Topological quantum bit reading implementation method based on scanning tunnel spectrum

Abstract

A topological quantum bit reading implementation method based on a scanning tunnel spectrum is implemented through a topological quantum bit reading device comprising a pair of superconducting islands arranged on a topological insulator substrate and superconducting quantum dots located between the superconducting islands, and the pair of superconducting islands are isolated from each other. A pair of MZEM exists in the magnetic flux vortex in each superconductive island and the edge of the superconductive island, and the MZEM at the edges of the two superconductive islands can be controlled and fused at the superconductive quantum dots. According to the invention, the verification of the non-Abell statistical characteristics of the Margarner zero-energy module before the execution of the topological quantum bit logic operation can be ensured; the requirement for accurate positioning of the magnetic flux vortex during topological quantum bit reading is lowered, and controlled connection and isolation between one or more topological quantum bit reading devices and the weaving area are achieved through the reading isolation area.

Description

Technical Field

[0001] This invention relates to a technology in the field of topological quantum mechanics, specifically a method for reading topological qubits based on scanning tunneling spectrum. Background Technology

[0002] The core challenges in realizing topological quantum computing include determining the non-Abelian statistical properties of Majorana zero modes (MZMs) and reading the states of topological qubits. Existing techniques utilize fast radio frequency circuits to achieve parity-check readings in Majorana nanowires based on capacitance measurements; however, this method struggles to distinguish between topological Majorana zero modes and non-topological Andreev bound states, requiring further verification of the non-Abelian statistical properties. Existing techniques for weaving non-Abelian anyons using magnetic field arrays also face difficulties in precisely controlling the manipulation position during readings, leading to significant computational errors. Summary of the Invention

[0003] To address the aforementioned shortcomings of existing technologies, this invention proposes a method for reading topological qubits based on scanning tunneling spectrum. This method ensures the verification of the non-Abelian statistical properties of Majorana zero modes before performing logical operations on topological qubits, reduces the requirement for precise positioning of magnetic flux vortices during topological qubit reading, and enables controlled connection and isolation between single or multiple topological qubit reading devices and the braided region through a reading isolation region.

[0004] This invention is achieved through the following technical solution:

[0005] The present invention relates to a topological qubit readout device based on scanning tunneling spectrum, comprising: a pair of superconducting islands disposed on a topological insulator substrate and a superconducting quantum dot located between the superconducting islands, wherein: the pair of superconducting islands are isolated from each other, a pair of Majorana zero modes exist in the magnetic flux vortex and at the edge of each superconducting island, and the Majorana zero modes at the edges of the two superconducting islands can be controlled to merge at the superconducting quantum dot.

[0006] The aforementioned topological insulator substrate is used to provide large-area topological surface states with uniform properties, and is preferably made of a three-dimensional topological insulator material.

[0007] When the topological insulator substrate and the superconducting island react during the evaporation process, it is preferable to place an intermediate layer with a large area of ​​uniform topological surface states between them.

[0008] The area of ​​the superconducting island is larger than the range of the spatial distribution of Majorana zero-energy mode wavefunctions in the magnetic flux vortex and smaller than the area that allows multiple magnetic flux vortices to occupy. This ensures that the Majorana zero-energy mode at the edge of the superconducting island is not coupled with the Majorana zero-energy mode in its internal magnetic flux vortex, while also preventing the occurrence of multiple magnetic flux vortex states and ensuring the existence of the Majorana zero-energy mode at the edge of the superconducting island.

[0009] The charging energy of the superconducting quantum dot is greater than its superconducting band gap to produce charge-dependent superconducting ground state parity that can be distinguished by scanning tunneling spectra.

[0010] Both the superconducting quantum dots and the superconducting islands are made of superconducting materials.

[0011] The present invention relates to a topological qubit readout assembly, comprising several pairs of topological qubit readout devices, each pair of topological qubit readout devices being connected by a braided region, wherein: an isolation region is provided between the superconducting island on the topological qubit readout device and the braided region.

[0012] The isolation region includes: a superconducting layer located on a topological insulator substrate and connected to the superconducting island; an insulating layer disposed outside the superconducting layer for superconductivity suppression; and a heating layer. When the topological qubit is initialized or read, the superconductivity of this read isolation region should be suppressed to avoid coupling between the Majorana zero mode of the topological qubit read device and other Majorana zero modes present in the braided region, i.e., the read isolation region is turned off. When the Majorana zero mode is moved out of the read device after the topological qubit is initialized, or when the Majorana zero mode is moved into the read device after the topological qubit is braided, the superconductivity of this read isolation region should be restored, thereby providing a channel for the Majorana zero mode to enter and exit the read device, i.e., the read isolation region is opened.

[0013] The heating layer is preferably made of an electrothermal material.

[0014] This invention relates to a topological quantum bit readout method based on scanning tunneling spectrum using the aforementioned device, comprising: a topological quantum bit initialization stage and a topological quantum bit readout stage. By probing the charge parity-dependent scanning tunneling spectrum caused by the fusion of edge Majorana zero modes at superconducting quantum dots, the non-Abelian statistical properties of Majorana zero modes are effectively verified, ensuring the robustness of the topological quantum computing process to disorder and decoherence.

[0015] The aforementioned topological qubit initialization phase specifically includes:

[0016] A. A voltage pulse is applied to the superconducting quantum dot through the tip of a scanning tunneling microscope to initialize its charge state;

[0017] The amplitude and width of the voltage pulse are such that the charge state of the superconducting quantum dot is initialized to a definite odd or even charge state without destroying the crystal structure and geometry of the superconducting quantum dot.

[0018] B. Majorana zero modes were induced at the edges of two superconducting islands using a magnetic field, fused in a superconducting quantum dot, and their non-Abelian statistical properties were verified by scanning tunneling spectroscopy. They were then decoupled.

[0019] The scanning tunneling spectrum relies on the charge parity result caused by Majorana zero-mode fusion, which can verify the Abelian statistical characteristics and characterize the state of the topological qubit.

[0020] The aforementioned topological qubit readout stage specifically includes:

[0021] C. After the Majorana zero mode in the flux vortex leaves the readout device and enters the braided region, the charge state of the superconducting quantum dot is reinitialized;

[0022] D. After the Majorana zero modes in the flux vortex are woven and moved back to the superconducting island from the woven region, the edge Majorana zero modes are fused at the superconducting quantum dot, and the state of the topological qubit is read by scanning the tunneling spectrum.

[0023] In step D, the Majorana zero energy mode in the flux vortex is not limited to a precise position; it is satisfied as long as it is located within the superconducting island.

[0024] Technical effect

[0025] This invention utilizes the localization of the fusion of edge Majorana zero modes at superconducting quantum dots during topological qubit reading, thereby reducing the requirement for precise localization of Majorana zero modes in magnetic flux vortices; by achieving controlled connection and isolation between single or multiple topological qubit reading devices and braided regions through the reading isolation region, the state of multiple topological qubits can be read simultaneously. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the structure of the present invention;

[0027] In the figure: topological insulator substrate 1, superconducting island 2, superconducting quantum dot 3, where (a) is a top view of the device and (b) is a cross-sectional view of the device at section AA.

[0028] Figure 2 This is a flowchart of an implementation example;

[0029] In the figure: γ1~γ4 are Majorana zero modes, (a) is the charge state of the initial superconducting quantum dot, and (b) is the state for verifying non-Abelian statistical properties or reading the topological qubit.

[0030] Figure 3 This is a schematic diagram of an embodiment of the present invention, showing two topological qubit readout devices connected to the same braided region;

[0031] In the figure: superconducting layer 4, insulating layer 5, heating layer 6, braided region 7, (a) is a top view of a single topological qubit readout device and readout isolation region, (b) is a cross-sectional view of the readout isolation region BB section, and (c) is a top view of two topological qubit readout devices connected to the same braided region;

[0032] Figure 4 This is a schematic diagram illustrating the steps of an embodiment of the present invention, in which two topological qubit readout devices are connected to the same weaving region and sequentially weave Majorana zero modes and simultaneously read them.

[0033] In the figure: (a) to (f) are top views of the process, respectively. Detailed Implementation

[0034] like Figure 1 As shown, this embodiment illustrates a topological qubit readout device based on scanning tunneling spectrum, comprising: a topological insulator substrate 1, a superconducting island 2, and a superconducting quantum dot 3. The topological insulator substrate is a three-dimensional topological insulator with two-dimensional topological surface states, and the Dirac point positions of these surface states can be modulated by their chemical composition. The interface between the superconducting island and the topological insulator exhibits topological superconductivity. The charging energy of the superconducting quantum dot is greater than the superconducting band gap to generate charge-dependent superconducting ground state parity distinguishable by the scanning tunneling spectrum.

[0035] In this embodiment, the material of the topological insulator substrate is antimony-doped bismuth telluride (Bi). 1-x Sb x )2Te3); lead (Pb) is used for superconducting islands; lead (Pb) is used for superconducting quantum dots.

[0036] This embodiment is based on the above-described method for fabricating a topological quantum bit readout device, including:

[0037] A. The topological insulator substrate was fabricated using ultra-high vacuum molecular beam epitaxy. The silicon (111) substrate was degassed at 500 °C to achieve a base vacuum of 2 × 10⁻⁶ in the fabrication chamber. -10 Below Torr, a 7×7 reconstruction was obtained on the silicon surface through flash heat treatment. High-purity Bi (99.9999%), Sb (99.9999%), and Te (99.999%) materials were co-evaporated from a standard Knudsen evaporation source onto a silicon substrate maintained at 180°C to form (Bi... 1-x Sb x The growth quality of the 2Te3 thin film was monitored using a high-energy reflection electron diffractometer. The Te / Bi ratio was maintained at 10:1 by controlling the evaporation source temperature, and the Sb doping ratio x was adjusted according to the Dirac point position of the topological insulator substrate.

[0038] B. The superconducting islands are grown using a mask-assisted molecular beam epitaxy method. The mask is made of silicon nitride and patterned using standard electron beam exposure. The mask is mounted on a support and positioned micrometers close to the topological insulator substrate to precisely deposit superconducting islands of specified size and location on the substrate. In this embodiment, the preferred shape of the dual superconducting islands is cylindrical, with a diameter of 100 nm, a height of 5 nm, and a center-to-center spacing of 170 nm.

[0039] C. Superconducting quantum dots are grown using mask-assisted molecular beam epitaxy. The mask is made of silicon nitride and patterned using standard electron beam exposure. The mask is mounted on a support and positioned micrometers close to the topological insulator substrate to precisely deposit superconducting quantum dots of a specified size and location on the substrate. In this embodiment, the preferred shape of the superconducting quantum dots is cylindrical, with an effective diameter of 10 nm and a height of 3 nm, located between two superconducting islands.

[0040] like Figure 2 As shown, this embodiment illustrates the topological quantum bit readout method based on the aforementioned device, comprising:

[0041] A. A topological qubit readout device fabricated by ultra-high vacuum molecular beam epitaxy is in situ transferred into the cavity of an ultra-high vacuum scanning tunneling microscope. Using the scanning tunneling microscope, a voltage pulse of 5V amplitude and 50 μs width is applied to the superconducting quantum dot through a platinum-iridium (Pt-Ir) needle tip to initialize its charge state. Figure 2 (a) By performing differential conductivity spatial mapping under the characteristic density of states peak of the scanning tunneling spectrum, it is ensured that the residual charge is completely cleared on the superconducting quantum dot;

[0042] B. Applying a 0.6 T vertical magnetic field (B) induces Majorana zero modes at the edges of two superconducting islands, causing them to fuse in the superconducting quantum dot. Non-Abelian statistical properties are then verified using scanning tunneling spectroscopy. Figure 2 (b) The main difference between the fusion of non-trivial and trivial Majorana zero modes lies in the charge probability density of the fusion region, which is then decoupled by increasing the vertical magnetic field (B) to 0.8 T.

[0043] C. When the Majorana zero mode in the flux vortex is far from the readout device, a voltage pulse of 5 V amplitude and 50 μs width is applied again to the superconducting quantum dot through a platinum-iridium (Pt-Ir) needle tip to initialize the charge state of the superconducting quantum dot, such as... Figure 2 (a);

[0044] D. After the Majorana zero modes in the flux vortex are woven together and moved separately into the superconducting island, the vertical magnetic field (B) is reduced to 0.6 T to fuse the edge Majorana zero modes at the superconducting quantum dot. The state of the topological qubit is read by scanning the tunneling spectrum, such as... Figure 2 (b)

[0045] like Figure 3 As shown, this embodiment relates to a topological quantum bit readout component, which includes: a pair of topological quantum bit readout devices and a braided region, wherein: a superconducting layer 4, an insulating layer 5 and a heating layer 6 are provided between the superconducting island 2 on the topological insulator substrate 1 and the braided region 7, the superconducting layer and the topological insulator interface have topological superconducting properties and their superconductivity can be easily suppressed or restored by the heat conduction of the superconducting suppression layer; the heating layer 6 is an electrothermal material, and its heat can be rapidly increased or decreased by an external circuit.

[0046] In this embodiment, the superconducting layer is made of lead (Pb); the insulating layer in the superconducting suppression layer is made of silicon dioxide (SiO2), and the heating layer is made of titanium (Ti) wire heating wire.

[0047] This embodiment relates to a method for fabricating the above-mentioned topological quantum bit readout component, including:

[0048] A. The superconducting layer is grown using a mask-assisted molecular beam epitaxy method. The mask is made of silicon nitride and is patterned by standard electron beam exposure. The mask is mounted on a support and brought close to the topological insulator substrate at the micrometer level to achieve precise deposition of a superconducting layer of a specified size and position on the topological insulator substrate.

[0049] The superconducting layer is preferably cylindrical in shape, with a length of 50 nm, a width of 35 nm, and a thickness of 5 nm. The superconducting layer connects the superconducting islands and the braided regions.

[0050] B. All superconducting suppression layers are patterned using standard electron beam lithography. The insulating layer is grown by electron beam evaporation, with a length of 340 nm, a width of 25 nm, and a thickness of 10 nm. The heating layer consists of titanium (Ti) wire heating filaments grown by electron beam deposition, with a length of 340 nm, a width of 10 nm, and a thickness of 5 nm. The long side of the filament is perpendicular to the short side of the superconducting layer in-plane. The heating layer is connected to an external circuit during operation. Specifically, a millivolt-level voltage is applied to the heating layer when the read isolation region is turned off, and the voltage is removed when the read isolation region is turned on.

[0051] like Figure 4 As shown, this embodiment illustrates the reading method of the aforementioned topological quantum bit reading component, including:

[0052] A. Turn off the read isolation regions of the two readout devices, and simultaneously initialize the topological qubits, such as... Figure 4 (a);

[0053] B. Open the left-side read isolation area and bring the left-side Majorana zero-energy modulus into the weaving area, such as Figure 4 (b);

[0054] C. Turn off the left read isolation region, initialize the charge state of the left read region, turn on the right read isolation region, and allow the right Majorana zero mode to enter the braided region, such as... Figure 4 (c);

[0055] D. Shut down the right-side read isolation region, initialize the charge state of the right-side read region, and weave the two Majorana zero modes, such as... Figure 4 (d);

[0056] E. Simultaneously open the read isolation regions of both readout devices, move the Majorana zero mode into both readout devices respectively, and then close the read isolation regions of both devices. Figure 4 (e);

[0057] F. Perform the reading of the topological quantum states in the two readout devices, such as... Figure 4 (f).

[0058] The state of the read isolation region being off is S1, and the state of the read isolation region being on is S2.

[0059] Compared with existing technologies, this invention can effectively verify the non-Abelian statistical properties of Majorana zero modes before topological qubit reading, ensuring the robustness of the topological quantum computing process to disorder and decoherence. Furthermore, by utilizing the localization of edge Majorana zero modes fused at superconducting quantum dots, the requirement for precise localization of Majorana zero modes in magnetic flux vortices is reduced during topological qubit reading. Moreover, by configuring a superconductivity-suppressing heating wire in the reading isolation region, the controlled connection and isolation of single or multiple topological qubit reading devices and the braided region enable the simultaneous reading of the states of multiple topological qubits. This invention is beneficial for the large-scale deployment of topological quantum computing devices and the application of topological quantum algorithms.

[0060] The above-described specific implementations can be partially adjusted by those skilled in the art in different ways without departing from the principles and purpose of the present invention. The scope of protection of the present invention is defined by the claims and is not limited to the above-described specific implementations. All implementation schemes within the scope of the claims are bound by the present invention.

Claims

1. A topological qubit readout device based on scanning tunneling spectrum, characterized in that, include: A pair of superconducting islands and a superconducting quantum dot located between the superconducting islands are disposed on a topological insulator substrate, wherein: the pair of superconducting islands are isolated from each other, and a pair of Majorana zero modes exist in the magnetic flux vortex and at the edge of each superconducting island, and the Majorana zero modes at the edges of the two superconducting islands can be controlled to merge at the superconducting quantum dot.

2. The topological qubit readout device based on scanning tunneling spectrum according to claim 1, characterized in that, The aforementioned topological insulator substrate is used to provide a large area of ​​uniform topological surface states. When reacting with the superconducting island during the evaporation process, an intermediate layer with a large area of ​​uniform topological surface states is provided therein.

3. The topological qubit readout device based on scanning tunneling spectrum according to claim 1 or 2, characterized in that, The area of ​​the superconducting island is larger than the range of the spatial distribution of Majorana zero-energy mode wavefunctions in the magnetic flux vortex and smaller than the area that allows multiple magnetic flux vortices to occupy. This ensures that the Majorana zero-energy mode at the edge of the superconducting island is not coupled with the Majorana zero-energy mode in its internal magnetic flux vortex, while also preventing the occurrence of multiple magnetic flux vortex states and ensuring the existence of the Majorana zero-energy mode at the edge of the superconducting island.

4. The topological qubit readout device based on scanning tunneling spectrum according to claim 1, characterized in that, The charging energy of the superconducting quantum dot is greater than its superconducting band gap to produce charge-dependent superconducting ground state parity that can be distinguished by scanning tunneling spectra.

5. A topological quantum bit readout component, characterized in that, It includes several pairs of topological qubit readout devices based on any one of claims 1-4, with each pair of topological qubit readout devices connected by a braided region, wherein: an isolation region is provided between the superconducting island on the topological qubit readout device and the braided region.

6. The topological quantum bit readout component according to claim 5, characterized in that, The isolation region includes: a superconducting layer located on a topological insulator substrate and connected to the superconducting island; an insulating layer disposed outside the superconducting layer for superconductivity suppression; and a heating layer. When the topological qubit is initialized or read, the superconductivity of this read isolation region should be suppressed to avoid coupling between the Majorana zero mode of the topological qubit read device and other Majorana zero modes present in the braided region, i.e., the read isolation region is turned off. When the Majorana zero mode is moved out of the read device after the topological qubit is initialized, or when the Majorana zero mode is moved into the read device after the topological qubit is braided, the superconductivity of this read isolation region should be restored, thereby providing a channel for the Majorana zero mode to enter and exit the read device, i.e., the read isolation region is opened.

7. An application based on scanning tunneling spectrum using the device described in any one of claims 1-4, characterized in that, include: In the initialization and readout phases of the topological qubits, the non-Abelian statistical properties of the Majorana zero modes are effectively verified by detecting the charge parity-dependent scanning tunneling spectrum caused by the fusion of edge Majorana zero modes at the superconducting quantum dot, thus ensuring the robustness of the topological quantum computing process to disorder and decoherence.

8. The application according to claim 7, characterized in that, The aforementioned topological qubit initialization phase specifically includes: A. A voltage pulse is applied to the superconducting quantum dot through the tip of a scanning tunneling microscope to initialize its charge state; B. Majorana zero modes were induced at the edges of two superconducting islands using a magnetic field, fused in a superconducting quantum dot, and their non-Abelian statistical properties were verified by scanning tunneling spectroscopy. They were then decoupled. The aforementioned topological qubit readout stage specifically includes: C. After the Majorana zero mode in the flux vortex leaves the readout device and enters the braided region, the charge state of the superconducting quantum dot is reinitialized; D. After the Majorana zero modes in the flux vortex are woven and moved back to the superconducting island from the woven region, the edge Majorana zero modes are fused at the superconducting quantum dot, and the state of the topological qubit is read by scanning the tunneling spectrum.

9. The application according to claim 8, characterized in that, The amplitude and width of the voltage pulse are such that the charge state of the superconducting quantum dot is initialized to a definite odd or even charge state without destroying the crystal structure and geometry of the superconducting quantum dot.

10. The application according to claim 8, characterized in that, The scanning tunneling spectrum relies on the charge parity results caused by Majorana zero-mode fusion to verify Abelian statistical characteristics and characterize the state of topological qubits.

Images