Quantum device and quantum information processing device

Abstract

This quantum device two-dimensionally arranges quantum dot-type quantum bits formed by a field plate. The quantum device comprises: a semiconductor layer having a plurality of regions in which electrons are stored; and a field plate which is disposed on the semiconductor layer and which extends in a first direction and stores electrons in the plurality of regions by forming an electric field through application of a voltage thereto. The quantum device enables two-dimensional coupling and movement of each quantum bit by providing a weak coupling part to the field plate, and can perform quantum information processing that requires a large number of quantum bits.

Description

Quantum devices and quantum information processing devices

[0001] The present invention relates to quantum devices and quantum information processing devices, and more particularly to the structure of an apparatus used as a quantum device and a control method thereof.

[0002] Currently, many groups around the world are conducting research aimed at realizing quantum computers. Experiments are being conducted using a variety of physical systems, but regardless of the physical system used, the first requirement for realizing a quantum computer is to create qubits in an isolated system that does not exchange matter or energy with the outside world, and to be able to maintain the coherence of the quantum system for a long period of time. However, in real physical systems, it is impossible to completely avoid decoherence due to interactions with the outside world. In experiments using any physical system, efforts are continuing to suppress qubit decoherence and extend the coherence time. Furthermore, to operate as a quantum computer, it is not enough to simply create a single qubit; multiple qubits must be configured into a device that meets the following three requirements:

[0003] The first requirement is scalability. One of the reasons quantum computers are capable of high-speed calculations is that by utilizing quantum superposition, the dimension of Hilbert space increases exponentially with the number of qubits. However, it would be meaningless if the costs (time, space, energy, etc.) required to control qubits also increase exponentially. Controlling qubits requires electrical circuits to apply RF pulses and dilution refrigerators to cool qubits to extremely low temperatures, but a mechanism is needed to expand the number of qubits without increasing the costs required for these experimental devices.

[0004] The second requirement is that arbitrary quantum operations must be possible. Like classical computers, quantum computers are composed of basic logic gates, which, in the case of quantum computers, are called quantum gates. Examples include a rotate gate, which is a one-qubit gate, and a controlled NOT gate, which is a two-qubit gate. "Any quantum operation is possible" means that any quantum state can be reached with a finite number of quantum gate operations. It has theoretically been shown that in gate-type quantum computers, any quantum operation is possible by combining a rotate gate and a controlled NOT gate. In other words, if these quantum gate operations can be performed on any quantum bit, any quantum operation will be possible.

[0005] The third requirement is the ability to correct errors. To realize a quantum computer using real quantum bits with decoherence, a function to correct errors caused by decoherence (quantum error correction) is required. Many algorithms for quantum error correction have been proposed, but all of them involve "initialization" and "readout" to eliminate the entropy caused by decoherence. "Initialization" is an operation to return the superposition state of quantum bits to an initialized pure state when decoherence causes the superposition state to become mixed. "Readout" is an operation to measure the state of quantum bits with an accuracy allowed by quantum mechanics. Currently, an algorithm called Surface Code is considered to be the most promising method for error correction. Surface Code operates on an array of physical quantum bits arranged in a two-dimensional square lattice.

[0006] In other words, if it is possible to expand the number of quantum bits to two dimensions while using the same device to control quantum bits with long coherence times, and if any quantum bit can be configured as a quantum bit string that allows ``initialization,'' ``rotation gate operation,'' ``controlled NOT gate operation,'' and ``readout,'' it is expected that it will be possible to operate it as a quantum computer.

[0007] US Patent Application Publication No. 2022 / 07147314

[0008] A common method for forming quantum dots is to create a state in which electrons are distributed two-dimensionally at the semiconductor interface (two-dimensional electron gas), and then confine this two-dimensional electron gas using the electric field created by a gate electrode (field plate) formed at the interface. When forming quantum dots using a field plate, the shape of the quantum dot is defined by the electric field. Compared to methods that use a state in which electrons are distributed one-dimensionally using thin wires formed in semiconductors (one-dimensional electron gas), this method has the advantage of being less susceptible to interface roughness and distortion, making it easier to control the properties of the quantum dots.

[0009] On the other hand, because a voltage must be applied to the field plates, all field plates must be electrically connected. Therefore, when attempting to arrange quantum dots two-dimensionally, field plates will be in a floating state (a state where no voltage can be applied), making large-scale integration difficult. In fact, while there are examples of forming two one-dimensional quantum dot arrays using field plates, there are no examples of actually forming a structure that can be expanded in two dimensions.

[0010] It should be noted that Patent Document 1 discloses a quantum device having a semiconductor channel with a proximity region having strong interaction with an adjacent semiconductor channel and a region where this is not the case, but does not describe in detail the gate electrode that controls the electrons, and there is a possibility that the gate electrode may become floating.

[0011] An object of the present invention is to solve the above problems and to provide a quantum device and a quantum information processing device that define the shape of quantum dots using field plates and can handle the coupling and movement of quantum bits arranged two-dimensionally.

[0012] The quantum device of the present invention is a quantum device comprising: a semiconductor layer having a plurality of regions in which electrons are stored; and a first gate electrode disposed on the semiconductor layer, extending in a first direction, and storing the electrons in the plurality of regions by applying a voltage to the first gate electrode to form an electric field, wherein the first gate electrode comprises a weak link portion and a non-link portion having a width in a second direction different from the first direction than the weak link portion, and the semiconductor layer comprises a first region opposite the non-link portion and a second region opposite the weak link portion, and the second region is a region through which the electrons stored in the region can pass and move in the second direction.

[0013] The quantum device of the present invention is a quantum device comprising: a semiconductor layer having a plurality of regions in which electrons are stored; a first gate electrode disposed on the semiconductor layer, extending in a first direction, and storing the electrons in the plurality of regions by applying a voltage to form an electric field; and a second gate electrode extending in a second direction different from the first direction and formed on a portion of the first gate electrode and a portion of the semiconductor layer, wherein the second gate electrode comprises a first weak link portion and a first non-coupling portion that is wider in the first direction than the first weak link portion, and the semiconductor layer comprises a third region facing the first non-coupling portion and a fourth region facing the first weak link portion, and the fourth region is a region through which the electrons stored in the region can pass and move in the first direction.

[0014] The information processing device of the present invention is a quantum information processing device comprising a control device that controls electrons and a quantum device, wherein the quantum device comprises: a semiconductor layer having a plurality of regions in which the electrons are stored; and a first gate electrode disposed on the semiconductor layer, extending in a first direction, and storing the electrons in the plurality of regions by applying a voltage to the first gate electrode to form an electric field, wherein the first gate electrode comprises a weak link portion and a non-coupling portion that is wider in a second direction different from the first direction than the weak link portion; the semiconductor layer comprises a first region facing the non-coupling portion and a second region facing the weak link portion; and the second region is a region through which the electrons stored in the region can pass and move in the second direction.

[0015] According to the present invention, the shape of quantum dots can be defined by a field plate, and the coupling and movement of quantum bits arranged in two dimensions can be handled. Note that the effects described herein are not necessarily limited to those described herein, and may be any of the effects described in this disclosure.

[0016] FIG. 1A is a top view and a cross-sectional view showing the shape of a field plate constituting a quantum device of the present invention. FIG. 1B is a cross-sectional view showing the shape of a field plate constituting a quantum device of the present invention. FIG. 1C is a cross-sectional view showing the shape of a field plate constituting a quantum device of the present invention. FIG. 2A is a top view showing a different shape from that of a field plate constituting a quantum device of the present invention. FIG. 2B is a cross-sectional view showing a different shape from that of a field plate constituting a quantum device of the present invention. FIG. 3A is a top view showing a different shape from that of a field plate constituting a quantum device of the present invention. FIG. 3B is a top view showing a different shape from that of a field plate constituting a quantum device of the present invention. FIG. 3C is a diagram showing formulas (1) and (2). FIG. 4A is a top view showing the shape of a field plate constituting a quantum device of Example 1. FIG. 4B is a cross-sectional view showing the shape of a field plate constituting a quantum device of Example 1. FIG. 4C is a cross-sectional view showing the shape of a field plate constituting a quantum device of Example 1. FIG. 4D is a cross-sectional view showing the shape of a field plate constituting a quantum device of Example 1. FIG. 5A is a top view showing the shapes of the second and third layers of gate electrodes constituting the quantum device of Example 1. FIG. 5B is a cross-sectional view showing the shapes of the second and third layers of gate electrodes constituting the quantum device of Example 1. FIG. 5C is a cross-sectional view showing the shape of the second and third layers of the gate electrodes constituting the quantum device of Example 1. FIG. 5D is a cross-sectional view showing the shape of the second and third layers of the gate electrodes constituting the quantum device of Example 1. FIG. 6A is a top view and a cross-sectional view showing the shape of the fourth and fifth layers of the gate electrodes constituting the quantum device of Example 1. FIG. 6B is a cross-sectional view showing the shape of the fourth and fifth layers of the gate electrodes constituting the quantum device of Example 1. FIG. 6C is a cross-sectional view showing the shape of the fourth and fifth layers of the gate electrodes constituting the quantum device of Example 1. FIG. 6D is a cross-sectional view showing the shape of the fourth and fifth layers of the gate electrodes constituting the quantum device of Example 1. FIG. 7A is a top view showing the shape of the second layer of the gate electrodes constituting the quantum device of Example 2. FIG. 7B is a cross-sectional view showing the shape of the second layer of the gate electrodes constituting the quantum device of Example 2. FIG. 7C is a cross-sectional view showing the shape of the second layer of the gate electrodes constituting the quantum device of Example 2.FIG. 7D is a cross-sectional view showing the shape of a second layer of gate electrodes constituting the quantum device of Example 2. FIG. 7E is a cross-sectional view showing the shape of a second layer of gate electrodes constituting the quantum device of Example 2. FIG. 7F is a cross-sectional view showing the shape of a second layer of gate electrodes constituting the quantum device of Example 2. FIG. 8A is a top view showing a method of performing individual manipulation of quantum bits in the quantum device of Example 2. FIG. 8B is a cross-sectional view showing a method of performing individual manipulation of quantum bits in the quantum device of Example 2. FIG. 8C is a cross-sectional view showing a method of performing individual manipulation of quantum bits in the quantum device of Example 2. FIG. 8D is a cross-sectional view showing a method of performing individual manipulation of quantum bits in the quantum device of Example 2. FIG. 8E is a cross-sectional view showing a method of performing individual manipulation of quantum bits in the quantum device of Example 2. FIG. 8F is a cross-sectional view showing a method of performing individual manipulation of quantum bits in the quantum device of Example 2. FIG. 9A is a top view showing a method of performing individual manipulation of quantum bits in the quantum device of Example 2. FIG. 9B is a cross-sectional view showing a method of performing individual manipulation of quantum bits in the quantum device of Example 2. FIG. 9C is a cross-sectional view showing a method of performing individual manipulation of quantum bits in the quantum device of Example 2. FIG. 9D is a cross-sectional view showing a method for performing individual operations on quantum bits in the quantum device of Example 2. FIG. 9E is a cross-sectional view showing a method for performing individual operations on quantum bits in the quantum device of Example 2. FIG. 9F is a cross-sectional view showing a method for performing individual operations on quantum bits in the quantum device of Example 2. FIG. 10 is a top view showing the shapes of field plates and gate electrodes that constitute a quantum information processing device of Example 3. FIG. 11 is a diagram for explaining the schematic configuration of a quantum information processing device using quantum devices. FIG. 12 is a diagram for explaining the schematic configuration of a quantum information processing device using quantum devices. FIG. 13 is a diagram showing a specific configuration example of a quantum information processing device.

[0017] First, the structure of the quantum device will be described. An example of the shape of a field plate that constitutes a quantum device is shown in Figures 1A to 1C. Figure 1A is a top view showing an example of the shape of a field plate. Figure 1B is a cross-sectional view taken along line AA' in Figure 1A. Figure 1C is a cross-sectional view taken along line BB' in Figure 1A.

[0018] Two-dimensional electron gas is distributed at the interface of a channel layer 101 made of a semiconductor (e.g., pure silicon). A field plate 102 made of a conductor (e.g., amorphous silicon) is formed on the channel. Wiring lines YCG0 to YCG4 are electrically connected to the field plate 102. The field plate 102 is connected to a control device (not shown) via the wiring lines YCG0 to YCG4. The control device (not shown) is capable of applying a voltage of a desired potential to the field plate 102.

[0019] The electric field created by applying a voltage to the field plate 102 creates a potential 103 distribution in the channel layer 101, restricting the movement of electrons. By using other gate electrodes, electrons are isolated in the valleys of the potential 103, forming quantum dots 104. By setting the potential barrier between the quantum dots 104 to an appropriate height, interactions 105 can be exerted. In this case, the width of the field plate 102 is not made uniform, but regions of multiple widths are formed.

[0020] For example, a portion 106 of the field plate 102 is relatively wide, and the potential barrier is high in a first region, which is a region of the channel layer 101 (semiconductor layer) facing the portion 106, so that interaction 105 does not occur between the quantum dots 104 aligned in the horizontal direction. A region with this function is called a non-coupling portion 106. On the other hand, a portion 107 of the field plate 102 is relatively narrow, and the potential barrier is low in a second region, which is a region of the channel layer 101 (semiconductor layer) facing the portion 107, so that interaction 105 occurs between the quantum dots 104 aligned in the horizontal direction. A region with this function is called a weak link portion 107.

[0021] If the width of the field plate 102 is made uniform as shown in FIGS. 2A and 2B, the height of the potential barrier between all quantum dots arranged horizontally on either side of the field plate 102 will be the same, making it difficult to control the quantum dots individually.

[0022] 3A and 3B, if portion 301 of field plate 102 is separated, portions 302 of field plate 102 separated on both sides become isolated and electrically floating, making it impossible to apply voltage and making it difficult to form quantum dots 104. For the above reasons, the problem can be solved by forming regions with multiple widths as shown in FIGS.

[0023] 1A to 1C , the quantum device includes a plurality of field plates 102 that are aligned while being spaced apart from one another in a second direction orthogonal to the first direction in which the field plates 102 extend. The quantum device has first row regions in which weak link portions 107 and non-link portions 106 of the field plates 102 are aligned alternately on a line along the second direction, and second row regions in which the non-link portions 106 of the field plates 102 are aligned continuously on a line along the second direction. The first row regions and the second row regions are arranged alternately in the second direction.

[0024] 1A to 1C, the weak link portions 107 and non-link portions 106 are arranged alternately to make the quantum dots 104 uniform in size, as in the first row region, but the weak link portions 107 and non-link portions 106 may be arranged freely depending on the application of the quantum device. Some examples will be described in the examples below. To individually control the strength of the interaction between the quantum dots 104 in the weak link portions 107, the voltage of the field plate 102 can be changed.

[0025] We will consider the change in the height of the potential barrier formed when the distance between quantum dots 104 is changed by varying the width of the field plate 102. In quantum computing, it is necessary to complete the execution of a quantum computing algorithm within the coherence time, which is the time during which quantum information in a quantum bit can be retained. Therefore, when operating a two-qubit gate, which is one step in quantum computing, the application of interaction between quantum bits must be completed within a time that is sufficiently shorter than the coherence time.

[0026] On the other hand, if the time required for the interaction is sufficiently longer than the coherence time, its effect can be ignored. As described above, in order to operate quantum bits independently in quantum computing, it is necessary to establish a magnitude relationship in which the "time required for the interaction" is greater than the "coherence time" in the region where the width of the field plate 102 is wide, and the "time required for the interaction" is less than the "coherence time" in the region where the width of the field plate 102 is narrow.

[0027] The time required for the interaction depends on the reciprocal of the magnitude of the overlap integral S (equation (1) in Figure 3C) of the wave functions of the electrons that make up the quantum bit. Here, φ1 and φ2 are the single-electron wave functions of the electrons that make up the quantum bit, and r is the position coordinate. For simplicity, if the electron potential shape is considered to be two harmonic oscillator side potentials, the magnitude of S becomes equation (2) in Figure 3C. Here, a is the distance between the quantum bits, a ｘ is the radius of the wave function in the direction of the quantum dots, a ｙ is the radius of the wave function in the direction perpendicular to the direction in which the quantum dots are arranged, e is the elementary charge, B is the magnitude of the magnetic field, h is the Dirac constant, and c is the speed of light. From the above, the time required for the interaction is proportional to the exponent of the square of the distance between the quantum bits. Since the time required for the interaction can be significantly changed depending on the distance between the quantum bits, it is easy to set an appropriate width for the field plate 102.

[0028] A first aspect of the present invention is a quantum device characterized in that electrons can move in two dimensions by providing weak links 107 in field plate 102. A second aspect of the present invention is the quantum device according to the first aspect, characterized in that it includes a gate electrode (potential barrier control gate 601 (see FIG. 6A )) that controls the strength of electron coupling in a second region of the semiconductor layer (channel layer 101) facing weak links 107. Example 1 described below corresponds to the first and second aspects.

[0029] A third aspect of the present invention is a quantum device according to the first aspect, characterized in that electrons can be selectively moved by providing a weak link 701 in the potential barrier control gate 501 (see FIG. 7A ). Example 2, which will be described later, corresponds to the third aspect.

[0030] Examples of the present invention will be described below with reference to the drawings. However, the present invention should not be construed as being limited to the following embodiments. Those skilled in the art will readily understand that the specific configuration can be modified without departing from the spirit or scope of the present invention. <<Example 1>> A method for two-dimensionally integrating and controlling quantum bits using a quantum device will be described. Figures 4A to 4D show the shape of the field plate 102. Figure 4A is a top view of the shape of the field plate 102. Figure 4B is a cross-sectional view taken along line A-A' in Figure 4A. Figure 4C is a cross-sectional view taken along line B-B' in Figure 4A. Figure 4D is a cross-sectional view taken along line C-C' in Figure 4A. The field plate 102 is sometimes referred to as a "first gate electrode."

[0031] The quantum device comprises a plurality of field plates 102 arranged at a distance from one another in a second direction orthogonal to the first direction in which the field plates 102 extend. The quantum device has first column regions in which weak link portions 107 of the field plates 102 are arranged continuously on a line along the second direction, and second column regions in which non-link portions 106 of the field plates 102 are arranged continuously on a line along the second direction. The first column regions and the second column regions are arranged alternately in the second direction.

[0032] In the field plate 102, non-linking portions 106 and weak linking portions 107 are arranged in a lattice pattern.

[0033] With this structure, the quantum dots can be expanded both horizontally and vertically. At this point, unlike in Figure 1, the quantum dots appear to vary in size depending on the location, but in reality, the sizes can be made uniform by the gate electrodes that will be formed later. Wiring YCG0 to YCG4 are electrically connected to the field plate 102. The field plate 102 is connected to a control device (not shown) via wiring YCG0 to YCG4. The control device (not shown) is capable of applying a voltage of a desired potential to the field plate 102.

[0034] 5A to 5D show the shapes of the first layer potential barrier control gate 501 and quantum bit control gate 502 formed on the field plate 102. FIG. 5A is a top view of the state in which the potential barrier control gate 501 and quantum bit control gate 502 are formed on the field plate 102. FIG. 5B is a cross-sectional view taken along line A-A' in FIG. 5A. FIG. 5C is a cross-sectional view taken along line B-B' in FIG. 5A. FIG. 5D is a cross-sectional view taken along line CC' in FIG. 5A. Each of the potential barrier control gate 501 and quantum bit control gate 502 may be referred to as a "second gate electrode."

[0035] The potential barrier control gate 501 and the quantum bit control gate 502 are formed on the non-connecting portion 106, and by applying a voltage in combination with the field plate 102, a potential distribution is created, forming a two-dimensional array of quantum dots (two-dimensional rows of quantum dots).

[0036] Wirings XJG0 to XJG9 are electrically connected to the potential barrier control gate 501. The potential barrier control gate 501 is connected to a control device (not shown) via the wirings XJG0 to XJG9. The control device (not shown) is capable of applying a voltage of a desired potential to the potential barrier control gate 501.

[0037] Wirings XQG1 to XQG9 are electrically connected to the quantum bit control gate 502. The quantum bit control gate 502 is connected to a control device (not shown) via wirings XQG1 to XQG9. The control device (not shown) is capable of applying a voltage of a desired potential to the quantum bit control gate 502.

[0038] 6A to 6D show the shapes of potential barrier control gate 601 and quantum bit control gate 602 formed on the first layer of potential barrier control gate 501 and quantum bit control gate 502. FIG. 6A is a top view of a state in which a potential barrier control gate 601 and a quantum bit control gate 602 are further formed on the first layer of potential barrier control gate 501 and quantum bit control gate 502. FIG. 6B is a cross-sectional view taken along line A-A' in FIG. 6A. FIG. 6C is a cross-sectional view taken along line B-B' in FIG. 6A. Note that the quantum bit control gate 602 is omitted from FIG. 6C. FIG. 6D is a cross-sectional view taken along line C-C' in FIG. 6A. Note that each of potential barrier control gate 601 and quantum bit control gate 602 may be referred to as a "third gate electrode."

[0039] The potential barrier control gate 601 and the quantum bit control gate 602 have a shape that extends in a direction different from that of the first layer, thereby forming a quantum dot in the weak link 107 .

[0040] Wirings YJG0 to YJG4 are electrically connected to the potential barrier control gate 601. The potential barrier control gate 601 is connected to a control device (not shown) via the wirings YJG0 to YJG4. The control device (not shown) is capable of applying a voltage of a desired potential to the potential barrier control gate 601.

[0041] Wirings YQG1 to YQG4 are electrically connected to the quantum bit control gate 602. The quantum bit control gate 602 is connected to a control device (not shown) via wirings YQG1 to YQG4. The control device (not shown) is capable of applying a voltage of a desired potential to the quantum bit control gate 602.

[0042] 6B, potential barrier control gate 601 contacts channel layer 101 at weak link portion 107, but does not contact channel layer 101 at non-link portion 106 because it is blocked by field plate 102, as shown in the cross-sectional view of Fig. 6C. In other words, the width of potential barrier control gate 601 is greater than the width of non-link portion 106 of field plate 102, and potential barrier control gate 601 is provided so as to cover field plate 102 and contact channel layer 101.

[0043] 1 , the strength of the interaction between the quantum dots 104 in the weak links 107 can be controlled by changing the voltage applied to the potential barrier control gate 601, rather than the voltage applied to the field plate 102. In Example 1, since there is no need to change the voltage applied to the field plate 102 in order to control the strength of the interaction between the quantum dots 104 in the weak links 107 (in other words, the height of the potential barrier between the quantum dots 104), stable quantum dots can be formed by keeping the voltage applied to the field plate 102 constant. As described above, it is possible to realize the formation of a two-dimensional array of quantum dots, the movement of quantum bits in two dimensions, and the formation of quantum dot interactions in two dimensions.

[0044] According to the first embodiment, the weak links 107 enable electrons to be supplied to multiple regions, and a voltage can be applied from outside the quantum device without the field plate 102 floating. <<Embodiment 2>> A structure in which weak links 701 are formed in gate electrodes other than the field plate 102 and a method for controlling the structure will be described. Figures 7A to 7F show the shape of the potential barrier control gate 501. Figure 7A is a top view of the first-layer potential barrier control gate 501 formed on the field plate 102. Figure 7B is a cross-sectional view taken along line A-A' in Figure 7A. Figure 7C is a cross-sectional view taken along line C-C' in Figure 7A. Figure 7D is a cross-sectional view taken along line D-D' in Figure 7A. Figure 7E is a cross-sectional view taken along line E-E' in Figure 7A. Figure 7F is a cross-sectional view taken along line F-F' in Figure 7A.

[0045] For the potential barrier control gate 501, regions of a plurality of widths are created as in the field plate 102 of Example 1, thereby forming weak link portions 701 and non-link portions 703. In such a structure, when an appropriate voltage is applied to the potential barrier control gate 501, it is possible to create a difference in height of the potential barrier formed in the first region of the channel layer 101 facing the non-link portion 703 and the second region of the channel layer 101 facing the weak link portion 701.

[0046] 8A to 8F and 9A to 9F show methods for moving quantum bits 702. By setting a potential barrier height such that electrons cannot move in non-linked portion 703 but can move in weakly linked portion 701, and forming a potential gradient using quantum bit control gate 502, it is possible to move only quantum bits 702 in the second region of channel layer 101 opposite weakly linked portion 701 to the left. For example, in the steps of FIGS. 8A to 8F, only quantum bits 702 located at lines CC' and E-E', where weakly linked portion 701 is located, move to the left, and in the steps of FIGS. 9A to 9F, only quantum bits 702 located at lines CC' and D-D', where the second region of channel layer 101 opposite weakly linked portion 701 is located, move to the left through the second region. In this way, by preparing multiple patterns of weak links 701 and sequentially repeating the movement of the quantum bits 702, it is possible to select and move a specific one of the quantum bits 702 arranged in the vertical direction (second direction). <<Example 3>> Example 3 is a quantum device that combines the features of Example 1 and Example 2. As in this quantum device, it is also possible to install both the weak link 107 of the field plate 102 and the weak link 701 of the gate electrode (potential barrier control gate 501) shown in Example 2 in the same device. An example is shown in FIG. 10. Only the field plate 102 and some of the potential barrier control gates 501 are illustrated, with the other gate electrodes omitted. By combining multiple types of weak links (weak links 107 and weak links 701) in this way, it is possible to achieve both multidimensional linking of quantum bits and individual control of quantum bits. The weak link 701 may be referred to as a "first weak link." The non-link portion 703 may be referred to as a "first non-link." The weak link portion 107 may be referred to as a "second weak link portion." The non-link portion 106 may be referred to as a "second non-link portion." The region of the channel layer 101 facing the non-link portion 703 may be referred to as a "third region." The region of the channel layer 101 facing the weak link portion 701 may be referred to as a "fourth region." <<Example 4>> Example 4 is a quantum information processing device using a quantum device.FIG. 11 is a diagram illustrating the schematic configuration of a quantum information processing device using a quantum device. The quantum information processing device includes a measurement device 1101 and a quantum device 1103 housed in a refrigerator 1102. The quantum device 1103 can be any of the quantum devices 1103 described in Examples 1 to 3. The quantum device 1103 must be cooled to cryogenic temperatures using a refrigerator 1102 to eliminate the effects of thermal noise. For example, as shown in FIG. 11 , the quantum device 1103 is enclosed within the refrigerator 1102, and a measurement device 1101 placed outside the refrigerator 1102 is used to apply DC voltages and RF signals and measure currents. Note that the quantum information processing device may also include a control device 1104, which has some of the functions of the measurement device 1101 and operates at cryogenic temperatures, enclosed within the refrigerator 1102, as shown in FIG. 12 . This configuration reduces the number of wiring connections between the inside and outside of the refrigerator 1102.

[0047] Figure 13 is a diagram showing a specific example configuration of a quantum information processing device. The quantum information processing device in Figure 13 corresponds to the configuration of the quantum information processing device in Figure 12. The quantum information processing device has a quantum chip 1301, an analog chip 1302 that inputs control signals for controlling the quantum chip 1301, a digital processing device 1303 that inputs control signals for controlling the analog chip 1302, and a dilution refrigerator 1304. The quantum chip 1301 includes a quantum device and peripheral circuits. Note that the quantum chip 1301 and the analog chip 1302 correspond to the quantum device 1103 and the control device 1104 in Figure 12, and the digital processing device 1303 corresponds to the measuring device 1101 in Figure 12. The dilution refrigerator 1304 corresponds to the refrigerator 1102.

[0048] The dilution refrigerator 1304 is separated by a housing 1305 and a room temperature plate 1306 to separate the air atmosphere outside the dilution refrigerator 1304 from the vacuum atmosphere inside the dilution refrigerator 1304. The degree of vacuum inside the housing 1305 of the dilution refrigerator 1304 is controlled by using a pump device installed outside the dilution refrigerator 1304 to exhaust air through a vacuum tube 1307. The temperature inside the dilution refrigerator 1304 is controlled by circulating diluted liquid helium through a pulse tube 1308 shown in Figure 13. Figure 13 shows an example in which two pulse tubes 1308 are connected. The diluted liquid helium is a mixture of two isotopes of helium, ３ He and ４ He is liquefied, ３ He phase ４ It was poured into the He phase and diluted.

[0049] In the example of dilution refrigerator 1304 in FIG. 13, multiple metal (mainly oxygen-free copper) plates (plate 1309 (set to -223°C), plate 1310 (set to -269°C), plate 1311, plate 1312, and plate 1313 (set to approximately -273°C)) are installed and stored inside housing 1305 of dilution refrigerator 1304.

[0050] Plates 1311 and 1312 are controlled at a temperature between 4 K (-269°C) and 131 mK (approximately -273°C). The temperature is controlled and maintained in a thermal equilibrium state using temperature control heaters (not shown) mounted on each plate (plate 1309, plate 1310, plate 1311, plate 1312, and plate 1313) and a temperature controller (not shown) installed outside dilution refrigerator 1304 that controls the amount of power input to the temperature control heaters. In the example of FIG. 13 , diluted liquid helium is circulated from pulse tube 1308 to heat sink 1314. This causes plates 1310 and 1313, to which heat sink 1314 is connected, to be cryogenically cooled via heat sink 1314 through which diluted liquid helium circulates. Therefore, plates 1310 and 1313 can be maintained in a cryogenic atmosphere of 10 mK to 100 mK.

[0051] The quantum chip 1301 is mounted on a cooling plate 1315 for the quantum chip 1301, which is arranged below the plate 1313. The cooling plate 1315 is thermally connected to the plate 1313 via four cooling rods 1316 (two of which are not shown). In other words, the heat sink 1314 is a refrigerating tube that cools the cooling plate 1315, which is a metal body, using diluted liquid helium. The cooling plate 1315, which is a metal body, is thermally connected to the plate 1313 via the cooling rods 1316.

[0052] In this embodiment, the quantum chip 1301 is not directly mounted on the plate 1313, but is installed below the plate 1313. The reason for this is to perform quantum operation while applying a static magnetic field (external magnetic field) to the quantum chip 1301. Due to space constraints for arranging the magnet 1317 for generating the static magnetic field in the lowest layer of the dilution refrigerator 1304, the quantum chip 1301 is arranged as shown in FIG. 13 in the configuration example of the dilution refrigerator 1304 in this embodiment. Note that electrical signals required for quantum operation of the quantum chip 1301 are output from a digital processing device 1303 and an analog chip 1302 installed outside the dilution refrigerator 1304, and the control signals among the electrical signals are electrically connected to the quantum chip 1301 via coaxial wiring 1318a and 1318b, and the power supply voltage and power supply current among the electrical signals are electrically connected to the quantum chip 1301 via DC twisted wiring 1318c and 1318d.

[0053] The fourth embodiment described above is a quantum information processing device using a quantum device in which quantum dot quantum bits formed by field plates 102 are arranged in a two-dimensional manner, and by coupling and moving each quantum bit in a two-dimensional direction, quantum information processing requiring a large number of quantum bits can be performed. <<Modifications>> The present invention is not limited to the above-described embodiments, and various modifications can be adopted within the scope of the present invention. Furthermore, the above-described embodiments can be combined with each other as long as they do not deviate from the scope of the present invention.

[0054] The present invention can also have the following configurations: [1] A quantum information processing device including a control device that controls electrons and a quantum device, wherein the quantum device includes: a semiconductor layer having a plurality of regions in which electrons are stored, a first gate electrode that is disposed on the semiconductor layer and extends in a first direction and stores the electrons in the plurality of regions by applying a voltage to the first gate electrode to form an electric field, and a second gate electrode that extends in a second direction different from the first direction and is formed on a part of the first gate electrode and a part of the semiconductor layer, wherein the second gate electrode includes a first weak link and a first non-coupling part that is wider in the first direction than the first weak link, the semiconductor layer includes a third region facing the first non-coupling part and a fourth region facing the first weak link, and the fourth region is a region where the electrons stored in the region can move in the first direction through the fourth region.

[0055] 101...channel layer, 102...field plate, 103...potential, 104...quantum dot, 105...interaction, 106...non-linking portion, 107...weak linking portion, 501...potential barrier control gate, 502...qubit control gate, 601...potential barrier control gate, 602...qubit control gate, 701...weak linking portion, 702...qubit, 703...non-linking portion

Claims

1. A quantum device comprising: a semiconductor layer having a plurality of regions in which electrons are stored; and a first gate electrode disposed on the semiconductor layer, extending in a first direction, and storing the electrons in the plurality of regions by applying a voltage to the first gate electrode to form an electric field, wherein the first gate electrode includes a weak link portion and a non-coupling portion that is wider in a second direction different from the first direction than the weak link portion, the semiconductor layer includes a first region facing the non-coupling portion and a second region facing the weak link portion, and the second region is a region through which the electrons stored in the region can move in the second direction.

2. A quantum device according to claim 1, which forms a state in which two of the electrons that straddle the first region do not interact with each other, and two of the electrons that straddle the second region do interact with each other.

3. A quantum device according to claim 1, which creates a state in which the electrons do not move through the first region and move in the second direction through the second region.

4. A quantum device according to claim 1, comprising: a second gate electrode extending in the second direction and formed on the first gate electrode; and a third gate electrode extending in the first direction and formed on the second gate electrode.

5. A quantum device according to claim 4, wherein the second gate electrode is formed on the non-coupling portion and is not formed on the weak link portion, and a portion of the third gate electrode is formed so as to be stacked on the weak link portion of the first gate electrode and on portions of the semiconductor layer on both sides of the weak link portion in the second direction.

6. A quantum device according to claim 5, wherein the potential barrier of said second region is selectively controlled by applying a voltage to said third gate electrode.

7. A quantum device according to claim 5, wherein the strength of the bond between the two electrons across the second region is controlled by changing the magnitude of the voltage applied to the third gate electrode.

8. A quantum device according to claim 1, comprising a plurality of the first gate electrodes arranged spaced apart from one another in the second direction perpendicular to the first direction, and a first column region in which the weakly linked portions and the non-linked portions of the first gate electrodes are alternately arranged on a straight line along the second direction.

9. A quantum device according to claim 8, comprising second column regions in which the non-connected portions of the first gate electrodes are continuously aligned on a straight line along the second direction, and the first column regions and the second column regions are arranged alternately in the first direction.

10. A quantum device according to claim 1, wherein the plurality of regions in which the electrons are stored are arranged in a two-dimensional array.

11. A quantum device comprising: a semiconductor layer having a plurality of regions in which electrons are stored; a first gate electrode disposed on the semiconductor layer, extending in a first direction, and storing the electrons in the plurality of regions by applying a voltage to the first gate electrode to form an electric field; and a second gate electrode extending in a second direction different from the first direction and formed on a portion of the first gate electrode and a portion of the semiconductor layer, wherein the second gate electrode includes a first weak link portion and a first non-link portion that is wider in the first direction than the first weak link portion, and the semiconductor layer includes a third region facing the first non-link portion and a fourth region facing the first weak link portion, and the fourth region is a region through which the electrons stored in the region can move in the first direction.

12. A quantum device as described in claim 11, wherein the first gate electrode includes a second weak link portion and a second non-link portion that is wider in the second direction than the second weak link portion, the semiconductor layer includes a first region facing the second non-link portion and a second region facing the second weak link portion, and the second region is a region through which the electrons can pass and move in the second direction.

13. A quantum information processing device comprising: a control device that controls electrons; and a quantum device, wherein the quantum device comprises: a semiconductor layer having a plurality of regions in which the electrons are stored; and a first gate electrode disposed on the semiconductor layer, extending in a first direction, and storing the electrons in the plurality of regions by applying a voltage to the first gate electrode to form an electric field; wherein the first gate electrode comprises a weak link portion and a non-coupling portion that is wider in a second direction different from the first direction than the weak link portion; the semiconductor layer comprises a first region facing the non-coupling portion and a second region facing the weak link portion; and the second region is a region through which the electrons stored in the region can move in the second direction.

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