Magnetic components, especially quantum components

Abstract

The present invention relates to a magnetic component comprising a substrate (6) supporting at least a pair of permanent magnets (2) extending in a first direction (X), each magnet (2) having interacting ends (21 a, 21 b) arranged opposite each other, the pair of magnets (2) being arranged such that, under the influence of a magnetic field generated by external magnetic means, they exert an antisymmetric magnetic field having a high magnetic field gradient along a second direction (Z) orthogonal to the first direction (X).

Description

Detailed Description of the Invention

[0001] The present invention relates to magnetic components in the field of micro- and nanoelectronics, in particular quantum components, which are intended in particular, but not exclusively, for producing quantum computers, and may also be of interest in the fields of spintronics, topological superconductivity, magnetic actuation of nano-elements and nano-beads, or near-field magnetic detection using scanning probes.

[0002] There are devices designed to generate a magnetic field in a specific direction via a magnet, referred to as micromagnets by those skilled in the art of micro- and nanoelectronics.

[0003] One object of the present invention is to propose a new quantum component architecture that makes it possible to significantly reduce the quantum mismatch observed in prior art quantum components, thereby improving the performance of these components.

[0004] [Object of the Invention] To this end, according to a first aspect, the invention proposes a magnetic component comprising a substrate supporting at least a pair of permanent magnets extending in a first direction, each magnet having an interacting end, the interacting ends being arranged opposite each other, the magnet pair being arranged so as to exert, under the influence of a magnetic field generated by external magnetic means, an antisymmetric magnetic field with respect to the X=0 plane with a high magnetic field gradient along a second direction orthogonal to the first direction, and a symmetric magnetic field with respect to the X=0 plane along a first direction (X) orthogonal to the Y and Z directions.

[0005] For the purposes of the above and the remainder of the description, the following terms have the following definitions:

[0006] - Quantum component: an assembly of electronic circuits and / or devices that uses nanotubes as its conductive or semiconductive elements, the circuit having single, double or multiple quantum dots in series or parallel, using a single nano object with selected properties as the channel element, or multiple separately selected nano objects.

[0007] -Quantum dots: are parts of nano-objects where electrons are trapped / confined in three dimensions and can only occupy discrete energy levels.

[0008] - Nano object: an object having at least one of its external dimensions (typically from its height, width, thickness, length) less than 100 nanometers; if its three external dimensions (defined along three orthogonal axes) are less than 100 nanometers, it is a nanoparticle; if two of its external dimensions (preferably defined along two orthogonal axes) are less than 100 nanometers, it is a nanofiber, for example a hollow single- or multi-walled nanotube that can be closed at at least one end, or a solid fiber. Conductive or semiconductive nanofibers are hereinafter referred to as nanowires. If the external dimension (typically its thickness) is less than 100 nm, it is a nanosheet.

[0009] - Electrode: The end of a conductor positioned to emit or capture electrical current.

[0010] - Gate electrode: an electrode that allows transmitting a microwave signal or setting a potential (volts).

[0011] - Microwave gate electrode: a gate electrode that transports and emits microwave signals that enable the interaction between the microwave cavity and the nano-objects.

[0012] -Low frequency gate electrode: A gate electrode that allows setting an electrostatic potential to create a double quantum dot.

[0013] - Magnet: A magnetic element that becomes magnetized under the influence of a magnetic field.

[0014] - Electrostatic potential allowing the formation of two quantum dots: The electrostatic potential modulates the potential energy barrier, making it possible to create double quantum dots.

[0015] - Spin-photon coupling: a controllable interaction or "coupling" between the magnetic aspect of the qubit, i.e., its spin, and the microwave electric field coming from the microwave cavity. Since the electric field is composed of photons, we call it spin-photon coupling.

[0016] -Quantum gate: A logical operation that can change the state of a superposition of qubits. For example, a qubit can have a 1 / 2 chance of being in one or the other of two states.

[0017] - non-uniform magnetic field: a magnetic field generated by any variation of the magnetic field around and / or along at least one nano object element, preferably to generate a magnetic dipole, e.g., a vertical and / or horizontal component of the magnetic field changes its sign along or around at least one nano object element, preferably at or perpendicular to at least one magnetic gate electrode. According to a particular example, a magnetic field gradient horizontal to or along at least one nano object element, preferably a component of the magnetic field along the axis or direction of at least one nano object, which makes the total magnetic field along the at least one nano object element non-uniform, changes its sign along the at least one nano object element.

[0018] - spatial extent: a zone along and / or around at least one nano-object element, preferably in the radial direction, preferably located between the suspended electrodes, according to one embodiment an extent corresponding to the distance between two quantum dots.

[0019] Substrate: An element of a component that has high resistivity, e.g. a higher dielectric constant than air, especially at low temperatures.

[0020] According to a second aspect of the present invention, a quantum component is proposed, comprising:

[0021] At least two suspended electrodes: a source electrode connected to an electron source and a drain electrode connected to a reference potential, designed to receive a quantum device integrating a double quantum dot; at least three gate electrodes disposed between two suspended electrodes, the two suspended electrodes being elevated relative to the at least three gate electrodes; A magnetic component according to the invention, designed to exert an antisymmetric magnetic field having a high magnetic field gradient along a second direction perpendicular to the first direction under the influence of a magnetic field generated by external magnetic means, said antisymmetric magnetic field being applied to said quantum element.

[0022] According to a third aspect of the invention, a method for manufacturing a quantum component according to the invention is proposed, said method comprising the following steps:

[0023] - etching the substrate to receive the magnetic element; - depositing at least one pair of magnets extending in a first direction (X), each magnet having an interacting end, the interacting ends being positioned opposite each other; - performing a low-angle etching of a substrate on which at least one pair of magnets has been deposited; - depositing an oxide layer on the treated substrate; depositing a suspended electrode and a gate electrode on the oxide layer;

[0024] Preferably, according to any of the aforementioned aspects, the component or method may include one or more of the following features.

[0025] -The pair of magnets themselves generate an antisymmetric magnetic field (z-axis component) between the two dots (with respect to the x=0 plane), and an applied external magnetic field generates a symmetric field between the two dots.

[0026] Between quantum dots separated by distances between -60 and 120 nanometers, these gradients result in asymmetric field components that can reach approximately 30 mT or 40 mT (millitesla).

[0027] When considering dots arranged symmetrically with respect to the field distribution, the field at the two dots of a double quantum dot consists of a symmetric part and an antisymmetric part.

[0028] For each field component, it is possible to define i=u,v,w.

[0029]

number

[0030] Here, L;R refer to the left (L) and right (R) quantum dots, respectively. This definition of symmetric / asymmetric magnetic field for each vector component i (where u, v, w refer equivalently to directions in space x, y, z) makes sense in the context of double quantum dots.

[0031] The effect of the stray fields on the energies in the left and right parts of the double quantum dot can be expressed as:

[0032]

number

[0033] where:

[0034]

number

[0035] is the probability density of the presence of an electron at the dot p (left or right), the prefactor 2 represents the Landé factor of the electron spin, and μB is the Bohr magneton.

[0036] This corresponds to the mathematical definition of the magnetic coupling constant between electrons in the quantum dots and symmetric and anti-symmetric magnetic fields respectively. What is considered to be the quantity to be optimized (maximized) will be described later.

[0037] Therefore, the gradient must be considered as the non-uniformity between two quantum dots of the field averaged over each dot.

[0038] Next, consider a pair of dots with linear confinement, such as seen in double quantum dots in a nanowire. The dots are aligned along the x-axis and are defined between -250 nm and -150 nm for dot L and between 150 nm and 250 nm for dot R.

[0039] The nanowire is suspended at z = 200 nm above a magnetic layer extending from -100 nm < z < 100 nm.

[0040] The external magnetic field is preferably applied along the nanowire, but since a lateral gradient is required, assume a uniform magnetization along +x.

[0041] Here, since we are considering dots located above the magnetic system, the following is used.

[0042]

Equation

[0043] Here, L and R are interchanged with respect to the above. The definition of Q is the quantity to be optimized (refer to the previous coupling constant between the magnetic field and the dots).

[0044] To ensure a practical shape, constraints are applied such that the magnet is uniform along the z-axis.

[0045] The optimization therefore consists in determining the presence or absence of a magnet in each cell or one or more cells or one or more elements across the entire thickness along the Z axis at all X and Y positions. This method of optimizing the quantity Q is linear with respect to the individual magnetic elements / cells.

[0046] Higher magnetic saturation MS directly favors higher parasitic fields and gradients, which also facilitates the formation of magnetic domains in the nanomagnets and therefore requires higher external fields to reach saturation.

[0047] This external field is expressed as a term

[0048]

number

[0049] From the symmetric part of the parasitic field in the formation of dot energy levels

[0050]

number

[0051] Add it with.

[0052] The non-uniformity of the field acting on the dot is defined as follows:

[0053]

number

[0054] This figure of merit decreases when a strong external field is used.

[0055] Therefore, to optimize heterogeneity, it is necessary to identify the pair of MS and Bext values ​​that provides the highest:

[0056]

number

[0057] This last point corresponds to the definition of the contribution of the external magnetic field to the symmetric component.

[0058] BRIEF DESCRIPTION OF THE DRAWINGS Other features and advantages of the present invention will become apparent from the following detailed description of the invention which refers to the accompanying drawings.

[0059] FIG. 1 is a schematic diagram of a quantum component with electrodes extending substantially perpendicular to two series of magnets, according to one embodiment.

[0060] [Figure 2] Figure 2 shows two series of magnets extending parallel to each other within the same series and between the two series, with the magnet ends of the first series facing the magnet ends of the second series, and with the magnets of both series lying in the same plane.

[0061] FIG. 3 is a schematic diagram of two opposing magnet ends and a nanotube connecting the two ends, according to one embodiment of a quantum component, arranged in a three-dimensional reference frame.

[0062] [Figure 4] Figure 4 is a nanoscale depiction of the saturation of the magnetic field at the ends of the two magnets.

[0063] 5 shows the curves of the magnetic field components along a carbon nanotube, in particular the magnetic field distribution along the carbon nanotube obtained with the micromagnet according to FIG. 2.

[0033] FIG.

[0064] [Figure 6] Figure 6 shows the effect of an external magnetic field on various physical quantities using three different magnet materials.

[0065] For greater clarity, identical or similar elements of the various embodiments are designated by the same reference numerals in all figures.

[0066] Detailed Description of the Invention 1 and 2, one embodiment of a quantum component is shown, a substrate 6, for example made of a high resistivity material; a magnetic device 2 acting as a magnetic electrode and arranged to generate a magnetic field experienced by the quantum component 1, comprising two comb-shaped portions 2A, 2B arranged opposite each other and separated by a central gap 22 in which a dedicated magnetic field is generated; a set of gate electrodes 8 arranged above the central gap 22, the set of gate electrodes 8 being surrounded by a source electrode 9.1, a cut source electrode 9.2, a cut drain electrode 9.3, and a drain electrode 9.4; A nanotube or nanowire (not visible in Figure 1) connected to a suspended electrode, the nanotube or nanowire suspended linearly above the gate electrode and above a set of substantially parallel magnets, preferably made of carbon.

[0067] The source and drain electrodes are disposed on the conductive layer via an insulating layer. They act as suspended electrodes for the nanotube or nanowire and are elevated above the gate electrode. This arrangement is unique to quantum components containing carbon nanotubes.

[0068] Referring to Figure 2, the magnetic device 8 comprises permanent magnets arranged in the form of two opposing combs 2A, 2B, i.e., a first comb and a second comb. Each comb 2A, 2B comprises a plurality of generally rectangular magnets 20A, 21A, which are arranged parallel to one another. The magnets in each series in each comb are connected to two opposing ends of a corresponding one along the Z axis.

[0069] According to the illustrated embodiment, each comb 2A, 2B comprises 15 magnets. Each magnet is 1.5 micrometers wide and 8.5 micrometers long. The width is selected so that the magnetic moment is parallel to the boundary due to the internal dipole energy. Preferably, each magnet is laterally spaced apart by a distance of 0.75 micrometers along the Y axis. Preferably, each comb 2A, 2B has a thickness of 400 nanometers. Preferentially, each magnet comprises iron and cobalt, which preferably have high remanence.

[0070] 2 and 3, each magnet 21A of the first comb 2A has an interacting end or pole 41A positioned to face an interacting end or pole 41B of a magnet 21B of the second comb 2B. Each cross section faces a cross section of a magnet on the second comb. Preferably, the distance between the two interacting ends or poles is 0.4 to 1 micrometer. The spacing is measured between the distal points of the interacting ends.

[0071] Preferably, each interaction end has a rounded shape when viewed along the two-dimensional or longitudinal plane indicated by the XY plane in Figure 2. In addition, Figures 3, 4, and 5 show the optimal shape of the saturated nanomagnet in the case of a quantum dot of finite extension, particularly a uniform magnetization imposed along x, maximizing the field difference Bz. Preferably, a rounded distal portion, particularly a three-dimensional oval shape, contributes most to field optimization. The shape of the interaction end aligns the magnetic moment in a single direction.

[0072] In addition, each magnet 21A has a connection end 31A opposite the interaction end 41A. Each comb 2A, 2B further comprises a magnet connection piece 200A, 200B, so that each magnet of the comb 2A, 2B is connected to the connection piece 200A, 200B of that comb 2A, 2B via a connection end. According to the embodiment shown, the connection pieces 200A, 200B are 4 micrometers wide.

[0073] This embodiment provides an anisotropic shape and generates a uniform magnetic field in the Y direction relative to the nanotube. The reduced dimensions of the magnets result in shape anisotropy, and the magnetic moments tend to be parallel to the boundaries due to internal dipole energy.

[0074] Preferably, the two magnetic combs 2A, 2B are embedded in a substrate 6.

[0075] Furthermore, the quantum component comprises external magnetic means (not shown) arranged to exert a magnetic field along the X direction. For example, a toroid (not shown) surrounds the electrodes and the combs. Preferably, this toroid generates a magnetic field of 200 to 500 mT.

[0076] Therefore, the quantum component is proposed to exert an antisymmetric magnetic field with a strong field gradient along the Z direction perpendicular to the X direction, under the influence of a magnetic field generated by external magnetic means. For example, tests carried out have shown that the antisymmetric field constant reaches 26.8 microeV and the symmetric field constant reaches 29 microeV, making it possible to optimize spin-photon coupling.

[0077] The quantum components optimize the distribution of magnetic moments around the quantum dots, the magnetic field gradient, and therefore the interaction between the magnets and the nano-objects or nanotubes containing at least two quantum dots, preferably located about 100 nanometers above the magnet pair under consideration.

[0078] Figure 6 shows the results of micromagnetic simulations of a geometry optimized for an inhomogeneous component Bz with an external field Bext and a magnetization along x. Based on the external magnetic field, (a) the magnetization mx, (b) the symmetric (alpha s), (c) the antisymmetric (alpha as) coupling constants with the nanomagnet, and (d) the ratio between the antisymmetric and total symmetric fields.

[0079]

number

[0080] The different colors correspond to CoFe (square lines), Co (triangle lines) and NiFe (circle lines). [Brief explanation of the drawings]

[0081] [Figure 1] FIG. 1 is a schematic diagram of a quantum component with electrodes extending substantially perpendicular to two series of magnets, according to one embodiment. [Figure 2] Shown are two series of magnets extending parallel to each other within the same series and between the two series, with the magnet ends of the first series facing the magnet ends of the second series, and with the magnets of both series in the same plane. [Figure 3] 1 is a schematic diagram of two opposing magnet ends and a nanotube connecting the two ends, according to one embodiment of a quantum component, the diagram being arranged in a three-dimensional reference frame. [Figure 4] Nanoscale depiction of magnetic field saturation at the ends of two magnets. [Figure 5] 3 shows the curves of the magnetic field components along the carbon nanotube, in particular the magnetic field distribution along the carbon nanotube obtained with the micromagnet according to FIG. 2. FIG. [Figure 6] Three different magnet materials are used to demonstrate the effect of an external magnetic field on various physical quantities.

Claims

1. 1. A magnetic component comprising: a substrate (6) receiving at least a pair of permanent magnets extending in a first direction (X), each magnet having an interacting end, said interacting ends being arranged opposite each other, said pair of magnets being arranged to exert, under the influence of a magnetic field generated by external magnetic means, an anti-symmetric magnetic field with respect to the X=0 plane having a high magnetic field gradient along a second direction (Z) orthogonal to said first direction (X), and a symmetric magnetic field with respect to the X=0 plane along said first direction (X) orthogonal to said Y direction and said Z direction.

2. 10. The magnetic component of claim 1, comprising several pairs of magnets facing each other to form two combs.

3. A magnetic component according to any one of claims 1 to 2, wherein each magnet has a linear shape.

4. A magnetic component according to any one of claims 1 to 3, wherein each magnetic interaction end has a rounded shape.

5. The magnetic component according to any one of claims 1 to 4, wherein the rounded shape is a curve having a predetermined radius of curvature.

6. A magnetic component according to any one of claims 4 to 5, wherein each magnet end is three-dimensionally rounded.

7. A magnetic component according to any one of claims 1 to 6, wherein each magnet interaction end has a shape without protrusions.

8. A magnetic component according to any one of the preceding claims, wherein the at least one magnet is embedded in the substrate.

9. A magnetic component according to any one of claims 1 to 7, wherein the at least one magnet is deposited on the substrate.

10. A quantum component comprising: a source electrode connected to an electron source and a drain electrode connected to a reference potential, designed to receive a quantum element integrating a double quantum dot; at least three gate electrodes (9.1, 9.2, 9.3, 9.4) arranged between said two source and drain electrodes; - a magnetic component (1) according to any one of claims 1 to 9, designed to exert an antisymmetric magnetic field with a high magnetic field gradient along a second direction (Z) perpendicular to the first direction (X) under the influence of a magnetic field generated by external magnetic means, said antisymmetric magnetic field being applied to said quantum element.

11. Quantum component according to claims 1 to 10, characterized in that the source and drain electrodes constitute suspended electrodes raised relative to the at least three gate electrodes.

12. Quantum component according to claims 1 to 11, further comprising at least one nano object element (11) suspended between and electrically connected to said two suspended electrodes as quantum elements, said at least one nano object element being arranged above said at least three gate electrodes.

13. 11. The quantum component of claim 10, further comprising an electron gas located in the substrate disposed between the two source and drain electrodes as a quantum device.

14. Quantum component according to any one of claims 10 to 13, wherein the quantum device is positioned above the at least one magnet pair at a distance of about 100 nm.

15. Quantum component according to any one of claims 10 to 14, wherein the pair of magnets are arranged symmetrically with respect to a plane perpendicular to the direction of the at least one quantum element.

16. A method for producing a quantum component according to any one of claims 10 to 15, comprising the steps of: - etching the substrate to receive the magnetic elements; - depositing at least one pair of magnets extending in a first direction (X), each magnet having an interacting end, said interacting ends being arranged opposite each other; - performing a low-angle etching of said substrate on which at least one pair of magnets has been deposited; - depositing an oxide layer on the treated substrate; - depositing a suspended electrode and a gate electrode on said oxide layer.

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