of forming the groove and the depression.

(Appendix 18)
Introducing impurity atoms into the surface of the semiconductor substrate;
In an atmosphere containing water, an atomic force microscope probe to which a negative bias is applied is brought into contact with the surface of the semiconductor substrate, and an annular oxide film and a dotted oxide film are formed on the surface of the semiconductor substrate. Forming adjacent to each other;
Oxidizing the periphery of the annular oxide film and the dotted oxide film;
Removing the annular oxide film and the dotted oxide film, and removing the oxidized portion around the annular oxide film, thereby forming an annular groove and a dotted recess on the surface of the semiconductor substrate;
Forming quantum rings and quantum dots by growing a semiconductor film in the grooves and depressions;
The manufacturing method of the quantum device characterized by having.

(Appendix 19)
18. The method of manufacturing a quantum device according to appendix 17, wherein a plurality of quantum qubits including the quantum rings and quantum dots are simultaneously formed so that the quantum rings are adjacent to each other.

(Appendix 20)
The quantum device manufacturing method according to appendix 18, wherein a plurality of quantum qubits including the quantum rings and quantum dots are simultaneously formed so that the quantum rings are adjacent to each other.

It is a schematic diagram which shows the quantum device which concerns on embodiment of this invention. It is a figure which shows excitation of an electron. It is a figure which shows a hyperfine interaction. It is a figure which shows exchange interaction. It is a schematic diagram which shows the method of forming an oxide film using AFM. It is sectional drawing which similarly shows the method of forming an oxide film in order of a process. It is sectional drawing which shows the method of approaching the probe 22 and forming an oxide film in order of a process. 3 is a cross-sectional view showing a method of forming an oxide film by bringing a probe 22 into contact with a semiconductor substrate 10 in order of steps. FIG. It is sectional drawing which shows the method of manufacturing the quantum device which concerns on embodiment of this invention in process order. It is sectional drawing which shows the other method of manufacturing a quantum device in order of a process. FIG. 10 is a plan view corresponding to FIG. It is a schematic diagram which shows embodiment which changed arrangement | positioning of the quantum dot 3. FIG.

Explanation of symbols

1: quantum ring 2: P atom 3: quantum dot 4: electron 5: quantum qubit 10, 10a: semiconductor substrate 11, 12, 13, 19: oxide film 22: probe 27: groove 36: semiconductor film 50: cap Films 55 and 56: dopant 57: epitaxial layer

Claims (10)

With quantum rings,
A nuclear spin consisting of a single impurity atom surrounded by the quantum ring;
Quantum dots adjacent to the quantum ring;
Quantum devices, characterized in that it comprises a quantum qubit including.   The quantum device according to claim 1, wherein the quantum qubit contains SiGe. The quantum device according to claim 1, wherein the nuclear spin is of ³¹ P atoms.   4. The operation according to claim 1, wherein the operation on the quantum qubit is performed based on a hyperfine interaction between an electron spin and the nuclear spin in the quantum ring. 5. Quantum devices. A plurality of the quantum qubits;
5. The quantum device according to claim 1, wherein the quantum rings of the plurality of quantum qubits are arranged side by side on one line. A method of controlling a quantum device having a quantum qubit including a quantum ring, a nuclear spin composed of a single impurity atom surrounded by the quantum ring, a quantum dot adjacent to the quantum ring, and
A method for controlling a quantum device, comprising: a step of moving electrons existing in the quantum ring into the quantum dot by optical excitation. Returning the electrons in the quantum dots back into the quantum ring;
Rotating the nuclear spin by exerting a hyperfine interaction between the spin of electrons in the quantum ring and the nuclear spin;
The method of controlling a quantum device according to claim 6, comprising: The quantum device has a plurality of the quantum qubits,
Each quantum ring of the plurality of quantum qubits is arranged side by side on one line,
For two adjacent quantum qubits,
Returning the electrons in the quantum dots back into the quantum ring;
Rotating the nuclear spin by exerting an exchange interaction between spins of two electrons in the quantum ring;
The method of controlling a quantum device according to claim 6 or 7, wherein: In an atmosphere containing water, an atomic force microscope probe to which a negative bias is applied is brought into contact with the surface of the semiconductor substrate, and an annular oxide film and a dotted oxide film are adjacent to each other on the surface of the semiconductor substrate. And forming the process,
Removing the annular oxide film and the dotted oxide film to form an annular groove and a dotted recess on the surface of the semiconductor substrate;
Forming quantum rings and quantum dots by growing a semiconductor film in the grooves and depressions;
Have
The method for manufacturing a quantum device further includes a step of attaching a single impurity atom to the center of the annular oxide film before the step of forming the groove and the depression. Introducing a single impurity atom at a position to form a quantum ring on the surface of the semiconductor substrate;
In an atmosphere containing water, an atomic force microscope probe to which a negative bias is applied is brought into contact with the surface of the semiconductor substrate, and an annular oxide film and a dotted oxide film are formed on the surface of the semiconductor substrate. Forming adjacent to each other;
Oxidizing the periphery of the annular oxide film and the dotted oxide film;
Removing the annular oxide film and the dotted oxide film, and removing the oxidized portion around the annular oxide film, thereby forming an annular groove and a dotted recess on the surface of the semiconductor substrate;
Forming quantum rings and quantum dots by growing a semiconductor film in the grooves and depressions;
The manufacturing method of the quantum device characterized by having.

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