Carbon nanotube quantum dot modulation device based on acoustic cavity and method

Abstract

The application relates to the fields of quantum architecture design, quantum dots and phononic crystals, and particularly relates to a carbon nanotube quantum dot regulating device and method based on a sound cavity, wherein the device comprises a phononic cavity, a gate electrode, a metal coating, a carbon nanotube and a groove; the regulating method regulates a quantum bit through the coupling of the phononic cavity and the quantum dot from an external input signal, stores a quantum state by using cat state coding in the phononic cavity, improves the reliability of information storage, prolongs the retention time of quantum information, enhances the stability of regulation and reduces errors in the regulation. The design significantly reduces the size of a single quantum bit to micron level, thereby laying a foundation for realizing the chip integration of millions of quantum bits. The design based on the sound cavity not only improves the density and scalability of quantum bits in quantum computing, but also provides a new idea for the development of future large-scale quantum computing by introducing the efficient regulation of the phononic cavity on the quantum dot.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of semiconductors, quantum architecture design, quantum dots, and phononic crystals, and in particular to a carbon nanotube quantum dot regulating device and method based on an acoustic cavity. BACKGROUND

[0002] Quantum computing is a new computing model based on the principles of quantum mechanics, which uses phenomena such as quantum superposition and quantum entanglement to perform complex calculations that traditional computers cannot handle. Since the early 1980s, quantum computing has made significant progress and has gradually become a research focus for governments, technology companies, and academia around the world. Quantum computing not only has the potential to bring revolutionary breakthroughs in cryptography, materials science, drug design, and optimization problems, but also has a profound impact on the advancement of artificial intelligence, machine learning, and other cutting-edge technologies. Around the world, governments and businesses are increasing their investment in quantum computing research. Countries and regions such as China, the United States, and the European Union are particularly competitive in the field of quantum computing. The key to manufacturing a general-purpose quantum computer with quantum advantages lies in a large number of (millions) of quantum bits that are coupled to each other, so the integrability of quantum bits is very important. Our solution can control the area of each bit on the quantum chip to 4 square microns and achieve stable regulation of quantum states, enabling large-scale integrated quantum chips. SUMMARY

[0003] To achieve the above-mentioned application purposes, the technical solutions of the present application are as follows:

[0004] A carbon nanotube quantum dot regulating device based on an acoustic cavity, comprising a phononic cavity, a gate electrode, a metal coating, a carbon nanotube, and a groove,

[0005] The phononic cavity is connected by multiple grids, prepared using piezoelectric material, and located between two electrode plates, with one end receiving external input electrical signals for control and the other end connected to the gate electrode.

[0006] The groove is made of silicon dioxide, with a recess in the middle and a first metal coating and a second metal coating set on the protruding parts on both sides of the recess for grounding.

[0007] The gate electrode is made of metal and located at the bottom of the recess of the groove for controlling the quantum dots on the carbon nanotube.

[0008] The carbon nanotube is suspended in the middle of the recess and spans the groove at both ends, with the first metal coating and the second metal coating in contact.

[0009] As a preferred mode, the quantum bits are regulated by coupling the phononic cavity with the quantum dots from external input signals.

[0010] As a preferred mode, the phonon cavity is made of piezoelectric material LiNbO3 crystal.

[0011] As a preferred mode, the cross-sectional area of the phonon cavity is 1 square micrometer, and the total length of the phonon cavity is 20 micrometers.

[0012] As a preferred mode, the phonon cavity is arranged perpendicularly to the bottom of the groove.

[0013] As a preferred mode, the area occupied by each quantum bit is 4 square micrometers.

[0014] As a preferred mode, the electrode at the end of the phonon cavity receiving the external input electrical signal is separated from the outside by a capacitor, and the capacitor is grounded at the end connected to the phonon cavity.

[0015] As a preferred mode, the first metal coating, the second metal coating and the gate electrode are all made of noble metal.

[0016] As a preferred mode, the first metal coating, the second metal coating and the gate electrode are made of platinum, gold or silver.

[0017] A second object of the present application is to provide a carbon nanotube quantum dot control method based on a sound cavity, using the control device, the quantum bit is controlled by the coupling of the phonon cavity and the quantum dot, the storage of the quantum state is realized by the cat state encoding in the phonon cavity, the reliability of information storage is improved, the retention time of quantum information is prolonged, the stability of control is enhanced and the error in control is reduced.

[0018] The present application has the following advantages: the present application replaces the traditional microwave cavity with the phonon cavity made of piezoelectric material (such as LiNbO3 crystal) to couple with the quantum dot and control the quantum bit. The design significantly reduces the size of a single quantum bit to micrometer level, thereby laying a foundation for the realization of chip integration of millions of quantum bits. This design based on sound cavity not only improves the density and scalability of quantum bits in quantum computing, but also provides a new idea for the development of future large-scale quantum computing by introducing the efficient control of the quantum dot by the phonon cavity, and realizes the stable storage of quantum state based on the cat state encoding of the sound cavity. Compared with the traditional microwave cavity scheme, the sound cavity is more flexible and has more potential. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 A single quantum bit and its control unit are shown.

[0020] Figure 2 A detailed circuit diagram of the link between the sound cavity and the gate electrode.

[0021] Figure 3 An equivalent circuit diagram when storing quantum state, the right side of the dashed line is the external circuit, and the left side of the phonon cavity is connected to the gate electrode.

[0022] Wherein, 1-phonon cavity, 2-gate electrode, 3-first metal coating, 4-second metal coating, 5-trench, 6-carbon nanotube, 7-capacitor, 8-grounding and ATS, 9-phonon crystal acoustic cavity, 10-recess, 11-filter, 12-grounding, 13-ATS. Detailed Implementation

[0023] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0024] Example 1

[0025] like Figure 1 As shown, a carbon nanotube quantum dot manipulation device based on a phonon cavity includes a phonon cavity 1, a gate electrode 2, a metal coating, carbon nanotubes 6, and trenches 5.

[0026] The phonon cavity 1 is composed of multiple interconnected cells, is made of piezoelectric material, and is located between two electrode plates. One end is controlled by an external input electrical signal, and the other end is connected to the gate electrode 2.

[0027] Trench 5: Made of silicon dioxide, with a depression 10 in the middle and a grounded first metal coating 3 and a second metal coating 4 respectively on the surface of the raised parts on both sides of the depression 10.

[0028] Gate electrode 2: Made of metal, located at the bottom of the trench recess 10, used to control quantum dots on carbon nanotubes 6;

[0029] Carbon nanotube 6: The middle part is suspended above the depression 10, and the two ends are across the groove 5 and are in contact with the first metal coating 3 and the second metal coating 4 respectively.

[0030] Specifically, the qubits are controlled by inputting signals from the outside through the coupling of phonon cavity 1 and the quantum dot.

[0031] Specifically, phonon cavity 1 is prepared using piezoelectric material LiNbO3 crystal.

[0032] Specifically, the cross-sectional area of the phonon cavity 1 is 1 square micrometer, and the total length of the phonon cavity is 20 micrometers. The phonon cavity 1 of the present application is not a single structure, but is composed of multiple acoustic cavity units. This modular acoustic cavity design makes the entire regulation system more scalable and flexible, and can adapt to different scales of quantum computing requirements. In addition, the distance between the two sides of the groove is controlled to be about 0.5 micrometers, which ensures the close coupling between the quantum dots and the electrodes. This design makes the conduction path of the electric field and the acoustic field shorter, and the response time faster, effectively improving the operation speed and energy efficiency of the entire quantum bit system.

[0033] Specifically, the phonon cavity 1 is arranged vertically to the bottom of the groove 5.

[0034] Specifically, the area occupied by each quantum bit is 4 square micrometers.

[0035] Specifically, the end electrode of the phonon cavity 1 receiving the external input electric signal is separated from the outside by a capacitor 7, and the capacitor 7 is connected to the ground at the end of the phonon cavity 1. Figure 2 The detailed circuit diagram of the phonon cavity 1 connected to the gate electrode 2.

[0036] The capacitor 7, in order to prevent external interference signals from affecting the regulation process of the quantum dots in the phonon cavity 1, the present application designs the end electrode of the acoustic cavity receiving the external electric signal to be isolated from the outside by the capacitor 7. This capacitor not only plays a protective role for the acoustic cavity and quantum dots, but also can filter the input signal to ensure the signal quality entering the system. This design greatly enhances the anti-interference ability of the system, making the quantum bit regulation process more stable and reliable. In addition, the electrode connected to the phonon cavity 1 needs to be grounded, which further ensures the stability of the electric field of the entire system and the anti-electromagnetic interference ability.

[0037] Specifically, the first metal coating 3, the second metal coating 4 and the gate electrode 2 are all made of noble metals. They have high electrical conductivity.

[0038] The selection of noble metals is mainly based on their high electrical conductivity and oxidation resistance. These characteristics ensure that the electrodes will not have problems such as decreased electrical conductivity or material loss under long-term work. In addition, the application of noble metals further enhances the electric field control effect between the electrodes and the carbon nanotube quantum dots, making the regulation process of quantum bits more accurate. Through the optimization design of noble metal electrodes, the entire system not only has high electric signal conduction ability, but also maintains stable performance under different temperature, pressure and environmental conditions. This provides important technical support for the field of quantum computing, which is sensitive to environmental changes.

[0039] Specifically, the first metal coating 3, the second metal coating 4 and the gate electrode 2 are made of platinum, gold and silver.

[0040] The embodiment also provides a carbon nanotube quantum dot regulation method based on an acoustic cavity.

[0041] The phononic crystal cat state encodes a quantum state to be stored as a quantum storage unit. The cat state encoding is a way to generate a physical quantum bit by encoding a quantum bit with multiple phonons. This actually increases the distance between the 0 state and the 1 state in the physical space, and forms two potential barriers in the potential energy space, thereby greatly reducing the probability of bit flip error and maintaining the stability of the bit in a noisy environment. The cat state is less sensitive to phase noise, which makes it better able to resist quantum coherence loss problems and helps to extend the storage time of quantum information. Cat state encoding of the quantum bit can reduce the coherence decay caused by environmental interference, thereby improving the storage quality of the quantum state. In addition, in quantum algorithms, noise or errors are easily introduced when operating quantum bits. Cat state encoding helps to stabilize the phase relationship of the quantum bit, thereby making the quantum gate operation more accurate, which is very important for improving the execution reliability of quantum algorithms. In summary, after cat state encoding, the stability of various operations of the quantum bit is greatly improved, thereby providing a more stable foundation for the regulation of the quantum bit, and helping to improve the reliability of quantum storage and quantum computing, and reducing the practical threshold.

[0042] The phononic cavity 1 is coupled with the quantum dot, and the application adopts the phononic cavity 1 as a regulation unit coupled with the quantum dot, and uses a piezoelectric material LiNbO3 crystal to prepare the acoustic cavity. The acoustic cavity structure can replace the traditional microwave cavity, realizes more precise quantum bit control, and the size of a single quantum bit is greatly reduced to the micron level. Through the design, the density of quantum bits on the quantum chip is greatly improved, which provides a possibility for future integration of millions of quantum bits.

[0043] Embodiment 2

[0044] The difference between the embodiment and the embodiment 1 is that:

[0045] (1) Preparation of the phononic cavity 1

[0046] The fabrication process of phononic crystals is a precise nanofabrication process. Lithium niobate (LiNbO3) thin film is used as the phononic crystal material, and the common film thickness is 200 nanometers, deposited on a high-resistance silicon substrate (resistivity greater than 3 kΩ·cm). Lithium niobate is a piezoelectric material that can efficiently couple between mechanical vibration and electric field, so it is very suitable for this device.

[0047] Firstly, the film needs to be thinned. The LiNbO3 thin film is thinned from the original thickness (such as 500 nanometers) to the required 200 nanometers by argon ion etching. This is to ensure that the thickness of the film is suitable for the propagation of high-frequency sound waves and the manufacture of phononic crystal structures. Then, in order to create a one-dimensional or two-dimensional periodic structure on the film, electron beam lithography technology is used. These structures usually have sub-micron dimensions. In this process, the lattice constant is 1 micrometer to ensure that a phononic band gap can be formed near the target frequency (such as 6 GHz).

[0048] Through periodic patterning, the phononic crystal can form a complete band gap in a certain frequency range (such as 6.0-6.5 GHz), i.e. there will be no sound wave propagation in this frequency range. A defect region with a size of 1.6 micrometers (length) and 500 nanometers (width) is introduced at the center of the lattice. This helps to localize mechanical vibrations and form a resonance mode, which can bind the sound wave to the defect and achieve an ultra-small mode volume (<1 cubic micrometer).

[0049] Aluminum (Al) is deposited on the film to make a superconducting Josephson junction using the "Dolan bridge double-angle evaporation process". The thickness of the electrode is usually 200 nanometers, and the electrode is arranged at a distance of 200 nanometers from the defect point to couple the phonon mode and the microwave circuit, achieving control and readout of the electrical signal.

[0050] In order to eliminate the clamping loss of phonons, the phononic crystal structure is suspended by selectively removing the silicon substrate (such as by using XeF2 gas etching), so as to avoid the loss of phonons to the substrate.

[0051] (2) Cat state encoding and storage of quantum states

[0052] The phonon crystal cat state is encoded to store quantum states as a quantum storage unit. The cat state encoding is a kind of multi-particle entangled state, which is an important encoding method in quantum computing and quantum information. In which, the quantum bit can be in the superposition of two extreme states, with the significance of noise resistance, enhanced entanglement, etc. The storage unit in the present application is divided into three parts, one is the phonon crystal, the second is the reservoir, and the third is the readout and write unit of the phonon state. The phonon crystal serves as a storage medium for phonon states, while the reservoir serves as a regulating unit for regulating phonon states to assist in cat state encoding. The key device of the reservoir is ATS and filter, and the filter is set here to filter out waves of specific frequencies.

[0053] Among them, ATS is an asymmetrically threaded superconducting quantum interference device (Asymmetrically Threaded Superconducting Quantum Interference Device), which is usually composed of two Josephson junctions and inductance, and its characteristic is that the magnetic flux passing through it is asymmetrically distributed. This asymmetric structure is usually realized by applying different currents or different geometric designs on the two Josephson junctions. The quantumization of electromagnetic excitation of ATS is "photon", which can absorb the noise in the quantum dot of the acoustic cavity and filter out unnecessary frequency components to a certain extent, helping to maintain the coherence and stability of the cat state quantum bit. Therefore, the ATS as a buffer plays a role in stabilizing the system and prolonging the lifetime of the quantum state through interaction with the cat state quantum bit.

[0054] In the process of storing quantum states, the circuit diagram is as shown in Figure 3 The electrical signal input by the external circuit or waveguide enters the parallel circuit of the capacitor and the ATS after passing through the filter, and after filtering out unnecessary frequency components, it acts on the phonon crystal. Quantum vibration modes of corresponding frequencies are generated in the phonon crystal to obtain cat states. The phonons in the cat state are converted into photons in the circuit due to nonlinear interaction, and when they are transferred to the buffer zone (ATS), they can temporarily store the energy to avoid premature decoherence of the cat state.

[0055] The above embodiments only illustrate the principles and effects of the present application, and are not used to limit the present application. Any person skilled in the art can modify or change the above embodiments without departing from the spirit and scope of the present application. Therefore, all equivalent modifications or changes made by those skilled in the art without departing from the spirit and technical idea disclosed by the present application should be covered by the claims of the present application.

Claims

1. A carbon nanotube quantum dot manipulation device based on an acoustic cavity, characterized in that: Including phonon cavities, gate electrodes, metal coatings, carbon nanotubes, and trenches. The phonon cavity is composed of multiple interconnected cells, made of piezoelectric material, and located between two electrode plates. One end receives external input electrical signals for control, and the other end is connected to the gate electrode. Trench: Made of silicon dioxide, the middle of the trench is concave, and the raised parts on both sides of the concave are respectively provided with a grounded first metal coating and a second metal coating. Gate electrode: Made of metal, located at the bottom of the trench, used to control quantum dots on carbon nanotubes; Carbon nanotubes: The middle part is suspended above the depression, and the two ends span the groove and are in contact with the first metal coating and the second metal coating respectively; The phonon cavity is positioned perpendicular to the bottom of the trench; One end of the phonon cavity that receives the external electrical signal is separated from the outside by a capacitor, and the end of the capacitor connected to the phonon cavity is grounded. A phonon cavity is composed of multiple acoustic cavity units; Quantum bits can be controlled by inputting signals from the outside through the coupling of phonon cavity and quantum dot; By controlling the distance between the two sides of the trench, a tight coupling between the quantum dot and the electrode is ensured.

2. The carbon nanotube quantum dot manipulation device based on an acoustic cavity as described in claim 1, characterized in that: The phonon cavity was prepared using the piezoelectric material LiNbO3 crystal.

3. The carbon nanotube quantum dot manipulation device based on an acoustic cavity as described in claim 1, characterized in that: The phonon cavity has a cross-sectional area of ​​1 square micrometer and a total length of 20 micrometers.

4. The acoustic cavity-based carbon nanotube quantum dot manipulation device as described in claim 1, characterized in that: Each qubit occupies an area of ​​4 square micrometers.

5. The carbon nanotube quantum dot manipulation device based on an acoustic cavity as described in claim 1 is characterized in that: The first metal coating, the second metal coating, and the gate electrode are all made of precious metals.

6. The carbon nanotube quantum dot manipulation device based on an acoustic cavity as described in claim 1 is characterized in that: The first metal coating, the second metal coating, and the gate electrode are made of platinum, gold, and silver.

7. A method for controlling carbon nanotube quantum dots based on an acoustic cavity, using the control device according to any one of claims 1 to 6, characterized in that: The quantum bits are controlled by inputting signals from the outside through the coupling of the phonon cavity and the quantum dot, and the quantum state is stored by using the cat state encoding inside the phonon cavity.

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