JP2022133191A - Quantum information processing device - Google Patents

Abstract

To efficiently cool quantum bits of a quantum information processing device including a plurality of quantum bits.SOLUTION: A quantum information processing device comprises: a quantum bit array part in which a plurality of quantum bits are disposed; a cooling plate layer; a control circuit which controls the quantum bit array part; and a heat conductive material layer which is disposed between a first layer including the quantum bit array part and the cooling plate layer and electrically independent of the quantum bit array part and the control circuit.SELECTED DRAWING: Figure 3

Description

The present invention relates to the structure of semiconductor devices, particularly devices used in quantum information processing.

Currently, many groups around the world are conducting research aimed at realizing quantum computers. Quantum computers are expected to use quantum mechanical phenomena such as superposition and quantum entanglement to solve problems that conventional computers could not solve in a realistic time and scale. Experiments are being conducted in various physical systems, but regardless of which physical system is used, what is first required to realize a quantum computer is to create quantum bits in an isolated system that does not exchange matter or energy with the outside world, is to be able to maintain the coherence of

However, in a real physical system, decoherence due to interactions with the outside world cannot be completely avoided. Efforts to reduce the decoherence of qubits and increase the coherence time are ongoing in experiments using any physical system. Furthermore, in order to operate as a quantum computer, it is not enough to fabricate a single qubit, and multiple qubits must be configured as a device that satisfies the following three requirements.

The first requirement is to be extensible. One of the reasons why quantum computers can perform high-speed operations is that the dimension of the Hilbert space increases exponentially with respect to the number of qubits by utilizing quantum superposition. However, it would be meaningless if the costs (time, space, energy, etc.) required to control the qubits would increase exponentially at the same time. In order to control the qubits, an electric circuit for applying RF pulses (Radio Frequency Pulse) and a dilution refrigerator for cooling the qubits to extremely low temperatures are required. A mechanism is needed that allows the number of qubits to be expanded without increasing the cost.

The second requirement is that arbitrary quantum operations are possible. Quantum computers, like classical computers, consist of basic logic gates, specifically called quantum gates in the case of quantum computers. Quantum gates include rotation gates, which are one-qubit gates, and controlled-NOT gates, which are two-qubit gates. "Any quantum operation is possible" means that an arbitrary quantum state can be reached with a finite number of quantum gate operations. In gate-type quantum computers, it is theoretically shown that arbitrary quantum operations are possible by combining rotation gates and controlled-NOT gates. In other words, if these quantum gate operations can be performed in arbitrary quantum bits, arbitrary quantum operations become possible.

A third requirement is that error correction is possible. In order to realize a quantum computer using real quantum bits with decoherence, it is necessary to have a function (quantum error correction) to correct errors caused by decoherence. Many algorithms have been proposed for quantum error correction, but in any algorithm, "initialization" and "reading" are performed to eliminate the entropy caused by decoherence. “Initialization” is an operation to reinitialize a pure state when the superposition state of qubits has become a mixed state due to decoherence. "Reading" is the operation of measuring the state of a qubit with quantum-mechanically acceptable accuracy. At present, an algorithm called Surface Code is expected to be the most promising method for error correction. Surface Code operates on physical qubit strings arranged in a two-dimensional square lattice.

In other words, it is possible to extend the number of qubits two-dimensionally while maintaining a common device for controlling qubits with long coherence times, and in any qubit, ``initialization'', ``rotation gate operation'', and `` If it can be configured as a quantum bit string capable of "control NOT gate operation" and "readout s", it is expected that it can be operated as a quantum computer.

Special Table 2018-532255 US2013/0258595 A1

In order to operate qubits as a quantum computer, it is essential not only to pursue the performance of a single qubit, but also to construct a device that includes multiple qubits. Since it is widely recognized that a two-dimensional extension is necessary for operation as a quantum computer, such a structure of a quantum bit string has been proposed (Patent Document 1).

This is intended to individually control a two-dimensionally extended quantum bit array by switching with wires and transistors formed in the upper layer. However, if a quantum bit with a complicated structure is formed in the lower layer, the crystallinity of the substrate cannot be maintained up to the upper layer, so it is difficult to form a transistor in the upper layer with current semiconductor fabrication technology. On the other hand, we have devised a structure of a qubit array that can be extended to two dimensions and that can be fabricated using current semiconductor manufacturing methods, and a fabrication method thereof.

Also, regarding quantum computers, the problem of heat control is known as a problem to be considered (Patent Document 2).

When operating semiconductor or superconducting qubits, cooling to cryogenic temperatures using a dilution refrigerator is widely used to reduce the effects of thermal noise. The number of wires electrically connecting the inside and outside of the dilution refrigerator is limited. Therefore, in order to operate a qubit array including multiple qubits that requires a large number of input signals and output signals, the input signal and the output signal are controlled inside the dilution refrigerator in addition to the qubit array. A control circuit for this is required.

Since many electrical wires are required between the qubit string and the control circuit, part of the control circuit must be placed in the vicinity of the qubit string. Joule heat is generated when the qubit array and control circuit operate, but if the temperature of the qubit array rises due to heat, the coherence time of the qubit string will shorten, which will eventually lead to the performance degradation of the quantum computer.

An object of the present invention is to efficiently cool the qubits of a quantum information processing device including a plurality of qubits.

A preferred aspect of the present invention is a first layer comprising a qubit array unit in which a plurality of qubits are arranged, a cooling plate layer, a control circuit for controlling the qubit array unit, and the qubit array unit and the cooling plate layer and electrically independent of the quantum bit array section and the control circuit.

Another preferable aspect of the present invention includes a substrate, a qubit array unit arranged on the substrate and having a plurality of qubits arranged thereon, a control circuit for controlling the qubit array unit, and a first a first cooling plate layer arranged on the surface side of the substrate, a second cooling plate layer arranged on the second surface side of the substrate, and between the qubit array unit and the first cooling plate layer , and between the qubit array section and the second cooling plate layer, and is electrically independent of the qubit array section and the control circuit. A quantum information processing device characterized by having a material member.

Another preferable aspect of the present invention includes a substrate, a qubit array unit arranged on the substrate and having a plurality of qubits arranged thereon, and a control circuit arranged on the substrate and controlling the qubit array unit. , a first cooling plate layer disposed on the first surface side of the substrate, and at least one of a vacuum region and a heat insulating material region disposed between the qubit array section and the control circuit. A quantum information processing device characterized by

ADVANTAGE OF THE INVENTION According to this invention, the quantum bit of the quantum information processing apparatus containing several quantum bits can be cooled efficiently.

1 is a top view of a quantum information processing device of the present invention; FIG. 1 is a cross-sectional view of a quantum information processing device of the present invention; FIG. 1 is a sectional view of Embodiment 1 of a quantum information processing device cooling structure of the present invention; FIG. FIG. 4 is a cross-sectional view of Embodiment 2 of the quantum information processing device cooling structure of the present invention; FIG. 5 is a cross-sectional view of Embodiment 3 of the quantum information processing device cooling structure of the present invention; FIG. 10 is a cross-sectional view of Embodiment 4 of the quantum information processing device cooling structure of the present invention;

Embodiments will be described in detail with reference to the drawings. However, the present invention should not be construed as being limited to the description of the embodiments shown below. Those skilled in the art will easily understand that the specific configuration can be changed without departing from the idea or gist of the present invention.

In the configurations of the embodiments described below, the same reference numerals may be used in common for the same parts or parts having similar functions in different drawings, and redundant description may be omitted.

When there are a plurality of elements having the same or similar functions, they may be described with the same reference numerals and different suffixes. However, if there is no need to distinguish between multiple elements, the subscripts may be omitted.

Notations such as “first”, “second”, “third” in this specification etc. are attached to identify the constituent elements, and do not necessarily limit the number, order, or content thereof is not. Also, numbers for identifying components are used for each context, and numbers used in one context do not necessarily indicate the same configuration in other contexts. Also, it does not preclude a component identified by a certain number from having the function of a component identified by another number.

The position, size, shape, range, etc. of each configuration shown in the drawings, etc. may not represent the actual position, size, shape, range, etc., in order to facilitate understanding of the invention. Therefore, the present invention is not necessarily limited to the positions, sizes, shapes, ranges, etc. disclosed in the drawings and the like.

All publications, patents and patent applications cited herein are hereby incorporated by reference into this description.

Elements presented herein in the singular shall include the plural unless the context clearly dictates otherwise.

A first aspect of the present embodiment includes a qubit array section in which a plurality of qubits are arranged, a cooling plate layer of a dilution refrigerator, a control circuit for controlling the qubit array section, and the qubit array section. A quantum information processing device characterized by having a thermally conductive material layer disposed between the first layer and the cooling plate layer and electrically independent of the quantum bit array section and the control circuit This is the structure of the cooling mechanism.

A second aspect of the present embodiment is a method for manufacturing the quantum information processing device cooling mechanism according to the first aspect.

First, a standard cooling method for a quantum information processing device including a qubit array and a control circuit will be described.

FIG. 1 shows a top view of a quantum information processing device. The quantum information processing device 101 includes a quantum bit array 102 and a control circuit 103 . Quantum information processing device 101 has a configuration of 1 cm square, which is created by applying semiconductor manufacturing technology, for example, and has quantum bit array 102 arranged in the center, and control circuit 103 surrounds quantum bit array 102 .

A plurality of wirings 104 are provided between the qubit array 102 and the control circuit 103, and the qubit array 102 and the control circuit 103 are electrically connected. In addition, there are a plurality of pads 105 which are electrically connected to the control circuit 103 . The quantum information processing device 101 is installed inside a dilution refrigerator (not shown), and the quantum information processing device 101 and the outside of the dilution refrigerator are electrically connected through pads 105 . The dilution refrigerator is, for example, a 3-m-cubic housing, and a plurality of quantum information processing devices 101 can be arranged in the dilution refrigerator.

FIG. 2 shows a cross-sectional view of the quantum information processing device of FIG. The qubit array 102 and the control circuit 103 are formed on a silicon substrate 201 (thickness of several hundred μm). The qubit array 102 and the control circuit 103 are respectively composed of a channel 202 made of silicon and a gate 203 made of polysilicon, the channel 202 and the gate 203 forming a transistor structure.

In the qubit array 102, single electrons are trapped in the transistor structure and act as qubits. In control circuit 103, the transistor structure operates as a normal transistor. Channels and gates are electrically separated from each other by an interlayer insulating film 204 made of silicon oxide and spacers 205 made of silicon nitride, and are electrically connected to each other by wirings 104 .

Since it is electrically connected to the outside of the dilution refrigerator through the pad 105 on the upper side of FIG. 2, it is fixed to the cooling plate 206 of the dilution refrigerator through the silicon substrate 201 on the lower side of FIG. The cooling plate 206 is cooled to an extremely low temperature (temperature of several 10 mK), and the heat generated by the qubit array 102 and the control circuit 103 is transferred to the cooling plate through the thermal resistance 207 between the quantum information processing device 101 and the cooling plate 206. 206. At the same time, heat generated in control circuit 103 is conducted to qubit array 102 through thermal resistance 208 between control circuit 103 and qubit array 102 .

Hereinafter, embodiments according to the present invention will be described with reference to the drawings. However, the present invention should not be construed as being limited to the description of the embodiments shown below. Those skilled in the art will easily understand that the specific configuration can be changed without departing from the idea or gist of the present invention.

In the first embodiment, differences from the configuration of FIG. 2 will be described.
As shown in FIG. 3, a structure is fabricated in which the substrate 201 made of silicon in FIG. 2 is replaced with a substrate 301 made of a thermally conductive material. First, as shown in FIG. 2, a quantum bit array 102 and a control circuit 103 are fabricated based on a substrate 201 made of silicon. After fabrication, the substrate 201 made of silicon is removed by etching. The remaining portion is attached to a substrate 301 made of a thermally conductive material having a lower thermal resistance than silicon. Examples of thermally conductive materials include metallic materials such as aluminum and copper. Examples of thermally conductive materials are the same for other embodiments.

This configuration reduces the thermal resistance 207 between the quantum information processing device 101 and the cooling plate 206 . As a result, the heat generated by the qubit array 102 and the control circuit 103 is quickly transferred to the cooling plate 206, preventing the temperature of the qubit array 102 from rising. The substrate 301 made of a heat-conducting material is electrically independent from the quantum bit array 102 and the control circuit 103 by the interlayer insulating film 204 and the like. no.

In a second embodiment, differences from the configuration of FIG. 2 will be described.
As shown in FIG. 4, a part 401 made of a thermally conductive material is formed on the upper side of the quantum bit array 102 (on the side opposite to the substrate 201). At the same time, the interposer 402 and the second cooling plate 403 are used to hold down and fix the quantum information processing device 101 from above.

A thermally conductive material region 404 is formed where the interposer 402 made of an insulator such as silicon oxide contacts the quantum bit array 102 . The thermally conductive material region 404 may be a bulk of thermally conductive material, or may be a via structure formed in the substrate of the interposer plated with a conductive material such as metal. Examples of thermally conductive materials include metallic materials such as aluminum and copper.

This configuration reduces thermal resistance 406 between qubit array 102 and cooling plate 403 . As a result, the heat generated in the quantum bit array 102 is quickly transferred to the second cooling plate 403, and the temperature of the quantum bit array 102 can be prevented from rising.

When the interposer 402 is used to fix the quantum information processing device 101 in this way, it is not necessary to bond the quantum information processing device 101 and the cooling plate 403 together, and it is sufficient to just press them together. This provides an effect of preventing either of the quantum information processing device 101 and the cooling plate 403 from being damaged due to a difference in thermal expansion coefficient between them when the temperature changes.

On the other hand, a wiring 405 is formed in a portion where the interposer 402 is in contact with the pad 105 . Thereby, cooling of the quantum bit array 102 and electrical connection between the quantum information processing device 101 and an external control device or power supply device of the dilution refrigerator can be simultaneously obtained. The substrate 201 made of silicon in FIG. 2 may be replaced with the substrate 301 made of a thermally conductive material in FIG. 3 to further improve the cooling efficiency.

In Example 3, differences from the configuration of Example 2 (FIG. 4) will be described.
As shown in FIG. 5, a vacuum region or insulating material region 501 is formed between the qubit array 102 and the control circuit 103 . After fabricating the qubit array 102 and the control circuit 103 as shown in FIG. 2, the interlayer insulating film 204 is etched from the lower side of the substrate 201 to form grooves to form vacuum regions, and a heat insulating material is deposited in the grooves. Insulating material area.

Examples of insulating materials include silicon oxide and silicon nitride. Then, the thermal resistance between the qubit array 102 and the control circuit 103 increases. Although the effect is greater in the vacuum region than in the heat insulating material region, when the quantum information processing device 101 is fixed using the interposer 402, stress is applied in the vacuum region and the quantum information processing device 101 may be damaged. Therefore, in that case, a heat insulating material area is used. Thereby, it is possible to prevent the heat generated in the control circuit 103 from being transferred to the quantum bit array 102 and the temperature of the quantum bit array 102 from rising.

As in Embodiments 2 and 3, the first cooling plate layer arranged on the first surface side of the layer in which the qubit array 102 and the control circuit 103 are arranged, and the second cooling plate layer of the first layer two second cooling plate layers disposed on the face side, at least one between the qubit array and the first cooling plate layer and between the qubit array and the second cooling plate layer; Furthermore, by providing a thermally conductive material member electrically independent of the quantum bit array section and the control circuit, efficient cooling becomes possible.

In the fourth embodiment, differences from the configuration of the third embodiment (FIG. 5) will be described.
As shown in FIG. 6, an electrically conductive material region 601 is formed between the qubit array 102 and the control circuit 103 . The electrically conductive material region 601 can be formed by depositing an electrically conductive material over a portion of the vacuum region or the insulating material region 501 .

With this configuration, an electromagnetic field generated when the control circuit 103 operates as a transistor is shielded, and can be prevented from being transmitted to the quantum bit array 102 . Accordingly, together with the mechanism shown in the third embodiment, it is possible to simultaneously prevent deterioration of the coherence time of the qubits of the qubit array 102 due to heat and electromagnetic fields.

The present invention is not limited to the above-described embodiments, and includes various modifications. For example, it is possible to replace part of the configuration of one embodiment with the configuration of another embodiment, or to add the configuration of another embodiment to the configuration of one embodiment. Moreover, it is possible to add, delete, or replace a part of the configuration of each embodiment with the configuration of another embodiment. For example, the quantum bit array 102 does not have to be placed in the central part of the quantum information processing device 101, and a plurality of quantum bit arrays 102 may be placed in arbitrary places. The control circuit 103 does not have to be arranged in the peripheral part of the quantum information processing device 101, and a plurality of control circuits may be arranged at arbitrary places. Although Example 1, Example 2, Example 3, and Example 4 can be implemented independently, a plurality of them may be combined and implemented at the same time.

The terms “electrode” and “wiring” in this specification and the like do not functionally limit these components. For example, an "electrode" may be used as part of a "wiring" and vice versa. Furthermore, the terms "electrode" and "wiring" include the case where a plurality of "electrodes" and "wiring" are integrally formed.

DESCRIPTION OF SYMBOLS 101... Quantum information processing apparatus, 102... Quantum bit array, 103... Control circuit, 104... Wiring, 105... Pad, 201... Silicon substrate, 202... Channel, 203... Gate, 204... Interlayer insulating film, 205... Spacer , 206... Cooling plate, 207... Thermal resistance between quantum information processing device and cooling plate, 208... Thermal resistance between quantum bit array and control circuit, 301... Substrate made of thermally conductive material, 401... Thermal conduction Parts made of material 402 Interposer 403 Second cooling plate 404 Thermal conductive material area in interposer 405 Wiring in interposer 501 Vacuum area or insulating material area 601 Electric conduction material area.

Claims (15)

a qubit array unit in which a plurality of qubits are arranged;
a cooling plate layer;
a control circuit that controls the quantum bit array unit;
characterized by having a thermally conductive material layer disposed between the first layer including the qubit array section and the cooling plate layer and electrically independent of the qubit array section and the control circuit. do,
Quantum information processing device. The thermally conductive material layer is a layer containing a metal material and having a lower thermal resistance than silicon,
The quantum information processing device according to claim 1 . disposing a second cooling plate layer on the side of the first layer opposite to the side on which the cooling plate layer is disposed;
characterized by having a second thermally conductive material layer between the second cooling plate layer and the qubit array section,
The quantum information processing device according to claim 1 . placing an interposer between the second cooling plate layer and the first layer;
the interposer has a thermally conductive material region thermally connecting the second thermally conductive material layer and the second cooling plate layer;
4. The quantum information processing device according to claim 3. characterized by having at least one of a vacuum region and a heat insulating material region between the qubit array unit and the control circuit,
The quantum information processing device according to claim 1 . characterized by having an electrically conductive material region between the qubit array unit and the control circuit,
The quantum information processing device according to claim 1 . a substrate;
a qubit array unit arranged on the substrate and having a plurality of qubits;
a control circuit that controls the quantum bit array unit;
a first cooling plate layer disposed on the first surface side of the substrate;
a second cooling plate layer disposed on the second side of the substrate;
provided between the qubit array unit and the first cooling plate layer and between the qubit array unit and the second cooling plate layer, the qubit array unit and the control characterized by having a thermally conductive material member having a lower thermal resistance than silicon, which is electrically independent of the circuit,
Quantum information processing device. the thermally conductive material member comprises a metallic material,
8. The quantum information processing device according to claim 7. the thermally conductive material member provided between the qubit array unit and the first cooling plate layer is a first metal material layer,
The thermally conductive material member provided between the qubit array section and the second cooling plate layer includes a second metal material layer provided on the substrate and between the substrate and the second cooling plate layer. metal disposed in a via structure formed in an interposer interposed between
8. The quantum information processing device according to claim 7. characterized by having at least one of a vacuum region and a heat insulating material region between the qubit array unit and the control circuit,
8. The quantum information processing device according to claim 7. characterized by having an electrically conductive material region between the qubit array unit and the control circuit,
8. The quantum information processing device according to claim 7. a substrate;
a qubit array unit arranged on the substrate and having a plurality of qubits;
a control circuit arranged on the substrate and controlling the quantum bit array unit;
a first cooling plate layer disposed on the first surface side of the substrate;
Having at least one of a vacuum region and a heat insulating material region disposed between the qubit array unit and the control circuit,
Quantum information processing device. characterized by comprising a thermally conductive material member having a thermal resistance lower than that of silicon provided between the quantum bit array section and the first cooling plate layer and electrically independent of the quantum bit array section and the control circuit. do,
13. The quantum information processing device according to claim 12. disposing a second cooling plate layer on a side of the substrate opposite to the side on which the first cooling plate layer is disposed;
characterized by having a second thermally conductive material layer between the second cooling plate layer and the qubit array section,
13. The quantum information processing device according to claim 12. characterized by having an electrically conductive material region between the qubit array unit and the control circuit,
13. The quantum information processing device according to claim 12.

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